Oh, of course your mileage may vary. I just meant 12.6 rms times 1.414 means 17.8 volts peak. As I recall my original tube driver was around +-16v.

Jamie

The most recent posted schematic appears to be more accurate than the previous ones based on my old tube driver. Rectified voltage from the filament (12.6 vac) should be around +/- 17.8 volts. I just noticed the post above that asked for clips - sorry I missed it previously. I'll try to record some ...

Just an update if anyone cares. I don't hate it as much as I did but I still believe it's a total waste of a good idea. I believe I'm either going to sell it or put a mini dual triode in place of the battery and make it a "real" 4 knob tube driver in a small enclosure. I haven't traced it ...

OK, been busy. Fiddled with the trimpots a bit. I can only adjust the drains as low as 7 volts with the trimmers so that's a little odd. It didn't seem to make much of a difference anyway. Still sounds just so-so compared to the real deal. I wanted to love this thing- I really did. James Santiago ma...

15v on drain? What a waste of LND150's Totally. I just don't get it. Why use a 500 volt part where a much lower value part can be made to work similarly? And if you've got a 500 volt part and you're already using a boost converter, why not run the things at "real" plate voltages? Maybe th...

So I bought one of these because no one has traced it yet and I was curious how it's built and how compares to my DIY tube driver. It'd be nice to have that sound in a more compact format, right? First off- it uses LND150's at +-15 volts. I found that interesting. I haven't tried to trace it but at ...

I keep forgetting there is no edit button!

I don't have clear LED knobs. I have clear knobs, from BLMS. That is all.

JT

Thanks! It was fun to build. I use it every Sunday at church, mostly in front of a catalinbread DLS but occasionally by itself. It sounds every bit a tube driver, in fact it sounds quite a bit better than my old 4 knob one. It's based mostly on the rackmount single tube version (with the black panel...

I made my own "smaller" version. It has a jfet on the front end and a footswitchable gain boost with a high pass.

JT

Sure it can- you just can't be sure it'll sound exactly the same. By adjusting the gain control, source resistors and bypass caps you should be able to get the same sound, more or less. We don't know what they're doing to build them- they might be selecting transistors of specific gains anyway. My g...

I'm familiar with RG's articles, I'm just wondering if there is a tonal difference when distorted.

JT

I guess the 1k resistors between the top and bottom jfets should increase the gain and lower the output impedance of each stage- but do they distort differently than the earlier versions?

Thanks for tracing, looks rad!

JT

Thanks for the tips. I'll probably put a small o-ring around the LED to space it carefully and hot glue it from the back. I guess this demands soldering on leads and heatshrinking them in advance. It's annoying but it'll look nice that way. Next time I'll just get some plastic diffused LED holders f...

I bought a bunch on EBay because they looked cool in the pictures and they were stupid cheap. The old ones I had (possibly US made?) had a black rubber thing to hold the LED in and worked really nicely. These things have some crappy little white plastic thing that doesn't quite fit the LED or the LE...

It's funny how different people like different things. My cousin is a studio engineer in Nashville and he said there were 4 Varidrives at a session he did last week- his and the ones brought by the artists. He's sold quite a few people on buying Varidrives after they used his at a session. If you do...

Just noticed I got the 470k thing wrong on my prototype, I'll have to fix it and get back to you about the tonal difference. It'll double the signal getting to the second triode as well as making the clipping of the second triode much sharper/crunchier. It could also explain the excess top end on my...

Here's a picture of my clone/prototype. It's powered by a nixie supply from ebay instead of a bulky EI lam transformer. It was wired up to the input jack at first and I couldn't get it to be quiet- it injected all kinds of noise into the circuit and anything else on the power supply because it's a h...

One other thing I forgot to mention- the power transformer is a dual 120 volt primary dual 6.3 volt secondary transformer. One of the primaries is used as a secondary and the leads have been cut off of the other secondary. In other words: -120v in to one of the primaries -6.3v out to tube filament -...

Looks like the 100pf is on the gain control. Makes sense.

Jamie

I traced one of these a while back. I found a few errors on your schematic, it should be easy enough to verify if I'm right by desoldering and measuring or looking closely at the pictures. I guess it's also possible that I'm wrong or they're different, but I don't think I am! -treble pot is a 500k l...