New Design, SE 6005 Directly Coupled Audio Amplifier
- Thread starter drlowmu
- Start date
- Status
Yes, I know about Joe. I do things a bit differently.
Unlike Joe, I prefer 15 inch woofers, especially when they are front horn loaded, and I never use " one simple cap". I will avoid a bent 32 Horn. I will use a cap on a 802 tweeter, but it will have multiple bypasses. I THINK I have six or seven bypasses on my present A7-8 speakers, in just "one" cap position.
By the way Prem, twenty minutes ago, I started to play this new amp, after it had been idling all night long. This is day three. I am in an adjacent room at my computer. This amp is playing the VOTT ALTECs, on a reference ( Steve Clarke, " Solo Drums " WEN 020 CD ) drum recording. It sounds / plays - easily, 20% better than ANY other amp I have ever built or have ever heard, anywhere, in my entire life.
Honestly, I am surprised, amazed ( and pleased, excited ), at how wonderfully this plays the speakers..................... with total freedom, precision, and all-out abandon !!! I now have to wonder, where will this amp and specific design lead me, in the future ??
Jeff
Last edited:
Maybe you should also make an assessment of this build using the Tuttle-designed, Fulton-modified, dual-mono Bravura that, until very recently, you had been using and in love with for the past forty years.
Have you actually given thought as to whether a two-stage dc-coupled 12AX7-based preamp with "passive" RIAA equalization is even feasible ? If you have, perhaps you could share a sketch which illustrates a proposed conceptual design topology which shows some idealized operating points for the two tubes. Also, in 1960 you were just out of middle school, which leads me to wonder how you were able to afford LPs which were easily $3 each at the time. Lastly, with a collection of thirteen thousand LPs, how are you able to store and keep track of them all?
Excellent question again !!! What a pleasure.
I do not ever precisely measure or even know the dB.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
After building these two stage DC amps for well over a decade, I use a " formula". There is a certain amount of gain required - to get the amp to have a decent / mentally-involving " jump factor". The " ideal " gain.
Below it, and the listening experience and music presentation is BORING ..... to hear.
The magic number I always shoot for is 400 Xs Prem.
It is is not based on any measured or " made good " gain, but rather, on the spec sheet rated mu of the two tubes, when simply multiplied by each other.
So lets look at as few of the popular two - tube DC amp examples.
For a 2A3 Triode, with a rated mu of 4, the proper rated gain of the DRIVER tube ............must be............... 100 !!
100 Xs 4 = 400.
A mu of 70 DRIVER tube, such as half a 6SL7 will not " cut the mustard ", not as much fun to hear ( 70 Xs 4 = only 280 ). 280 is too low ..........VS 400. Half a 6SN7 is inappropriate, a total wasted effort ( 20 Xs 4 = 80 ).
So what tubes with a mu of 100 are really good Drivers............... with a mu of 4 Type 2A3, in a DC amp ???
1/2 a 12AX7, or a 7B4 at about 0.75 mills, or 1/2 a 12BZ7 at about 1.1 mills, these I would use today.
Lets look at useful Tetrode Finals tubes Prem : a KT88, KT150, or a 6AQ5 / 6005.
Depending upon how executed, I would say their rated gain may be roughly ( estimated ) 12 to 15 times.
So the DRIVER tube for these Tetrodes needs to be in the mu of 33 to 35 range, doesn't it, to approximate 400.
In the 2021 6005 amp, it's Russian 6N23P-EV Driver tube may have a rated mu of 33 to 35. Lets see how that works :
Mu of 33 times mu of 12 is 396...............close to 400 !!! Mu of 35 Xs mu of 12 is .................420, ...............that will also do.
On the highest side, a mu of 35 times Driver into a mu of 15 Output tube equals 525, and that would surely NOT be a boring two stage DC amp to hear.
Around 400 does FINE. My favorite two DRIVER tubes for Tetrodes in 2021 would be the 6N23P-EV ( better than any 6DJ8 ) at about 5 mills, and the Russian 6E6P-DRU triode-connected at about 10 mills, a potent driver - a killer .
These tube combinations, and the resultant amp, will have a sufficient music-listening " jump " factor. Such amps will be FUN to hear listening-wise ( with a good power supply ) powering my home's ALTEC horn loaded speakers !!
Well there you have it Prem. Truly a great question on your part !!
Jeff
Last edited:
Hello YogiBear,
I have been meaning to ask you, I do not know much about these three tubes you like. ( F2a, EL12 and RS1003 ).
Can you either HFV PM me, or perhaps email me direct, with info sheets on these ? Can you let me know what you like about them, and how you use them ? No rush.
Are they plentiful in Europe, and easy to source ??
Live and learn !! Thanks.
