Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: studiodunn on February 27, 2017, 02:21:34 pm

Title: Metro Loop install
Post by: studiodunn on February 27, 2017, 02:21:34 pm
Hello all,

I'm putting a Metro Loop into my 100watt 2 channel FrankenBassman and have a question.
The amp is 2 channels feeding the PI off of a relay, with a PPIMV.

So hooking the loop up, do I just disconnect the relay feed to the PI input and route it to the send/out of the loop and then run the return/in to the PI input?

Thanks
Title: Re: Metro Loop install
Post by: Backwoods Joe on February 27, 2017, 02:51:10 pm
Do you the effects loop to affect both channels or just one?
Title: Re: Metro Loop install
Post by: studiodunn on February 27, 2017, 02:54:09 pm
Do you the effects loop to affect both channels or just one?
I will use it on both channels.

 I'm also wondering if I need to add a coupling cap at the PI input. The amp currently has each channel/preamp with a coupling cap into the mechanical relay and the relay feeding the PI direct, but I'm thinking the loop, having make-up gain would need a coupling cap going into the PI. Sound sensible?
Title: Re: Metro Loop install
Post by: Backwoods Joe on February 28, 2017, 11:24:21 am
I think you just need to go from the relay into the loop, and out of the loop into the PI. If there is no DC going into the relay, you shouldn't need the added cap. I have one of these loops that I've never used. Please report back how well it works. THX joe
Title: Re: Metro Loop install
Post by: studiodunn on February 28, 2017, 11:37:23 am
I think you just need to go from the relay into the loop, and out of the loop into the PI. If there is no DC going into the relay, you shouldn't need the added cap. I have one of these loops that I've never used. Please report back how well it works. THX joe

Thanks Joe.

The loop is up and running and works great. That is exactly how it hooks up and it does need a coupling cap going into the PI. I used a .022uf. The loop was designed to go into a Marshall, so that is the value it would normally see.