TUBE STAR - 12V-50V tube overdrive

Renegadrian · March 15, 2009, 10:17:58 AM

Tweaked the circuit a little more...I think I will experiment a little more with the 12AT7, it made me forget about the AU7...
Lotsa more gain!!! And Hell knows how much I am after HIGH GAIN devices...Man, this Star SCREAMS!!!

I tried the conventional "GAIN" pot wiring (which actually is a volume control between the two stages...) but liked the variable resistance on the first cathode better...So I went with it...

snap · March 15, 2009, 01:25:18 PM

crackle OK ?

kurtlives · March 15, 2009, 08:40:25 PM

Ya thats what I was thinking...

Ditch the variable cathode resistor and either add a gain pot in between stages, or have a high/low cathode resistor switch.

Ripthorn · March 16, 2009, 09:59:25 AM

Quote from: snap on March 15, 2009, 01:25:18 PM
crackle OK ?

I've never actually read about this, but is the crackle just when adjusting the pot value, or does it crackle the whole time? I only ask because I have a variable cathode resistor on my breadboard, and if this causes some noise or something, I may rework it.

Adriano, looking great, I look forward to hearing clips with the AT7, I am just a little disappointed because I guess I jumped the gun and already ordered AU7's.

Oh well, plenty of good stuff with those, too.

Caferacernoc · March 16, 2009, 10:48:21 AM

It just crackles when you turn the knob.

Renegadrian · March 16, 2009, 11:31:49 AM

Actually it rarely cracks, after all I just put the gain as it is in the Valvecaster. Nothing that shouldn't be done at all...I know that the usual way is to wire the pot between stages, as a MASTER (I wouldn't call it gain, actually it's more than a volume at the end of the first stage) but you know, that seemed more useful to me...

Brian, the first schematic on this topic, at the previous page, uses a 12AU7 at its best (or at MY best!!!

)
Basically you have a good hot overdrive (running it at 48V or more). You can choose to have
a) no gain control
b) the gain at the first cathode, Valvecaster style
c) the usual MASTER control between the two stages.

As you heard on the quick clip I recorded of it, it is quite gainy, but you know I am an ol' METALHEAD

so I just wanted more...Up to eleven!!!
So expect a gain monster from the other schematic (the 12AT7 one)...

Renegadrian · March 16, 2009, 11:55:19 AM

12AU7 TUBE STAR - NO GAIN
12AU7 TUBE STAR - CATHODE GAIN (VALVY STYLE)
12AU7 TUBE STAR - MASTER VOLUME

Ripthorn · March 16, 2009, 01:29:20 PM

It's funny you mention up to eleven. In the amp I am working on, I have a footswitchable triode boost in front of the preamp (built into the amp) and the front panel label for its gain control is "Eleven".

Anyway, I did quite like the sound of the AU7 one, so I will build that (As much as I would like to try the AT7 version, let's be honest, I probably have enough high gain pedals, if such a thing is possible). I kind of like the cathode gain control. I think the breadboard needs a little more attention on that matter.

frequencycentral · March 16, 2009, 02:22:02 PM

Adriano - your soundclips are very cool, great sound, nice chops!

I'm just loving it that there is a renaissance of tube circuits right here right now on this forum. People have built the Valvecaster and are moving on and experimenting with their own designs. Lovin' it!

Renegadrian · March 16, 2009, 02:41:23 PM

Yeah it's the TUBE RENAISSANCE and we're just deep in it!!!

Ripthorn · March 16, 2009, 02:57:35 PM

Yeah, it is funny how people on the outside would see us as using "inferior" technology. I talked to my filter design professor about something and he said "But that is going to distort the signal" and I said "I know, it's for electric guitar" and he just said "Oh"

. When I have my designs a little more firmed up, I will share them, but for the time being, I will enjoy the designs of you guys posted here.

Renegadrian · March 25, 2009, 06:59:47 PM

Added a couple of Vero layouts. The "Master Volume" layout will be online soon...

