One-Bottle Preamp

[Brown Note]

The tubes I got were in GE boxes and 12AV7 was printed on both the box and the tube.

They took a few days to ship my order, so I'm sure you can call them and make sure you're getting what you want.

 

[NewYorkDave]

Mine shipped the next day... or at least they sent me a tracking number the next day! I'm not really worried 'cause Antique is a good company (although I haven't used them in something like ten years) and I don't have any particular reason to believe that they would make a substitution without asking. I just got a little concerned when you mentioned GE because it seems many of the 5965 bulk backs came from GE.

 

[CJ]

Whats up with the 6955?
No good?

 

[Kingston]

if you mean the 5965, some people here have found them noisier than the GE 12AV7, at least on this particular design.

Although in my case the some of the noise could be due to my "beginners layout syndrome".

But at least analag seems to swear by them on his stuff.

 

[skipwave]

[quote author="CJ"]Whats up with the 6955?[/quote]

6955? Problem is they don't exist. :razz:

My experience was that the 5965 worked in the One-Bottle design, but not as well. Tamas offered a good explanation back on page 13.

[quote author="tk@halmi"]Some computer tubes are now worshipped by Audiophiles like many red base RCA tubes.
Anyhow, the 12AV7 has two major characteristics that the 5965 comes short of:
1. The 12AV7 can handle about twice the plate current of the 5965
2. The plate resistance is of the 12AV7 is 30% less than the 5965.

In the case of Dave's preamp, the 5965 is not a good sub because the design relies on the 12AV7's driving capability. In other applications it might be just fine. It all depends on the circuit.

Tamas[/quote]

 

[Freddy G]

Hi Dave and all,
Well I've read this whole thread 3 times now and I'm ready to build 2 channels of NewYorkDave's 2 bottle pre.
Dave, you posted 2 different schematics for power supplies.
One that's called "onebottlepsu" and another called "smallpsu".
First, can I use the Hammond 261C6 power transformer?
Second, which power supply schem should I go with?
Third, how can I get 48V phantom power?
Best Regards,
Freddy G :sam:

 

[khstudio]

Is the second cap really 470uf... thats big?

Also, Did anyone ask about adding a direct input for bass?


Freddy G,
Probably need another transformer or one with extra taps for the Phantom. I've never done it but if the transformer you listed has a 50+ volt bias tap you could probably use that.


I have an external Phantom power box made by Rolls... does anyone see a problem with using this?

 

[NewYorkDave]

"SmallPSU" was just an illustration of what I used to power the prototype; it was designed around parts I had on hand and is not necessarily what I would recommend. In fact, I've removed the schematic to avoid further confusion. Use "onebottlepsu."

The Hammond 261C6 is fine to power two channels.

As for phantom, I don't recommend trying to derive it from the plate supply. A P48 (phantom) supply should be able to source up to 14mA per mic without smoking; and with a smaller power transformer, that's more current than you can "steal" from the plate winding without it becoming angry :wink:. Instead, I recommend a separate, small power transformer for the phantom supply.

24V and 25.2V transformers are readily available, and one of those with a fullwave voltage doubler would provide plenty of DC to regulate down to +48 for phantom. The transformer should be rated for 4X the amount of current the phantom supply needs to be able to source. Therefore, multiply the number of mics by .014, then multiply that by four, and there's the minimum current rating you need in Amps.

There's no problem with using an external phantom box. I haven't built phantom supplies into any of my homemade pres (yet), so I'll need to do the same if I want to use them with condensers.

As for a DI input: you'd want to take a look at "onebottleinputoutput.pdf" linked on page 10... except it's not there anymore! This is the second file of mine I've noticed missing today from groupdiy.twin-x.com. WTF?? Are files being deleted?

 

[Freddy G]

Thanks Dave,
Yeah, I noticed some links that are bad....would you e-mail that "onebottleinputoutput.pdf" to me?
Also, in your schematic of the one to two bottle mod there are 2 polarized caps that don't have a value marked down. What are they?
I'm really excited to build this, thanks so much for taking the time to help.
Regards,
Freddy G :sam:

 

[hodad]

A couple of quick questions:
What's the deal with the DS1 lamp in the power supply? What purpose does it serve? Where can I find one?

