Lower gain in YS Audio linestage

[Beranga]

Hello:

I need help with lowering the gain of my YS Audio Symphonies Plus-R line stage. My source has a 3 V output and my amplifier a 0.750 V sensitivity. I like the sound (coloring?) of the Symphonies and would like to have better volume control as now I can´t go above 9 o´clock position. Thanks in advance and I attach the schematic:

[Eli Duttman]

Build resistive voltage dividers out of 1/8 W. 1 % metal film resistors into the RCA plugs, at the preamp end of the interconnect cables. The total resistance of the dividers should be as close to 10 KOhms as you can get, without going below 10 K.

It seems like dropping 2/3 of the I/P voltage will do the trick.

[Alastair E]

Alternatively you could add a 100K in the signal-end of the pre-amp vol-pot...
--Assuming its 47K pot that is....

[Beranga]

Originally Posted by Eli Duttman

Build resistive voltage dividers...

Originally Posted by Alastair E

Alternatively you could add a 100K in the signal-end of the pre-amp vol-pot...

Thanks for the quick responses. I´ve considered a voltage divider, but I think it would be better at the amp´s input, lowering the floor noise. Am I wrong?

What I´m looking for is a way to lower the line stage gain without messing with I/O impedances as with a voltage divider. Again, am I wrong?

Thank you for your help.

[Eli Duttman]

What I´m looking for is a way to lower the line stage gain without messing with I/O impedances as with a voltage divider.

While S/N ratio is important, wave form fidelity is even more important. This is a "line" level situation and metal film resistors are quiet. The odds are long that your digital signal source will have little trouble driving a 10 KOhm impedance. After all, that's the IHF "standard". OTOH, the 100% tubed circuitry may get into trouble driving a comparatively low impedance voltage divider. IMO, taking the road most likely to yield success is best.

BTW, building the voltage dividers into the RCA plugs allows you to adjust things as needed, on a source by source basis. For example, should you acquire a phono preamp, zero extra attenuation is almost certainly in order.

[Johnny2Bad]

Originally Posted by Eli Duttman

While S/N ratio is important, wave form fidelity is even more important. This is a "line" level situation and metal film resistors are quiet. The odds are long that your digital signal source will have little trouble driving a 10 KOhm impedance. After all, that's the IHF "standard". OTOH, the 100% tubed circuitry may get into trouble driving a comparatively low impedance voltage divider. IMO, taking the road most likely to yield success is best.

BTW, building the voltage dividers into the RCA plugs allows you to adjust things as needed, on a source by source basis. For example, should you acquire a phono preamp, zero extra attenuation is almost certainly in order.

I believe the YSAudio preamps have an input labeled "CD" (or something similar) so it would not be difficult to keep track of which is attenuated specifically for his digital source. That does not, by itself, mean that incorporating them into the RCAs is a inherently bad idea, though.

Were it me, I would consider adding the resistance at/near the volume pot and selected via a front panel switch. Then you could use it as a "true mute" circuit that attenuates the output on all inputs (rather than a "tv mute" which simply cuts output completely), which is useful even if you were using phono as an input (like, say, when the phone rings) to just lower the volume a known amount. A few preamps/integrated amps of the 70's had a similar muting circuit.

[DF96]

Your signal is 3V, and you need 0.75V, so you need a voltage division of 1/4. Your line stage gives you a gain around 8, so the combination of volume control and extra attenuation must give you around 1/32. The quick way to do this is to ditch the line stage as it is unnecessary, but you like the way it modifies the signal.

You could reduce the line stage gain by changing R9 and R10 to 68K. This gives gain of 2 instead of 8. There is a slight risk of HF instability, so it might not work. It might change the sound too by lowering distortion.

Alternative is a resistive divider at the input, as others have suggested. This will end up presenting exactly the same signal at the first grid as you currently get by reducing the volume pot, so the noise and 'sound' should be the same.

[Beranga]

Originally Posted by Eli Duttman

While S/N ratio is important, wave form fidelity is even more important. This is a "line" level situation and metal film resistors are quiet. The odds are long that your digital signal source will have little trouble driving a 10 KOhm impedance.

Thank you for pointing that out.

Originally Posted by Johnny2Bad

Were it me, I would consider adding the resistance at/near the volume pot and selected via a front panel switch. Then you could use it as a "true mute" circuit that attenuates the output on all inputs...

The Symphonies has remote controlled such circuit, high attenuation, not "TV mute". However a resistance at the volume pot is interesting as I understand it would increase the impedance seen by the source by whatever the value of such resistance is.

Originally Posted by DF96

You could reduce the line stage gain by changing R9 and R10 to 68K. This gives gain of 2 instead of 8. There is a slight risk of HF instability, so it might not work. It might change the sound too by lowering distortion.

This information is what I was looking for, however I had considered the possibility of lowering the distortion and changing the sound.

Thank you all for your responses. I seems there is consensus that the better solution is some kind of voltage divider at the input, so that´s the way I´ll go. I love this forum

[goblin141]

a high and a low. I run mine on the high out as my speakers want lots of power. I dont remember the difference in gain but 6db reduction sticks. Not sure if this is what you are looking for?

[Beranga]

Originally Posted by goblin141

a high and a low. I run mine on the high out as my speakers want lots of power. I dont remember the difference in gain but 6db reduction sticks. Not sure if this is what you are looking for?

Yes, there are two outs in the back, but both are the same level.