Jeff
PS,........................................... I take back what I wrote above, after just viewing eBay.
There was only one F2a available, asking $950. There were asking $450 for two EL12s, and they are plentiful, but a Pentode I believe. The RS1003 were somewhat pricey, but also a Pentode. I prefer, Yogibear, to avoid using Pentode vacuum tubes. My building is either with a Triode ( JJ 2A3-40 ) or a Tetrode vacuum tube. Four elements is the most I would use ( KT88, KT150, 6005, 6E6P-DRY ).
My honest question is, can the $2.00 6AQ5 or $10.00 6005 tetrodes easily outperform these expensive pentodes..... sonically ?? With the 6AQ5/6005's close element spacing, round tube elements, and high transfer efficiency, it may be the case. I will let others find out !! I feel, there is more to be gained with a really great power supply, than than using unobtainium and expensive tubes. A pair of NOS VAIC 2A3 mesh plates might go for $3,000 today. But in mid 2019, my SE amp with two $39.00 E.H. KT88s, just ATE that VAIC tubed amp we A-Bed. Same audio circuit, mine had a different level of B+ design treatment.
" In the end, we all listen to a modulated B+ supply. How good is it ?? "
Last edited:
Yogibear,
To be complete, so that particularly you, and ANY casual reader will understand, I need to add this :
Without having the same type and same level of power supply that is in the 6005 2021 amp, no one will get anywhere near the result, that has been obtained. It is impossible. I am very sure of this, and have been - for 39 years now.
Jeff
To be complete, so that particularly you, and ANY casual reader will understand, I need to add this :
Without having the same type and same level of power supply that is in the 6005 2021 amp, no one will get anywhere near the result, that has been obtained. It is impossible. I am very sure of this, and have been - for 39 years now.
Jeff
Dear Yogibear,
Cool post. To discover and use the best sounding tube amps possible, you need to own and use 100 dB speakers , with a large radiating surface ( another way of saying, using a 15 inch or larger woofer ) , as the minimum sensitivity.
Actually, 101 dB and up, with a large radiating surface is even better. ( No small radiating area / highly efficient / single drivers , eg: Lowthers )
I don't think you guys do that.
If not, you have the wrong speakers to be making listening decisions for ultra audio !!!
So Yogibear, you will do a post, as your's above, discussing eight Watt tube amps !!
Speaking frankly, I would tend to discount all your three tube suggestions, if you are not using 101 dB speakers for evaluation, and ..... if you are also using a conventional tube amplifier's power supply.
This is where we differ - and we will obtain different results.
As I lay in bed last night, I kept thinking to myself, how can ANYONE ever be in the tube audio, the high performance game, and not have GTO caps in his ( or her ) power supply ( bypassing caps to the Finals, and also on the speaker crossovers ) ??
Also, I ask myself, how could they have any performance when using power supply chokes " by the book " that meet critical inductance, at the expense of higher DCR ??
So there is where I THINK we are Yogibear.
I do not know what Perm runs, but he too is discussing F2a tubes. You guys are both VERY decent human beings, and honest. Someone like Perm also knows much more than me technically, anyone can easily tell.
Knowing things technically, certainly does not mean you are any good at all in audio, and that you approach audio " playing with a full deck ". Dr.Gary comes to my mind actually, L.O.L., all his life, as THE PERFECT example of this.
If you folks had your best performing amps, in my modest sized living room, powering my VOTT A7-8s ( with 515Bs and 802s ), I would expect that the new 6005 effort ( as soon as I finish it and it breaks in ) would easily and thoroughly outperform any amps you brought. L.O.L., this 6005 amplifier uses a small 7 Pin, ten dollar, twelve Watt plate rated vacuum tube. Not so - not the case, if I was visiting in India, results might likely be opposite, when listening on someone's 97 or 98 dB speakers !!
I would 100% love to remain respectful and on friendly one-on-one terms with both of you. We all chase the same dream !! But at this moment, I sense our personal experiences, backgrounds and approaches in audio, are somewhat unique and different from each other !!
Do you, and can you " get " what I am trying to say, and are you able to accept my thoughts without malice - and openly continue to " talk audio " ?? I sure hope so !!!
Let us openly continue to DO things together Yogibear. For all of us tube amplifier enthusiasts, I would like to think, most likely, " the best is yet to come " !!!
Personal best to you,
Jeff Medwin
Cool post. To discover and use the best sounding tube amps possible, you need to own and use 100 dB speakers , with a large radiating surface ( another way of saying, using a 15 inch or larger woofer ) , as the minimum sensitivity.
Actually, 101 dB and up, with a large radiating surface is even better. ( No small radiating area / highly efficient / single drivers , eg: Lowthers )
I don't think you guys do that.