Can the vol. pot be 1/4 Watt?

Thanks
Tom

 

[NewYorkDave]

It dawned on me, after I posted that message, that I was indeed the one who nuked that PDF after I realized there was an error in the drawing for the 20dB pad. I meant to correct it but never got around to it. As for that other file that disappeared from Twin-X, that was definitely not me. But anyway...

Here's the "gist" of how to add a hi-Z input (instrument DI) and, if desired, a hi-Z output:

Schematic

You really don't need the hi-Z output unless you must have that extra 12dB, and you can be certain that the load connected to that output is never going to be less than 10K.

On the "Two-Bottle" mod, the B+ decoupling cap should be 10uF or greater (22uF is convenient) and the cathode bypass cap 47uF or greater. The B+ decoupling cap should be rated 350V or greater.

A 1/4W pot is fine for the gain control.

"DS" is just the designator my schematic drafting program uses for a lamp. It's just an on/off indicator, a pilot lamp. Any ol' 6V lamp (such as the popular #47) will do.

I think this answers everyone. I gotta go do some cooking now...

 

[khstudio]

Getting my 12av's tomorrow... is this project diyong ouy? I haven't really seen a lot of success stories but I'd love to hear some :green:

I got sidetracked on my PM1000 rack but the NYD-1BP is next. I will put it to the test & post back when done.

Kevin

 

[NewYorkDave]

diyong ouy?

Huh? Is that Vietnamese?

 

[khstudio]

:green: I laughed myself...

My damn keyboard is broke & drives me nuts.


Dying out.

OK, that works

I'm still crackin up

 

[NewYorkDave]

Dying out? I'm not sure it ever really took off. The only person here (besides me) who built a One-Bottle is Skipwave, and I believe his worked out pretty well. Kiira and Kingston built the two-bottle mod and both liked the sound but had some issues that may be layout-related. Consul's One-Bottle is still in progress, last I heard. Outside of that, I don't know of anyone else who's built one.

Projects for which there is no ready-made PCB never seem to catch on around here. I just don't see the fun in making a PCB for such a simple circuit when it's more enjoyable (and works just as well, and looks cooler) to wire it up the old-fashioned way.

 

[khstudio]

I'm on it :wink:

 

[Freddy G]

yeah Dave,
I'm all over it too...after just finishing my 5th point to point LA2a I'm confident that I've learned some valuable lessons. For my build of the NYD two bottle pre I'll be laying out the components using turret boards just to keep things neater than P-P and also because I'm going to use film caps wherever I can (20 uf= large physical size). I'm glad I don't have to etch PC boards....yuck! The only thing I have to decide is about in and out transformers.....I really like Lundahls, I use them on all my DIY however they are PC mount and I do want to stay away from that. I've been looking at cinemag for in and edcor for out (save me a pile of dough too!)
Cheers,
Freddy :sam:

 

[Kingston]

[quote author="NewYorkDave"]Kiira and Kingston built the two-bottle mod and both liked the sound but had some issues that may be layout-related. [/quote]

I think this sound is absolute spot on. I expected it to be a great all round tube tool, but out comes a luxury sheen fairy dust on anything it touches. NYD has been far too modest about the sound on this thread. :grin: With a well engineered and optimised design like this, I think it all comes down to quality caps and transformers (jensen 1:8 and OEP 4:1 on my unit).

My layout issues are pretty much sorted now, but I'm still working on perfecting it. I do wish I would've breadboarded this first, as I read in another thread even NYD himself was fighting layout gremlins with the 12AV7 (if I understood it correctly, even turning caps has surprising effects on things). I had no idea layout was *that* crucial part of everything. Physically, the more it looks like the schematic, the better.

Soon as I've finished, I'll post examples.

 

[khstudio]

Just got my 12av7's from Antique ES... they're ALL RCA's. That's killer :green:

Now I'm ready.

 

[Brown Note]

Outside of that, I don't know of anyone else who's built one.

I built the one-bottle, and I thought it sounded great. There were some noise issues, but my layout wasn't anything to write home about. I've since torn it apart, and I'm awaiting another power transformer for a second channel. After which I'll be putting together a 2-channel box with a more meticulous layout. I'll post pics when I come up with something worth showing off.

-ben