Tone Factor of Caps

[ajeffcote]

I recently changed some caps in my DRRI.Vibrato/reverb channel.Coupling caps first,then the tone stack caps.All of this was done to make the amp a little warmer sounding.The first time around I used all Orange Drops.Then I bought some Mallory's and replaced the OD's with the same values.All except for one.A phase inverter coupling cap,C25 on the schematic.That was a .001uf to be replaced with a .0022uf.I didn't have one the first time around so I left it stock.I also did not change the bass and mid caps at first because of the size of the OD's.
After the Mallory's I expected to get an even warmer tone because of the construction differences between the OD's and the Mallory's.The normal channel became a lot closer to what I am looking for,and I am attributing that to the phase inverter cap change.I changed nothing else on that side.
The vibrato channel became brighter,a lot brighter.I did not change the values,only the brands.So I went back to the stock tone stack caps and the that side warmed up again.
I guess my assumptions were wrong.I plan on putting the Mallory's back in the vibrato side and try some tweaking to remove some high-end.From what I have read the Mallory's should make the amp smoother sounding.
Here's the question.Where would be the best place to tweak that side to get rid of some treble?My first thought would be the treble cap,But,it is the same value as the normal side treble cap.The vibrato side high pass cap(C10) was removed before I started any of this.So maybe in the vibato or reverb circuit? C13 is a high pass cap.I removed it.R32 and R33 is a voltage divider.Maybe a small cap across R33 to ground?C12 is a coupling cap that I left at stock value.Maybe replace that with a .047 or larger?
Any thoughts would be appreciated.Aubrey

[Shea]

If the vibrato channel is more trebly than the normal channel, one place I would look at is the small cap that bypasses a 3 meg resistor that mixes the dry signal with the reverb before the 3rd gain stage. Unless that's one of the caps you said you already removed.

If all else fails, you can always experiment with putting small caps across a plate load resistor or two in the preamp.

Shea

[txstrat]

You might simply check your tubes. I recently changed (in a ChampII circuit) to JJ's 12AX7 (ECC83S) who I heard of would be less trebly and they are. My amp lost a good audible amount of treble. Before the change I used to have the treble pot on 10 on the dial now it's on 12 and even less trebly sounding.

Matt

[cbarrow7625]

What kind of OD's & Mallory's? Polypropylene film? Polyester film? Polypropylene & foil?

Did you chage the ceramic caps to mica or did you leave those alone? If you look around hard enough you can find polyester caps in pF sizesin the voltages needed for tube amps. They will have a very different tone than ceramic or mica.

A little more info on the caps makeup would be helpful. Especially the ceramics questions.

Chris

[ajeffcote]

What kind of OD's & Mallory's? Polypropylene film? Polyester film? Polypropylene & foil?

Did you chage the ceramic caps to mica or did you leave those alone? If you look around hard enough you can find polyester caps in pF sizesin the voltages needed for tube amps. They will have a very different tone than ceramic or mica.

A little more info on the caps makeup would be helpful. Especially the ceramics questions.

Chris

The only ceramic I changed was the treble cap on the vibrato side,from the stock 250pf to a 390pf silver mica.Tried a 10pf silver mica in place of the 10pf ceramic that jumps the 3meg resistor,but when I went back in I removed it completely.
The Mallory's are 150M's(polyester film?) and the OD's are 715P's(polypropylene?).
So,polyester caps are going to be the ones to tone it down?
Tonight I'm going to put the M150's back in the tone stack and try a 600pf in the treble slot.If that doesn't do it then I will up the .022 coupling cap to .047.If that doesn't work maybe make a filter out of the load resistor on the wet side right before it mixes.I just have a feeling that all the extra treble is coming from the reverb/vibrato side .
I think I will get to it tonight,anyway.A neighbor has 8 cases of beer iced down for a little party tonight.Hmmmm????

[ajeffcote]

You might simply check your tubes. I recently changed (in a ChampII circuit) to JJ's 12AX7 (ECC83S) who I heard of would be less trebly and they are. My amp lost a good audible amount of treble. Before the change I used to have the treble pot on 10 on the dial now it's on 12 and even less trebly sounding.

Matt

I have all new JJ's in it now,and it's biased a little on the warm side.Aubrey

[ajeffcote]

If the vibrato channel is more trebly than the normal channel, one place I would look at is the small cap that bypasses a 3 meg resistor that mixes the dry signal with the reverb before the 3rd gain stage. Unless that's one of the caps you said you already removed.

If all else fails, you can always experiment with putting small caps across a plate load resistor or two in the preamp.

Shea

That may be what I end up doing.Thank,Aubrey

[mac1amps]

Try removing the "bright" cap on the Vib. channel volume control, which is the equivalent of a permanantly "on" bright switch (which ALWAYS sound harsh on Fenders....at least to my ears). I've done it to many Deluxes' for my clientele, and they're always happy with the results. This cap. isn't on the "Normal" channel volume control, which is why you prefer the sound of that channel.

[ajeffcote]

I finally figured out where the tone went.It went to ground!!The M150's are larger than the stock plastic caps,quite a bit larger.When I installed them I didn't take that into consideration and the .1uf cap's lead made contact with the chassis when I put the little PC board back in.I re-installed the Mallory's and raised the treble cap value to 500pf.I had changed the mids resistor from the stock 6.8K to 10K.I adjusted that down to about 7.5K.
It now sounds really good!!The Mallory caps did the trick by smoothing things out a bit.
Thanks to all of you for your help.Aubrey