If not, you have the wrong speakers to be making listening decisions for ultra audio !!!
So Yogibear, you will do a post, as your's above, discussing eight Watt tube amps !!
Speaking frankly, I would tend to discount all your three tube suggestions, if you are not using 101 dB speakers for evaluation, and ..... if you are also using a conventional tube amplifier's power supply.
This is where we differ - and we will obtain different results.
As I lay in bed last night, I kept thinking to myself, how can ANYONE ever be in the tube audio, the high performance game, and not have GTO caps in his ( or her ) power supply ( bypassing caps to the Finals, and also on the speaker crossovers ) ??
Also, I ask myself, how could they have any performance when using power supply chokes " by the book " that meet critical inductance, at the expense of higher DCR ??
So there is where I THINK we are Yogibear.
I do not know what Perm runs, but he too is discussing F2a tubes. You guys are both VERY decent human beings, and honest. Someone like Perm also knows much more than me technically, anyone can easily tell.
Knowing things technically, certainly does not mean you are any good at all in audio, and that you approach audio " playing with a full deck ". Dr.Gary comes to my mind actually, L.O.L., all his life, as THE PERFECT example of this.
If you folks had your best performing amps, in my modest sized living room, powering my VOTT A7-8s ( with 515Bs and 802s ), I would expect that the new 6005 effort ( as soon as I finish it and it breaks in ) would easily and thoroughly outperform any amps you brought. L.O.L., this 6005 amplifier uses a small 7 Pin, ten dollar, twelve Watt plate rated vacuum tube. Not so - not the case, if I was visiting in India, results might likely be opposite, when listening on someone's 97 or 98 dB speakers !!
I would 100% love to remain respectful and on friendly one-on-one terms with both of you. We all chase the same dream !! But at this moment, I sense our personal experiences, backgrounds and approaches in audio, are somewhat unique and different from each other !!
Do you, and can you " get " what I am trying to say, and are you able to accept my thoughts without malice - and openly continue to " talk audio " ?? I sure hope so !!!
Let us openly continue to DO things together Yogibear. For all of us tube amplifier enthusiasts, I would like to think, most likely, " the best is yet to come " !!!
Personal best to you,
Jeff Medwin
Last edited:
Your statement " Knowing things technically, certainly does not mean you are any good at all in audio, and that you approach audio " playing with a full deck " may well be true. However, it's only because of my technical knowledge that you currently have a working Tuttle-designed, Fulton-modified dual-mono Bravura preamp that that you have been using and in love with for the past forty years.
RtoR King
Active Member
I'm kind of with you here DrGary. I have followed this thread on and off and while drlowmu clearly loves his hobby and builds his amps with incredible detail, the technical information being offered is seriously lacking even basic electronic knowledge. And the fixation on these mundane details like a #4 capacity wire lug. If that's what you need, fine. If that's all you have in your parts bin that evening, that's fine too. But it's hardly a revelation in audio product design.
And I don't get these 1500v rated capacitors. These are actually commutation capacitors for VFD motor drives, large UPS systems, and enterprise class Solar inverters. They have no benefit for HiFi audio applications. But hey, if you want to use them I guess they will work. But a Sprague Orange Drop or a good quality electrolytic cap will work just as well and be a lot more reasonable size plus a lot cheaper.
I also find these statements that all other amplifiers are designed wrong and that this is the only way to build a high quality audio amplifier rather arrogant! There is no "best audio amplifier" because there are numerous other factors that influence HiFi audio reproduction starting with speakers.
But keep in mind drlowmu advocates the bypassing of the AC line fuse with a switch in a previous post. If I did that I too would be leery of a wood chassis!Hmmm... I do not want to inflame, to turn the world around and stir up controversy.
Right: wood cannot and would not be acceptable for industrial use, because of its weakness (it burns!) but it is far superior to steel as a chassis in all respects... but this is ONLY my opinion; do not expect to be believed and I really do not want a debate/argument pro/against it.
It is just a personal approach and a way of doing things!
-----------------
Jeff, I do not want/need advertising, neither do I want to argue, or pollute your topic.
-----------------
Looking forward to hearing experience from you, after such a complex, over-engineered tube amplifier (well, 6 of them, afterall!).
Then we can then talk about acoustics, enclosures and tube amplifiers in other topics.
I am only glad to have found a builder with such a passion and who works down to the ultimate detail, just like you.
With friendship...
Last edited:
That's nice. When did you have that ??
When I rented a home in the 1980s, I "once had" a full RCA movie theatre speaker system. It used lovely MI-9449 alnico woofers, a 15 inch pair of great drivers, FRONT horn-loaded in " Ubangies". For the top end, a rare / highly desirable pair of RCA' MI-1428 Field Coil compression drivers, on the correct RCA horns. Ever hear such a set up ??
