Pics of My Home Brew Tube Bass Preamp

[lneal]

Here are a few bad pics of an all tube bass preamp that I designed and hand built myself called "Magnum". I have been reluctant to post anything much about it before now because I didn't feel it was "ready" until recently. Yes, I use it on every gig now and it has proven itself reliable. It has 6 audio tubes and 1 rectifier tube, is mostly transformer coupled (except for the tone section), input to output and weighs over 23 pounds! The "Gain" control is a 5 position sealed switch that selects taps on an attenuator transformer to control the input gain instead of the usual potentiometer. The input and output are push-pull and it has a transformer coupled DI output. The tone section is 3 band, tube driven by 6CG7 tubes and adds just enough grit to give it balls and can also be bypassed. The sound? Clean and natural with stunning clarity with the tone bypassed. Switch in the Tone section and it adds smooth, natural lows and highs and if I crank the Mid it can get as nasty as I want, but never peaky like those SS op amp things. The schematic will be forthcoming and one day I'll get the web site up with full details. I posted this to prove that you can have exactly what you want, no compromises, but you pretty much have to do it yourself.....

The 1st pic is the front panel; the 2nd shows the audio tubes, in order: 6SN7GT (Input), 6CG7 (DI Output), 6CG7 (Mid), 6CG7 (Low/High), 6SN7GT (Buffer/Driver), 5691 (Output)

[lneal]

First pic is the whole thing from the top and the second shows the vintage Triad A65J output tranny for the Stage out as well as the 5Y3GT rectifier tube. You can also see in the upper left from top the B+ tranny, Filament tranny and the filter chokes at the bottom. The 2 black capacitors are for the DC filament supply.

[Bass Mule]

That is awesome. I love how all your knobs go to 11. This one goes one louder.

[fdeck]

Purdy.

[Fat.Mike]

10 is just NOT enough. Long live the Tap! Awesome work!

[rodl2005]

Awesome.... great JOB!!!! espesh the '11' Must be extra special tones & extra loud with that! ;-)

[Bard2dbone]

NIce. So what do you use as your power amp?

[msquared]

Originally Posted by Bass Mule

That is awesome. I love how all your knobs go to 11. This one goes one louder.

And how could this thread go without mentioning the color? It's like, how much more black could this be? And the answer is none. None more black.

[jokerjkny]

hehehehe...

to "11"...

[Passinwind]

Beauty! How about some sound clips?

Where did you get the rack case BTW?

I'll be posting some pics of my new DIY tube line driver in the next week or two, hopefully. All the parts should be in by later this week.

[svtb15]

Originally Posted by lneal

First pic is the whole thing from the top and the second shows the vintage Triad A65J output tranny for the Stage out as well as the 5Y3GT rectifier tube. You can also see in the upper left from top the B+ tranny, Filament tranny and the filter chokes at the bottom. The 2 black capacitors are for the DC filament supply.

that looks like a high end piece of studio gear... if that does not sound Tubey.. nothing will...
very nice..

[Trevorus]

What's with the somewhat out of the ordinary tube compliment?

[okabass]

Oh, yeah. Huh.

Those Lundahl, Sowter and Hammond irons costs at least 20 times more than a "normal" modern IC-bass pre.

Never seen that kind of bass pre. Great.

However, two answeres.

You are using polypropylen Solen caps. Why the big blue electrolyte? Why all tube bases are not ceramic?

Triad xformer? I have about 20 JS (Jörgen Schou, DK) line irons. Interested?

[getz76]

That's pretty hot. I'd buy it without even listening to it (mostly due to the "11").

[markjazzbassist]

looks cool. how much?

[seanm]

Looks nice!

I noticed an XLR on the back, does it have a tube DI?

[seanm]

Originally Posted by Passinwind

Beauty! How about some sound clips?

Where did you get the rack case BTW?

I'll be posting some pics of my new DIY tube line driver in the next week or too, hopefully. All the parts should be in by later this week.

Could you post a link here when you do? I, for one, don't want to miss it.

[BartmanPDX]

WOW!!! For a preamp, that really looks "beefy." Looks like you didn't shortchange the transformers.



<Couldn't really think of another word than beefy.>

Nice work!

[lneal]

Thanks for the compliments, guys. I'm mighty proud of it.
To answer some questions:
I use a QSC 1700 power amp and yes I have drawn up plans for an all tube transformer coupled power amp.

As far as the look, I was going for that 1950's laboratory gear look, stark and badass.

The out of ordinary tube lineup comes from my dislike of the ubiquitous, non-linear 12A_7 junk, I wanted the input and output sections to be clean and clear, not distorted and colored, letting the tone section provide the warmth and goodness.

The electrolytics are for the B+ supply only and the Solens are in the signal path. There are also a few NOS Siemens plastic caps in there.

The DI gets a feed from the input stage off the Lundahl and is a totem-pole cathode follower driving a Sowter plate to line tranny.

The rack case is from Hammond.

I'm going to work and won't be able to reply anymore til tonight.

[broerevb]

Cool, very cool! Congratulations!