Behringer - GI100 Ultra-G Cabinet Simulator  [schematic]

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george giblet
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Post by george giblet »

I found a video with a few pics of the PCB and managed to trace cabinet sim section.



When I compare the frequency response of the circuit as drawn it doesn't seem to match up with the response plots of the GI100 I've seen. It's not bad but it looks a little bottom heavy and the mid dip frequency looks a little high. Having said that the impulse responses I've seen all seem to disagree in the low end. I don't know what to believe.

I'm sure the part values that matter are correct on the schematic. Where a difference is likely is the parts are connected slightly differently. I could not see all the PCB tracks in the video.

If someone has a real unit it shouldn't be too hard to kick the schematic into shape without too much effort. With the exception of the through-hole parts the designators on the schematic should match the PCB.

Ultra-G GI100 SchV1.0.png

Moderator: Moved the thread from the Boutique forum, as it hardly qualifies as boutique, considering either the brand or the price. Let me know if I should undo the moving.

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FiveseveN
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Post by FiveseveN »

I always thought it was a clone of some version of the Hughes & Kettner Red Box.
Ignorance more frequently begets confidence than does knowledge. (Charles Darwin)

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ppluis0
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Post by ppluis0 »

Moderator: Moved the thread from the Boutique forum, as it hardly qualifies as boutique, considering either the brand or the price. Let me know if I should undo the moving.
Personally, considering this brand, I think this thread can be moved to Pimp-my-cheap-pedal subforum :mrgreen:

Cheers,
Jose

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george giblet
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Post by george giblet »

Moderator: Moved the thread from the Boutique forum, as it hardly qualifies as boutique, considering either the brand or the price. Let me know if I should undo the moving.
Thanks for moving it. As soon as I went back to the main menu I realized I was in the wrong section - don't post before you go to bed :) .

R16 should have value 100k, not designator R2.

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Post by tritonus »

I bought a Behringer Ultra-G GI100 Cabinet Simulator a few years ago, but I have not used it often. I'm very interested in the schematic, so I have opened my GI100 to find answers for the questions in your schematic. I have tested the connections between the components with my multimeter
1) C18 does not connect with R30/R31. It is connected at the junction between C19 and R20.
2)Yes, R36 connect with C24/R36
3) Yes R17 and R18 are drawn swapped. R17 is the feedback resistor an R18 connect with C104
4) The Value of the greencap C100 is 15nF (0.015uF)
5)the 220 Ohm Resistor is not connected to the Output of the OpAmp. I haven't got the time to find where the signal goes. Maybe on weekend I have time for a closer look to the pcb.
Some additional information:
The OpAmp seems to be an TL064 because there is 064 printed on the ic.
The through hole electrolytics on the schematic are drawn correctly and the values are 10uF/25V.

greetings Klaus

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george giblet
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Post by george giblet »

I bought a Behringer Ultra-G GI100 Cabinet Simulator a few years ago, but I have not used it often. I'm very interested in the schematic, so I have opened my GI100 to find answers for the questions in your schematic. I have tested the connections between the components with my multimeter
Thanks a lot for checking your board. I've updated the schematic to reflect the changes.

Moving C18 fixes my concern with the frequency response. It looks pretty close to what I expected now. The response I saw on-line has less bass boost but I'm sure that's a measurement issue as the flat response on the same site had some bass cut.

Compared to some of the later DIY cab sims that people like the GI100 cuts the high end more.
Behringer Ultra-G GI100 Schematic V11.png
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Behringer Ultra-G GI100 Response V11.png

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george giblet
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Post by george giblet »

Back in 2006 I fitted a circuit to an impulse response of the GI-100 I found on-line. I may have fitted to the average of the all the stuff I found. The main idea was to have a "workalike" circuit that was representative of the GI-100 frequency response. So here's a comparison.
GI-100 V11 vs UltraGiblet1 V11.png
As mentioned I already suspected the LF response from the IR's are off. You can see the HF response is a bit off as well. Perhaps due to low sampling rates or re-sampling, or perhaps due to fitting fuzzy curves.

There are some features which at least show the GI-100 V1.1 schematic is on the right track. I trust that schematic more than the fitted IR response anyway.

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Post by Glandbolt »

Behringer Ultra G GI-100 200118.png
Behringer Ultra G GI-100 200118.png
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Behringer Ultra G GI100 200304.png

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george giblet
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Post by george giblet »

@ Glandbolt
You should be clear that you are suggesting mods (not corrections to the schematic).

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Post by Lani »

Had one ripped apart and couldn't find it until now so I thought I would throw these pics up before I lose it again :lol:
If anyone needs better pics of something or anything specific let me know and I'll see what I can do.
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