Back then, I actually owned three Ubangies at once, but only could use two, due to the living room's size .
See Johnathan Weiss discuss this speaker here:
LOL, a friend from way back, Alan Sides proudly introduced me to Ubangies, when he started his first recording studio ( on " Ocean Way ", not in Hollywood, etc. ).
.......................................
..........................................But Yogibear, how about me - now, 2021, today ???
Today I live in a modest two bedroom apartment, so I run a smaller simple two-way FRONT horn-loaded ALTEC A7-8 VOTT system. It is very lightly modded. I photographed and posted it on Page ONE of this thread. I love them.
Tell me, what precisely do you use for speakers now / today ? Size and rated efficiency ??
Jeff
Last edited:
Dear RtoR King,
It is evident from your above posting that there is much - that you simply do not understand. As you say, you followed this thread " on and off ". You have not thoroughly read and understood this entire ( almost year - long ) build process, which this thread represents to interested tube DIYers.
You have not put things together in your mind, because your focused attention to my thread has been admittedly incomplete. Precisely like Dr.Gary, who never read or grasped my early pages of thread comments : on regulated VS passive filtering !!
This IS a far different amp build than anyone sees, 99.999 percent of the time.
It is the result of my own involvement with audio, from the earliest age.
I was born November 27 , 1944. So this month, in December, seventy seven years ago , my Mom brought me home from the hospital. She nursed me to the sounds of my Dad's original field coil fifteen inch ALTEC 604 duplex speaker, playing back classical FM music, likely from WOR in NY city. So, I do have extensive from-birth experience with high sensitivity speakers !! ( When the ALTEC 604B alnico came out, I was just a little kid. Dad bought one, and our family switched to STEREO reproduction in our home's finished basement recreation room. )
Lets start with a #4 wire capacity lug : This thread is documenting my own 2021 amp build. The thread serves multiple positive uses. One is to share information, with other interested tube audio DIYers. Another, is to specifically show three DIY friends, how to build the amp. ( They will use three of the six chassis I had made. )
BACKGROUND : These three guys, at one time or another, solicited me to design a great amp, for their horn loaded ( mostly ALTEC ) speakers. I had to disappoint them all, by telling them the ST Type 45 amp they sought, can NEVER play any HORN speaker properly, full range, single amped, due to faults in the tube. I told them the best POSSIBLE solution would be a DC designed amp, with a circa 1950s 6005 tetrode tube. The many pictures and descriptions in this thread, is for their benefit, along with the rest of the world.
The #4 lug.
My power supplies are UNlike everyone's " by the book " tube designs, thank goodness !!! The " 100+ year old book" power supply, features large value, high DCR chokes, and sometimes large values of filter capacitors. This is to reduce AC ripple, and operate as a " energy storage reservoir".
The 2021 6005 amp's supply design has a supply described by an acronym LSES , which stands for " Low Storage Energy Supply ". Unlike the hundred year plus old " large reservoir " power supply, this amp's supply was aptly described by ( E.E. and horn builder ) John L. Hasquin , simply as a " source fed supply ".
You obviously missed-out reading about the unique and special properties of a GTO cap ( totally defining the leading edges, precisely, of all transients). Boli46's independent comments on his experiences, of the same 5uF GTO cap I use, was either not read by you, or simply lost on you. Read it ..... to learn.
New Design, SE 6005 Directly Coupled Audio Amplifier
12- 11 -2021 Mini Photo Update ............ Ground BUSS, ........... Each Channel - to STAR Central Ground 12 AWG Mil Spec wire, Teflon jacket stripped- off below photo. Beautiful quality silver plated copper stranded wire, leading to STAR GROUND, the central chassis brass bolt...
www.hifivision.com
OK, OK, back to the #4 lug. I decided to make this " super-dooper " ( a great E.E. term I say
) GTO 5uF cap, ( bypassing C2 ), become the Main B+ feed for the entire amp, rather than using the larger uF WIMA C2 main supply cap. For effective transfer of energy, I often use those ( orange colored ) 12 AWG M22759/11 wires, for main B+ feeds in this supply.C2's GTO 5 uF bypass in this stereo amp would thus, directly feed the following circuits, ( with my preferred choice of 12 AWG Military-Secified wire to each ) :
1) The left output transformer's primary
2) The right output transformer's primary
3) The left input stage B+ ( Ra )
4) the left output tube's super sensitive G2 supply
5) The right input stage B+ ( Ra )
6) the right output tube's super sensitive G2 supply
7) PLUS, we need a 12 AWG " feed " wire, into the GTO, from the WIMA film main C2 cap.
