effect on bright cap valu on mids...

[hebaton]

I find My JTM45 bright channel somwhat "hard" sounding. I looked at the cap value ( on the volume pot ) and found a 750pf. I clipped it out and now find it a bit dull. So I was going to try 500, but I read somewhere, hoewever not well explained, that the cap also has an effect on the mids response. It seems poeple are playing around anyhere from 100pf to 1000pf on there. I am looking for not harsh, not too bight and I do want to feel the wieight of the mids as much as possible....
What to expect from different values then ?

[Stevem]

Your being too general in your description of what your hearing.

Is this harshness at all levels of volume?

Is this harshness when you first pluck the note which will have the pick attack responce in the overall sound being made, or once the note is just ringing out?

Is there any setting of the amps presence control that begins to tame or even eliminate what your dislike is with the sound?

Does the tone pot on your guitar have any effect on this issue?

What speakers are you playing the amp through?

[Colossal]

Also, did you use a mica or ceramic bright cap?

[pdf64]

I don’t think the query makes sense. Whatever the value used, its tonal effect is totally dependent on the particular setting of the volume control.

[hebaton]

I don’t think the query makes sense. Whatever the value used, its tonal effect is totally dependent on the particular setting of the volume control.

Please explain your view. Are you saying in the general use of the amp, knowing there will be numerous different circumstances calling for different settings and other variables, it makes no sense to try to find something that keeps me in the general ballpark I wish to be in ?

[pdf64]

No.
I suggest that you try a few values and find what suits you. But one value is inevitably a compromise.
I use a switch to select different values according to different guitars, volume control settings, speaker cabs and the acoustic environment.

[brewdude]

The bright cap lets high frequency signal pass around the volume pot’s attenuation. If the volume is set very high the bright cap has little to no effect. If the volume is set very low the bright cap will have a much larger influence on the sound letting all the frequencies it passes through unattenuated.

I have begun looking at the mid content you are seeking to be a double edge sword. Too much is not always better, especially if lows and highs are not controlled.

Sometimes too much high is not enough bass.
Too much bass is not enough high, or maybe just smearing the mid content.

Marshalls often use series resistors bypassed with small caps (peakers?). I have found that these circuits can have a large effect on the frequency curve of the amp.

I also think speaker/cabinet can make huge difference.

[hebaton]

Your being too general in your description of what your hearing.

Is this harshness at all levels of volume?

Is this harshness when you first pluck the note which will have the pick attack responce in the overall sound being made, or once the note is just ringing out?

Is there any setting of the amps presence control that begins to tame or even eliminate what your dislike is with the sound?

Does the tone pot on your guitar have any effect on this issue?

What speakers are you playing the amp through?

Yes the "hardness" I feel at all levels.
It is more eveident on attack but remains as the note rings out.
Presence control even all the way down does not correct that.
Tone on guitar has some effect, mainly using 335 50's wiring
Cab is a Marshall 1936V but speakers have been switched to Scumback M75 PVC

[hebaton]

FInally tried a 500pf and a 250pf today. Decided to stay with the 250. Not only did I prefer the tone, just enough bite with still a good low mid presence but, I felt, compared to no cap , more gain / distortion on tap. I don't understand why that would be, if anyone cares to comment on that particular aspect of the thing...