No, the output offset is generated by the op amp itself, not what is connected to the input - so you'll always need the output coupling cap to avoid high offset.
Mike, I think Bas meant that the transformer is on the input of the preamp. Not the input of the opamp.
Still, I do not know if it would be a good idea to expose the transformer to the possibility of core saturation because of DC.
Still, I do not know if it would be a good idea to expose the transformer to the possibility of core saturation because of DC.
Don't allow any DC offset current to pass into the signal transformer.
Ugh. Late night. Misread.
Yeah - what Andrew said. A line input transformer can only take a very small DC current before saturating, and the VSPS output will have offsets up around 1 volt without C3 to block the DC signal.
Yeah - what Andrew said. A line input transformer can only take a very small DC current before saturating, and the VSPS output will have offsets up around 1 volt without C3 to block the DC signal.
Hi. I bought pcb from VSPS400. I see you're using OPA134.
I ask how to recognize original copies.
From Uruguay you can only access purchases by Ebay.
regards.
Josè
I ask how to recognize original copies.
From Uruguay you can only access purchases by Ebay.
regards.
Josè
Alternative OPA134 manufacturer or a fake chip?
Please read down to the part where the "fake" chip is found to actually have been a genuine part. In short, I wouldn't worry.
Please read down to the part where the "fake" chip is found to actually have been a genuine part. In short, I wouldn't worry.
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I think rayma already answered it. You are welcome to experiment with RFI filters like that on the preamp inputs. I do not include in my projects as they not part of the circuit per se. and completely optional. The filter is best implemented at the RCA jack.
Hi. A question has arisen. I see the S-reg circuit of the CrystalFET and I realize that it has a CRC filter and Q7-Q8 is MOSFET, that the VSPS 400 does not have it.
Would it improve my future VSPS400 something if I make these modifications? or is it better to leave the circuit as designed?
Greetings.
Would it improve my future VSPS400 something if I make these modifications? or is it better to leave the circuit as designed?
Greetings.
@ALPUY
The story there is the extra capacitor lowers the ripple but it is not needed with the VSPS/Phonoclone since the PSRR of the op amps is already high. The CrytalFET has a PSRR of negative 20 dB so I had to pull out all the stops so to speak.
@Lohengrimas
I'm no longer so enamored with the GC to be able work up the enthusiasm needed to develop that, though I do agree a one box phono amplifier as an idea has a certain merit.
The story there is the extra capacitor lowers the ripple but it is not needed with the VSPS/Phonoclone since the PSRR of the op amps is already high. The CrytalFET has a PSRR of negative 20 dB so I had to pull out all the stops so to speak.
@Lohengrimas
I'm no longer so enamored with the GC to be able work up the enthusiasm needed to develop that, though I do agree a one box phono amplifier as an idea has a certain merit.
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OpAmps for the VSPS 200/400.
The OPA 134 works perfectly in these circuits. The Analog Device's AD797 however does'nt - too my surprise I might add. The sound being highly distorted and with no signal "motorboating" is clearly audible.
Any suggestions would be appreciated as the AD's are rather costly.
The OPA 134 works perfectly in these circuits. The Analog Device's AD797 however does'nt - too my surprise I might add. The sound being highly distorted and with no signal "motorboating" is clearly audible.
Any suggestions would be appreciated as the AD's are rather costly.