BT80... Boobtube @80V

[nzCdog]

This is the same demo from my Build Thread just posted here for ease of reference

http://www.mediafire.com/?lh9195stby1ygu8

[JakeFuzz]

Wow, that thing sounds really good. Sounds very sensitive to pick attack. Hopefully the lower voltage SMT rump roast will sound this awesome. Have you tired running it at lower voltages to see if it changes the sound? It seems to get around 100 volts you could pull the 120 from the wall and send it through a rectifier and a high volt regulator...

[nzCdog]

Thanks Jakefuzz!  Yeah its so responsive I have a feeling I won't need 2 dirt pedals on my board anymore!  Plus it has the beautiful upper harmonic texture you can't quite get from a SS pedal   I havent personally tried the lower volts, but other guys have successfully with the same project...  I'm sure the SMT will be great.

Not sure if it'd be worth the cost trying to run this straight from the wall however... This was cheap and easy to build... and it runs on 12V from your pedal power II etc.   To plug it onto the wall you'd definitely need to use some sort of a transformer for safety... rather than just a regulator alone, and then you'd need a rectifier bridge to get DC for the circuit...   I'm sure there must be mains powered tube pedals out there, but I'd say they'd be a lot more complex and costly in design than this one. 

[JakeFuzz]

Sweet I cant wait to build one of these tube pedals.

I am thinking you could leave out the transformer. You can rectify the AC wall voltage and throw a fuse in there somewhere but if you could cut out the transformer that would save a huge chunk of change. I am not too sure about this though, I have never seen anyone directly rectify and use wall voltage as DC just because not many things run at that voltage. In theory it should be doable though. I think after rectifying, filtering and maybe a regulator you could get 100 volts DC. That would be awesome. Ill see if it is doable.

Hmm yeah probably not. There is no earth isolation. It would just be unsafe to work with. Darn looks like its time to find a pedal sized step down transformer.

[juansolo]

We've run them with a variety of voltages. The lowest you can really put into it is 9v (meaning you'll have to run the heaters in series at 6v, which is fine, it just draws twice the current). Plate voltages, BoobTube 1 is running 24v out the back of a road rage with 12v in, and it sounds great. The higher the plate voltage the more headroom. The difference is there back-to-back. It's not massive, but it's noticable. We've stopped at 40v to the plates with ours. Seems a good compromise. But running higher in theory should only make it better.

[juansolo]

Sweet I cant wait to build one of these tube pedals.

I am thinking you could leave out the transformer. You can rectify the AC wall voltage and throw a fuse in there somewhere but if you could cut out the transformer that would save a huge chunk of change. I am not too sure about this though, I have never seen anyone directly rectify and use wall voltage as DC just because not many things run at that voltage. In theory it should be doable though. I think after rectifying, filtering and maybe a regulator you could get 100 volts DC. That would be awesome. Ill see if it is doable.

Hmm yeah probably not. There is no earth isolation. It would just be unsafe to work with. Darn looks like its time to find a pedal sized step down transformer.

Wouldn't mess with AC unless you really know what you're doing. Potential for serious injury is there. Where as at the voltages we're messing with DC, it's still really quite safe.

[JakeFuzz]

Totally agree. I was hoping to find a quick way to get to higher voltage without having to buy a transformer. It is definitely possible and would work fine, but if you touch any part of the circuit other than ground you are going to shock the crap out of yourself. Same reason they went to 3 prong on old amps. This is because the primary is referenced from earth and so are our bodies forming a current path from our curious fingers to our feet  Yeah better use an isolation transformer when messing with wall AC. At that point though you might be better off buying a step up and running the tubes at the rated plate voltage.

[nzCdog]

Build another amp?

[Diamond]

Wow, this sounds so incredibly dynamic! How much gain can you get out of this btw?

[nzCdog]

Thanks man. The 12AU7A I used gives about the same gain as at tube screamer or similar. If you wanted more gain you could use a tube with a higher gain factor, like a 12AT7A, 12AY7A or 12AX7A. 

[Diamond]

Damn you, now I HAVE to build one of these! 

[nzCdog]

  Yes you do!

[maxihard]

why can't a guitar pickup generate its own plate voltage?
Use a bug zapper transformer and a mosfet.
Don't have the time to try it yet but i have a 12 AX7 pre amp circuit with a 4049 voltage ladder candidate.
Just finished restoring a TEAC 144 Porta studio and I'm not rusty anymore. 

[gtr2]