Batery powered DIY CNC phono stage

[sachu888]

New PCB layout

It now has an uncut ground plane on top. The capacitors have 5mm & 12.5mm spacing for the RIAA caps. The output caps have 5mm, 12.5mm & 20mm spacing with larger holes to accommodate thicker cap leads. Filtering cap placement and routing is fine tuned.

Few more pics from Vincent's build:

Regards,
Sachin

 

[john_k_antony]

Sachin,

Do you have the new kits available with bigger caps? I would need to build one more soon for my newly acquired vintage Technics SL-Q33 .

Thanks,
John.

 

[sachu888]

Sachin,

Do you have the new kits available with bigger caps? I would need to build one more soon for my newly acquired vintage Technics SL-Q33 .

Thanks,
John.

Yes I do have.

Regards,
Sachin

 

[john_k_antony]

Yes I do have.

Regards,
Sachin

Sachin,

I assume the new PCB will fit into the cab provided by Raghu and I can use the same power supply you send me earlier for CNC + Pass B1. If yes, I would like to get one new CNC kit. My address has changed. Sent you a PM.

EDIT : My cart on SL-Q33 is AT 120E. I hope the stock caps and resistors in the kit are good for loading AT 120E.

Thanks,
John.

 

[sachu888]

Sachin,

I assume the new PCB will fit into the cab provided by Raghu and I can use the same power supply you send me earlier for CNC + Pass B1. If yes, I would like to get one new CNC kit. My address has changed. Sent you a PM.

EDIT : My cart on SL-Q33 is AT 120E. I hope the stock caps and resistors in the kit are good for loading AT 120E.

Thanks,
John.

Hi John,
yes it will fit in cab provided by Raghu,but you will need to drill new holes to mount new board.New board is little bigger than earlier PCB.
You can use the same power supply to run this PS.
It will work perfect with AT120E

Regards,
Sachin

 

[john_k_antony]

Thanks Sachin.

Looking forward for the new kit .

 

[Tanoj]

Looking forward for the new kit

Mee too

 

[anujmishra]

Even I want this kit now. But at present I am abroad. Trasferring money is problem for me. I have to arrange through friends. How much is current kit price including power supply and box?

 

[john_k_antony]

Hi Sachin,

I finished my second CNC with the new board and I am using it with my Pass B1 build. I finished the build today and having some issues.

All the high frequencies are missing. It sounds very very dull. I tried all the combinations in DP switch and also tried different op-amps. No luck .

I will give the build details in a diagram later on.

Also my old CNC build that runs from the batter also seems to have dead. Thre is NO sound. The batteries are new though.

It would be great if you can point me to some resources that talks about debugging the CNC issues.

Thanks,
John.

 

[jls001]

@John: pls upload lots of closeup shots to help troubleshoot. Also, if you can upload hand drawn circuit diagram of your battery connection. Did you test the batteries with a voltmeter?

I use two 12V DC adapters instead of 9V batteries and they sound better. Plus they don't need regular charging (it can be quite a pain if the batteries die on you).

 

[john_k_antony]

@John: pls upload lots of closeup shots to help troubleshoot. Also, if you can upload hand drawn circuit diagram of your battery connection. Did you test the batteries with a voltmeter?

I use two 12V DC adapters instead of 9V batteries and they sound better. Plus they don't need regular charging (it can be quite a pain if the batteries die on you).

jls001,

I will do that soon. I was wondering if this was a "known" issue with some quick fix already available.

Yes I checked the battery using a DMM and they are fine.

Thanks,
John.

 

[Tanoj]

I think i can Help

I already did B1, MM @ Mc Phonostage of schin,

Regards

Tanoj

 

[sachu888]

Hi Sachin,

All the high frequencies are missing. It sounds very very dull. I tried all the combinations in DP switch and also tried different op-amps. No luck .

Thanks,
John.

This is strange.It sounds bright initially because Russian caps take time to settle down.Could you please cross check all resister values?A close up pic should help.

Regards,
Sachin

 

[Tanoj]

Not to Mention

My new MM Phonostage sounds out of box .... with that AT Cart

Thank you, and i cant appreciate enough about your patience in packing, naming the parts

Regards

Tanoj

 

[john_k_antony]

This is strange.It sounds bright initially because Russian caps take time to settle down.Could you please cross check all resister values?A close up pic should help.

