Batery powered DIY CNC phono stage

[crosstalk]

Very inspiring reubensm. Thumbs up.

 

[reubensm]

Since posting this build, I have received quite a bit of interest, mostly over phone. People are interested to know a lot more about my version of the CNC, especially because of the spend on it, so I thought I'll do a post answering these, with Sachin's due permission.

Here are some of the queries:

1) Why did I use low quality components and how come my costs are so low?

I usually buy components for my DIY projects (since childhood) from the local electronics market. If a certain component is not available, I always deliberately use a substitute or an alternative. This is based on an old logic which our father taught us. Being an old-school engineer, he would always say that a good design will sing moderately well even if the components used are not the best, while an average design is more dependent on quality of components for good sounds. In short, great circuit designs have greater levels of tolleraance factored (though not always). Rating components available at the local electronics store as "Poor" is highly subjective. Yes,the quality is not that great, but they will still play. My father would always advise me to try a local component first before importing the expensive high quality version so I have gained a lot of experience with the limitations of these low quality components over the years. When repairing or servicing manufactured electronics, I prefer to use only imported OEM spares.

2) How easy it is to build your version of the CNC?

To build the CNC my way, is extremely easy, but that is provided you have knowledge of electronics and have the capability to interpret electronics circuits. When using bread boards, you have to not just get the layout of components right but you also have to wire the connections between the components on the other side of the board. Its not like using pre-fabricated PCBs with component slots printed, wherein you just have to drop the matching component in and solder. My version takes time, concentration and patience. PCBs can be easily designed and fabricated for even this version but will cost much more than a humble bread board.

3) Since it is less expensive, and the build quality is not up to the mark, the overall performance will also be not up to the mark.

Yes, that may be true. But when one talks about performance, there are lots of factors and variables. Beauty is in the eye of the beholder. Likewise, performance of audio equipment is the ears of the listener. I made a generic comparison which my NAD 3020's phonostage and found the CNC to easily out-perform it. This is indeed a big statement as the NAD 3020's phonostage is internationally acclaimed and has legendary status. Also my 3020 is in un-touched original condition. My CNC phonostage had more distinct highs, deeper bass and a flowing mid range, where as the 3020's phonostage is more upfront (though not harsh), sounded loud and threw up all the ticks and pops, prominantly. The CNC offered brilliant imagary and I felt the music was playing live in front of me. It sounded very listenable and I just kept listening on and on (for argument's sake, perhaps this was psychological and driven by the satisfaction of having built it). With a Rs.200 investment, honestly I did not expect anything but to have got such a good sounding phonostage, what else could one ask for. If I spent $20 to buy a low-end phono-box, I would defintely have got something no where close to this. The concept and design of the CNC phonostage is simply fantastic and thats why it works so well in whatever avataar. In audio, getting to a point where you get great SQ results, is considered as the threshold. Making critical improvements will raise the bar higher than this threshold, however one must also be in a position to experience it (with suitable competance, equipment and speakers) or listen to the type of music which allows for the experience. For example, listening to Metallica and AC DC may not throw up these improvements while listening to Classical or instrumental music will defintely throw them up. Critical improvements definitely comes at a cost, mostly astronomical

4) Because you are using Hitachi Japanese 741s, the quality is good. The same will not be the case with other 741s. These OP amps are generally very low end and not used in Hi-Fi.

I purchased a set of 741s yesterday and tried them. Yes there was a very marginal drop in the gain but everything else remained. I thought, the old time Japanese ICs were always better. I remember having a couple of TBA810s ICs made by Hitachi/Japan, driving my 7 watt stereo poweramp when I was in school. I replaced them later with local TBA810 ICs and even with BEL CA810 ICs just to check on the quality. The replacements where by no means, comparable with the Japanese ones. I had these Hitachi 741 ICs since my college days. They have been used previously in cassette head preamps, universal preamps, tone controls and many other similar projects. By using IC sockets, one can always retain one's favourite ICs Yes, 741s are not used in Hi-Fi but that's the idea. Innovation is all about breaking traditions, trying new things. I intentionally did not build the regular CNC avataar (have the PCB with me) as I wanted to see how it would play in a humble avataar.

5) Can you build the CNC for us?

This is a one-off project done just to get a kick out of DIY, experience the design and more importantly, help a dear friend. This project demands time, I took nearly 5 hours to carefully wire the board together. That paid off when it worked straight off when I plugged it in. Unfortunately, I just don't have the time to spend on these projects. Its been nearly 4-5 months since JK requested me to build one for him. If I can find the time, I will definitely help out. I always have.

