Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: aabbs20 on October 09, 2017, 01:14:40 pm

Title: 1-tube reverb issue
Post by: aabbs20 on October 09, 2017, 01:14:40 pm
Hey all.

I'm trying to add Tubenit's 1-tube reverb circuit to a hybrid amp I'm building and I'm having some trouble.  The amp has Princeton reverb input and tone stack, and a 5G9 LTP phase inverter and tremolo.  It runs perfectly with the reverb circuit omitted, but the when I connect the reverb pot/330k resistor to R2 I lose almost all of my volume.  A hard strum will make a much louder sound, but that will fade very quickly back into super quiet.  I think it has some reverb on it but its hard to tell.  I've inserted the reverb after the second gain stage (post volume control) and just before the phase inverter.  I've checked and re-checked my wiring and soldering and I'm stumped.

My voltages on the Reverb tube:

Pin 1 - 316
Pin 3 - 3.03
Pin 6 - 159.5
Pin 8 - 1.45

reverb circuit: http://el34world.com/Forum/index.php?topic=7957.0 (http://el34world.com/Forum/index.php?topic=7957.0)
http://www.thevintagesound.com/ffg/schem/tremolux_5g9_schem.gif (http://www.thevintagesound.com/ffg/schem/tremolux_5g9_schem.gif)
http://www.thevintagesound.com/ffg/schem/princeton_reverb_aa1164_layout.gif (http://www.thevintagesound.com/ffg/schem/princeton_reverb_aa1164_layout.gif)
Title: Re: 1-tube reverb issue
Post by: SILVERGUN on October 09, 2017, 01:23:57 pm
Can you blend the 2 schematics together to come up with an actual schematic for your amp?
 
Where did you connect RV and RV2 in your amp?
Title: Re: 1-tube reverb issue
Post by: tubenit on October 09, 2017, 03:55:38 pm
IF you can cut and paste schematics together to show your schematic and reverb insertion points, we may be able to help?   I've had the one tube reverb work on every single amp I've tried it in.

With respect, Tubenit
Title: Re: 1-tube reverb issue
Post by: aabbs20 on October 09, 2017, 04:38:52 pm
RV and R2 are connected in pretty much the same places as the princeton reverb. 

I drew up a quick schematic of the area in question.  I'll complete it later tonight when I'm home from work.  This is my first time doing any kind of amp design so forgive me if I forgot something dumb!  I've read your posts on this circuit over and over and I'm confident it will work too.

Thanks a ton. 
Title: Re: 1-tube reverb issue
Post by: 2deaf on October 09, 2017, 05:05:13 pm
Do you have a cap. in front of the V3A grid?
Title: Re: 1-tube reverb issue
Post by: aabbs20 on October 09, 2017, 07:00:43 pm
No I do not...
Title: Re: 1-tube reverb issue
Post by: 2deaf on October 09, 2017, 07:34:09 pm
You need the .02-400 cap. in front of the LTP as shown on the 5g9 schematic.  The junction of your 100K and 330K resistors should connect to the other side of that cap.
Title: Re: 1-tube reverb issue
Post by: sluckey on October 09, 2017, 08:04:07 pm
That input cap for the PI is very important. Needs to look like this...
Title: Re: 1-tube reverb issue
Post by: aabbs20 on October 10, 2017, 12:34:34 am
I had a feeling it was something small that I should have known.  Thanks guys, it's sounding killer now!  I LOVE the reverb.