TUBE STAR
TUBE STAR CATHODE GAIN

German · March 25, 2009, 07:04:23 PM

Cathode gain is bad thing - becose you change tube bias.. all gets cranked up.. Or pot value could be about 0-2K2..
Only mastergain style between two triodes is accepted.

Ripthorn · March 25, 2009, 08:06:51 PM

Yes cathode gain changes the bias, but as long as it is within normal limits, I don't see a problem with it. For example, I have a cathode bias booster that has a small resistor in series with it (so that the cathode never goes to ground) and it works fine. Tubes are meant to be run at different biases, that is what is great for guitars.

I think that the volume control between triode stages is good for general use, but it can be nice to have things a little different once in a while.

frequencycentral · March 25, 2009, 08:15:33 PM

Quote from: Ripthorn on March 25, 2009, 08:06:51 PM
For example, I have a cathode bias booster that has a small resistor in series with it (so that the cathode never goes to ground)

This is a good idea, I've mentioned a few times the audible thunk of the Valvecaster as gain control is turn to maximum. Valvecasters can also whistle when bypassed when at maximum gain. A 1K resistor would do it - what did you use Brian? I have to say though, I do prefer fixing the bias and using an interstage gain control.

Ripthorn · March 25, 2009, 08:30:36 PM

The value of the resistor really depends on how much umph you want out of the thing. I use a 470R if I want really high gain and 820R or 1k8 for slightly lower levels. I choose the values depending on what I want and I got them from looking at amps like Mesas, Marshalls and other high gainers. I do prefer the interstage control for most situations, I am just saying that I think a variable bias has its place and I think that for a booster that is not always in use, it is not a bad way to go (though I think I am going to make a back panel control for an interstage control on the boost just because if I want it to boost the clean channel, it gets a lot louder than if I boost the dirty channel, perhaps a trimmer).

I am just totally digging all the tube stuff going on here, lots of great ideas going about. I look forward to seeing your Promiscuous Girlfriend, Rick

, though i was thinking you might want to consider some terms like hussy or fluzie (you come up with the greatest names to go with your projects).

frequencycentral · March 25, 2009, 08:35:42 PM

Quote from: Ripthorn on March 25, 2009, 08:30:36 PM
I look forward to seeing your Promiscuous Girlfriend, Rick ,

Brian, out of context, that comment seems inappropriate!

Quote from: Ripthorn on March 25, 2009, 08:30:36 PM
(you come up with the greatest names to go with your projects).

Thanks - I design the names first, then come up with a project to fit the name!

Ripthorn · March 25, 2009, 09:13:06 PM

Then I almost hate to ask you what the inspiration was for this upcoming project

Renegadrian · March 26, 2009, 03:01:19 AM

I know that cathode fain is not the common way, but I found that it could be used without issues...
So German, I made 3 schematics and there will be 3 layout, with a fixed gain (just a resistor to ground), with the typical "master volume" between stages and the cathode gain pot, as seen in the Valvecaster too...
So German, if you are so strict about that, you can go with the classic way...Else, I have to tell you that I breadboarded all the 3 versions, and the cathode gain is a good solution, no strange crackles or issues...It works good, at least for me, and I found it more useful (it acts more like the gain control I was after) than the volume pot that is between the triodes.

Renegadrian · March 26, 2009, 03:03:04 AM

Quote from: Ripthorn on March 25, 2009, 08:06:51 PM
Yes cathode gain changes the bias, but as long as it is within normal limits, I don't see a problem with it. For example, I have a cathode bias booster that has a small resistor in series with it (so that the cathode never goes to ground) and it works fine. Tubes are meant to be run at different biases, that is what is great for guitars.

I think that the volume control between triode stages is good for general use, but it can be nice to have things a little different once in a while.

Yeah!!!

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TUBE STAR - 12V-50V tube overdrive