NewYorkDave

One-Bottle Preamp
« on: April 05, 2005, 11:16:26 PM »
Here's a little something I whipped up during some lunch breaks and other stolen moments at work. This is based on a design idea that I presented originally over on the Drawing Board.





JustinS

One-Bottle Preamp
« Reply #1 on: April 05, 2005, 11:26:01 PM »
Hey Dave,

Looking good.  I love the blue, reminds me of some old Pye pres and compressors I guy I know has.  I think I need to build some of these!!  What are you using for the power supply??

Justin.

rafafredd

One-Bottle Preamp
« Reply #2 on: April 05, 2005, 11:39:53 PM »
Looks awesome, dave! Show us a pic of your point-to-point work, come on...

soundguy

One-Bottle Preamp
« Reply #3 on: April 05, 2005, 11:43:10 PM »
thats a nifty little box dave!

Did you design for maximum clarity or color?  Looking forward to hearing that sometime!

dave

chips are good with dip...

chrissugar

One-Bottle Preamp
« Reply #4 on: April 06, 2005, 01:38:32 AM »
Very nice little boxes. They  remind me of those sweet guitar tube amps made by ZVEX.
http://zvexamps.com/

chrissugar
Christian Mike Sugar
        CMS-LAB

pstamler

One-Bottle Preamp
« Reply #5 on: April 06, 2005, 02:10:59 AM »
Very nice design and beautiful build!

A thought and a question: Dave mentions the possibility of using a 4:1 output transformer. That would make the maximum output before clipping +18dBu (high gain) to +15dBu (low gain). I'd rather not; if balanced output is needed, I'd forego the 600-ohm drive and go with a 1:1 xformer.

The question: Dave, have you tried hanging a 500k resistor across the input xformer's secondary in addition to the zobel? And if so, how did it affect the response?

Peace,
Paul

clintrubber

One-Bottle Preamp
« Reply #6 on: April 06, 2005, 04:39:55 AM »
Nice boxes indeed !

Have done a quick look around for an European equivalent of the 12AV7 but didn't found anything yet in ECC/PCC/...-land. Different heating-requirements wouldn't be a problem. Anybody knows ?

Thanks,

  Peter

PS
This is for your ribbon, right ? Any testdriving with that or other mics yet ?
Is the 56dB gain enough for the ribbon ? Stop, enough question marks. :wink:

gyraf

One-Bottle Preamp
« Reply #7 on: April 06, 2005, 04:51:24 AM »
There's no direct european sub for the 12AV7.

Maybe an ECC99 would do..?

Jakob E.
..note to self: don't let Harman run your company..

mikka

One-Bottle Preamp
« Reply #8 on: April 06, 2005, 04:58:14 AM »
Massive Edit:  Got my 12AV7 mixed up with my 12AZ7.  Sorry if I caused confusion. :oops:

clintrubber

One-Bottle Preamp
« Reply #9 on: April 06, 2005, 05:06:15 AM »
Thanks for the suggestions, I'll look a bit around at http://frank.pocnet.net and see what it gives.

And just curious, which input-TX (brand/type) did you use NYDave ?

Regards,

  Peter


VacuumVoodoo

One-Bottle Preamp
« Reply #10 on: April 06, 2005, 05:30:19 AM »
Nice work, proves again that less is more.  :cool:

Alex
Alex Niemand
_____________________________________
Life's a party but you get invited only once...
Tubewonder amps
"L

rafafredd

One-Bottle Preamp
« Reply #11 on: April 06, 2005, 10:06:13 AM »
What do you think about this list as subs?

12AV7
6414
5965
6829
7062
E180CC

Found it here:

http://www.artsandmedia.com/5965.html

clintrubber

One-Bottle Preamp
« Reply #12 on: April 06, 2005, 10:28:06 AM »
Quote
What do you think about this list as subs?


Thanks Rafael, that broadens the options. :thumb:

Regards,

  Peter

kent

One-Bottle Preamp
« Reply #13 on: April 06, 2005, 11:00:11 AM »
Is Dave not cool?  

Wow, I've been away so long I forget about the juicy stuff you guys come up with.

cheers,
kent
I don't really know what I'm playing.  It's just a bunch of notes.

fum

One-Bottle Preamp
« Reply #14 on: April 06, 2005, 11:54:19 AM »
Dave,

This looks really sweet!

