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HOT TUBES!


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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!!  
 
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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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