is thing an amp or some kind of limiter

[cannikin]

:wink:

 

[cannikin]

6H6 is a dual diode -- used as Clipper Circuit??

"A type 6H6 dual diode tube is employed in a clipper circuit to clip both positive and negative audio peaks at a predetermined level to provide greater sideband power without overmodulation."

From Here

 

[Curtis]

I'm gonna take a stab and suggest the 6H6 is acting as a rectifier, converting the audio output of the 6V6 into DC which is then passed back to the 6SN7, varying it's bias and providing some degree of AGC. Sorta Federal AM864-ish. Probably not "clipping" as such.

 

[Larrchild]

Yeah, I agree. Single-ended though. Probably thumps like crazy.

 

[emrr]

I've had a few SE variants similar to this, and they didn't really thump so much as have tons of low freq distortion at all times. Put voice freq stuff through them and they are much cleaner, since there's no lows to freak out the circuit. Definitely more an effect type box.

 

[PRR]

> Probably thumps like crazy.

Not as bad as a Corgi in the dryer.

What Doug said.

The attack time is like 30ms, so the thump is like 5Hz. The 0.01+330K interstages low-cut at 60Hz. So it approaches 40dB thump-reduction, plus the output transformer's bass-cut. The AGC voltage may be near 100 times the threshold signal. So thump will generally be lower than signal. The release time is like 1 second so for many programs it won't be thumping constantly. Unless you really abuse it.

Note the limit-level control is "Volume speaker". The idea is that the loudspeaker will not exceed a set level. But it isn't really supposed to be limiting sweetly; it is too crude and has no GR indicator. I think it is a line-amp with accidental overload protection for driving a power amp rack. The short-bass interstages suggests it is speech-only, not say a movie theater house system.

 

[Larrchild]

Perhaps it's crying to go into a guitar amp effects loop!

Maybe with variable time constant.

 

[cannikin]

Well I have a couple....

 

[beatpoet]

How does it sound?

 

[PRR]

> I guess I'll gut it

That's disgusting.

It IS a line amp. It's got "a look".

For instant studio use, clip R101 2200r and feed mikes to the 300 input. There's +36dBm at 600 ohms true balanced floating output, or the Phones jack gives you an unbalanced signal that can be nominal +8 levels while the poor 6V6 is slapped silly trying to make +47dBm. Or if you don't like the 6V6 cliping, turn Vol Spk until the clip goes down.

It is really too beautiful to cut-up. They don't make em like this no more.

 

[emrr]

Try it first, why the hell are you listening to our theories instead of that box? Or sell sell sell. for real $$$$. Count that; it's 4 digits on purpose. Buy something else. I'm not kidding.

 

[Animatic]

Listen to PRR he's the man on this old tube stuff.

A little work and that things useful and way cool.

It is very close to a classic tube amp as is, a bit of tweaking
and it can be working and a conversation piece.
I love it what a cool box.

 

[tardishead]

Have you heard what this sounds like yet???

 

[tardishead]

bump

 

[beatpoet]

Ditto - how's it sound?

 

[cannikin]

Hey guys,

I don't have any time to test this unit and/or restore it for a long time

Sorry don't know