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January 18, 2020, 09:36:41 PM

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Author Topic: 12 v tube preamp  (Read 546 times)

flester

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12 v tube preamp
« on: December 17, 2019, 12:25:40 PM »
I've seen a few references to building tube preamps e.g. https://www.instructables.com/id/The-ValveLiTzer-Low-voltage-Tube-Booster/
https://www.instructables.com/id/The-Valve-Caster-20-Tube-Boost-and-Overdrive/
Any comments on whether this is worth doing e.g. will it really sound any different to  solid state version?

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willpirkle

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Re: 12 v tube preamp
« Reply #1 on: December 17, 2019, 03:34:40 PM »
The tube-purists will hate the starved-plate designs but I’ve done this myself by altering a tube-screamer. It was noce and spongy distorted, but a little noisy (I used mini co-ax cable for critical runs). I was a tube-purist also until I got a Radial Tri-Mode ToneBone for $5 off a broken hardware table at Sam Ash. It only needed a 15V regulator to fix, and was yet another starved plate design. I liked how it sounded so I tried it with the tube screamer as a side-project.

gfr

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Re: 12 v tube preamp
« Reply #2 on: December 17, 2019, 08:17:29 PM »
http://www.valvewizard.co.uk/Triodes_at_low_voltages_Blencowe.pdf

Some theory, and some ideas for improvements.

willpirkle

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Re: 12 v tube preamp
« Reply #3 on: December 18, 2019, 04:10:27 PM »
Great article, man! The Butler patents are worth checking out too.

flester

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Re: 12 v tube preamp
« Reply #4 on: January 17, 2020, 04:32:08 AM »
I ordered some 12*U7 and sockets and am going to give this a try.
I see that there are some hybrid amps e.g. the Orange Tiny Terror which has a 12 AX7 preamp and uses a 15v power supply. Is that likely to be a starved plate or is the voltage stepped up internally? Is this a realistic option for DIY?

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phatt

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Re: 12 v tube preamp
« Reply #5 on: January 17, 2020, 08:59:30 PM »
hi Flester,
AFAIK, Tiny Terror is all valve running on high voltage.
I have no doubt that running Valves on low voltages will work but I doubt you will do much better than SS pedals.
The big thing with Valve rigs is the High voltage and the way in which the supply is delivered to each stage.
I think the term is  High Impedance supply, these sag as power is increased giving the classic compression feel. There are of course many other things that make all valve amps do the magic but just altering the values of the drop resistors in the supply chain changes the way the whole amp responds to how you play.
I doubt that will happen if running an AX7 at 12Volts.
Phil.

flester

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Re: 12 v tube preamp
« Reply #6 on: Today at 04:00:56 AM »
Sorry I meant Orange Micro Terror which has a solid state power amp. Just curious about how they run the 12AX7 preamp using a 15 v power supply.

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g1

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Re: 12 v tube preamp
« Reply #7 on: Today at 01:55:26 PM »

Enzo

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Re: 12 v tube preamp
« Reply #8 on: Today at 05:39:59 PM »
You can get a tube to do SOMETHING at 15v, but don't expect it to work like a 12AX7 in a real circuit at real voltages.