OD Brightness

[orca]

I need some help from the more experienced builders; the OD channel
is a bit too bright for my taste.I already have a 220K resistor in front
of the trimmer;what makes it less bright?
Increasing the snubbers to 330p or even 470p like the Two-Rock amp?
Increasing the 0,005uf capacitor after OD2 to 0,01uf?
Help is very much appreciated.
Wolfgang

[Guitarman18]

Check out this thread and others that mention ayan's treble bleed cicuit which gives excellent results.

https://tubeamparchive.com/viewtopic.ph ... eble+bleed

A search for 'treble AND bleed' will also link you to some stunning audio clips from people who have used it, such as ayan and larsmuller to name but two.(There are probably many others - apologies for missing you out)

Good luck.

[Guitarman18]

ayan wrote:

...treble bleed circuit made up of a 250K ohm pot in series with a .001uF cap from the top of the OD master volume (100K pot) to ground.

[Luthierwnc]

The bleed works and you don't have to have a bright cap across the master either. sh

[Fischerman]

What grid stopper do you have on the grid of V2B (i.e. OD2)? Some use 150k and some use 180k. The higher value cuts some highs...go too far and it gets muffled.

Also, the total load on the output of V1B (i.e. CL2) makes a difference. Notice the non-HRM is 220k+100k=320k but some had higher loads...higher is fatter but again...go too far and it gets murky/muddy.

[llemtt]

Wolfgang

a properly built non-HRM, without bright cap on master, is not bright at all.

First check that everything is ok and is built almost like #124 (see all those detailed pictures..).

Shielded wires are in place where needed?

teo

[orca]

thanks to all helpers;
I will check my amp and see, what can easily be done.I like the
idea with the treble bleed.
Wolfgang

[greiswig]

Wolfgang

a properly built non-HRM, without bright cap on master, is not bright at all.

If this is true, I'd be curious as to what constitutes "properly built." My non-HRM was bright enough even with the 330pF snubbers that I put in a treble bleed. This has shielded wiring, although it has always struck me as odd that people are always looking for low capacitance cable for this, but then find the amp too bright. My cable isn't particularly low capacitance.

What did I do improperly?

[orca]

my amp is a Ceriatone Overtone Special,which IMHO is mechanically
well built.Some components could be better,yes,but the shielded cables
are perfect.
I wonder,if anybody changed the capacitors in the OD channel to a
different brand.In my experience the SBE or Orange Drop capacitors
are more on the bright side,in some places even harsh sounding,especially the 715P type.
I still have some old Mustard Capacitors-the ones the early Marshall
and Vox amps had- they are more on the mellow side.I think I will give
them a try and add a treble bleed too.Maybe a Kiwame resistor is a
good try in some spots.

[Luthierwnc]

Orca;

There are a few theoretical things that may help. One, resistors generally resist high frequencies more than lows. Two, increasing the size of a cap doesn't diminish highs, it just lets more lows through. Third, to really get rid of highs, you have to send them to ground. That's why the treble bleed is so effective. You can adjust for either the cap value or the resistance until it is just how you like it. FWIW, I clipped the master bright cap off mine.

Skip

[dobbhill]

Do the Dumble ODS's have a treble bleed circuit?
I have found that a treble bleed is not needed unless the brite is on. I have also found that the brite is not needed at stage volumes, but then I play a Tele. I also use 500pf snubbers.
FWIW.........
D

[Fischerman]

Here's a thread that might have some good info. In case you don't know, Gil Ayan is an admitted HRM fan and he says he usually adds the treble bleed.

IIRC others have built amps as close to #124 as possible and they didn't sound like #124. Apparently #124 sounds browner and breaks up quicker than it 'should' (note that I've never heard nor seen it...just what I have gathered from comments made about it).

[llemtt]

I'd be curious as to what constitutes "properly built."

I think the most important thing is avoiding "high freq signal coupling" between different circuit points, but also the right components as already suggested.

How to do it? I don't know a method sorry, maybe it's only a matter of experience and good practice. Only after building more than 3-4 amps one day I had two amps supposed to be identical but one was OD brighter: it took me months to discover why (it was peculiar to my own circuit design however), then I fixed it (moved around some components by less than 1/2 inch and less than 2 additional inches of coax cable) and the amp now behaves as expected.

At least you can always try this: dime every control to max but turn the OD ratio/volume to zero and then play -> can you hear some subtle thin sound out of the speaker?

cheers
teo

[greiswig]

At least you can always try this: dime every control to max but turn the OD ratio/volume to zero and then play -> can you hear some subtle thin sound out of the speaker?

Teo,

I think I see what you're driving at, but I want to make sure: if you do this test, and you hear something, that means that you've got undesired coupling somewhere? This could be really useful.

[greiswig]

Dupe deleted