New preamps?

[Mistertaz]

Hi!

There was some talk of new Bottlehead preamp designs... What's happening with them? Is a new Foreplay in the works?

Taz.

[Doc B.]

We're working on something. It's not finalized yet.

[Chris]

A directly heated triode otl preamp would be spectacular.... in the future someday....

[Doc B.]

That is one of the things we are working on. I am in the throes of finishing the Smack assembly manual at the moment -

"Cut and strip back 1/4" (6mm) a 3/4" (19mm) red Teflon wire and attach one end to terminal 15L, do not solder yet"...AAUUUUUGGGHHHH! I'll sign your f***ing confession! Just make the assembly instructions stop!

When we have that wrapped up we will start working on the DHT version of the IDHT POC prototype preamp we have had working for a few months now. Might try to have it done for the meet on the 19th.

[Paul Joppa]

n.b. POC is Proof Of Concept, not what you think it is...  :^)

[Mistertaz]

Is it going to be an affordable Foreplay replacement, or a high end (ie. expensive) preamp?

[xcortes]

And the I

[Grainger49]

n.b. POC is Proof Of Concept, not what you think it is...  :^)

Back in the 70's it was the Infinity POS.

Xavier, I think it is "indirect."

[Paul Joppa]

Is it going to be an affordable Foreplay replacement, or a high end (ie. expensive) preamp?

Our latest thinking has been that our entry-level amps (S.E.X. and Stereomour) are integrated and do not need a preamp, so we're thinking something to match Eros and Paramount. But we're looking for a really high end product as well. Eros is the "trickle down" technology from the high end Repro tape preamp, so a similar path is not out of the question.

In fact, nothing is out of the question until we finish trying out different concepts. At one point I was investigating a very low cost preamp, between Foreplay and Quickie. It and many others were never tested, but we have built and listened to 4 or 5 quite different designs so far.

[Doc B.]

Is it going to be an affordable Foreplay replacement, or a high end (ie. expensive) preamp?

Yes. ;^)>

[Chris]

my own humble opinion..... with careful matching to the amp, which, of course, you guys will do, I can't think of a BETTER preamp than a DHT OTL pre...... that should be as "high end" as it can get and a brilliant partner for the premium BH gear.... ok exciting news!! thank you D & P...

[Paul Joppa]

...I can't think of a BETTER preamp than a DHT OTL pre......

I could not pass up remarking on this post. Obviously we agree in principle, or we would not be experimenting with it (!)  I have a couple examples of the difficult boundary between principle and practice though.

1) A DHT preamp means a really quiet filament power. There is no known theoretical reason why DC filament power should have any sonic problems, but it is widely accepted that it does unless it is done really really carefully. Our previous designs were quiet enough for power output tubes, but can't possibly cut it for a serious preamp - there will have to be some development work!

2) You want a DHT OTL pre? Quickie is a DHT OTL pre. And you can buy a hundred of them for the price of a commercial high-end preamp. One hundred! (Batteries not included.)  OK, it's really a triode-wired pentode. For ten grand, I'll make you a version that uses a Type 31 real triode. I'll even supply batteries!

[Dr. Toobz]

With the PJCSS and more expensive capacitors in the cathode bypass and coupling positions, the Quickie is already a pretty darn good DHT preamp. A really quiet, higher voltage power supply, stepped attenuators, a metal plate, a rotary selector switch and extra set of input jacks, and some way of floating the tube sockets on the plate (to reduce micophonics) would be a nice upgrade kit. This still would probably cost less than the IDHT Foreplay III.

Of course, give me a 01A, 76, 10Y, or 30 preamp (maybe even battery operated, off lantern batteries, for some of the 5V or 2V tubes?) and then I'm in!

[Doc B.]

Part of my design requirement is that the tube should have a very low output impedance to get the bass performance optimal, like 500 ohms or less. The 3S4 is of a little higher output impedance than my design goal, but it does indeed make a rockin' little DHT preamp. We have a high school intern working with us these days, who just started building a Quickie for his final presentation. I think he's going to blow some minds at his school.

[coca]

Re Dr Toobz's concern about floating the tube socket in a way so as to really decrease tube microphonics, this can easily be done by mounthing the sockets on a piece of 1/4"  teflon. This works very well.

Bernie.