Mica Across Master

[UltraHookedOnPhonix]

Zoom in on the master of #234 and.....OMG!!!! MICA!!! Pure Evil!!!

[IMG768]http://i205.photobucket.com/albums/bb17 ... on/234.jpg[/img]

[JimiB]

but what value is it?

[ayan]

but what value is it?

It's the bloody clean channel, who cares?

Gil

[Bob-I]

but what value is it?

It's the bloody clean channel, who cares?

Gil

That's not what I'm seeing.

Actually lots of builders use mica in select places and it sounds great. The only place I've felt better served by ceramic is the tone stack. The rest of the small caps seem to respond fine to mica, sometimes even better.

[Fischerman]

Is it possible that one sounds better when 'passing' signal but the other sounds better when 'shunting signal to ground'?

[greiswig]

Is it possible that one sounds better when 'passing' signal but the other sounds better when 'shunting signal to ground'?

That's been my perception before (subject to change on a whim). But, interestingly, the Dumble design seems to turn my previous experience on its ear: previously I've preferred film caps for passing signal, ceramics for shunting signal to ground. The graininess of the ceramics doesn't seem to matter when what is going through the ceramic is getting thrown out anyway. But the midrange grit of a Dumble design seems like it needs that ceramic element. Just goes to show you, what sounds best in a stereo amp isn't necessarily best in a guitar amp.

[groovtubin]

Is it possible that one sounds better when 'passing' signal but the other sounds better when 'shunting signal to ground'?

That's been my perception before (subject to change on a whim). But, interestingly, the Dumble design seems to turn my previous experience on its ear: previously I've preferred film caps for passing signal, ceramics for shunting signal to ground. The graininess of the ceramics doesn't seem to matter when what is going through the ceramic is getting thrown out anyway. But the midrange grit of a Dumble design seems like it needs that ceramic element. Just goes to show you, what sounds best in a stereo amp isn't necessarily best in a guitar amp.

I can def see WHY he`d use a mica there, the bluesmaster clean on my twin trannies is A BIT WARM, i may go to mica and see if it LIVENS it up, which is prob what the customer wanted in first place?

jim@Omegaamps.com

[Funkalicousgroove]

I agree, that little network across the Preamp out/power amp in jacks in #124 sounds better with Mica to my ears.

[ayan]

{double post}

[ayan]

but what value is it?

It's the bloody clean channel, who cares?

Gil

That's not what I'm seeing.

Hmm... int he picture posted, where else do you see a SM other than across the clean's master?

Dumble used SM in the preamp in the 70s. Since then, I have only seen three SM caps used in two different amps:

1. S/N 234 across the clean's MV.
2. A local 1982 ODS amp which had a 250pF SM treble cap. However, that amp had been modded by Lee Jackson (where it got its active FX loop, among other things), so there is a high likelihood it was put in by someone else.

Of everything I've seen , all other than these amps have used ceramic caps exclusively.

Cheers,

Gil

[jelle]

I do not see the 500pf cap across the 220k v1b grid resistor. Is it a 220k anyway?

I do see a mica treble cap like the 70's amps on the mid boost switch. Great place for a mica IMHO. Now the big question for me is: what cap is under the HRM goo?

[makrisp]

Looks looks like Mica to me.

['67_Plexi]

but what value is it?

It's the bloody clean channel, who cares?

Gil

That's not what I'm seeing.

Actually lots of builders use mica in select places and it sounds great. The only place I've felt better served by ceramic is the tone stack. The rest of the small caps seem to respond fine to mica, sometimes even better.
Personally I prefer a good ceramic in the tonestacks myself.

Couple of points on this.

My reaction to that photo was more.....ahhhhh Illinois Smoothing caps, pure shite !!!

There are many different qualities, brands and ratings of ceramics.
Any silver Mica will sound better in any position than a low quality ceramic in the same position.

Not to name drop, but it helps emphasize a point, but Eric Johnson preferred the sound of a Silver Mica in the tone stack compared to a really good quality ceramic. It definately leans more towards the Marshall thing, which ain't that bad. For him it cleared up some 'garbage' on top of the high notes. His words, not mine.

To say a silver mica is evil is like saying a Stratocaster is evil if you like Les Pauls. It's horses for courses and depends on your end point and in this case, the rest of your circuit.

Personally I generally also prefer a good ceramic in the tonestack.

On a similar note, I'm preferring a Carbon Film slope resistor in the OD channel and a Metal Film in the clean channel right now.

[greiswig]

There are many different qualities, brands and ratings of ceramics.
Any silver Mica will sound better in any position than a low quality ceramic in the same position.

What is considered to be the Orange Drop 6PS quality equivalent in ceramics?

[Funkalicousgroove]

Y5P Temp Coefficient, lots of brands available, buy them in big batches and go through them all.

MuRata, Mallory, Panasonic, Xicon(seen plenty o these in dumbles) Ususally 1KV or higher.