ToneMerc wrote:SB, the MCI transformer that I used for my 5B6 build was supposedly 350@117V, but actually was 403VAC unloaded at 124V mains, which was about 30 volts too high for 124. However, once it was loaded the voltages dropped right in range to the target circuit.
I rarely use an off the shelf power transformer anymore.
TM
Yes! This illustrates my problem, as loading does not bring it down for me.
What sort of transformer would you recommend to get my plates down to ~430? 720CT 200mA apparently is not working for me, though it's "spec".
In itself there's nothing with those 325-0-325 specs perse'. If I make some assumptions that it's 5% high @122 and biased like these amps typically are, you should have about 460 volts on the plates.
The real issue is the differences across manufacturers in how they reference loading.I have been using one manufacturer for over 4 yrs. and I like them because they are generally consistent in results with rated specs that I give them. For me it's a piece of mind and one less thing I have to worry about.
I dont think all manufacturers are consistent though. For example, no Tweed Bassman PT thats 350@120, 200mA should put well over 500V on the plates with GZ34 rectifer in a Dumble circuit.
Nevertheless, you need to put some closure here. I would not toss another PT at this project, but do you now want 430 volts on the plates?
Indeed, I need to implement some closure here. As I figure we all know, it's difficult to be out of control, in a field where so much of it is controllable. That's really what's fucking with my head. Sure , I can bump up the string for preamp voltages, or zener it, but ya know..
Nonetheless, yes! I would like 430 by way of a properly specd transformer...for the next project, of course.
Thanks John.
I'm revisiting this amp with a better attitude after a break from it
Concerning dropping voltages, what is the effect of leaving the plates high, and dropping the rest of the amp down to specs via dropping string, versus dropping everything, including the plates, down to spec?
Disregarding the ultimate power output, IMO, varying the output tube voltage changes the tone to less degree than a change in the preamp voltage. IF your output tubes are in a safe operating range and biased accordingly, I would adjust the preamp filter string accordingly to bring the preamp voltage inline.
Ok, now I've got 6k8,18k,4k7 string and voltages are
V1 212.218
V2 198 206
V3 307 312
plates 475
This is a nice drop for the preamp from what I had, and the OD is less harsh, but it still sounds like a fizz fuzz box. Just not musically pleasing to my ear. Cleans sound great. Any tips on smoothing this out?
I've got .1 outputs so I'll drop those. It has so much bass(too much) with the bass pot ccw lugs together, but without it it's very thin. Either way I have to crank the bass down or it farts. I can go either way with the mid cap. 3k3 on 6L6 grids. Pre-OD network installed. 100k OD pots. I burned up my 100k trimmer so I just have 47k split right now. FB on V1 implemented, as well.
Truth be told I'd like to get it close to the vid of Nicky Moroch & Dumble 183. I'm hoping I can get close, as the d'lite is really pretty close to 183 in "rock" mode, with 4xEL34 of course instead of my 2x6L6... I think
Smokebreak wrote:
Truth be told I'd like to get it close to the vid of Nicky Moroch & Dumble 183. I'm hoping I can get close, as the d'lite is really pretty close to 183 in "rock" mode, with 4xEL34 of course instead of my 2x6L6... I think
It the small stuff that makes the circuits. For example both 102 and 183 are both high plate skyliners, yet they are different. A d'lite is nowhere near 183, look for the differences.
I shouldn't have made such a gross generalization. What I assumed were subtle differences are indeed not.
I put in the 183 stack(granted, maintaining the D'lite stack lift, not the 22M shorts) and things are already getting better. Now the clean channel has a really nice mild breakup, for me, when pushed. I'm going to carry on with 183 specs, as much as possible here.
