Tweed Pro Volume Pot & Cap Question

[Jammin'John]

I have a Weber build with a crappy 1 meg normal channel volume pot.
I don't know what kind it is.
I tried playin' in the bright channel and it was too bright.
There is a cap on the bright channel pot.
I don't know the value.
If I want less treble should I go up or down on the cap value ?
What is the best quality 1 meg pot that I can buy and where would I buy it ?

JJ

[Structo]

Do you have a schematic for the amp?

That would tell you what the values are.

As far as pots go.

Alpha for inexpensive good pots.

CTS maybe a step above, though I think they are making them cheaper now with plastic shafts.

PEC, Good quality sealed pots, expensive.

Clarostat

NTS

There are many brands.

My amp has all Alpha pots and they work fine.

[Jammin'John]

This is what it is BUT it has been changed to cathode bias.
http://www.ampwares.com/amp.asp?id=147
Larger or smaller pot on the vol control for less treble ?
Is the pot list in order of quality ?
https://taweber.powweb.com/store/kits_50a.htm#5E5A

JJ

[Structo]

A different valued pot isn't going to change the tone. It would just change the range of adjustment.

You can try to eliminate the bright cap on the volume pot by unsoldering one side of the cap and bend it out of the way to try it without it.

I'm not that familiar with that amp other than you may have to change some values in the coupling or bypass caps to tweek it towards what you want.

But first, you should try some different preamp tubes.

Even tubes of the same brand can sound different from each other.

JJ's tend to be a little darker in the 12ax7's.

Does your amp have 12ax7's for V1 and V2?

That one schematic shows 12au7's for V1 and V2.

So try different tubes and snip the bright cap on the second volume pot for starters.

[rfgordon]

Alpha pots are OK, CTS better, and Bourns better yet. You can get Bourns at AntiqueElectronicSupply now.

As for the bright cap across that one pot, the smaller the value, the higher the frequencies it lets bypass the pot. I once made a list of the bright cats Fender used, from the tweed days into the blackface era, and it's quite a varied list--from 47pF all the way up to 500 pF. Try different values and pick the one you like best--no right or wrong answers here.

Also, silver mica, ceramic disk, and styrene all sound a bit different.

[billyz]

I like the PEC because the taper feels better. Old timers liked to jumper the channels and blend to taste. If you want to give it balls, lift the 220k going to ground after V2 and I like to lift the 5meg local feedback around V2.

[Jammin'John]

Those PEC pots sound interesting. Best price ?
I have 12ay7 in V1,V2,(GE & Sylvania) & a 12ax7 in V3 (RCA).
I'm runnin' Shuguang KT66's and a potato masher 5R4.
385v,46ma
I want to replace the bad pot on the normal channel and change the cap on the bright channel for less trebles. I play tele's.
Those are small value caps.
I've jumpered before & it's fun.
I'll check out Bourns.

Thanks,
JJ

[Jammin'John]

Those Bourns pots seem like they are pretty cheap.
They are very good ?

http://www.apexjr.com/Bourns.htm JJ

[Structo]

Apex is a great place to buy stuff.

He also usually has good prices on Teflon wire if you ever need that.

Yes Bourns pots are very good.

Why do you think the pot you have is bad?

[Bob-I]

I have a Weber build with a crappy 1 meg normal channel volume pot.
I don't know what kind it is.

Weber has his components made in China, yes they're not great.

I tried playin' in the bright channel and it was too bright.
There is a cap on the bright channel pot.
I don't know the value.
If I want less treble should I go up or down on the cap value ?
What is the best quality 1 meg pot that I can buy and where would I buy it ?

JJ

To reduce the treble, lower the value of the cap across the pot. The stock value is 100pF, try dropping it to 47pF.

Another easy choice is to bridge the 2 channels. Simply connect a short guitar wire from input 2 on the normal channel to input 1 on the bright channel. Adjust the volumes as needed for the tone you want, turn the bright channel up for more highs, down for less.

[Structo]

You usually have to double or halve the value of a cap to hear a change.

So you could try a 47pf or even no cap to see how it sounds.

[Jammin'John]

I can't bridge channels right now 'cause the pots bad in the normal one.
The reason I think it's bad is 'cause when I twist it, it makes loud scratchy noises and if I tap it,it almost sounds like a microphonic tube.
I know it's not a tube 'cause I subbed known good tubes and got no improvement.
I'll have to get some good quality pots and try a smaller cap on the bright channel volume pot.
Are there different qualities of bourn pots 'cause they are a LOT cheaper than PEC.

http://www.apexjr.com/Bourns.htm

http://store.triodestore.com/pecpot1meg.html

JJ

[Jammin'John]

Don't they have to be 1 meg,2 watt ?
Some that I see offered are 1/4 watt.
How many watts do they have to be ?

http://www.tubesandmore.com/scripts/fox ... m=R-VB-1MA

http://www.tubesandmore.com/scripts/fox ... em=R-VC1MA plastic

http://store.triodestore.com/pecpot1meg.html

JJ

[Structo]

I'm pretty sure 1/4 watt is fine. There is very little power or volage on those pots.

Why do you think you have a bad pot?
Is it noisy? Scratchy?

If you do replace it make sure the bushing is the same size as you have in the amp. The bushing is the threaded portion.

[Jammin'John]

Noisey,scratchy & if you hit it,it make loud noises almost like a bad tube.

JJ