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Opamp for Phono Preamp

C

cayman711

New Member
Hello, I'm a new member in this forum.

I have an pcb from fosi audio tube phono. The sound is ok, but i wonder if i can improve the sound by replace the opamp ? The current opamp is JRC2068 and i have an unused OPA2134, can this be used here ? I don't have a schematic, but just a photo.

Thank you so much.
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Looks like they're socketed so you should be able to try out other DIP-8 op amps. The JRC2068 is pretty common for phono preamps and used by Denon, Yamaha and likely many others.

Impossible to say without a schematic but the tubes may be just buffering the signal while the op amps are doing the RIAA equalization and amplification.
 
2068 is a pretty good opamp. Imo using a opa2134 is not going to make much difference but some folks might think differently. It can be done however
 
Also, keep in mind the newer faster op amps (OPA2134, LM4562 etc.) will be less tolerant of poor circuit layout. You may need to add 10nf film or ceramic bypass capacitors between each supply pin and ground as close to the device as possible (preferably right at the pins). Also may need to add a resistor in series with the outputs to isolate from capacitive loads.

Your board may already have these but again hard to tell with surface mount components and no schematic.
 
WizardWG4 said:
Also, keep in mind the newer faster op amps (OPA2134, LM4562 etc.) will be less tolerant of poor circuit layout. You may need to add 10nf film or ceramic bypass capacitors between each supply pin and ground as close to the device as possible (preferably right at the pins). Also may need to add a resistor in series with the outputs to isolate from capacitive loads.

Your board may already have these but again hard to tell with surface mount components and no schematic.
Click to expand...

thank you so much!
 
The tubes you use may have more of an effect in sound in the buffer stage. What tube types does it use. 6922/6DJ8's, 12AU7's, ect.?
 
cayman711 said:
It's a 6J1, currently im using a 6j1p voskhod (rocket logo)
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The GE JAN 5654W is a nice substitute. They really woke up my little hybrid preamp. The Voskbod's should be a nice tube also though. Mine came with Chinese 6J1's, horrible things.
 
Lavane said:
The GE JAN 5654W is a nice substitute. They really woke up my little hybrid preamp. The Voskbod's should be a nice tube also though. Mine came with Chinese 6J1's, horrible things.
Click to expand...

i managed to replace the opamp to opa2134, sounds bit better than the jrc2068, especially in the high region. But i heard a little distortion, should i change the gain ?
 
It looks like there's three dip8 op amps. Did you change all three?

Making any mods to this is difficult with surface mount components and lack of schematic. The opa2134 may not be happy in the circuit due to lack of stability components mentioned above.

If you want to experiment you could also try the old reliable NE5532.
 
You should look up and compare the data sheets for the opamps before swapping. Make sure everything is compatible.

For example...
OPA627 and OPA637 look nearly the same and compatible.
However, OPA627 is unity gain stabile whereas OPA637 is stabile in gains equal to or greater than 5.
They are not compatible in certain situations.
 
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