Le Classe A - DIY Jean Hiraga Super 30W Class A Amplifier

[all4music]

Well done. Glad you liked the sound. I've always felt that full-range drivers are the best for tabla, mridangam and (in my humble opinion) the cello. These are very efficient drivers, so you will not need more than a few watts (5W or so) before they become unbearably loud. At this stage, do not spend too much time with less/more recron.

Pour yourself a nice drink (very, very important) and spend a month of evenings listening to the music that you love.
Cheers, ~hp

true they go real loud very easily.
and as you said, i'll spend some time listening to these. post that if i still feel the need to change the response, i might tweak with some fillers at the least or look for an altogether new box build [Pencils perhaps ].

couple of songs that sound really sweet are 'Tere Liye..' from Veer Zaara and the 'Hotel California..'

 

[all4music]

amp temperature in summer

with the summer temperatures, amp is running really hot..

the above temperature with top plate of the amplifier closed. with around 33 degrees, amp heat sink core temperature was around 61.

after this, i removed the top plate, and the temperature dropped by a very healthy 3-4 degrees. observe the increase in ambient temperature.

now i plan to do 2 things. drill more holes on top plate and drill holes bottom plate of the amp. and for this i've got couple of stepped drill bits. the regular ones either bend or break out - it is ultra hard drill holes on these metal sheets!

but to drill holes in the amp, i'm planning to remove the output transistors from heat sink to avoid any possible damage to them. but that means, i would have to put them back after cleaning the surfaces, applying fresh heat sink compound etc. hopefully will accomplish it today/tomorrow.


this time around, i've got Arctic Silver 5 !!

 

[all4music]

speaker tweaking..

carpenter had basically dumped the speakers at my place. it had many shortcomings when compared to original plan.
i'm trying to improve the speaker response: sometimes certain frequencies and vocals go very loud [surpassing other instruments] and i have to reduce the volume. thought i will start with fixing some known anomalies in this example.

speakers are not flush mounted,

and you can see that i've used only 3 screws since the screw holes were not aligned properly.

decided to use this tool for flush mount

after lot of effort, somehow got to this extent, it was very difficult.

later used this poly fiber layer for layering few panels which were not covered by carpenter,

also teased the same stuff and filled the box [might compensate a little for lost volume due to mis-calculation],

not exactly a flush mount but .. [don't wanted to risk cracking the panel by going deeper since the process was 'violent'..]

also got the allen key bolts, looks much better now. original allen key bolts were not handed over to me by carpenter [i had shipped many of the components directly carpenter so that he could complete the build at the earliest].

so far i have not tested the speaker response. will replicate this change on other speaker tomorrow. hopefully this change should help if not i would have to go for a simple Baffle Reflection Response circuit at speaker end.

 

[quad]

Good work.
Another possibility to get flush mount is to glue a 6mm thick
veneer or ply on the front face of the speaker, with the cut out diameter
equal to the outer diameter of the speaker frame, assuming your
speaker frame is roughly 6mm thick

 

[all4music]

Good work.
Another possibility to get flush mount is to glue a 6mm thick
veneer or ply on the front face of the speaker, with the cut out diameter
equal to the outer diameter of the speaker frame, assuming your
speaker frame is roughly 6mm thick

hi Quad, thanks for the suggestion. but in this case, i've the speaker grill magnets behind the veneer and also i don't wanted to mess the veneer finish. but in the course of finishing the cabinets i've already managed to mess up the finish on one of the boxes .

might go for similar solution- but the extra ply will be only around the speaker and will taper and merge in to baffle so that i doesn't cover the grill magnets. before that i need to salvage the finish to some extent if the speaker is going to be in living room. one more day for clear coat to dry and for finish.

 

[jls001]

Re: speaker tweaking..

i'm trying to improve the speaker response: sometimes certain frequencies and vocals go very loud [surpassing other instruments] and i have to reduce the volume.

Could this selective loudness be due to the "shouty" nature of the widebanders that tend to have a peaky FR somewhere in presence region?

 

[all4music]

Re: speaker tweaking..

Could this selective loudness be due to the "shouty" nature of the widebanders that tend to have a peaky FR somewhere in presence region?

quite possible. and this being my first wide-band speaker experience not sure what to expect. but this particular driver is known to have emphasis on vocals but sometimes voice does sound 'shouty'.

but one revelation is it does sound better overall when compared my Swans 1080MkII set-up [i've switched back to Swans as i'm still working on finishing the boxes]. Alpairs do sound more clear and crisp. but with Alpairs, sub volume level has to be past half way mark for it to gel well whereas with Swans it is at quarter level. hopefully better layering of poly lining, stuffing of teased poly fill and better offset of drivers on baffle will result in some improvements wrt to it's peaky nature. else i'll try BSC treatment [i've the inductors ready with me and they roughly match the requirements].

