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Vintage threads from the first ten years

HOT TUBES!

2/10/1997 7:04 AM
xstoogex	HOT TUBES! would very much like some info, schematics, etc. on old Electro Harmonix Hot Tubes boxes....seems like I got a schematic for one of these off a board a few months ago, but it didnt match up to the innards of the box i know and love...Ok....thanks in advance for the help!!

2/11/1997 5:48 PM
Mark Hammer	If you got the schematic from Jamie Heilman's schematic archive ("leper's schematics") or any of the boards that draw from his archive, then I'm the guy responsible for the schematic...and most errors occurring from it. I obtained the device in 1978/79 from a university technician who copied the board and parts layout from a friend's box. To the best of my knowledge, the board I have was simply photocopied, and the parts layout mimicked from the original. As far as I know, the original had a tone control, but the board I was given did not. I'm assuming from the schematic, and the traces on my board, that the tone control was likely analogous to guitar tone controls and stuck in between the output from the board and the volume control. In fact, I stuck one in the circuit, exactly as I'm describing it to you, and the box works great, with tons of gain, and a a meaty roar. This box is NOT a true fuzz, a la Big Muff, nor an overdrive a la Tube Screamer. It's more in the direction of a Boss Turbo Overdrive, only very forceful sounding and capable of mucho buzz. The high gain is guaranteed to push your preamp into its nonlinear range. Now, can I swear on my grandmother's lily-white skin that the schematic is absolutely flawlessly drawn from the board? No. Looking at the redrawn version posted on the web (which I think RG Keen did from the hand-drawn one I sent him), it SEEMS to be a workable device, and conforms to what it ought to look like, given what it does. Having said that, however, I will confess to never having built one from scratch, using only the schematic drawing as my guide. Your attention is drawn to the 4049 hex inverter employed in the circuit. When Craig Anderton posted his first 4049-based "tube-sound fuzz" in Guitar Player in 1977 (June? Jim Messina on the cover?), he mentioned that 4049's come in two flavours: unbuffered (suffix UB or UBE), and buffered for TTL interfacing (suffix B or BE). The buffered version will NOT work in either his original circuit (or its EPFM counterpart), or the Hot Tubes. I know. I built one with the wrong type and it frustrated me until I went and got the right kind of 4049. Hope this helps.

2/11/1997 5:48 PM

Mark Hammer

If you got the schematic from Jamie Heilman's schematic archive ("leper's
schematics") or any of the boards that draw from his archive, then I'm
the guy responsible for the schematic...and most errors occurring from it.

I obtained the device in 1978/79 from a university technician who copied
the board and parts layout from a friend's box. To the best of my
knowledge, the board I have was simply photocopied, and the parts layout
mimicked from the original. As far as I know, the original had a tone
control, but the board I was given did not. I'm assuming from the
schematic, and the traces on my board, that the tone control was likely
analogous to guitar tone controls and stuck in between the output from
the board and the volume control. In fact, I stuck one in the circuit,
exactly as I'm describing it to you, and the box works great, with tons
of gain, and a a meaty roar.

This box is NOT a true fuzz, a la Big Muff, nor an overdrive a la Tube
Screamer. It's more in the direction of a Boss Turbo Overdrive, only
very forceful sounding and capable of mucho buzz. The high gain is
guaranteed to push your preamp into its nonlinear range.

Now, can I swear on my grandmother's lily-white skin that the schematic
is absolutely flawlessly drawn from the board? No. Looking at the
redrawn version posted on the web (which I think RG Keen did from the
hand-drawn one I sent him), it SEEMS to be a workable device, and
conforms to what it ought to look like, given what it does. Having said
that, however, I will confess to never having built one from scratch, using
only the schematic drawing as my guide.

Your attention is drawn to the 4049 hex inverter employed in the circuit.
When Craig Anderton posted his first 4049-based "tube-sound fuzz" in Guitar
Player in 1977 (June? Jim Messina on the cover?), he mentioned that 4049's
come in two flavours: unbuffered (suffix UB or UBE), and buffered for TTL
interfacing (suffix B or BE). The *buffered* version will NOT work in
either his original circuit (or its EPFM counterpart), or the Hot Tubes.
I know. I built one with the wrong type and it frustrated me until I went
and got the right kind of 4049.

Hope this helps.

4/23/1997 1:21 PM
Jack Orman	I have a schematic of the E-H Hot Tubes that shows the tome control. It was similar to the one on the Big Muff if my memory serves me well.

4/23/1997 5:30 PM
R.G. Keen	I just finished a circuit board for cloning that old circuit. If you're interested in making one, send email to me at keen@eden.com. The circuit matches that from an old EH service schematic.

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