Next step is to put it in an enclosure and again, I am taking an "alternate" approach.

 

[sachu888]

Re: Battery powered DIY CNC phono stage

Very well written.

Regards
Sachin

 

[reubensm]

Also some have requested the schematic with 2 OP amps per channel. I have used the same schematic provided by FM Omishra in this thread. The component list can be had from the circuit. The only change is that I have provided power rails (+ and -) for each OP amp, separately, pin-7 for (+) and pin-4 for (-).

Here's the pin configuration:

Here's the schematic: http://www.hifivision.com/phono-tur...owered-diy-cnc-phono-stage-31.html#post315024

 

[nraghunadh]

Can some one expand the "CNC" in phono stage?
As i know CNC means "computer numerical control".

To come this phono stage build, it is very simple and easy build and very less price. I did this 4 years back by spending Rs 50 /- only
NE5532 each Rs 10 /- , 0.25 w Resisters each Rs 0.25/- caps 10 /- and.
Small size general PCB cost around Rs 10/-.
This is the link what i used the schematic, : Hi-Fi RIAA Phono Preamp
This is 4 years old build and you can notice the PCB degradation because of cheap quality board. I discorded this science i got a phono stage kit from Sachin.




Thanks,
Raghunadh

 

[reubensm]

Can some one expand the "CNC" in phono stage?
As i know CNC means "computer numerical control".

To come this phono stage build, it is very simple and easy build and very less price. I did this 4 years back by spending Rs 50 /- only
NE5532 each Rs 10 /- , 0.25 w Resisters each Rs 0.25/- caps 10 /- and.
Small size general PCB cost around Rs 10/-.
This is the link what i used the schematic, : Hi-Fi RIAA Phono Preamp
I will take some pics and will post soon to get some idea on this in expensive build.

Thanks,
Raghunadh

Interesting, what a beauty. Our forum is really fantastic, lots of options for everyone. Last night, I was reading through the threads on Audiokarma where Sachin and Omishra have posted extensively. Great stuff. Felt really proud when I saw the guys out there taking advise from our forum members.

However your phonostage looks very different from the one which I built. Sachin, kindly comment.

 

[sachu888]

Raghu's phono stage was based on VSPS. I have also built similar designed some times back. I really liked it over inbuilt phono stage of my Technics, but as Raghu said CNC is better.
We have also tried dual mini version with SOIC opamps, but original National circuit sounded more open.
Raghu is a genius and he has built so many DIY audio projects, but he rarely posted here. Most of his projects are unique. There are many Hfv members can vouch for him.
I don't want to discourage anyone but components and proper PCB do make a difference.
Edit I am sorry about Raghu's design. It is actually a Rod Elliot P06 phono stage, very popular amongst diyres. You can find reference in CNC thread at audiokarma. Hypnotoad actually had this before developing CNC.


Regards
Sachin

 

[nraghunadh]

I discorded this science i got a phono stage kit from Sachin.

Thanks,
Raghunadh

Noticed spell mistake and correcting the same in this update.

I discarded my prototype build since i got a phonostage kit from Sachin.

Thanks,
Raghunadh

 

[omishra]

That CNC is acronym of place "Charlotte NC in USA" of the AK member "FasterDamnIt" who developed this phonostage from National Semiconductors datasheet.

 

[sachu888]

That CNC is acronym of place "Charlotte NC in USA" of the AK member "FasterDamnIt" who developed this phonostage from National Semiconductors datasheet.

And also by big bill of Charlotte NC

Regards
Sachin

 

[reubensm]

Also some have requested the schematic with 2 OP amps per channel. I have used the same schematic provided by FM Omishra in this thread. The component list can be had from the circuit. The only change is that I have provided power rails (+ and -) for each OP amp, separately, pin-7 for (+) and pin-4 for (-).

