small tube preamps - which one?

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gusfinley

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Hi,

I'm looking into getting a tube preamp. I see a few mallsingle channelunits around like the ART and the Behringer. What kind of tube preamps have you had experience with, or would you recommed? I have heard that some of them sound best with a lower gain tube than a 12ax7.

Are there any smaller preamps which run the tubes in normal operating mode and not in "starved plate / starved current" configuration.

I am aslo willing to build my own preamp, if you know where I can find a good schematic.

Thanks,

Gus
 
gusfinley said:
Hi,

I'm looking into getting a tube preamp. I see a few mallsingle channelunits around like the ART and the Behringer. What kind of tube preamps have you had experience with, or would you recommed? I have heard that some of them sound best with a lower gain tube than a 12ax7.

Are there any smaller preamps which run the tubes in normal operating mode and not in "starved plate / starved current" configuration.

I am aslo willing to build my own preamp, if you know where I can find a good schematic.

Thanks,
Gus
Click to expand...

Hey fellow Utah resident :)

Unfortunately, all the little preamps you mentioned are "starved plate" and in fact, the tube is not even in the gain stage.

If you feel you are able to built your own preamp, by all means go for it. There are a lot of designes out there. Please let us know what is your budget, which features you are looking for, and what are your electronic/soldering skillz? Then it is not a problem to find a right project for you. If something goes wrong and sometime you are in SLC, I can always help you to debug things.
 
The only inexpensive tube pre I know of that runs a decent amout of voltage through the tubes is the new electro harmonix 12AY7 mic pre.

I got one a couple of months back and I really like it but I don't have experience with high end tube pres so I can't say how it stacks up against the UA's, fearns etc.

I'd love to take on a project like a simple mic pre but I don't know the first thing about electronics. I'd like to take an evening class and at least learn some of the basics first.

I'll get 'round to it someday. :D
 
Where does the Studio Projects VTB-1 fall in this spectrum? .........starved plate, or is the tube actually in the gain structure?

Thanks,

Rick

Just asking since I've already got two of them. :o
 
WERNER 1 said:
Where does the Studio Projects VTB-1 fall in this spectrum? .........starved plate, or is the tube actually in the gain structure?

Thanks,

Rick

Just asking since I've already got two of them. :o
Click to expand...

Starved plate, but they are reportedly good preamps for the price.
 
Marik said:
If you feel you are able to built your own preamp, by all means go for it. There are a lot of designes out there. Please let us know what is your budget, which features you are looking for, and what are your electronic/soldering skillz? Then it is not a problem to find a right project for you. If something goes wrong and sometime you are in SLC, I can always help you to debug things.
Click to expand...

I shouldn't have much of a problem building my own. I'll just need a good schematic. I'm studying electrical engineering and I am doing a special study on Vacuum tube amplifiers at the moment. I've already complete a 5W SE guitar amplifier and I am working on a 50W plexi circuit. A microphone preamplifier would be another great addition to my "lab projects."

As far as budget goes, I don't see how it could cost more than around $100 to build a single channel preamp. I should be fairly simple.....

Please suggest some chematics for me to start from.....

Thanks
 
gusfinley said:
As far as budget goes, I don't see how it could cost more than around $100 to build a single channel preamp. I should be fairly simple.....

Please suggest some chematics for me to start from.....

Thanks
Click to expand...

For full plate voltage transformer-balanced tube amp, yeah it's gonna be in the $100 range for parts, not including the box. It's more economical to build a two-channel unit, since you've already built the PSU and bought the box.

Start by hanging out here:

http://www.prodigy-pro.com/forum/viewtopic.php?t=1277
 
Excuse me for my ignorance, but what does "starved plate" mean?
 
Masters Of War said:
Excuse me for my ignorance, but what does "starved plate" mean?
Click to expand...

It means the plate voltage is below design spec for the tube, generally the cutoff is about 100V (although full voltage might be 200 or 300V, and starved plate designs usually supply around 45V). This causes the tube to go into saturation at much lower gain levels than normal, which is the intent of the starved plate design: the quality of the resulting harmonic distortion is controversial.

Anyway, since the gain of the tube is limited before the distortion becomes objectionable (usually something like 20dB), starved plate design typically incorporate opamp gain stages as their primary source of gain. They are also usually devoid of input and output transformers, which are used in full voltage tube amps. The sonic quality of these transformers is considered an important component of the tube amp sound.

The price of these transformers, as well as the larger transformer and other PSU components is the reason that full voltage tube designs are much more expensive than starved plate designs.

Another explanation on the paia site:

http://www.paia.com/tubesnd.htm
 
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Pre-amps

I just picked up the Presonus BlueTube DP (Dual Path) 2 channel mic pre-amp. It goes for $199 and you can choose between various levels of solid state and tube gain. You can't beat it for the price and it sounds GREAT.
 
Sal4001 said:
I just picked up the Presonus BlueTube DP (Dual Path) 2 channel mic pre-amp. It goes for $199 and you can choose between various levels of solid state and tube gain. You can't beat it for the price and it sounds GREAT.
Click to expand...

how many different pre's do you own???? :confused:
 
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There's not much out there. Groove Tubes made (maybe still does) a single channel tube preamp (Model MP1) and a matching tube EQ (Model EQ1) that are "real" tube preamps. Ran off the same power supply for their older tube mics (MD1, MD2 etc). Very nice, although pretty "hi-fi" in terms of sound. Used they go for @$400 or so, sometimes more. Then there is the GT Brick which seems to go for @$399 street price. I haven't used one but people seem to like them (I do have a couple GT Dittos and if the Brick is similar, it should be quite nice). After that, you are looking at a Peavey VMP-2 with 2 channels for @$600-800 used. They are quite nice and clean up well if you swap out the Sovtek tubes for better tubes (there are a lot of tubes in that box - figure on replacing all 6 12AX7s). There's not really anything else that is a real tube preamp at that price level that I'm aware of. Sebatron would be the currently produced "low price" real tube amp and they appear to go for $890 list and $800 street for a single channel.

The GT MP1 is pretty rare, so if I was looking for an inexpensive real tube mic pre, I'd probably look at either a Brick or a VMP-2. IMHO, the starved plate designs aren't worth it if you want a tube preamp that is more (better) than an effects box.
 
In terms of non-starved plate, there is also the Peavey TMP-1, a piece that was not on the market long. It utilized a 12ax7 and a 12at7 at full voltage. They can be noisy when cranked and slightly brittle on the top end, but for some applications they are really quite nice. Peavey stupidly only gave them 24volt phantom power, so either use a phantom power box or run them on loud sources with dynamics.
 
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