Author Topic: Presenting the 74W Tung Sten preamp  (Read 913 times)

antonis

Re: Presenting the 74W Tung Sten preamp
« Reply #20 on: July 09, 2019, 05:21:35 AM »
If the preamp is run at 18V, one might want to change these diodes to blue LEDs, or a pair of back-to-back Zeners with about 5V.
Pardon me, Andy, but a pair of back-to-back Zeners clips at a level similar to Si diodes (despite their nominal voltage rating)..  :icon_wink:
Can't follow your signature changes, Stephen..!!
but I like what follows:
"put the coffee down, Antonis, and nobody will get hurt."
"Arggg, Jim ...."

Fancy Lime

Re: Presenting the 74W Tung Sten preamp
« Reply #21 on: July 09, 2019, 07:52:32 AM »
If the preamp is run at 18V, one might want to change these diodes to blue LEDs, or a pair of back-to-back Zeners with about 5V.
Pardon me, Andy, but a pair of back-to-back Zeners clips at a level similar to Si diodes (despite their nominal voltage rating)..  :icon_wink:
By back-to-back I mean this:
https://upload.wikimedia.org/wikipedia/commons/1/17/Zener_Diode.svg
not this:
https://upload.wikimedia.org/wikipedia/commons/d/d7/Antiparallelschaltung_Dioden.svg
The latter, which is called anti-parallel, not back-to-back, if I am not mistaken, would indeed be the same for Zeners as for normal silicon diodes. But the former would clip at Zener-voltage + silicon diode forward drop. So about Zener-voltage + 0.7V.

Andy
My dry, sweaty foot had become the source of one of the most disturbing cases of chemical-based crime within my home country.

antonis

Re: Presenting the 74W Tung Sten preamp
« Reply #22 on: July 09, 2019, 07:58:04 AM »
My bad (english language skills), Andy.. :icon_redface:

Cheers.. :beer:  :beer: :beer:
Can't follow your signature changes, Stephen..!!
but I like what follows:
"put the coffee down, Antonis, and nobody will get hurt."
"Arggg, Jim ...."

sergiomr706

Re: Presenting the 74W Tung Sten preamp
« Reply #23 on: July 11, 2019, 05:04:05 AM »
Have you tried this preamp design with your ONKOtherium overdrive pedal? I m trying to make a stripboard out of this one but thought that maybe these two free inverters could be used somewhere and looking at the ONKO it seems like a chance to have it all together. Disto+Preamp in a little pedal maybe 125n size, but maybe these 2 effects together, or are redundant or does it make it sound like mudd or boomy? Thank you for sharing your work and ideas.

bool

Re: Presenting the 74W Tung Sten preamp
« Reply #24 on: July 11, 2019, 06:31:39 AM »
back-to-back = zener+1junction drop

Fancy Lime

Re: Presenting the 74W Tung Sten preamp
« Reply #25 on: July 11, 2019, 01:23:11 PM »
Have you tried this preamp design with your ONKOtherium overdrive pedal? I m trying to make a stripboard out of this one but thought that maybe these two free inverters could be used somewhere and looking at the ONKO it seems like a chance to have it all together. Disto+Preamp in a little pedal maybe 125n size, but maybe these 2 effects together, or are redundant or does it make it sound like mudd or boomy? Thank you for sharing your work and ideas.

The 74W and the Onkotherium are quite similar, so I would say having both in one enclosure may be a bit redundant. The Onkotherium has a higher gain range though. So what I would do, if I wanted to use those extra inverters and get more different sounds out of the thing, is add two more stages of the same design as the first clipping stage between the main gain stage and the bass control stage. You could use two footswitches for the boost switches of those stages and get footswitchable extra gain. I haven't tried this but the result should be fairly similar to a Red Llama with one switch engaged and a Red Llama on steroids with both engaged. Lots. Of. Steroids. If you try it, let us know how it went.

Cheers,
Andy
My dry, sweaty foot had become the source of one of the most disturbing cases of chemical-based crime within my home country.

anotherjim

Re: Presenting the 74W Tung Sten preamp
« Reply #26 on: July 11, 2019, 04:23:39 PM »
The Zener voltage (+ a diode drop) clipper would be "inverse-series" while normal back-to-back clipping diodes are "inverse-parallel". I prefer to call inverse-series "nose-to-nose".

"Designing with PLLs in production circuits is reserved to those with the courage of the thoroughly uninformed."
Nuts & Volts
"Turtles have the short legs, not for the walking."
-Kenji "Damo" Suzuki

sergiomr706

Re: Presenting the 74W Tung Sten preamp
« Reply #27 on: July 12, 2019, 05:25:00 AM »


Stripboard, I know there are people much better skilled than me, so all suggestions are welcomed. after looking a this a couple times more I think this should work. Layout is following exactly the schematic, if it works, I ll see if space allows me and I can make something more out of the 2 spare inverters. Instead of using the spare to make it sound more distorted, could these be used as a Clean blend from Q1/ R4 junction , then use an inverter as a Highs roll off at 400-800 Hz and then make a lo fi mixer out of the other inverter and make r21/c20 the dirty output, and both signals being thrown to the speaker sim, does it make sense?


« Last Edit: July 12, 2019, 08:57:11 AM by sergiomr706 »

Fancy Lime

Re: Presenting the 74W Tung Sten preamp
« Reply #28 on: July 12, 2019, 01:45:02 PM »
Awesome! Thanks, Sergio! I hope I can find the time to trace the schematic back from the layout, one of these days. Always a good way to check for errors.

Cheers,
Andy
My dry, sweaty foot had become the source of one of the most disturbing cases of chemical-based crime within my home country.

Marcos - Munky

Re: Presenting the 74W Tung Sten preamp
« Reply #29 on: July 13, 2019, 02:48:45 PM »
Very interesting. Stoner metal distortion is pretty nice to my ears. Any soundclips?

Fancy Lime

Re: Presenting the 74W Tung Sten preamp (now with demo!)
« Reply #30 on: July 14, 2019, 04:56:01 PM »
Hi there,

finally got my $#!+ together and made a sucky little demo. I am no guitar player, so no judgement, please. In fact the main reason I recently bought one and started learning to play is, so I can test pedals and make demos (that's not what I told the wife though, so: shhh!). Signal chain: Yamaha Pacifica 311, neck PU solo (P90, tone and vol full) --> Digitech JamMan solo XT  --> (modified Jordan Bosstone clone, true bypass) --> 74W Tung Sten preamp still on the breadboard --> Focusrite Scarlett 2i4  --> Audacity.

https://www.aronnelson.com/DIYFiles/up/74Wdemo.mp3

I start with Gain and Presence at 0, Bass and Treb at noon, Boost off. Then I first increase Gain, then Presence, then start fiddling with Bass and finally Treble. Around 2:30, Boost is switched on, then same procedure as before. Because a regular use case for a stoner rock amp seems to be hitting it with a big ol' fuzz, I switched on the Jordan Bosstone clone just after 4:20 (by happy coincidence). Some knob-fiddling ensues (only of the 74W, the Bosstone stays the same all the time), first with the Boost engaged, then, at 5:09, the Boost is disengaged.


Cheers,
Andy
My dry, sweaty foot had become the source of one of the most disturbing cases of chemical-based crime within my home country.