I'd like to thank you again for all you contribute to the forum.  This mere DIY mortal (the still learning kind) appreciates your straight forward, damn useful designs.

Regards

ju

alk509

One-Bottle Preamp
« Reply #15 on: April 06, 2005, 01:34:34 PM »
That thing is a f**king beauty!!!! Nice job, Dave! :thumb:

Peace,
Al.

Lest laziness get the best of you!

peterc

One-Bottle Preamp
« Reply #16 on: April 06, 2005, 02:05:31 PM »
Looking forward to trying one of these..

Well done Dave & thanks

Peter
If opportunity doesn't knock, build a door.

One-Bottle Preamp
« Reply #17 on: April 06, 2005, 03:00:21 PM »
That's a tits little package.  Very nice work and many thanks.   :thumb:

NewYorkDave

One-Bottle Preamp
« Reply #18 on: April 06, 2005, 03:52:17 PM »
Thanks for the kind remarks, guys. I'll try to answer some questions...

Quote
Show us a pic of your point-to-point work


I built these into some little 2.25" x 4" Bud boxes I had laying around. If I had to do again, I would have used an enclosure about 1.5 times the size. Because of the small space, the internal layout is cramped and not up to my usual standards of neatness... so I didn't take a picture of the innards.

Quote
Did you design for maximum clarity or color?


I was aiming for most linear amplification within the limits of a one-bottle design with the particular tube, range of gain and operating voltages and currents I chose. Since it's a transformer-coupled tube circuit running with a relatively small amount of feedback--between 18dB and 36dB of feedback depending on gain setting--I figured the "color" would take care of itself.

Quote
have you tried hanging a 500k resistor across the input xformer's secondary in addition to the zobel? And if so, how did it affect the response?


Yeah... All it did was introduce about a dB of loss across the band
 :wink:  I found that this transformer performed well with secondary unloaded. This particular transformer (UTC O-11, connected as 200:50K) dates from the time  when input xfmrs were usually run into unloaded grids. A more "modern" transformer might (or might not) do better with a resistive load on the secondary.

The Zobel tames a broad ~3dB rise centered around 16kHz. (The rise is correctly predicted by the curve on the UTC datasheet). Instead of trying to flatten out the rise completely, I compensated just enough to bring it down to 1dB, to keep my in-band response within the +/- 1dB spec. After compensation, 1kHz squarewave response looked very good, nice and square with only a slight overshoot. I didn't go for a "perfect" flat leading corner; I didn't want to clobber the high end.

Quote
equivalent of the 12AV7


Resources on the web suggest that types 5965, 7062 and E180CC are equivalent or at least close. Since those tubes were intended primarily for on/off service in computers, though, I would be prepared to sort for noise.

Quote
What are you using for the power supply??


Any well-filtered 300V supply capable of 7mA or more will do. Here's what I put together--it's pictured next to the preamp. The parts choices were driven mostly by what I happened to have laying around.
 


12.6VAC is NOT the best choice for the heater supply, however. 6.3VAC or DC, or 12.6VDC, would give lower noise with the 12A- family of tubes. I'll probably end up using this preamp with a DC heater supply most of the time. I didn't go with DC heaters on the little PSU because I wasn't sure if the transformer could handle the extra load of the rectification/filtering/regulation and I was too lazy to calculate it. :wink: The heater winding is rated to 300mA, and the 12AV7 draws 225mA.

nacho459

One-Bottle Preamp
« Reply #19 on: April 06, 2005, 04:20:14 PM »
Dave, This makes me rekindle my ideas of building a tube console, or at least a new front end for my old one. :guinness:


 

Related Topics

  Subject / Started by Replies Last post
7 Replies
7214 Views
Last post July 25, 2006, 12:15:56 AM
by shabtek
75 Replies
29384 Views
Last post October 06, 2012, 07:27:11 PM
by audiophreak
49 Replies
19685 Views
Last post July 19, 2010, 04:40:27 AM
by ilfungo
14 Replies
4467 Views
Last post February 28, 2009, 02:37:29 AM
by philsmuse