DIY Moving Coil phonostage

[sachu888]

Yes, I'm using rechargeable 9V batteries. A downside to using 9V batteries is the rather low life. They don't last me 34-36 hours on a charge anymore.

I could not complete my OPS build for want of cabinet. Hopefully this will be resolved once Bibin starts shipping out his B1 cabs.

BTW, where do you buy genuine opamps from? I got only 4 different types here in Lamington Road.

I buy from Authorised distributors like Element14,Rs Digikey etc.There are many fake Opamps in local market and Ebay

Regards,
Sachin

 

[tek]

Today while changing the 9v batteries on my phono stage, one of the red and black connector wires got pulled out, so the stage is not working at the moment I've had to resort back to my old Pro-Ject Phono Box.. and I have to say, the sound difference is worlds apart. The DIY stage blows it away.

Now I need to find someone who can help solder it back for me! Any audio/video repair guy should be able to do it right? Similar problem happened to my MM DIY phono stage also, so I figured I'd take both to get re-soldered. Any recommendations for people in South Mumbai who can help would be great!

These are both really fantastic Phono stages. I hope I can get them up and running again soon. My temporary phono stage is just no fun

 

[omishra]

Today while changing the 9v batteries on my phono stage, one of the red and black connector wires got pulled out, so the stage is not working at the moment I've had to resort back to my old Pro-Ject Phono Box.. and I have to say, the sound difference is worlds apart. The DIY stage blows it away.

Now I need to find someone who can help solder it back for me! Any audio/video repair guy should be able to do it right? Similar problem happened to my MM DIY phono stage also, so I figured I'd take both to get re-soldered. Any recommendations for people in South Mumbai who can help would be great!

These are both really fantastic Phono stages. I hope I can get them up and running again soon. My temporary phono stage is just no fun

Hi tek,
Later stage I found it easy to keep battery outside using 3 pin connector. If you are uncomfortable then send it to me. I will fix it free of cost, just bear 2 way courier charge and 3 pin connectors + new wire leads. Also I remember we fixed MX RCA to it. It is high time to upgrade for neutrik RCA connecters. Buy from Mumbai and send along.

 

[jls001]

Or drive down to Andheri W. We'll fix those errant solders.

 

[omishra]

Or drive down to Andheri W. We'll fix those errant solders.

That will great!

I was talking about this - It seems 'tek' already have that batteries outside of box. So its job made easy. Just need to move to better isolated RCA.

Here are two kit for forum members sent from Sachin.
They are almost complete but untested. I don't have MC cart.
Both are same kits only external parts are different. External battery or upgradable to regulated PS too. XLR for power supply connection.

This is for 'tek' using local cabinet and MX RCA connectors. Chassis isolation was made using tape and sleeves. I will put more sleeves on inside wires.

 

[tek]

Thanks Om and Josh - I managed to get it fixed by Pandu, and also got my old stage resoldered too coz one wire had come out.

Back to the sweet sound

 

[jls001]

Thanks Om and Josh - I managed to get it fixed by Pandu, and also got my old stage resoldered too coz one wire had come out.

Back to the sweet sound

That's good news indeed.

 

[jls001]

My Hypnotoad's stopped working some days ago. I did the easy thing and swapped out to my old phono stage for now.

Troubleshooting done:
1) used a pair of freshly charged 9V batteries - this did not help
2) removed the the OPA2134 opamp pair from the Hypnotoad and fitted it to the CNC MM phonostage - the CNC still works, meaning the opamps have not blown.
3) tried putting OPA2134 from CNC MM phonostage to the Hypnotoad - does not work
4) tried putting LME49990 into Hypnotoad - does not work.
5) soldering points rechecked and I have confirmed that nothing has come loose. But I have not gone to the extent of desoldering everything and soldering them back.

Any idea what could be wrong, and what should I do further? Thanks in advance.

 

[sachu888]

My Hypnotoad's stopped working some days ago. I did the easy thing and swapped out to my old phono stage for now.

Troubleshooting done:
1) used a pair of freshly charged 9V batteries - this did not help
2) removed the the OPA2134 opamp pair from the Hypnotoad and fitted it to the CNC MM phonostage - the CNC still works, meaning the opamps have not blown.
3) tried putting OPA2134 from CNC MM phonostage to the Hypnotoad - does not work
4) tried putting LME49990 into Hypnotoad - does not work.
5) soldering points rechecked and I have confirmed that nothing has come loose. But I have not gone to the extent of desoldering everything and soldering them back.

Any idea what could be wrong, and what should I do further? Thanks in advance.

Remove Opamps and measure voltage at both Opamps socket.

Regards,
Sachin

 

[jls001]

Remove Opamps and measure voltage at both Opamps socket.

Regards,
Sachin

Should I measure V+ and V- wrt the ground? And since I am using +9V and-9V supply, should I expect these voltages to show up, or should I allow some margin of voltage drop? Pin out here.

 

[sachu888]

Should I measure V+ and V- wrt the ground? And since I am using +9V and-9V supply, should I expect these voltages to show up, or should I allow some margin of voltage drop? Pin out here.

Yes it should be close to +/-9 V
Please keep black pin of DMM at G of HTMCPS and RED at Opamp sockets.

Regards,
Sachin

 

[jls001]

Yes it should be close to +/-9 V
Please keep black pin of DMM at G of HTMCPS and RED at Opamp sockets.

Regards,
Sachin

Thanks, I will try this.

 

[omishra]

There are 4 resistances which are kept for matching with the particular MC cart loading. Please check its connections on PCB and resistances are properly in contact. There if something is loose, output goes off.

 

[jls001]

There are 4 resistances which are kept for matching with the particular MC cart loading. Please check its connections on PCB and resistances are properly in contact. There if something is loose, output goes off.

I screwed the resistors on the (green) connector blocks. but I will check them again. May be I should take them out and carefully put them back. Thanks for this pointer.

 

[jls001]

V+ is 8.64 V on both opamps, and V- is 8.63V on both opamps

Rechecked connections of R1, R2, R9 and R10. All are securely tightened but I redid them all. On turning on or off the DPDT, I can hear a pop as usual, but I still don't have sound.

Any further steps to take?

 

[sachu888]

V+ is 8.64 V on both opamps, and V- is 8.63V on both opamps

Rechecked connections of R1, R2, R9 and R10. All are securely tightened but I redid them all. On turning on or off the DPDT, I can hear a pop as usual, but I still don't have sound.

Any further steps to take?

I/P, O/P RCA connections need to be checked.Try brand new batteries (non rechargeable).

Regards

 

[omishra]

V+ is 8.64 V on both opamps, and V- is 8.63V on both opamps. On turning on or off the DPDT, I can hear a pop as usual, but I still don't have sound.

Any further steps to take?

Tht means power supply + and - are okay, also output OPAMP and output wire are okay. Now input, supply ground wires and parts between two OPAMPs remained to be checked.