Each plus and minus termination on a GTO uses a large brass bolt in my amps. This entire terminal, unlike any other caps I have ever seen, is DESIGNED to pass huge energy flows ( each terminal's attachment bolt is M8 by 1.25mm by 12 mm long ).
I visualized the C2 GTO bypass cap, as becoming the " heart " of this 6005 amp's power supply, and the seven 12 AWG wires would effectively have to be tied into this DYNAMITE cap. ( see ....... great E.E. terms, " heart and dynamite " ).
Do you understand such language and the analogy?? I can.
After much thought and consideration, me showing the three copy-cat DIYers how to do this, ( with a #4 ring terminal ), became the very best direct-connection solution I could think of. We surely don't want to goof-up, in any way, the "plumbing " into and out of the heart, do we ???????? So by now, hopefully, you understand why this was detailed. Any other possible approach here, of seven into one that "I" can think of, would be less elegant !!!
You state
Well said. I realized many decades ago, from my work with Robert Fulton, that the weakest link in the audio chain, was those true TURKEY audio amplifiers, and NOT the loudspeakers. Very few cut the mustard, then and now, from my direct experience. I HAVE to build my own. Yes yes yes, I agree, you are right 100% to say the amp and the speaker are totally dependent upon each other.
This leads to the key question : " what can be assembled, to have perhaps the worlds best sounding audio system " ?? That is a good goal, eh ???
Since AMPs are the real turkeys in audio, you have to figure out, " What will be the world's best sounding amp and an appropriate speaker system , and WHO makes it ".
By providence, after Robert Fulton's death, I developed a trusted relationship in the 1980s, with a second audio mentor, Mr. Dennis Fraker of Livingston Montana USA. In 1989, he produced the then-world's best sounding tube amp, actually using SOME of the techniques my first mentor, Mr. Fulton, taught me. Since then and today, I consider Dennis to be my mentor, and the world's best tube amplifier builder. I drove thousands of miles from Kansas City for ten years to Denver RMAF shows, and in 2019, over 3,000 miles to Dennis' home, to HEAR directly his creations !!
We are SMART enough to know, that the best we can do ( amp - wise ) will be in the form of a low power, two stage, directly coupled all-tube ( including rectification ) audio amplifier. NOTE : This REQUIRES starting off the audio journey efficiently on the right foot, with large radiating area sensitive speakers having 100 to preferably 101 dB sensitivity .
There are three speakers in this world, made for professional use, that ideally fit the bill ( Japanese ALE $$$$$$, vintage unobtainium German Klangfilm, and USA ALTEC / sometimes GPA ).
Of the above three, ALTEC is clearly the most available, and best-value one can own and use, GPA, next.
The newest 6005 amp puts out maybe 1.5 Watts, so a simple ALTEC A7-8, like I have, will do the job. This 6005 amp build is UNLIKE what all others people ever see and hear. I am confident of what I am hearing and report. This thread, BTW, has over 23,000 hits. I do report from direct experience, it is certainly not just foolhardy " arrogance " as you term and processed it. YMMV, fine with me !!
I've got the amp and speakers, in my living room.
Thanks for your interest, I hope this helps you, please PM me with any additional questions, using HFV messages.
Jeff
Last edited:
12-30-2021 .......................Mini Report.....................On AC PHASING of tube amps ..................................
One seldom done thing by DIY builders, ( and likely many manufacturers ), is to check the AC phasing of an amp, to be sure the AC voltages are not " bucking " each other.
There are different ways to do this. A quick way is to use a scope, and see if the various AC wave forms are ALL moving in the same direction.
Another way, which I enjoy doing, is aligning the AC waveform s by ear, where you get to hear / decide and learn the sonic results, in a meaningful ( to me ) way.
Where ever you have multiple powered AC sources in a amp, this needs to be done, to prevent these various AC powered circuits from deleteriously-to-the-sound, BUCK each other.
With the 6005 amp circuit up, and smoothly running, I just spent a few hour's time, adjusting ALL the AC feeds to have a uniform and optimal sounding AC polarity.
I have made-up seven inch long JUMPERS, with pure copper alligator clips, and a insulating boot, at each end. Wire is m22759/11/14 AWG, so losses are lessened. At each place in the amp, where there is an AC feed, we unsolder the two wires, and make two new connections using these quality jumpers. This way, one can SWAP the alligator clips, and HEAR what a 180 degree AC feed reversal sounds like !!
The music program source used was musician Steve Clarke's " Solo Drums" CD from the UK. Cut one, playing each time from 4:00 to 4:39, 39 seconds. This is a very demanding full-blast drum solo, with multiple close-miked drums and cymbals going off explosively, IF the system is up to snuff.
