One-Bottle Preamp

[Nadege]

thanks guys :grin:

 

[Brown Note]

one bottle psu troubles...

i'm finishing up my two-channel one-bottle. both channels are working though far from perfectly. the main issue is my psu. i'm using the original psu schemo that dave published (the one you're not supposed to use) with a beefier transformer. it worked fine with my one-channel so why not 2? the problem:

as soon as i connect the B+ (outputting about 308vdc) to either or both of the preamps the B+ voltage drops to 238vdc. what am i missing?

ben

 

[NewYorkDave]

it worked fine with my one-channel so why not 2?

Because two channels draw twice the current of one, that's why. The transformer is only part of the equation. Apply some Ohm's law: if voltage drops when current draw is increased, that tells you... what?

(the one you're not supposed to use)

And that was for a good reason. Besides the issue of two channels vs. one, the first PSU schemo showed a circuit that was used only because it utilized a transformer I happened to have laying around, and I did make a comment to that effect. As a matter of fact, looking back in the thread, I'm reminded that I later removed the schematic because I didn't want it to become enshrined as "the" power supply for the One-Bottle.

So anyway, tell us about this power transformer of yours.

 

[Brown Note]

(the one you're not supposed to use)

looking back that may have come across as kind of flippant. i apologize. that was definitely not my intention. what i meant was "the one you shouldn't use but i'm using because i'm too broke to make another mouser order". i began work on this project shortly after you introduced it to the forum, and i had built the preliminary psu long before you posted the actual one-bottle psu. i chose to continue experimenting with this one for monetary reasons only.

Because two channels draw twice the current of one, that's why.

touche. the thought that that hadn't occured to me bothers me more than a little.

i promise to think these things through a little more before posting in the future.

ben

 

[Brown Note]

Success! I used it on a session last week. Here we have 2 channels of 'One-Bottle' built into an old rackmount pc case. I'm using Dukane 3A55 trafos in the inputs and Edcors on the outputs. I'll probably upgrade the input trafos in the near future. Thanks for the cool design, Dave!

Pics:

http://twin-x.com/groupdiy/displayimage.php?album=59&pos=0
http://twin-x.com/groupdiy/displayimage.php?album=59&pos=1
http://twin-x.com/groupdiy/displayimage.php?album=59&pos=2

 

[NewYorkDave]

Cool.
What are the toggles on the front panel? Pads and... polarity? And is that a 1/4" jack I see on the front as well? Are those WSM10K/600s on the outputs? I can't quite make out the details.

 

[Brown Note]

he he...the front panel will remain unlableled until i have a way to do it that looks good. the toggles are for pad and phantom (48v is from an external supply). the quarter inch is for di. wsm10k/600 on the outputs.

 

[Nadege]

HI

is this transformer : Hammond 370 AX good for this project?

http://www.hammondmfg.com/300series.htm


Could you checked my wiring?I'm in a 240V country
http://www.hammondmfg.com/300sch.pdf

I put for the primary the brown and black together, and feed the transfo with the blue and white

For the secondary the two red are going to the diode bridge,

the two greeen to the heater section

I forget all the other cable?

is it right?

thanks for your help

Nadege

 

[Nadege]

Any suggestion?

 

[NewYorkDave]

For that particular transformer, with its 240-0-240V secondary, you would use a full-wave rectifier (two diodes), not a bridge, and RED/YEL (the high-voltage secondary centertap) would be connected to circuit ground. Actually, I'd consider using a tube rectifier since the 5V rectifier winding is already there.

Other than that, the wiring as you describe it is correct. That transformer can power up to three One-Bottle preamps.

 

[Nadege]

Thanks for your answer NY Dave. :thumb:

how should I mod the original PSU circuit you presented here? And I didn't really understand the tube rectifier story ??

As you can see I'm not an expert in transformer wiring.... :roll:

 

[Nadege]

is this correct ?

http://twin-x.com/groupdiy/displayimage.php?album=random&cat=10050&pos=-311

I may not have understand all what you said, but does it seems correct ?

Sorry for my (really) bad paint drawing

Nadege

 

[Nadege]

Any idea? :sad:

 

[peterc]

According to these links is looks good, connect the centre tap to B-, though.

http://www.ibiblio.org/obp/electricCircuits/Semi/SEMI_3.html#xtocid182273
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/rectifiers.html
http://en.wikipedia.org/wiki/Rectifier

Peter

 

[Nadege]

Thanks Peter for this "really" quick answer :thumb:

Soon, my finished and (finger crossed) working preamp... :wink:

 

[Nadege]

Hello,

here is my layout for the onebottle project's PSU using the transformer mentionned a few post ago in this thread.

http://www.twin-x.com/groupdiy/displayimage.php?album=random&cat=10050&pos=-334

What do you think ?

Thanks for your help :thumb:

 

[NewYorkDave]

That looks good. Remember to use 10K/22uF (or higher) decoupling at each channel, too. And you might have to reduce the value of the 4.7K resistor in the PSU if you're running multiple channels.

 

[Nadege]

Whaaaoo

that's a quick answer... :shock:

Where should I put the ecoupling cap, Isn't it in your original schematic?

 

[NewYorkDave]

Yes, it's R13 and C6 on the original schematic. It should go right at the preamp.

 

[rotation]

Hi!
I'm trying to find out how to connect mic/line/di inputs to One Bottle. Is it ok if di goes directly to the first (half) tube, line through pad into transformer and mic as it is? I only need short description. I will go into details later.
Miha