Batery powered DIY CNC phono stage

[john_k_antony]

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

Oh really... That's strange.

Even I was little skeptical while using those caps (the yellow colored ones). I did measure the capacitance with the DMM before putting it in and I think it was measuring 33pF so I put it in. Any way I will remove it and test. Will let you know tomorrow.

Thanks for your help Sachin.

Thanks,
John.

 

[sachu888]

Hi John,
Those Yellow caps look like 33NF (not PF) to me.Kindly remove them.HF should be back

Regards,
Sachin

 

[john_k_antony]

Hi John,
Those Yellow caps look like 33NF (not PF) to me.Kindly remove them.HF should be back

Regards,
Sachin

Sachin,

I just removed those yellow caps from input loading and guess what... they are 33nF and NOT 33pF. Thanks a lot for guessing it right sir .

I am going to hook it up right away and check.

Thanks,
John.

 

[jls001]

All DIP switches are in off position. Shouldn't it be set for 47k?

 

[john_k_antony]

BINGO!!! :clapping: Problem Solved. It was that 33nF cap in the input loading stage that was taking away all the details and highs.

Now the CNC is sounding with all the details and highs . Sounds amazing. I could just hear one song as its pretty late and I have a 10 month old sleeping.

Wow Sachin.. super debugging. Thanks a lot once again.

Now I have a great little DIY system - CNC Phono + Pass B1 + 5 input source selector all powerd by a single power supply housed in a cool cabinet .

Also got my first battery powered CNC working too . Might think about adding a twin 12V DC power adapter recommended by jls001.

Will post pictures after I run in the setup for a while before I pack them inside the cabinet.

I will do some serious listening and pen down my listening impression soon. As you said, I might need to run those Russian Caps for a while to tame it down right? 30-40 hrs should be fine right ?

BTW, I am seeing a different issue now. I have observed it once before, but pretty noticeable now. When I play from my newly acquired vintage Technics SL-Q33, I see the woofers of my speakers moving back and forth very "freely". I am playing it at very low volume and while the woofers move, they are not reproducing any bass sound. I mean the woofers make this kind of movement all the time, no matter what is being played. This issue is not there with my Project Debut III. I am going to talk to Kuruvilla Jacob Sir from whom I bought this player. Just wanted to know if this is a "known issue" with vintage players. Like some grounding issue / some other loose connection inside the player. I can take a video of the same if you guys wanted to take a look.

The speakers are full range floor standers - KEF iQ7.

Thanks,
John.

 

[john_k_antony]

All DIP switches are in off position. Shouldn't it be set for 47k?

jls001, they are set at 47k . I think they are visible from the attached pictures right?

Thanks,
John.

 

[sachu888]

BTW, I am seeing a different issue now. I have observed it once before, but pretty noticeable now. When I play from my newly acquired vintage Technics SL-Q33, I see the woofers of my speakers moving back and forth very "freely". I am playing it at very low volume and while the woofers move, they are not reproducing any bass sound. I mean the woofers make this kind of movement all the time, no matter what is being played. This issue is not there with my Project Debut III. I am going to talk to Kuruvilla Jacob Sir from whom I bought this player. Just wanted to know if this is a "known issue" with vintage players. Like some grounding issue / some other loose connection inside the player. I can take a video of the same if you guys wanted to take a look.

The speakers are full range floor standers - KEF iQ7.

Thanks,
John.

It seems like a feedback problem.How far is your TT with speakers?Try placing TT away from speakers,and check.

Regards,
Sachin

 

[john_k_antony]

It seems like a feedback problem.How far is your TT with speakers?Try placing TT away from speakers,and check.

Regards,
Sachin

My TT is closer to the left speaker and pretty far from right speaker, 7-8ft. But the issue is seen with both the speakers. I think its better I take a short video and post it so that you guys can get a better view of whats going on.

-John.

 

[anilva]

It would be low frequency rumble or the cartridge compliance matching is not OK.

 

[jls001]

jls001, they are set at 47k . I think they are visible from the attached pictures right?

Thanks,
John.

Great to know that you now have sweet music playing.

 

[john_k_antony]

It would be low frequency rumble or the cartridge compliance matching is not OK.

Thanks anilva. I really don't want to high-jack this thread to discuss my TT issue. I will start a new thread to discuss the same.

Thanks,
John.

 

[vin_eme]

John,

i could clearly see in the pics that the russian caps (C7 and C16) the leads are touching the outer Aluminum can of the capacitor. Kindly isolate them by a pvc jacket or heat shrink tube.

thanks,
Vincent

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.

 

[john_k_antony]

Will do Vincent. Even I was wondering if that would cause any issues in the future.

Thanks,
John.

 

[vin_eme]

Sachin can explain more about this, if the leads are shorted.

 

[sachu888]

Electrolyte caps already has PVC cover,but its good practice to cover 2.2uf caps with heatshrink tubing.

Regards,
Sachin

 

[murali_n]

Hi,

Looks like an improved CNC kit with Dale Resistors, what's the OPAMP and what is the listening impression?

N.Murali

 

[john_k_antony]

Hi,

Looks like an improved CNC kit with Dale Resistors, what's the OPAMP and what is the listening impression?

N.Murali

Murali,

Sachin got this kit for himself and since he was not planning to build one soon, he offered me the same with upgraded components.

I am using the BB OPA2107 for this build as this CNC is powered by a power supply and these op-amps needs more voltage than 9V.

I haven't finished the "burn-in" of 30 hours yet. I will pen down a review after it crosses the first 30 hours.

Thanks,
John.

 

[haisaikat]

Guys,
Want to have a CNC but can anyone build it for me? I do not have that much time to invest in DIY build.

By the way, I found a similar looking per soldered circuit being sold on ebay uk Stereo MM Phono RIAA Preamp Module Board, OPA2134PA | eBay

Can anyone tell me if this is similar to the one we are discussing in this thread?

 

[sachu888]

Hi,
This Audiowind is a rip of Jim Hangarman's Buggle.You should avoid buying duplicate items.
CNC Phonostage is easy to build even for the first timers.I know few technicians who can build this for you.

Regards,
Sachin

 

[haisaikat]

Did some more searching based on your lead sachu, seems this guy Hagerman has also made aBugle 2 which he claims to be better. Wonder what would be the price of that and do you think the CNC will be compararable to that?