Tube Amp Archive

Well, in Niks defense, I didn't build the amp or buy it new, so I really didn't feel it was appropriate to bother the guy about 'mods and tweaks'..... so I bothered you guys! :D I did ask him stuff like when using the 1/2 power switch with an 8ohm speaker do I set the impedance at 4ohms? General stu...

I'm not aware of Nik's history here, but he sure is a responsive and nice guy to deal with, answering a few of my stupid 'read the manual' questions with a cheerful attitude. I tested my amp out with a 5k6 resistor to ground from the bass pot, and wow, really exactly the kind of scoop I was looking ...

Oh, sorry norburybrook!
Anyway, its not sorted yet, I was wondering about the midrange resistor value. Bigger = more of a scoop, or the other way around?

Nevermind, found the answer

''On the board there is a B+4 connection to a 22k/3w dropping resistor connected to 10uf/450v cap and to the 220k plate resistor. Yes that mid range resistor can be lower or increased to your desire.'' Thanks, thats the one I dropped to 10k and only got a marginal voltage increase? Also, can that dr...

I'm driving a 1x12 open back cab with a Fane Axiom alnico. Its a 103db speaker and sounds nice! Its funny, but my amp really sounds much cleaner than any other examples of a z-wreck circuit I've heard. Not sure whats going on with mine as I didn't build it, but it has a pretty pure clean tone up unt...

I realize all of that. However, the amp has a beautiful clean tone. I'm just trying to get the grit to come on a little later.
You guys, I'm a pro guitar player, I didn't build this amp. Its so close to being perfect for what I do, just asking for some suggestions other than ''buy a fender''.

Thanks, Hope I'm following. I changed the 22k/3w at the filter caps [b4] to 10k and there was no voltage increase, so I put the 22k back. There is a 22k/3w on the circuit board [also B4] that ties to v1. I changed that to 10k and the voltage went up to 170v but it seems a little bassier. If anything...

Pin 1 is empty. Pin 6 measures 159v

Thanks Mark, are you referring to the 27k/22k 3w resistors? What value would you recommend?

Well, it was still a little too grainy too early, so I put the 220k to ground back in and left the cap out. Thats much better in the clean department, but it really lost alot of volume. Might be loud enough still for this fall/winters club gigs though so I'll leave it this way. Any other suggestions...

Not sure, as my c-wreck has 5 filter caps [2-10uf/3-47uf] instead of 2+2, so the builder may have already upped the filtering. Its different than the z-wreck or rocket in that regard.
Photos prior to the cap/resistor removal.

Ok, pulled the 22uf and 220k to ground. Happy to report that it noticeably increased my clean headroom and tightened up the bass. Very happy with the results!
Thanks everybody for the suggestions!

Ok, thanks for that. Sorry for another 'newb' question, but just to be certain, are you referring to the 22uf V1 cap, or the 22uf v2 phase inverter cap? [PI right?]

Thanks Colossal..I have done the mod to my Rocket in the early days...I put in the bypass cap and I put in a 220k with a switch to ground for both the cap and the 220k> BUT, I still am confused as to how putting in the 220k/220k voltage divider, which will lessen the volts to the PI, will increase ...

It does appear to me that the resistor to ground would bleed off some signal or voltage, and removing it would increase the gain? Does it have some effect on stability? I'm here to learn something so please explain if you have a chance!
I will leave that split alone for the time being.