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PostPosted: Tue Jan 22, 2019 9:52 pm 
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I'm looking at my next project and the Triwatt is near the top of the list. I've seen the threads about the passive effects loop, and have also watched the youtube video posted by "tgandcnz" where he has a TC electronics G-system in the loop (incredible demo of the amp btw...sounds phenomenal).

While I don't have any rack effects, I do have a pretty extensive pedal board and was wondering if anyone has used time-based or modulation effects in the loop on this amp. In particular, I have a Strymon Timeline and JHS Alpine Reverb that I would like to use in the loop.

Anything you can share would be greatly appreciated.
Thanks!


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PostPosted: Thu Jan 24, 2019 10:10 pm 
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viewtopic.php?f=14&t=4849


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PostPosted: Sat Jan 26, 2019 9:27 am 
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Thanks Sazafraz...I did see that thread/schematic before. I'm just wondering if anyone has used this passive loop with success with pedals. Maybe I'm missing it but the only demo or mention of it I could find was where a G-system was used, which is rack mount.

My plan is to order the Triwatt kit, go with the passive loop and just see how it works with my pedals. If it has problems then I will install a JFET buffered loop or maybe get me a Kleinulator from Ceri@tone to run as an interface between the amp's FX loop and my pedals.


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PostPosted: Tue Feb 12, 2019 10:37 am 
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Upon looking at the schematic for the passive effects loop, I see that it is placed after the master volume (VR7) and before R17 which feeds pin 7 on V3. On some of the other buffered effects loops boards that I've looked at (mainly for Marshall style amps in which a cathode follower is driving the tone stack), the loop is inserted between the treble pot and master volume.

Is there a reason why the passive loop is inserted after the MV in the Triwatt? It seems that the MV setting would greatly affect how hard the external effects are driven, and may overload the effects anytime the volume is turned up. But if inserted between the treble pot and MV, it would seem that the effects levels would be much more consistent and less likely to change based on MV settings.

Or maybe the intention is for the MV to be used to regulate the signal fed to the effects, and the pre-amp volume controls are used mainly for overall loudness?

Apologize in advance if I'm missing the obvious here. Thanks for any help. Just trying to work up a game plan for my Triwatt kit.


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PostPosted: Wed Feb 13, 2019 11:49 am 
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This loop was the result of a builder's efforts. You could try it after the Treble pot and let us know how it works.

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PostPosted: Sat Apr 06, 2019 9:55 am 
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I've started the Triwatt build...just about done with the infrastructure (heaters, sockets, etc.) and about to tackle the board hopefully this weekend. I researched some old threads and came across this info regarding inserting an FX loop:
http://www.trinityamps.com/phpbb/viewtopic.php?f=14&t=1640&start=80

(Zaphod) "Just break between the wiper of MV pot VR7 and 22k resistor R17. You would need to place a 1M resistor between V3 Pin 7 and ground, to keep the grid biased to 0V, when an FX unit has been placed in the circuit. You may also want to place an isolation cap (0.1uF say) between the return jack and R17 if any of your pedals don't have a cap on their output."

I'm not seeing the 1M resistor on V3 Pin7 listed on the current schematic as a "tweak" for the FX loop. I'm wondering if this resistor was deemed unnecessary?

Thanks! Looking forward to finishing the build!


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PostPosted: Sat Apr 06, 2019 8:57 pm 
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Never had to use the 1M but it's a good idea if you can switch it in only when the Fx is plugged in.

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PostPosted: Sun Apr 07, 2019 3:24 pm 
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When you're done, without the 1M resistor, measure the voltage on pin7 with an Fx or jumper plugged in and see if it is non-zero DC. If so then try a 1M and retest.

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PostPosted: Mon Apr 08, 2019 3:35 pm 
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Sounds like a plan. no need to use shielded cable for the 1M resistor correct? However I do plan to use shielded for the "break" between the MV pot and R17.


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PostPosted: Tue Apr 09, 2019 8:25 am 
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PharmRock wrote:
Sounds like a plan. no need to use shielded cable for the 1M resistor correct? However I do plan to use shielded for the "break" between the MV pot and R17.


I think that would work.

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