Here's the pin configuration:

Here's the schematic: http://www.hifivision.com/phono-tur...owered-diy-cnc-phono-stage-31.html#post315024

Some have queries about specific resistors. Yes I have replaced with readily available alternatives. Here goes:

From the schematic,

R11, R12, R23 and R24 - 3.32K replaced with the readily available 3.3K resistor (if you really want to stick with the exact value, you can use a 3.3K resistor in series with a 20 ohms resistor to achieve 3.32K. Although I have taken a dare-devil approach here, its advisable to go with the exact value)

R19 and R20 - 3.83K replaced with the readily available 3.9K resistor (if you really want to stick with the exact value, you can use a 3.9K resistor in parallel with a 220K resistor to achieve 3.83K)

I generally use this calculator for my parallel resistor calculations: Parallel Resistor Calculator R1 + R2 = equivalent resistor R resistance circuit equiv total resistor finder made easy piggyback = parallel - sengpielaudio Sengpiel Berlin

Of course, I have replaced the single AD822N per channel with two 741s per channel and to accommodate these, I have connected separate power rails for each OP amp (pin-7 for +ve and pin-4 for -ve). I have used 4 parallel combos of 10mfd and 0.1mfd for filtering as specified in the schematic. I have used 2 parallel combos (one each for the +ve and the -ve rails to ground) for each IC pair.

 

[crosstalk]

Just saw the schematic.

 

[omishra]

And also by big bill of Charlotte NC

Regards
Sachin

Oh yes, not to forget HypnoToad who made iterative changes to this and is member here on HFV too.

 

[sachu888]

Another one alive and singing.I built it yesterday,for a FM friend.






Enclosure is temporary.I have used plastic box available at Electrical stores,because it was cheap, and can be later replaced with better one.In this layout in/out wires can be kept very short.I have intentionally use long wire for switch and battery connections, for easy access of DIP switches.I have used 3 PIN connector at back for easy swapping of batteries.

Regards,
Sachin

 

[reubensm]

so finally after a lot of posts and anticipatory commitments, here goes...

Finally got down to wiring up my version of the CNC phonostage which I have built for my good friend FM JK_Chaos. Connected it up with the batteries and had my SL3200's M44-7 provide the source feed. The output of the CNC went into the axillary input of the NAD 3020

Here are the long awaited pics, please note that I ran out of 3.3K resistors (son was playing with a couple of them and lost them) and had to use salvaged components from the junk box. Also I could not get the jumpers from local stores and hence had to make the pins myself.

I have used 2 Japanese Hitachi vintage (humble) 741 OP amps per channel (these were lying in my junk box since I was in college) but the rest of the circuit and design remains the same.

First impressions without engaging any of the loading resistors:

Dead silent, not background hiss or hum or anything, without the record playing
Good output gain, sounds very loud with the volume control in 9 o' clock position
Sound quality is superb, silky highs, deep lows, pronounced mids, left the NAD 3020's phonostage far behind (yes, this is true). I am sure this will even better up after some serious burn-in.

After adding the jumpers, thought it sounded very fluid with the 47k input loading. Shall experiment a bit more with it and post my findings.

There is an old saying - seeing in believing, in this case I would say, hearing is believing. This is indeed a brilliant phonostage and I am now a believer.

Thanks Sachin.

Prototype cabinet for the el-cheapo CNC phonopreamp, please note that the faceplate is yet to be painted and attached (its just resting against the cabinet)

The cabinet is a pen holder, costing Rs.40/-. The faceplate has been cut out of an old cd jewel case. Plan to give the faceplate a silver coat.

Have skipped the LED to conserve the batteries.

 

[hifipal4all]

Smart 'n' sensible build ... Congrats

 

[pathakajit]

good build.. looks really nice!

Just a thought.. the pen holder case may pose a dirt problem.

 

[pathakajit]

-Duplicate post deleted-

 

[reubensm]

Yes, dust will enter. I actually wanted to put it in a glass box but I did not have one. Lots of guys want to have a look inside when they come to know that I've built it hence the cage will help with that

Also my approach toward DIY has always been very old school which was all about trying to innovate and use bits and pieces that are lying around. I have never done a DIY project that can be compared with a professionally made or mass market manufactured piece of equipment. I think the Church PA project will be the very first professionally done project that I have been involved with. I also openly break all the rules and at times come up with stuff that works well.

Having said this, I may be building another CNC phonostage for my brother's NAD C320 using Sachin's PCB and the regular approach. More on that to follow later.

 

[Record Player]

Prototype cabinet for the el-cheapo CNC phonopreamp, please note that the faceplate is yet to be painted and attached (its just resting against the cabinet)

The cabinet is a pen holder, costing Rs.40/-. The faceplate has been cut out of an old cd jewel case. Plan to give the faceplate a silver coat.

Have skipped the LED to conserve the batteries.

WOW. That's a dashing looking build there mate. Very well done.