Ampeg tone stack modification

[Hangman]

Read the full article here

[tdbassman]

Thanks for this great info! I'm looking forward to you putting this on a circuit board.

What caps do you recommend for this mod? I've noticed a great deal of tonal difference between the various types. Also, what coupling caps do you recommend tone-wise for the V4-B (especially with a P bass using Jazz Flats)?

Your help on the fly-back diodes several years ago made a world of difference to me and my amp, and fixed a problem neither I nor our local tech could solve.

Regards,

Tom D (tdbassman)

[Hangman]

I have used the Illinois tubular film caps, mallory 150s, and sozo mustard caps for the larger values, for the .001 I have also used silver mica caps which I always use for the 470pf and 250pf caps.

I think all of the above listed capacitors are good sounding. I don't get too caught up in the capacitor wars. I did this mod because those PEC ceramic caps just sound awful. regardless of whether you use tubular film caps or orange drops, you will hear an improvement, and it will work a lot better for you.

happy to help with the flyback diodes!

[itsonlyadam]

I'm just curious about one minor mod for the Ultra Hi switch circuit. You state replace ALL capacitors (c101-c104) with the silver mica 250pF? Or is it only c102 and c103? The reason I ask is because, I can't make it out, but the schematic for the V-4 shows that c101 and c104 have drastically different values than c102 and c103. I know the mod allows there to be a boost of a wider "high" frequency range (hence the 250pF value) but what of the values for c101 and c104? Do they also move up to 250pF in this mod?

Also, any word on the 7 PIN module you said you were developing? I'm super interested in that component!

[Hangman]

I'm just curious about one minor mod for the Ultra Hi switch circuit. You state replace ALL capacitors (c101-c104) with the silver mica 250pF? Or is it only c102 and c103? The reason I ask is because, I can't make it out, but the schematic for the V-4 shows that c101 and c104 have drastically different values than c102 and c103. I know the mod allows there to be a boost of a wider "high" frequency range (hence the 250pF value) but what of the values for c101 and c104? Do they also move up to 250pF in this mod?

Also, any word on the 7 PIN module you said you were developing? I'm super interested in that component!

yes, I used 250pf for all of them. The ultra high boost was too shrill for my liking, and the ultra high cut removed too much high frequency and was pretty unusable. by allow some more lower frequencies through and using a silver mica cap, the boost sounds smoother and less harsh. by cutting only the higher frequencies the high cut is not as boomy/woofy. everyone's guitars have tone controls on them, if you want your guitar to sound like its under water, just turn the tone all the way down.

the module is almost done. I have the boards mapped out just haven't put them into production.

-steve

[tdbassman]

+ 1 I'd be interested in one of those modules too.

[Denton]

I would be as well. I have a 73/74 VT-22 and a '72 V4B.

[Liquids]

One thing people forget in terms of the bright switch on/off, in the case that "off" might seem to dark (not a problem for me) and on seems to bright (definitely my opinion) is that the cap is completely jumping all series resistance, which can be significant for much of the clean volume range of most amps.

There is a viable in between--put a cap and a resistor in series. You can expiriment, but this means that high frequencies (set by the cap) may pass, but not as if at full volume compared to others. 100k should make a difference in series with the cap, 220k, maybe even 330k or 470k in series might make sense. It will depend on where you set the volume pot ususally and what your ears prefer, but it is worth trying if you are in there. With the V series, there are two channels, so you can make it so one channel has a cap with no series resistance and the other has some, and compare the two to a degree (no two pots have the same taper and apparent volume is never quite the same). Tweak to taste.

Again, worth a shot if you never use the bright/ultra high on an amp, or if the ultra high seems a little too edgy but off seems too dark, etc. (PS: there is also tone stack cap type and cap value mods you can do in conjunction with this to help get better control of the highs especially in these Ampegs).

[Hangman]

Circuit boards for the PEC tonestack replacement board have been ordered and I'm waiting on a few things (and a few free hours) to get some ready for purchase.

as soon as they are ready I will make a post and let you all know!

[itsonlyadam]

Awesome!! I'm eagerly anticipating their production! Put me down for 4 (I have 2 V-4's, a V-2, and a VT-22 that can use some quality tone stacks)!