Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: punkykatt on February 23, 2011, 03:42:27 pm

Title: passive efx loop location
Post by: punkykatt on February 23, 2011, 03:42:27 pm

Hey guys, Im building a single channel 6G16 type amp and I installed a passive efects loop as shown on the attached schematic. I want to run a Boss Ch 1 Super Chorus( input Z= 1M  output  Z= 10k or greater)  through it. The unit is way over driven and does not work well in the effects loop.   Is there a better  location to install the loop?  Thanks for any help or suggestions.  Punky

Title: Re: passive efx loop location
Post by: sluckey on February 23, 2011, 03:59:30 pm

I'm pretty sure that CH1 is meant to be operated at instrument signal level.

Title: Re: passive efx loop location
Post by: punkykatt on February 24, 2011, 08:17:57 am

I used this Chorus pedal with a TOS build and it worked fine in that effects loop?

Title: Re: passive efx loop location
Post by: sluckey on February 24, 2011, 09:07:04 am

Your loop is in the optimum position IMO. Before moving the FX loop jacks, try changing that 470K resistor on V3B grid to a 3.3meg. If that doesn't help, move the jacks back to the grid of V3B. You won't be able to send the tremolo'd signal thru the loop but I don't see any way around that.

Title: Re: passive efx loop location
Post by: OldHouseScott on February 24, 2011, 10:54:03 am

Per Steve's suggestion, here's one way to do it, moving the loop before the reverb. You could further play with the values of the split plate resistors on V1b, always making sure they total about 100k, but that will affect the overall gain through the amp. That might not be a bad thing, as this amp would seem to have an abundance of gain.

Title: Re: passive efx loop location
Post by: punkykatt on February 24, 2011, 01:29:48 pm

 Thanks for the suggestions Guys.  Hmmmmmm, I like the idea on not sending reverb and tremelo through the FX loop!! I think I will give that a go.

Title: Re: passive efx loop location
Post by: punkykatt on February 24, 2011, 07:33:07 pm

OldHouseScott, I wired up the FX loop per your schematic mod. Huge difference, The Chorus works great there and I like not pushing reverb and trem through that circuit. How did you come up with the 2.2m to ground ?
Tomorrow I will mess round with the split plate resisters.  Thanks again for the  help.  Punky

Title: Re: passive efx loop location
Post by: OldHouseScott on February 24, 2011, 09:08:50 pm

If you're not overloading the input to the chorus, I wouldn't mess with the split plate resistors further (although I'm just lazy in that regard -- if it works, I leave it alone). The 2.2M is there just to reference that one side of the coupling cap to ground during the time a plug is inserted or removed from the send jack. It's an effort to reduce popping, but I'm not sure you couldn't just leave it out.

Title: Re: passive efx loop location
Post by: punkykatt on February 25, 2011, 11:03:29 am

Yeah,Im getting lazy now that Im in my 60`s. I fired it up this morning with fresh ears, smiled and put the chassis back in the cab for tonights gig. Thank you again. Anything to stop a pop is good.
Punky