 

[all4music]

it's been almost a month that one of the components in the amplifier failed : a toroidal transformer powering speaker protection board.

this transformer draws it's power from Soft Start board in parallel with main power transformer. the temperature around it is at constant 48-49 Degree Celsius [even after 4 + hours of playtime. so not sure of the reason for failure. according to manufacturer it could be due to high voltage.

here are the pics. just ordered replacement. planning to have few more vent holes on the bottom the amplifier chassis this time around.

 

[sadik]

Bad News Bro.... Before replacing, check the protection module also for any kind of damage.

 

[all4music]

hi all, it's been some time that i've been enjoying the music from my set-up.

but i need help in identifying an issue with my ALPS powered pot [rated at 10K ohms]. i always had a problem with my Kuartlotron buffer that it sometimes produced loud pops -especially when there is no music being played. hence decided take it out of the chain and use the powered ALPS pot as passive volume control till the time i figure out on the next move.

but volume doesn't track linearly with ALPS . it is somewhat like the pic below and also it doesn't get as loud as it used to sound with buffer in the chain or even the direct output from the DAC. also it tapers out abruptly at the max level. what could be the issue?

this issue was not there when paired along with K-buffer earlier.

 

[Aniket]

Hello all4music,

the potentiometer is probably messing with the input impedance of the amp. It can affect the DC offset too. as this is DC coupled amplifier it is not advisable to put a pot directly to its input. Better use an op-amp along with this pot, to take care of impedance matching and even tracking of volume. also, make sure this is a linear taper pot, not logarithmic.

Regards,
Aniket

 

[all4music]

thanks Aniket for the heads-up!

it behaves the same even with my Swan Active monitors too.. anyway i'll disconnect it for now.

 

[all4music]

as stated earlier, got a stop gap arrangement for pre-amp - a cheap 6J1 pre-amp from amazon based on various reviews.
but it turned out be noisy - the moment i connect it in the chain hissing noise is audible from speakers even at nil volume - it doesn't vary with increase in volume. raised a request for return on amazon. but seller partially refunded the amount and asked me to keep the pre-amp else I would have to bear the return shipping charges to get a toal refund. now i'm stuck with this guy!

now what could be the issue: power supply or tubes themselves?
this pre-amp needs 12V DC Input and comes with wall socket for this.

 

[deepjpr]

as stated earlier, got a stop gap arrangement for pre-amp - a cheap 6J1 pre-amp from amazon based on various reviews.
but it turned out be noisy - the moment i connect it in the chain hissing noise is audible from speakers even at nil volume - it doesn't vary with increase in volume. raised a request for return on amazon. but seller partially refunded the amount and asked me to keep the pre-amp else I would have to bear the return shipping charges to get a toal refund. now i'm stuck with this guy!

now what could be the issue: power supply or tubes themselves?
this pre-amp needs 12V DC Input and comes with wall socket for this.
View attachment 33277

 

[soundnovice]

Thanks Soma for inviting me for the listening session. The amps are superbly built. And sound awesome. The saturday has been well spent!

 

[all4music]

It was nice meeting you 'again' after many years
Well as I had mentioned, the mediocre pre amp and jittery source were a bit spoilsport.
After you left i tweaked around a bit on foobar output settings (changed the output to 16 bits from 24) .. it's sounding much better and crisp.
I had earlier changed it to 24bit from 16 as my Dac is capable of playing 24bit.

 

[all4music]

it's been some time that i updated this thread with updates - looks like i've been posting only when i encounter an issue or a doubt
Added new fascia to monoblocks and preamp..

And a short video clip of music being played..

 

[saikatbiswas82]

as stated earlier, got a stop gap arrangement for pre-amp - a cheap 6J1 pre-amp from amazon based on various reviews.
but it turned out be noisy - the moment i connect it in the chain hissing noise is audible from speakers even at nil volume - it doesn't vary with increase in volume. raised a request for return on amazon. but seller partially refunded the amount and asked me to keep the pre-amp else I would have to bear the return shipping charges to get a toal refund. now i'm stuck with this guy!

now what could be the issue: power supply or tubes themselves?
this pre-amp needs 12V DC Input and comes with wall socket for this.
View attachment 33277

I use similar preamp. I had no hissing issues.

 

[all4music]

I use similar preamp. I had no hissing issues.

Probably tubes are of poor quality.. also they are not matched.. one of them has higher gain. Equivalent tubes are out of stock on diyaudiocart.com as of now.

 

[saikatbiswas82]

Probably tubes are of poor quality.. also they are not matched.. one of them has higher gain. Equivalent tubes are out of stock on diyaudiocart.com as of now.

That could be the issue. However I've upgraded to GE tubes and upgraded the PSU as well.