IS there any OTL pre amps out there?

[djn]

I am thinking about building a pre amp but don't really need that much gain. I thought about a DHT pre amp but then started thinking about going OTL pre amp. I've never heard of one.....any help?

[Frank Berry]

Generally, preamps don't use output transformers. They use output coupling capacitors.
You could design a preamp without output coupling capacitors if you used bipolar voltages on the preamp. I'd be afraid of too much residual d.c. voltage on the output of the preamp as the tubes reach operating temperature and as they age. Readjustment of the bias would be necessary on a regular basis.
In general ... not a good idea. A tube failure could put a huge amount of d.c. on the output.

[DF96]

You have never heard of an OTL preamp because almost all preamps are OTL, so it doesn't need to be said.

[djn]

OK, here is where I am coming from knowledge wise. The last and only pre amp I had was a John Hogan Line Stage. "line stage" might be different than pre amp....I don't know. But the Hogan line stage has OTs so I assumed all pre amps had OTs.

Thanks for the clarification.

[atmasphere]

So- do you want to know how to set up a tube preamp with a direct-coupled output?

[djn]

Originally Posted by atmasphere

So- do you want to know how to set up a tube preamp with a direct-coupled output?

Why, yes I do. I was thinking OTL just to keep the signal path simple. Derect coupled sounds even cleaner.

[atmasphere]

Did you have anything in mind besides a direct-coupled output?

[dsavitsk]

Originally Posted by djn

Why, yes I do. I was thinking OTL just to keep the signal path simple. Derect coupled sounds even cleaner.

Try this: SYclotron Audio The Heretical Preamp

[djn]

Originally Posted by atmasphere

Did you have anything in mind besides a direct-coupled output?

Well, to be honest, I've been running my system (which I just sold off) with only a passive volume pot going into a Behringer 3400 then to three amps, each with a volume pot to balance the volume between drivers.

So, this whole preamp is new to me. Just before I got ride of everything, I put the Hogan line stage right in front of the 3400 and the system really came alive.

So in the new system I wanted to include a preamp/line stage.....if there is a difference.

I am building three amps at the moment. A 12HL7/GM70, a PP E-linar 807, and a Tim Mellow OTL.

I am also building a three way tube crossover.

My speakers are the big Heil on top, a large Tractrix horn with the TAD 4001 for mid, and a vented box with TD15M for midbass, and a pair of subs with Martin Logan Sub drivers.

I am using a passive volume pot/selector switch before the pre.

SO, I could use some advice as to what to include in the preamp.

[djn]

Originally Posted by dsavitsk

Try this: SYclotron Audio The Heretical Preamp

Interesting read. I think I need to print that one out and do some studing.