Primary Imp Mismatch

[Reeltarded]

Is there a technical way to negate the near 20% mismatch between 1k7 and 1k4 OT?

I will be starving the amp some, I run low voltages, and I was thinking simply mismatching the load up 100% would run it a bit colder anyhow. (Amp set @ 4 hoopties with an 8 hooptie load, usually variaced about 10% above the lights going out)

4 EL34s with a '69 Major rebuilt with a 100wt PT, and taped off UL taps. Whole thing wired as any typical mid-69 100wt otherwise. In my mind, the high rating on the OT will get me a little more squat than a basic 100.

Anyone have a better idea?

Discuss.

[selloutrr]

I'm not sure you would gain any benefit from attempting to remove the missmatch will all the other "theoretically negative things" you are doing to the circuit.

What is it you are actually trying to achive as an end result?

[rdjones]

Increasing NFB and/or using the ultralinear taps should have a similar effect to lowering the impedance.
Try reconnecting the UL and use larger (1k?) resistors on each screen, and increase NFB by your calculated 20%.
All bets are off with such low voltages, I suspect.

reddog

[Gaz]

As an aside, I'd love to know how it sounds with the UL taps hooked up an no NFB - always wanted to try that with a Marshall circuit.

[Reeltarded]

The outcome is a 100 watt amp I can tinker with. I don't need more working Majors. I was hoping that the overspec OT would just do a little something extra to the tone of a common 69 Super schematic.

Forget the voltage deal. That's a knob outside of the circuit.

EL34s look like broomsticks on the flight deck of a super-carrier. Totally silly. This thing is going to end up being my favorite amp, bet ya.

I don't want the UL hooked up. I WANT it to be an over spec OT in a 100wtr. I just thought I'd ask before I bake the cake.

If you have any other thoughts, I am all ears, which looks really odd but I do contract work for SETI.. HOLD ON! I hear beeping from Beta Sagittarius..

[selloutrr]

This reminds me of the http://mojaveampworks.com/amplifiers/dirty-boy/
They are made in Apple Valley, CA a few hours from my house. It's a neat amp not my go to amp.

The problem with the 100watt output or more amps. They require way to much volume to sing. Even in the studio a 100 watts knobs maxed is hard to isolate. Most start to open up , sing , and bloom around "7".. most players never turn up past 4, even live with a drummer. FIW I'd seriously consider adding a switch to cut the output power of the tubes.

[Lonely Raven]

I would love to see some photos of your amp-room sellout.

[Reeltarded]

I am not afraid of the volume knob on a Super.

Where are you, Volu Man!? I'm back in the day, when things didn't suck, and you couldn't help being moved by the music. The land before the end of rock, which is so totally effing over that the history books are just cut and paste from an article on harmony central.

I am not afraid of the volume knob on a Major, I just like the squatting gain of a Super *ummph* much better.

[Zippy]

I will be starving the amp some, I run low voltages, and I was thinking simply mismatching the load up 100% would run it a bit colder anyhow. (Amp set @ 4 hoopties with an 8 hooptie load, usually variaced about 10% above the lights going out)

Discuss.

I'm curious regarding your actual voltage (not knowing at what voltage your lights go out): What is the heater voltage? How low can that go and still work "correctly"?

[Reeltarded]

I dunno on this amp yet. Some of my smaller amps still make sounds in the 40vac range, and most of my larger amps start falling out in the 60-70vac range. Prolly just below 70 like the other Supers. They still make sound lower, just splatty, you could loud whisper over 'em. Same for a straight Major, basically. I just turn the knob til it sounds right. No idea what the internal voltages are, and my supply is a tad bit high, locally.

When you guys tear down amps, what heat range are you using to desolder?

[tubeswell]

Is there a technical way to negate the near 20% mismatch between 1k7 and 1k4 OT?

1k4 to 1k7 is not much of a mismatch.

For the purposes of a geetar tube amp, 1k4 = 1k7

[selloutrr]

I would love to see some photos of your amp-room sellout.

I'll take some pics when I get back Saturday. Want to come over and help me take them out of the ATA cases?

[rdjones]

Want to come over and help me take them out of the ATA cases?

Does anyone use lightweight fibre cases any more ?
Surely something going to a studio in town doesn't need to be flight worthy, protection for pricey gear notwithstanding.

rd

[selloutrr]

I've never used the fiber board cases. I grew up in the northwest with heavy rain and constant moisture. I'm not sure how well they would hold up along with the weight of the amp it seemed like a gamble.. Now I live in the desert which causes things to dry out and crack. Both I'd like to avoid. I've looked into fiberglass but they are not as easy to stack or buy in custom sizes. I don't often ship out amps, and I see your point for short distance, I use them for storage and dust control. With everything in a sturdy case it makes it possible to stack, ship, or tour without the need to locate a flight worthy case.
I take the do it right the first time aproach and I really like recessed handles.

[Reeltarded]

1k4 to 1k7 is not much of a mismatch.

For the purposes of a geetar tube amp, 1k4 = 1k7

Helpful! I'm a worried mind, thank you!