RCA RS177H just dosen't sound right! Caps?

[oldtexasdog]

I just finished replacing all the power and coupling caps and all the resistors on this and while it plays good and has bass the treble is just too high and sounds kinda "SCRATCHY" not smooth? I used metal foil coupling caps at .27uf just as the schematics called for? Should I have increased them to say .35uf?
Thanks as always for your time and thoughts folks

 

[HollowState]

If you have replaced all the original paper capacitors with modern plastic dielectric types, the frequence response will be increased on the high end over what it was, And if you replaced the original carbon composition resistors with metal films, that exacerbates the problem. Somewhat less so for carbon films. It is not the numerical value, but the material "upgrade" that does it.

 

[SoNic_real_one]

Maybe now you are really hearing how it should sound. Give your brain some time to adjust, maybe it is still "compensating" for the high-end drop that it experienced before.

 

[oldtexasdog]

Well I'll try giving it a while It's just the high end sounds a little distorted.

 

[Frank Berry]

I don't have a copy of the schematic. If there is a capacitor in the feedback network, make sure that it's the correct value.

 

[oldtexasdog]

There is but I did leave those two and a power cap resistor orginal.
I cant seem to get the schematic to up load as it sayus the file is too large?

 

[Frank Berry]

Please email the schematic to me. You should be able to find my email address by looking at my profile.

 

[Frank Berry]

The site doesn't show my email address. Email me through this site and I'll respond. That will give you my email address.

 

[oldtexasdog]

The site doesn't show my email address. Email me through this site and I'll respond. That will give you my email address.

E-mail sent
Thanks

 

[oldtexasdog]

Well I took out the 5AS4A rectifier and rolled in a 5U4G and it sounds a LOT Smoother now

 

[Frank Berry]

a 5Y3 will give you more B+ voltage. A 5AR4 will give you even more.
Perhaps the 5AS4 tube wasn't delivering enough voltage.

 

[maxro]

a 5Y3 will give you more B+ voltage.

Perhaps. But, at 125mA maximum with cap input, it doesn't have the current capability for four EL84s at full power.

 

[Frank Berry]

Perhaps. But, at 125mA maximum with cap input, it doesn't have the current capability for four EL84s at full power.

You are absolutely correct. I wasn't thinking stereo. For some reason, I was thinking that this is a mono amp.
Scratch the 5Y3. 5AR4 would be a better choice.
Another advantage, the 5AR4 draws much less filament current.

 

[oldtexasdog]

So the 5Ar4 would be a better choice than the 5U4?

 

[Frank Berry]

The 5AR4 has a much lower voltage drop than the 5U4.