Hiwatt Tube Distortion - gutshots & schematic  [schematic]

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tarivol
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Post by tarivol »

As promised in my previous post about Hiwatt Tube Overdrive, here is the second pedal from this tube series of pedals. Unfortunately, I don't have access to the remaining three (hi-gain distortion, phaser and tremolo).
Hiwatt Tube Distortion
Hiwatt Tube Distortion
You can get really great sounds from this one. The controls are versatile enough to give a wide range of sounds from medium overdrive to nice big distortions.
Gutshots:
Front of PCB
Front of PCB
Back of PCB
Back of PCB
Again, I went and whipped up a schematic:
Schematic
Schematic
As you may remember from the Tube Overdrive topic, again the tube is heated directly with 18V... And this time, I suppose that the tube CAN provide some distortion, especially when you crank the Volume and Drive knob. This time LEDs were used as clipping diodes and there is no hard-clipping, so the levels on the tube input might get high enough.
Also, that is one interesting tone section. It looks like two low pass filters, and when the tone knob is turned all the way up the response is flat.

As always - all corrections, questions and suggestions are more than welcome :)
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ppluis0
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Post by ppluis0 »

Hi tarivol,

You have made a great sixth post !!! :applause:
tarivol wrote: ↑15 May 2020, 10:35 As you may remember from the Tube Overdrive topic, again the tube is heated directly with 18V...
And this time, I suppose that the tube CAN provide some distortion, especially when you crank the Volume and Drive knob.
Feeding this tube heater with such extreme voltage only conduct to shorten their life expectancy and does nothing to the resulting sound.
Cut a track on the tube board and place a 39 ohms 2watt resistor in series with the pin 5. This suggestion is also valid to the overdrive pedal you have.
tarivol wrote: ↑15 May 2020, 10:35 As always - all corrections, questions and suggestions are more than welcome :)
Try to connect in parallel the unused tube section (jumper under the board pin 1 to 6; 2 to 7; and 3 to 8)and tell us what happen. :roll:

Finally, a question: the tube in this unit is of the same brand (kentron) that your overdrive ? I can't find info on the web about this manufacturer or distributor :scratch:

Cheers,
Jose
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tarivol
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Post by tarivol »

ppluis0 wrote: ↑15 May 2020, 18:48 Try to connect in parallel the unused tube section (jumper under the board pin 1 to 6; 2 to 7; and 3 to 8)and tell us what happen. :roll:

Finally, a question: the tube in this unit is of the same brand (kentron) that your overdrive ? I can't find info on the web about this manufacturer or distributor :scratch:
Hmm... nice suggestion, seems similar to what is done in the BKB Tube Driver. I won't do this in the Distortion, as it is not mine and the owner doesn't want to change anything, but I'll try it on my overdrive. I WILL drop the voltage on the heater on both units for sure, I'm going to the parts shop tomorrow :)

Yup, the tube is the same as in the drive. I am also stumped on the brand, any leads I found were for tubes from the 50's, manufactured by Kentron for General Electric. I sense some Chinese business here ;)
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freefrog
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Post by freefrog »

ppluis0 wrote: ↑15 May 2020, 18:48 Feeding this tube heater with such extreme voltage only conduct to shorten their life expectancy and does nothing to the resulting sound.
Cut a track on the tube board and place a 39 ohms 2watt resistor in series with the pin 5. This suggestion is also valid to the overdrive pedal you have.

Try to connect in parallel the unused tube section (jumper under the board pin 1 to 6; 2 to 7; and 3 to 8)and tell us what happen. :roll:

Finally, a question: the tube in this unit is of the same brand (kentron) that your overdrive ? I can't find info on the web about this manufacturer or distributor :scratch:

Cheers,
Jose
Zombie thread...

The tube in mine is an EHX 12AU7.

Have tried briefly the two halves of the tube in parallel: it didn't work for me.

But the 39 Ohm resistor between the 18v supply (blue wire) and the heater is easy to mount and works well. Thx to have underlined this problem and shared its solution, ppluis0! :-)

Thx also and of course to tarivol for the schematic!

I've done a few screenshots showing the frequency response and distortion of the pedal with various settings. I might post this stuff when I'll be less busy.

This Hiwatt Tube Distortion is not without merit, IMHO: it's possible to set the drive @ zero and to work only with the volume + master in order to obtain a bit of grit. Nice to my ears. YMMV.
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