Tube Amp Preamp Duplication?

[TryingToDo613]

Hi all. I've just spent the majority of my two hour delay in the JetBlue terminal in ft. lauderdale listening to clips from
http://www.runoffgroove.com/
and I'm facinated with duplicating classic preamps. I do plan to build several of these on this site with Jfets but I'd also like to try them with tubes. I actually have three trannies specifically for tube pedals I bought a while back as a "I'll need these at some point".  Is there a rule of thumb for getting a usable output level from a tube preamp as a pedal? Are there projects in these boards anywhere of specific circuits? I have seen the McTube and Shaka but these aren't specifically amp circuits.  Those clips at runoffgroove btw are incredibly good. I strongly urge you to check them out. -ph

[petemoore]

For HV Tube stuff check out Ampage or tube sites, great stuff there.
 I think there are links to tube stuff in links too.
 If you have 12ax7's or tubes you want to use and power supply, the rest of the wiring is quite similar to any other 9v, 18v etc. gain or buffer, tone control etc. stage. Except the potentially lethal voltages and problems with oscillation due to layout or amount of gain, as I understand it anyway.
 The power supply part is what I would like to tackle next. I'm into steady work again and want to start into more tube stuff.
 Check out the first thread, Aron has B+supply [IIUC] transformers there.

[TryingToDo613]

I don't see how the voltages could be prohibitory. I have a V-twin and a blackfinger tube compressor in a pedal and there were no outside warnings, though I admit I havne't looked at either (we're in the middle of a move and they are packed) since I started looking at building these preamps. The trannies I got were from Allen amps I think and are specifically for HT and filiments on tube pedals. I didn't see that Aaron had any. Just did a big order from him on the parts page here. I've seen several firefly builds use toroid trannys but have yet to find a US source for them or really understand what is different and why about them, but they are supposed to be as quiet as a dead mouse, and they definately fit in a small package.  There is another thread here right now with an amp that uses them.  He apparently buys them by the thousand.

From what I've seen in researching the back posts on this board, many many people seem to be fascinated with duplicating tube sounds with transistors and jfets. I personally don't have an ear that can say that tube tone is far superior to silicon duplication of them. In fact I love my POD.  But I can say that there is an enormous cool beans factor with tube pedals. Very surprised not more back threads about this, especially where fairly exact duplication of some actual amp circuits has been done so well. -ph

[12afael]

I recently build a tube guitar preamp I take a couple of ENGL schematics and mix some parts. is a really versatil preamp cristal clean , crunch sounds 3 or 4 stage gain really a lot of gain.  
I put the ed rembold marshall speaker simulator so I can record direct to the soundcard. work better than my sansamp I think it`s more easy to get a good sound. and it cover the marshall, boggie sound .

[TryingToDo613]

So if I'm undestanding correctly, you just built the preamp for the amp and used it as a pedal, simple, nothing complicated. I guess I'll go try that. thanks. -ph

[fikri]

since tube preamp have a bigger impedance, i think you have to do some mods to bring it down a little bit, otherwise, you can have a huge output level. Becarefull, because it can ruin your amp especially tube amps !

[TryingToDo613]

Do you have any experience with the ratios we're dealing with? Would you have to use an OT of some type or could you do it with resistors in parralel, which I think would also bring it down? -ph

[12afael]

So if I'm undestanding correctly, you just built the preamp for the amp and used it as a pedal, simple, nothing complicated. I guess I'll go try that. thanks. -ph

well I not use it as pedal because is a little big . 2 12ax7 , two transformer for the supply , etc. I build it on a 19" rack.

since tube preamp have a bigger impedance, i think you have to do some mods to bring it down a little bit, otherwise, you can have a huge output level. Becarefull, because it can ruin your amp especially tube amps !

yes , the engl 530 preamp have a couple of stage with op amps. line out , speaker simulator , balanced out and a 1,5 watt power amp for headphones or speakers. but you could get out an all tube signal too.
I´m still working on the board of that circuit. the all tube signal out is the  loop send , it have a atenuator a couple of resistor in voltage divisor and a pot for master vol.

if you copy a preamp until the loop send you will have a friendly out.
I conect it to the power of my plexi amp and work well too. on the input work well too ,but too much controls and a 7 gain stages don`t work very well hehe. .

[TryingToDo613]

I think it's just going to be a trial and error for a while with it. Have a bunch of things to do first anyway, maybe more posts will pop up here or RG will write an article and make it all clear as day. Thanks for the info. -ph