FX Loop question

Mod is short for "Modification". It will entail a little bit of technical work, but nothing a good tech couldn`t handle in 30 minutes. The only part you`d have to purchase would be a switched 1/4" jack that will function as your return.

As I sit here looking at the schematic, it looks like the solution they`ve given me is adding an insert jack. If you`re not familiar, an insert is a stereo (TRS, to be accurate) jack that has both a send and a return in the same plug via an insert cable (two 1/4" plugs into one 1/4" stereo, one is the send, the other is the return). I will message them shortly for clarification.

Great thanks! So if i take the schematic to the tech service of a shop they can implement it?

trifonius wrote:Great thanks! So if i take the schematic to the tech service of a shop they can implement it?

Oh yeah, it will be a very simple operation for an amp tech. Not sure what labor rates are in your area but I`d be surprised if the procedure cost you more than about $60.

And you will post the instructions? If so, you're a life saver!!

Hi voodooJeff,

Any news on this topic?
Thanks!

I`m actually going to swing by the electronics store and get the piece I need on Monday,so give me a few days and I`ll have some news

Thanks a lot!

works like a champ. I`ll convert the PDF to something I can post here and anyone interested can see how it`s done. Keep in mind that despite coming straight from the engineer that designed the amp, it WILL void the warranty.

That sounds great!!! Thanks so much!!

So you use a switching jack here. It taps into the outermost wire on the ribbon shown. Took me about 15 minute to get it to functioning condition. I still need to devise a permanent mount for the jack but it does work.

Thanks a lot. I'll take it to a tech guy.

That's really interesting Jeff. Thanks for posting. At first sight it seems a really simple way of getting round the problem and hats off to the Herren at H&K for coming up with it.

Ideally, before I would feel comfortable with it as an absolute problem free cure, I would like to see what is before and after that point. You could possibly run into impedance matching problems if it isn't being driven effectively or it feeds back into an awkward impedance. I know I poohpooh "tone suck" but that is only in the light of today's understanding of the problem and correctly designing to prevent it. The designers have given this fix the thumbs up but it has not been a feature they would have anticipated and designed into the original circuit. It's really a well thought out hack and should be treated with a little caution until heavily tested!

It may pay to make sure the first pedal that new loop sees is a very high impedance, almost all will be of course but some well loved (but let's be honest shagged out) "classic" models may not, also that the final one before the return has a really good drive capability.

I would keep an ear open for any signs of instability and noise/radio breakthrough too.

"So you use a switching jack here. It taps into the outermost wire on the ribbon shown. Took me about 15 minute to get it to functioning condition. I still need to devise a permanent mount for the jack but it does work. "

Hi Jeff. I know I'm a little late to the conversation as I've just stumbled across this, but I have a few questions.

1. How are you using it?
2. The op was wanting to use a looper sans effects. Does this mod allow you to for example: loop a clean tone and then play over it with a crunch tone or can you simply add effects like chorus trem delay to the tone you are using to playing over the loop while staying in the same channel? Put another way can you loop one channel and play over with another?
3. Did you install the permanent jack and if so, do you have any images of your install?

Thanks in advance!

I use the new FX loop exclusively. originally it was to facilitate the growing frequency of solo guitar shows I was getting, but now it`s just the way I use it all the time. No need to swap back and forth. The only downside is that you lose footswitch control over the loop on/off, but that`s so minor it`s hardly worth mentioning. All I did was program my H9 to go into bypass when I`m on a preset that doesn`t use it.

Yep, either loop allows you to loop one channel and play over it on another. The problem with the original FX loop is that it changes the effects on the looped sample. For instance, I run a short, subtle delay on my clean tones. I make a rhythm to loop, using the built in effects. When I switch to my lead channel, the looped sample is run through the built in effects now with the longer and more pronounced delay I use there. The modded loop fixes that .

I did not get a permanent mount, but not without reason. I`m going to be running two GM36`s in stereo soon, and I`ll be making a custom panel, almost like a miniature patch bay to simplify and clean up the wiring between the two amps and my Eventide. It would go just above the DI socket, on the little flat panel, center of the chassis, otherwise. There is precious little open real estate inside the amp!

Thank you!
A frustration I've had has been the looped rhythm having effects added. So much so I AB'd my GM 36 to an old Line 6, just to get the two tones I wanted. Looks like this would solve it and I can clean up all the extra wiring plus pedals!

Jeff,

While I plan to have capable amp tech perform this mod, I'm interested in learning more. Two more questions.

1. You mention a "switching jack". Does this mean your TRS stereo jack has a manual inline switch in addition to the TRS stereo mount?
2. Since this is a stereo connection am I correct in assuming you use a TRS stereo to Y cable to make the loop?

Thank you in advance.

Raf0419 wrote:Jeff,

While I plan to have capable amp tech perform this mod, I'm interested in learning more. Two more questions.

1. You mention a "switching jack". Does this mean your TRS stereo jack has a manual inline switch in addition to the TRS stereo mount?
2. Since this is a stereo connection am I correct in assuming you use a TRS stereo to Y cable to make the loop?

Thank you in advance.

Man, thanks for asking. I left out a HUGE detail: It`s not a trs jack/y cable setup. A switching jack is really nothing fancier than one that closes the circuit when nothing is plugged into it, effectively bypassing the jack.

And nope, the "send" will be the 1/4" line out on the back of the amp. (you know, that thing that we never use for anything anyway LOL).

Ah!! That makes sense to me now. Thank you so much for clarifying!

Hi, is there anyone else that has done this mod? Where did you put the new switch jack? I don't like the idea to have it hanging out oft the amp.