more headroom possible?

[loudthud]

Quit whining, get a scope. On second thought, you won't know how to use the scope so we'll have to put up with more whining. So, quit whining, go to Tech school.

Edit: Are you one of those who don't understand why the power tubes have to clip first ?

[Chuck H]

Quit whining, get a scope. On second thought, you won't know how to use the scope so we'll have to put up with more whining. So, quit whining, go to Tech school.

Edit: Are you one of those who don't understand why the power tubes have to clip first ?

Oh, c'mon. Daz is cool and he's just frustrated. He did put a lot of work into this project and he's done several and always found his way to the other end. And he clearly understands that the power tubes should clip first because that's the focus of his last inquiry. Don't we help everyone in any stage of the technical learning process? I agree he should get a scope though. It would have helped him throughout his entire journey.

I've seen a lot of "difficult" members here get called out for being uncooperative, but never daz before now.

[daz]

Well, they just have a different mindset than I do and don't understand why i don't think like them. I could write a long drawn out post as to exactly what my reasoning is, but why should that matter to anyone but me? I just posted to ask a question, not to be psychoanalyzed for my reasoning that some don't understand. The simple answer is i'm not you, u aren't me, there are lots of reasons behind my motivation but i'm not motivated to explain myself to everyone who doesn't understand. Questioning my motivation is

[Mick Bailey]

I used my Laney AOR30 in a band situation for many years and it was OK for small venues both clean(ish) and overdriven. It's a similar output stage topology to your own amp. What's the voltage on your PI plates?

Schematic here for comparison; https://schematicheaven.net/newamps/laney_aor30.pdf

[daz]

I used my Laney AOR30 in a band situation for many years and it was OK for small venues both clean(ish) and overdriven. It's a similar output stage topology to your own amp. What's the voltage on your PI plates?

Schematic here for comparison; https://schematicheaven.net/newamps/laney_aor30.pdf

About 230v on the PI. By the way, i got out those 6v6>el84 adapters i mentioned that i made years ago and checked the pinout to make sure all pins on the octals are to the correct pins on the el84 sockets. Then i removed the wire to the fixed bias and put a 130R and 50uf cap in parallel between ground and the 220k bias resistors on the grids and tried it with el84's. I get sound but it's super low even cranked. I didn't replace the 220k's with 470k's as i see on 18 watt schematics. Could that be why? I wouldn't think so. Second question...it's a 6.6k OT and i'm on the 4 ohm tap because it IS a 4 ohm speaker. Should i use a different tap or would it need to go the opposite direction so that at 4 ohms i'm out of luck? Not sure how that works.

[Helmholtz]

Cathode bias results in lower power output as you're losing voltage across the cathode resistor.
EL84s like an OT primary impedance of 8k.

I don't think insufficient grid drive with the 6V6s is your problem.

[Mick Bailey]

I'm not sure I follow your description - the paralleled resistor/cap goes between the EL84 cathodes and ground - why does it connect to the grids?

[daz]

I'm not sure I follow your description - the paralleled resistor/cap goes between the EL84 cathodes and ground - why does it connect to the grids?

It doesn't, it goes to the cathodes. What i meant is the 220k resistors at the grids of the power tubes should be 470k and the bias R/C goes to that junction. In any case that doesn't matter because i found the issue which was a loose wire in one of the adapters. I had to solder several that had come off in the years they were in a parts drawer getting banged around and i apparently didn't solder one well. In any case i got it working and i don't know how it will fare volume wise, but one tube is not getting hot so theres another issue i need to find. But even as is i think i prefer the 84's because they sound tighter and that was one thing i wasn't digging about the 6v6's. They seemed fuzzier in the lows. Anyways i gotta troubleshoot that cold tube and see if i can fix it so i can evaluate whether or not i want to permanently convert it, and if so i would convert to fixed bias too.

[daz]

Ok, found the issue with the tube and it now works fine and i definately like the tone much more than the 6V6. Volume? Hard to tell but while it seems about the same it's much tighter and clearer so i think it will cut better and thereby sound as loud at lower settings. Plus it's cathode biased so when i convert it i assume it should be even louder or even clearer/tighter? In any case i am going to convert it because it sounds great and even if i don't use it for band use I like it enough that i'll want to use it at home. So looking at the schematic, can anyone tell me what i would have to change in the bias circuit to get in range for el84s? Also, considering the 6.6k OT, what tap would work best now with el84's? I would be willing to find a decent deal on another speaker for the amp with the tone the way it is now and go for a higher SPL one to kill 2 birds.

[Helmholtz]

6.6k is already low for EL84s, squeezing out more power than good for the tubes.
Using higher impedance taps with your 4 Ohm speaker would even lower primary impedance.

[loudthud]

The problem could be the 1K screen resistors are too big for 6V6. Be done with it and shove some EL34s in there.

[glebert]

The problem could be the 1K screen resistors are too big for 6V6. Be done with it and shove some EL34s in there.

I think the PT he is using is only rated for 3A heater current, so it seems like EL-34s could overstress it.

[daz]

I think the PT he is using is only rated for 3A heater current, so it seems like EL-34s could overstress it.

it's a heyboer 18w PT. Anyways, i A/B'd the 6V6 and el84s and i definately like the 84s more. Even when i paralleled the 1k screens with 1k's to get 500R each it sounded the same. A bit cleaner yes, but it doesn't have the tightness and clarity of the 84's so i'm converting it. I have questions about that but i'll start a new thread so as to eliminate all the off topic stuff this one brought out.

But before i do that i have one question i need to ask before i bother only to find the conversion is not viable. That would be as i asked before, is the 6.6k OT ok for a pair of el84's with a 4 ohm speaker and if not how would i optimize it? What tap to use and with what ohm speaker, because as i said i'd be willing to buy a 8 or 16 ohm speaker if need be. As i said a few posts above, "I would be willing to find a decent deal on another speaker for the amp with the tone the way it is now and go for a higher SPL one to kill 2 birds. "

[loudthud]

I think the PT he is using is only rated for 3A heater current, so it seems like EL-34s could overstress it.

Minor detail. Why would anyone who doesn't own a scope care ? It won't blow up immediately.

Don't EL34s remind you of a creepy Victorian mansion with a few bats flying around ? WAHAHAHAHA !

[Helmholtz]

That would be as i asked before, is the 6.6k OT ok for a pair of el84's with a 4 ohm speaker and if not how would i optimize it? What tap to use and with what ohm speaker, because as i said i'd be willing to buy a 8 or 16 ohm speaker if need be. As i said a few posts above, ]"

See post #25.