Good morning everyone!

First off, my apologies for speaking English instead of German, my German is not well developed enough that I feel confident describing my problem in German

Anyway, about 10 months ago I posted a question regarding the place where it would be best to insert the TT LND150 FX Loop in the Lummerland Express. A couple forum members advised some possibilities (for which I'm super grateful  ) but unfortunately I got mixed results after finally getting around to try them out. Schematics and photos for clarification are included below.

I first tried inserting the FX Loop at the C6/R28 junction (green lines in the schematic). I lifted the C6 side of R28 and connected the output of the FX loop there. The hole that was freed up by lifting R28 I used for the input of the FX loop. Initially I used the InA input with the standard 1M/100kOhm input voltage divider. However, the sound was quite brittle, ratty and harsh. The amp was also rather quiet at this point, certainly less loud than I'd expect. Could this be due to an impedance mismatch of some kind? Or is it because I need another gain stage to compensate for the low input sensitivity of the cathodyne phase inverter as one forum member suggested here?

Being unsatisfied with the results, I tried inserting the FX loop in another place as another forum member suggested (red lines in the schematic). This time I inserted it at the R10/V3-7 junction. I lifted the V3-7 side of R10 and connected the FX loop output there. I tied the FX loop input to the lifted side of R10. This time the sound was much better! The amp awakened, sounded fantastic and was loud! However, another issue arose as soon as I started using time-based effects such as delay. The sound comes through good and doesn't distort the input of the delay effect but when the delay repeats echo away they sound less overdriven than the input with each subsequent repeat. I suspect this is because the following preamp stage (logically) gets less signal because the signal level of the delay repeats is decreasing with each subsequent repeat and thus overdrives the preamp stage less (V3).

I'm wondering if there is a way to insert the FX loop at the junction I first mentioned in the post - at C6/R28 - and finding a workaround to make it sound the way it should.
If it might help, I could make some audio/video recordings showing how the FX loop behaves with delay effects connected.

Thank you all for taking the time to read, I am looking forward to your replies

Best regards,

Kerin

Amp overview


FX loop insert close-up


FX loop close-up


Schematic with insert points

Hi,

insert the Loop after the Tone-Stack. Please see the JimHP-Layout how to do this as you need another capacitor.

Regards, Dirk