" Back and forth" listening between the two polarities, by reversing the alligator clips at one end. Only when you are absolutely sure, you remove the clip leads, and permanently solder-in the best sounding polarity. Move on to the next AC feed pair !! I did this in this order :
1) The separate 6.3 VAC filament transformer feeding the input tube. WHY first ?? The input tube has a rated mu or gain of about 33-35, maybe three times higher in gain than the output tube. It is the most sensitive tube. Also, importantly, I am keenly aware if you don't optimize the input stage, " information lost there, never gets made up in later stages ".
2) Next I optimized the filaments of the separate rectifier tubes' filament transformer. ( 5VAC / VCT at 6 A. ) Why?? It feeds the whole amp !! HEY, it was 180 degrees out as I had it originally wired. The amp sounded better on the repeated drum solo selection. Swap 'dem alligator clips, listen back and forth, and solder it permanently !! Yup, we gained performance forever, doing that.
3) Next came the AC high voltage feeds from the ends of the main power transformer's high voltage secondary.
It is about 400 VAC-0-400 VAC. Be extra careful, when clip leading such a high and lethal potential !! HEY again, it also sounded better reversed. The amplifier again, became incrementally better sounding. - L.O.L., so much so that I started to pull out some of my reference music, to hear. I was amazed and very pleased.
4) After about 45 minutes of re-listening to reference selections, and really enjoying this new playback, I suddenly realized, I had not done the Output tubes' AC filament feeds. Tested them. Back and forth.
HEY, it was 180 degrees out, from how it was originally wired. A certain amount of mud and fog on the low end, totally vanished, and dynamics on the drum and cymbal strikes improved, along with resolution. It surprised me.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
The final result of all the AC phase optimizations combined, one after another, was / is just lovely to hear. I was up until 1 :30 A.M., listening to well recorded program material. So , in under two to three hours of time, I obtained about an 8 to 10 percent confirmed-by-focused-listening subjective improvement, in the sound of this new amp.
Anyone can do this now. If the whole system is up to snuff, you get a nice subjective permanent result in the amplifier's playback.
Oh, a hint, particularly on any stereo amp : I like to use two colors of filament wiring, ( eg : gray and white ) and hook up tube filaments uniformly , color wise, onto like - numbered PINS of the tube sockets.
Really a fun process and worthy result. I hope this information benefits some of you folks.
Jeff
One seldom done thing by DIY builders, ( and likely many manufacturers ), is to check the AC phasing of an amp, to be sure the AC voltages are not " bucking " each other.
There are different ways to do this. A quick way is to use a scope, and see if the various AC wave forms are ALL moving in the same direction.
Another way, which I enjoy doing, is aligning the AC waveform s by ear, where you get to hear / decide and learn the sonic results, in a meaningful ( to me ) way.
Where ever you have multiple powered AC sources in a amp, this needs to be done, to prevent these various AC powered circuits from deleteriously-to-the-sound, BUCK each other.
With the 6005 amp circuit up, and smoothly running, I just spent a few hour's time, adjusting ALL the AC feeds to have a uniform and optimal sounding AC polarity.
I have made-up seven inch long JUMPERS, with pure copper alligator clips, and a insulating boot, at each end. Wire is m22759/11/14 AWG, so losses are lessened. At each place in the amp, where there is an AC feed, we unsolder the two wires, and make two new connections using these quality jumpers. This way, one can SWAP the alligator clips, and HEAR what a 180 degree AC feed reversal sounds like !!
The music program source used was musician Steve Clarke's " Solo Drums" CD from the UK. Cut one, playing each time from 4:00 to 4:39, 39 seconds. This is a very demanding full-blast drum solo, with multiple close-miked drums and cymbals going off explosively, IF the system is up to snuff.
" Back and forth" listening between the two polarities, by reversing the alligator clips at one end. Only when you are absolutely sure, you remove the clip leads, and permanently solder-in the best sounding polarity. Move on to the next AC feed pair !! I did this in this order :
1) The separate 6.3 VAC filament transformer feeding the input tube. WHY first ?? The input tube has a rated mu or gain of about 33-35, maybe three times higher in gain than the output tube. It is the most sensitive tube. Also, importantly, I am keenly aware if you don't optimize the input stage, " information lost there, never gets made up in later stages ".
2) Next I optimized the filaments of the separate rectifier tubes' filament transformer. ( 5VAC / VCT at 6 A. ) Why?? It feeds the whole amp !! HEY, it was 180 degrees out as I had it originally wired. The amp sounded better on the repeated drum solo selection. Swap 'dem alligator clips, listen back and forth, and solder it permanently !! Yup, we gained performance forever, doing that.
3) Next came the AC high voltage feeds from the ends of the main power transformer's high voltage secondary.
