Tech21 SansAmp - TRI-A.C. (TRI-AC)  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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analogguru
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Post by analogguru »

Here should be a schematic of the Sansamp (Tech 21) Tri-A.C.:
http://www.amtshop.com/index.php?productID=90
scroll down a bit.

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Post by Dirk_Hendrik »

I need help understanding the diodes in the feedbackloop of DA2.2... ;)

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Post by analogguru »

Maybe they are instead of 1N 4148 zener diodes e.g. ZPD 2V7 ?
also the diode in the feedback loop of DA 2.1 ?


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Post by bajaman »

analogguru - you have surpassed yourself yet again :shock: :shock: :shock:
The Tri OD as well :D :D :D
I knew dark angel would be the one :wink: :wink:
The op amp choices are what makes them - unlike the silly behringer clones with the wrong op amps fitted :wink: :wink: :wink:
I did not know that they used diodes in the feedback loops - hmmmmm
VERY interesting - MANY thanks once more - you are THE man :lol: :lol:
Cheers
bajaman

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Post by karul »

here it is
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triac.jpg
SansAmp_TRI-AC.pdf
(141.39 KiB) Downloaded 380 times

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Post by karul »

Before I've opened this and the tread for TRI OD, I've search the forum for existing threads. Only Sansamp thread showed up, there were links and attachments for both of them, but non-working. I've decided to create two new treads.

However later I realized that there were already two treads, but with dots in the title A.C. and O.D. that didn't showed up when I do the searching . Mod can decide weather to move my threads or whatever...

TRI-A.C. (link is dead)
viewtopic.php?f=7&t=206

TRI-O.D. (there are active attachments for both pedals)
viewtopic.php?f=7&t=205

Tech21 - Character Series (non-active links and attachments)
viewtopic.php?p=70760&hilit=tech21+TRI+OD#p70760

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Post by Liquids »

Here's a relatively easy mod for this device - these are clearly designed for going direct, rather than run into a traditional guitar amp. I suspect many people grab them and plug them into an amp and get less than pleasant results due to the mid notch circuit. But with a simple mod this will sound less mid-scooped if you use it like an overdrive into a guitar amp that already has a "classic" marshall/fender type tone stack.

If you do use this direct, this is not the mod for you. However you can effectively get rid of the mid notch of the Tri-AC by removing the two components shown in the photo with a red box around them. On the schematics available in previous posts, these components are the 6.2k resistor connected to 1/2U as well as the 22n capacitor joined to that resistor.
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20230311_213003.jpg

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