impedance mismatch...bad enough to break an amp and/or pedal?

[alphadog808]

Hey guys,  
  I know this isn't *quite* a stompbox thing, but I know the electrical gurus here will know the answer to this.  

  I have a Fender Blues Jr and a line6 HD500.  I'd like to put the HD in the effects loop of the blues jr, but unfortunately, there isn't one built in. However, there is a reverb tank and I have read that people have speculated using the reverb in/out as an effects loop.  However, I hear that the impedance doesn't match, so that might not be a good solution.

With that being said, would a impedance mismatch possibly break the amp and/or the HD500?  I would rather not be putting out smoke or using a audio probe to fix something I could/might break...

I suspect not, but I figure I'd check before really trying.  I did hook up my guitar to the reverb out for a short time and it did work.  I could hear stuff and the volume was controlled by the reverb knob(which is a good thing).  I just want to make sure that doing this is electronically safe before hooking up and going loud, ya know?

I would only plan on using the reverb out with the HD500...basically to just bypass the preamp.

I also saw there is a line or amp switch on the HD, I figure those change the impedance, maybe one of those settings might help match the impedance better?

[ashcat_lt]

It's not likely to cause any damage unless one or the other of the devices is already defective.  I would worry more about level mismatch than anything.  Even that won't break anything, it'll just probably distort.  Sounds like you've tried it, though, and it works, so where's the question?

[alphadog808]

Thanks for the response, ashcat, I appreciate it.  I only plugged in my guitar for a few seconds and strummed.  What I ultimately want to do is hook up my HD500's output to the reverb return; I figure I couldn't fry my guitar(less likely), but I could possibly fry the HD500.   

From what I've been reading on the web, it *seems* safe, but the concern arises if the it's a tube buffer and you use the reverb send.  I'd only be using the return and the blues jr has a solid state reverb...

Thanks!

[Quackzed]

i think i read somewhere that a fender tonestack is pretty flat when you crank the mids and turn the bass and treble to 0, just as another option if the reverb thang doesn't pan...   

[alphadog808]

i think i read somewhere that a fender tonestack is pretty flat when you crank the mids and turn the bass and treble to 0, just as another option if the reverb thang doesn't pan...   

haha, I read that too, but I did a bunch of BillM mods and a speaker change, which are great, by the way.  After the mods, I strongly suspect those settings aren't flat anymore..

[slacker]

Assuming this is the schematic for your amp http://www.blueguitar.org/new/schem/fender/blues_jr.gif plugging the output of your HD500 into the reverb return is perfectly safe, it's a high impedance opamp stage so it's the same as plugging it into an opamp based pedal or solid state amp. Like ashcat_lt  said there might be a level mismatch.

I'm not sure if you can use the reverb send return as an actual effects loop, according to the schematic the shield of the send is not connected to ground (point P2 on the schematic), if you put a pedal in the loop then P2 would get shorted to ground via the shield of the return and the send opamp wouldn't work as intended. You could probably do it if you used only the hot of the send and relied on the shield of the return to provide ground for anything you put in the loop.

[alphadog808]

Thank you, slacker!