It is about 400 VAC-0-400 VAC. Be extra careful, when clip leading such a high and lethal potential !! HEY again, it also sounded better reversed. The amplifier again, became incrementally better sounding. - L.O.L., so much so that I started to pull out some of my reference music, to hear. I was amazed and very pleased.
4) After about 45 minutes of re-listening to reference selections, and really enjoying this new playback, I suddenly realized, I had not done the Output tubes' AC filament feeds. Tested them. Back and forth.
HEY, it was 180 degrees out, from how it was originally wired. A certain amount of mud and fog on the low end, totally vanished, and dynamics on the drum and cymbal strikes improved, along with resolution. It surprised me.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
The final result of all the AC phase optimizations combined, one after another, was / is just lovely to hear. I was up until 1 :30 A.M., listening to well recorded program material. So , in under two to three hours of time, I obtained about an 8 to 10 percent confirmed-by-focused-listening subjective improvement, in the sound of this new amp.
Anyone can do this now. If the whole system is up to snuff, you get a nice subjective permanent result in the amplifier's playback.
Oh, a hint, particularly on any stereo amp : I like to use two colors of filament wiring, ( eg : gray and white ) and hook up tube filaments uniformly , color wise, onto like - numbered PINS of the tube sockets.
Really a fun process and worthy result. I hope this information benefits some of you folks.
Jeff
Last edited:
RtoR King
Active Member
I don't understand this at all. Your B+ is no doubt from a center tapped rectifier topology. Your filaments are hopefully either center tap grounded or have a phantom center tap made from two 100 ohm resistors to ground or a hum pot centered to ground.
Either way you will still have a 180 degree difference from either winding end to ground?
What difference does it make in reality? I think that's the reason why the classic manufactures, current manufactures, and DIYers don't bother with it. The only time I worry about POWER transformer winding phasing is when I parallel dual primaries or secondaries. There it matters and can destroy the transformer if wrong.
But if you think you hear a difference, I guess going through all this extra work this doesn't hurt anything either.
Either way you will still have a 180 degree difference from either winding end to ground?
What difference does it make in reality? I think that's the reason why the classic manufactures, current manufactures, and DIYers don't bother with it. The only time I worry about POWER transformer winding phasing is when I parallel dual primaries or secondaries. There it matters and can destroy the transformer if wrong.
But if you think you hear a difference, I guess going through all this extra work this doesn't hurt anything either.
Last edited:
Member warned for violating forum rule No. 1
Forget about trying because there is no way to understand the absurd and nonsensical claims of a lunatic.
Here's another example, but involving the AC wiring of transformers that are used in a dual-mono preamp in which there are two independent power supplies, one for each channel and both of which are hard (actively) regulated.
Finished Preamp MODS
I bought this dual mono phono preamp new in 1981. It is called a NEXUS / Bravura Preamplifier. It was built by an EE and two musicians, primarily John Tuttle and Robert W. Fulton. It is solid state, integrated circuits. Like my tube SE amplifier, it has no coupling caps in it !! It's...
www.hifivision.com
Yes, every transformer used - has real center taps.
Yes, the phasing does and will make an audible difference on a well designed SE amplifier. That is why I am reporting this up here, to help others in their own future efforts. I figured, most audio builders are unaware.
This is particularly noticeable on amplifiers using multiple power transformers. In the past, I never paid attention to it, much like what you wrote.
About in early 2019, I designed and built an all out SE KT88 amp, with a separate power transformer for the front end tube filaments, and a separate power XFR for the dual 5U4GB rectifier tubes' filaments ( 5 VCT at 6 A. ) .
In 2019, I was aware of phase differences. They can certainly be easily seen on any working OK oh silly scope.
Out of curiosity, back then I experimentally listened to one of the filament XFRs connected iin BOTH polarities .
Indeed, there was an audible difference, and an audible improvement, to be had. In 2019, I used the same CD source " Solo Drums " and technique as previously described, to make these determinations. In every instance when evaluating phase sonics in both polarities, the best sonic result unambiguously made itself known. ( high efficiency ALTEC A7-8 VOTTS, 515Bs and 802Ds ).
The sum total result of getting four or five windings, all in the same phase, not bucking each other in any way, really adds up to a substantially higher sonic performance. I am still amazed listening today, at the new amp and how it is playing, VS one day ago and earlier this week.
I also could imagine, with lesser electronics, speakers, and system wiring, someone people could have a hard time determining AC polarity by ear. In which case, they need to use an oscilloscope. From zero on the scope, is the 1/2 sine wave raising or going down, from the start of the trace?? Can you synch all AC windings, so they all go in the same direction??
Of course, this raises the question " if the person can't tell by ear, in any one instance, will three or four instances, cumulatively determined on a scope, make an overall audible improvement for them ?? 'We don't know this.
Now you got it !! Interesting, ...........ehh !!