Regards,
Sachin

Sure Sachin,

I will take the pictures tomorrow and send across. Too tired now .

BTW, Pass B1 is a brilliant performer. I was listening to it using the following chain

Oppo 105 dedicated analog out -> Pass B1 -> Acoustic Portrait Power Amp -> KEF iQ7. I think Pass B1 is oozing out more details and at some point I feel that the sound signature is going slightly brighter. But the amount of details I hear is FANTASTIC. Before Pass B1, I was running my Oppo 105 directly connected to AP power amp.

I also feel that Pass B1 is really exposing the bad recordings more prominently. Is that expected? But good recording sounds very very lively and full.

I really wanted my CNC to sound equally good paired with Pass-B1.

-John.

 

[sachu888]

Pass B1 is very transparent.It will not add anything in sound.It will bring more details without colouring the sound.Let it run for 30-40 hrs,sq will improve more.I have read that NP recommends to keep it on for all night at first run.
Did you feel the same problem with previous CNC?

Regards,
Sachin

 

[john_k_antony]

Hi,

I got my old CNC build to work fine . The issue was the power supply. Thanks to Jls and Sachin to help me debug the issue. The new DPDT switch I got had some internal loose contact. And the batteries I was using was "Eveready" 9V cells and it seems like CNC build doesn't like them. Though DMM showing 9V for both the Eveready batteries, they are not able to power up the CNC build. I changed the batteries to the HiWatt white and blue color ones and my old CNC came back to life and its now singing great.

Coming back to the NO high frequency with my new build, the issue still exist .

I checked all the resistance values using DMM and they are all fine.

I disconnected the source selector in the chain and connected the CNC directly to my Pass B1. No luck.

Tried with both my TTs - Project Debut III and Technics SL-Q33. Same issue with both the players.

I tried two different op-amps - BB OPA2132 and OPA2107. Same results. No high frequency at all.

I finally took some closeup pictures of the build and attaching the same.


I did some comparison with my old CNC build that is working. Here are some differences I found.

For the new CNC board,

1. The caps at the output stage is marked as 1.5uF on the PCB and what came with the kit is 2.2uF.

2. There are 4 electrolytic 100uF caps in the new CNC board compared to 3 in the old one.

3. The new board has a 33pF caps at the input stage.

Thanks,
John.

 

[sachu888]

Hi John,
2.2 Uf caps don't make much difference here.Min value is 1uf and you can use upto 2.2 uf caps.There are 4 Electrolytes caps on older CNC.You can remove 33PF caps from input loading and check.I did not provide that caps.They are just for input loading and may not be required for your cart tonearm combo.What is the voltage provided to your new CNC.FM Vincent and Tanoj built this new layout CNC and did not find any issue.

Regards,
Sachin

 

[john_k_antony]

Hi John,
2.2 Uf caps don't make much difference here.Min value is 1uf and you can use upto 2.2 uf caps.There are 4 Electrolytes caps on older CNC.You can remove 33PF caps from input loading and check.I did not provide that caps.They are just for input loading and may not be required for your cart tonearm combo.What is the voltage provided to your new CNC.FM Vincent and Tanoj built this new layout CNC and did not find any issue.

Regards,
Sachin

Thanks Sachin,

Actually the 33pF caps were in the kit . So I used them. I will try removing them.

I have been powering this new CNC from the power supply I built for Pass B1 and source selector. I am tapping 12-0-12V from the power supply board to the CNC. I am using the premium BB op-amp.

Now I am planning to do the following steps one at a time.

1. Remove the input loading caps and check.
2. Power the CNC from the battery and use the BB opamp that requires 9V and check.

Do you recommend any other debugging steps?

Thanks,
John.

 

[sachu888]

Thanks Sachin,

Actually the 33pF caps were in the kit . So I used them. I will try removing them.

I have been powering this new CNC from the power supply I built for Pass B1 and source selector. I am tapping 12-0-12V from the power supply board to the CNC. I am using the premium BB op-amp.

Now I am planning to do the following steps one at a time.

1. Remove the input loading caps and check.
2. Power the CNC from the battery and use the BB opamp that requires 9V and check.

Do you recommend any other debugging steps?

Thanks,
John.

Hi John,
I am almost 100% sure that I never bought 33PF caps.They look like box type Polyester.Please remove them.They may be of some other values,which I sent you by mistake.

Regards,
Sachin