Express Parallel Capacitor

Express, Liverpool, Rocket, Dirty Little Monster, etc.

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Littlewyan
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Express Parallel Capacitor

Post by Littlewyan »

In my Express I currently have a .0022uF Cap for C8 and I believe that normally it is .002uF. Has anyone ever tried both? According to LTSpice there is a slight difference in bass. Also has anyone tried either paralleling two .001uF Caps (one ceramic and one orange drop) and just using a .0022uF Cap?
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Colossal
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Re: Express Parallel Capacitor

Post by Colossal »

For just a single cap at 0.002uF I think you might be hard pressed to hear any discernible difference as the tolerance for most caps used for guitar amp applications is 10% and rarely 5%. Using two caps of differing dielectrics however would be audible.
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Littlewyan
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Re: Express Parallel Capacitor

Post by Littlewyan »

Well might be worth tinkering with then. Just need to find the right size ceramic cap.
Mark
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Re: Express Parallel Capacitor

Post by Mark »

Using two caps of differing dielectrics however would be audible.
What would you expect to hear?
Yours Sincerely

Mark Abbott
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Colossal
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Re: Express Parallel Capacitor

Post by Colossal »

Mark wrote:
Using two caps of differing dielectrics however would be audible.
What would you expect to hear?
To my ear, ceramic has a certain grainy edginess and polyester a softer, smoother, fuzzy (not distorted fuzzy) quality to the midrange.
matt h
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Re: Express Parallel Capacitor

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RockinRocket
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Re: Express Parallel Capacitor

Post by RockinRocket »

Littlewyan wrote: Also has anyone tried either paralleling two .001uF Caps (one ceramic and one orange drop) ?
I was wondering about this too. One of the files I think I found on this site (Todd Helper preamp layout) says in the note some amps have been reported having .001 ceramic in parallel .001 pvc. Has this been debunked or mistaken for a .002 in parallel?
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geetarpicker
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Re: Express Parallel Capacitor

Post by geetarpicker »

Here is a letter Ken sent me back in the day. I had a Liverpool at the time that I liked but thought was a bit too bright, and he sent me some parts for a little tweak. It mentions that he was starting to do this in all his Liverpools from then forward. That said much more recently I also tried it in one of my Express clones and it definitely fattens up the tone of either circuit. I don't know if Ken ever did this in Express amps, but we can take Ken's word for it he did on the later "Pools"... Note that Ken is adding an additional .002 ceramic cap in parallel with the original .002 PCV orange drop, for a net doubling of capacitance. The tonal properties of the two different types of caps is also part of the recipe here obviously. GK
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Littlewyan
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Re: Express Parallel Capacitor

Post by Littlewyan »

I'll have to try a .002uf cap in parallel with the orange drop when I get a chance as my amp could perhaps do with some more bass. Give it a good low end thump.
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Re: Express Parallel Capacitor

Post by Mark »

I have tried two 0.001uF caps and one 0.002uF cap in my experimentation. I couldn't hear any difference between them. That's not to say the difference doesn't exist, but with the equipment I used I didn't hear a difference.

Glen thanks for the letter, it gives us some idea about the evolution of the Express amp.
Yours Sincerely

Mark Abbott
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Re: Express Parallel Capacitor

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geetarpicker
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Re: Express Parallel Capacitor

Post by geetarpicker »

It has been a while since I did the mod to my Liverpool, however when I added the 2nd .002 to one of my Express clones the added bass was quite noticeable.
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Re: Express Parallel Capacitor

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Littlewyan
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Re: Express Parallel Capacitor

Post by Littlewyan »

Well I think I may need to add the extra .0022uF (or .002uF) Cap to my Express to fatten up the tone a bit. At the moment it does have a lot of high end which you can especially hear when sitting down in front of the speaker cabinet. Its also high end that you can't seem to dial out easily with the treble knob without killing the tone altogether and if I go down to the 100pF Bright Cap again the tone just isn't there for me. I think its lower mids that I'm missing (or too much treble!).

Now I was just reading through old threads when I came across one regarding the type of wire used in an Express. One thing that has bugged me about my Express is that I used very thin solid care wire that had very thin insulation, whereas other clones or originals had nice thick solid core wire with thick insulation. It might be my mind telling me its giving me too much high end as I link the thin wire with a shrill sound but might be worth looking at.

Also I know my Express is very far from an original (in fact I believe Ken would hate the head cabinet its in!) but I still believe I can slowly make my way to the sound of an original. Lets not forget Ken built the first Trainwreck in a Fender Chassis.
Mark
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Re: Express Parallel Capacitor

Post by Mark »

It has been a while since I did the mod to my Liverpool, however when I added the 2nd .002 to one of my Express clones the added bass was quite noticeable.
This was my finding too, cap types no difference, but doubling the caps made a difference.

I found the Liverpool needed the 0.0044uF value coupled with a 68K grid leak resistor. A56K was just a bit too tame for my ear.
At the moment it does have a lot of high end which you can especially hear when sitting down in front of the speaker cabinet.
Don't sit in front of the speaker cab. :lol:

Seriously your issue is with the third stage, the Express without the third stage is a very different amp. The third stage doesn't give the amp tons of gain but it does a lot to shape the sound of the amp.

Have you tried the Komet third stage?
That might be more to your liking.
Yours Sincerely

Mark Abbott
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