Is there a SE 6L6 Wreck out there?

[ncusack]

I have a couple transformers I'm thinking of re-tasking.

PT - Hammond 270EX 275-0-275
OT - Hammond 125ESE 15W

I've seen a few SE threads around about low wattage wrecks but from what i've seen they all used el84's. I have a few spare 6L6 tube that need a home so id like to match something up here.

One thread I found that might be fun was sliberty's Mini Wreck and I was wondering if that could be adapted for the octal tube. the thread can be found here

https://tubeamparchive.com/viewtopic.ph ... mini+wreck

I was also wondering if you could use the spare triode as a parallel first stage or if that might be overkill.

Any suggestions here would be greatly appreciated.

Cheers

Neill

[JamesHealey]

sure that would work, don't forget to make a fake phase inverter.

No reason you can't use a 6L6 for a SE wreck.

[Zippy]

sure that would work, don't forget to make a fake phase inverter.

I've seen that suggested several times now but don't understand the "How?" and "Why?" of it.

Do you tie the two sides together or what???

(Hmm, I guess the only "?" I've left out are Who? and When?)

[JamesHealey]

litterally build a full PI and only take one tap from one side of the phase splitter to the power tube.

that would be the only way to get that true interaction I guess.

[Zippy]

"Interaction"?

Is the issue the same if one is building a Rocket (with cathode follower) vs an Express/Liverpool?

Thanks.

[RJ Guitars]

litterally build a full PI and only take one tap from one side of the phase splitter to the power tube.

that would be the only way to get that true interaction I guess.

That sounds like it would be fundamentally the same as removing one power tube... do I understand that correctly?

rj

[paulster]

Except that your bias point would be completely wrong with one tube pulled, and the OT wouldn't like the DC offset sat on it for long, but otherwise yes!

[Cliff Schecht]

I think Darin builds what is essentially a SE Express. IIRC it's parallel EL34's instead of PP.

[dartanion]

I think Darin builds what is essentially a SE Express. IIRC it's parallel EL34's instead of PP.

Indeed I do. It's called the Absinthe. 35W SE OT and can take most all popular octal output tubes. It uses the full PI but feeding the outputs from one side.

Alternatively, you can do what I call the Harmonics control which Mark Durham (RIP brother) used in his Vajra 18W amp. It is kind of like half a PPIMV, which cuts off signal to one tube while both tubes stay in the circuit, thus not OT impedance or core issues.

[paulster]

Alternatively, you can do what I call the Harmonics control which Mark Durham (RIP brother) used in his Vajra 18W amp. It is kind of like half a PPIMV, which cuts off signal to one tube while both tubes stay in the circuit, thus not OT impedance or core issues.

That'll be the same PP/SE control that Randall Smith subsequently went and patented.

Another one of his great inventions, except this one he stole from the grave...

But that's an aside. It's a really neat idea.

[RJ Guitars]

sure that would work, don't forget to make a fake phase inverter.

I've seen that suggested several times now but don't understand the "How?" and "Why?" of it.

Do you tie the two sides together or what???

(Hmm, I guess the only "?" I've left out are Who? and When?)

So what happens if you tie the two sides together? Do they cancel each other... something about that seems believable but still wrong.

rj

[JamesHealey]

yeah you'd get frequency cancelation, not true silence of course because the sides of the wave form are slightly asymetrical.

In short it would sound like one big horrific fart coming through your speakers.


Bit like a Matchless style crossline MV on a really really low setting.

[ncusack]

Looks like I've sparked a bit of discussion with this one.

I understand how the "fake PI" would work here im just curious how important it would be to a single ended design.

Zippy asked earlier about the rocket with the cathode follower and if that would need a PI and i would like to know this as well.

I've seen other mention of the fake PI as a bootstrapped PI on the ax84 site. I know the gain structure throughout the trainwreck amps plays a large part in how they achieve the sensitivity they have. Mainly the way they can clean up with a twist of your guitar volume knob. I just wonder if the PI would really be needed for the single ended idea.

If its a matter of gain could it be made up in the front end by paralleling V1 or does the PI make all the difference here?

[dartanion]

I would say the fake PI is making a driver stage to mimic the PI, thus a single triode and not the full PI.

[paulster]

The long-tailed PI is also a gain stage, not a particularly high gain stage, but a gain stage nonetheless. That's why it's important to include it or something equivalent even in a single-ended design.