Jeff
Last edited:
RtoR King
Active Member
Still not quite clear because if one side of the center tapped winding is going positive, the other side will be negative with respect to the CT or ground. And on the scope is it dual trace or are you using external sync? In which case one phase is the reference and the other phase is being evaluated? How do you know your reference phase is the right phase?
Or do you simply mean getting all tube filaments of the same type on the same phase. Let's assume the output tubes use pins 4&5 for the filament. Are you just making sure say all pin 4 are positive and all pin 5 are negative in this example? Now I have heard of some builders doing that. Still not sure it makes any difference, perhaps it might in a phono preamp or other high gain / low noise application.
Or do you simply mean getting all tube filaments of the same type on the same phase. Let's assume the output tubes use pins 4&5 for the filament. Are you just making sure say all pin 4 are positive and all pin 5 are negative in this example? Now I have heard of some builders doing that. Still not sure it makes any difference, perhaps it might in a phono preamp or other high gain / low noise application.
Last edited:
I have already told you, it makes a difference on my SE amp builds, when I started checking it out, the 2019 SE KT88 build back then, and also in this 2021 6005 amp's build.
One should AC-orientate not JUST ( or only ) the vacuum tube filament feeds, but the ends of the HV secondary winding, feeding the tube rectifiers.
Why worry about knowing the reason?? Just have a good enough piece of equipment, and A-B it. Its so very simple !! If you can not hear any difference, your hearing is AOK, but your audio system surely is not. !! ( Not revealing enough. ) If you hear a difference, after going back several times, and you are sure, solder the two AC leads permanently, in the AC phase relationship that sounds best to you. Simple.
Then.......try to do that for EVERY AC feed inside the unit.
On good gear, the cumulative effect can easily become a 10% give or take, overall improvement in the sonics - and one's enjoyment of the playback / music's performance. That is precisely what I obtained when doing so with this new 6005 build / design, two days ago.
Here is another extremely common example people may be able to readily relate to : For over 50 years, I have known, when you have a two prong AC wall plug, powering audio equipment, you plug the powered audio unit into your wall socket BOTH ways, and only ONE way will sound the best.
No scope, or understanding "why", is needed. But what it is, it is.
This causes me to MARK the AC plug, and always use the AC plug in it's very best / same orientation . Likely, many many people in audio have had this same experience. It is done by ear. ( God-given equipment ). No oh silly scope is needed !!
So, don't wonder WHY something is. Be aware it can and does occur, acknowledge it - and do your own very best with it !!! Optimize it !!! Unlike some others who may post here, I am not sharing this to you, in any mean / condescending way, I hope you realize !!!
This exchange we two shared very much reminds me of one of my favorite sayings to share with you all ......
............................" Don't tell me about the pregnancy, just SHOW ME THE BABY. "
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - -- - - - - - - -- - - - - -
Does everyone into " better " audio orientate their AC plugs, and mark them ??
If it is a modern three prong AC plug, you temporarily use a " cheater " plug, to lift the ground. LISTEN carefully both ways. If necessary, re- HARD WIRE the AC connection inside the chassis, and remove the cheater. Enjoy better sound.
This is " Audio set-up " 101.
Live and learn.
Happy New Year to all.
2022 will be a real challenge, for our entire planet. Let us all watch and see.
Jeff
Last edited:
RtoR King
Active Member
But keep in mind the flip side of that argument is that there is a flaw in the design or components used that makes the device sensitive to otherwise insignificant things like AC polarity prior to a rectifier and filter bank. One example would be an HK short on one of the tubes. As this is a DC coupled amp, is the VhK of the output within limits per the tube manufacture? This data is widely available in vintage tube books and online. You do need to consider this. It's why old Tektronix scopes for example had eight or more 6.3v filament windings on the power transformer. They used a lot of DC coupled circuits.
This is why I like to find out the root reason for an otherwise unconventional technique.
Where I come from the ability of an audio system to be "resolving" is mostly dependent on the speakers. Modern SS amps are pretty close to "wire with gain" these days. Tube amps will always have residual hum and noise, just comes with using vacuum tubes. I use both tube and SS gear so I'm not against tubes at all.
Off topic:
I don't know about this amp design or it's sonic behavior
The plug orientation is important if the component has a fuse, right?
Just to ensure the fuse is on "hot/live" rather than "neutral"
Cheers,
Raghu
I don't know about this amp design or it's sonic behavior
The plug orientation is important if the component has a fuse, right?
Just to ensure the fuse is on "hot/live" rather than "neutral"
Cheers,
Raghu
Last edited:
- Status
For excellent sound that won't break the bank, the 5 Star Award Winning Wharfedale Diamond 12.1 Bookshelf Speakers is the one to consider!
