Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on December 09, 2017, 02:50:44 am

Title: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: TIMBO on December 09, 2017, 02:50:44 am

Hi guys, This is a scratch build I started a very long time ago.
http://www.guitargear.net.au/discussion/index.php?topic=47812.0
I have added a one tube 6BM8 one tube reverb.
I have finally completed this project and thought all was done, took it to a gearfest and got heaps of feedback.
Removed the 6BM8 and found this to be the problem.
Tried a few more valves and problem persisted.
After some mods, this is the circuit now.
(https://i.imgur.com/GVnefbe.jpg)
Voltages-
pin2 - 15.8v
pin6 - 208v
pin7 - 208v
pin8 - 1.29v
pin9 - 131v
 :dontknow:

 

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: PRR on December 09, 2017, 10:48:48 am

Increase the 100K from * to #. A lot.

Note that Fender sometimes used 3,300K (3Meg) here, not 100k; which means adding another gain stage.

Resistors go both ways. This "dry" resistor also leaks-back wet signal INto the reverb path.

The Champ-class amp has just about enough gain stock, but adding a reverb path and mixer forces real compromise. Low dry gain, non-wild reverb strength, or extra gain.

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: kagliostro on December 09, 2017, 01:51:26 pm

On VOX Cambridge the 3.3M resistor is bypassed with a cap

(http://www.blueguitar.org/new/schem/vox/camb_rev.gif)

Franco

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: PRR on December 09, 2017, 03:23:05 pm

> On VOX Cambridge the 3.3M resistor is bypassed with a cap

Same on many Fenders. This network is just high-enough impedance it will lose treble, so we compensate.

AND the reverb driver is taken from the *second* stage. So much higher signal level, and we can take much more loss on the dry side of the reverb mixer. This loss works both ways: reverb return does not leak-back to reverb input as much.

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: TIMBO on December 09, 2017, 04:24:48 pm

SO, It would be much better to insert the reverb off pin1 V1??

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: PRR on December 10, 2017, 12:23:43 am

> better to insert the reverb off pin1 V1??

Then how are you going to bring the Return back in?

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: TIMBO on December 10, 2017, 12:30:07 am

Hi PRR, This is how I have done it.
(https://i.imgur.com/wfNBdsU.jpg)
(https://i.imgur.com/4Lp8TLe.jpg)
Works great, with lots of boing.
There is no signal loss or tone loss.

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: sluckey on December 10, 2017, 07:14:56 am

The reverb level pot has dc voltage on it. Does it sound scratchy when you turn the knob?

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: kagliostro on December 10, 2017, 08:53:59 am

Quote

The reverb level pot has dc voltage on it.

and the .001 cap between * and 1Ma pot ?

Franco

Quote

EDIT:


I was looking on the wrong side of the 3.3M resistor  :BangHead: :BangHead: :BangHead:

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: TIMBO on December 10, 2017, 12:58:51 pm

NO scratchy pot that I noticed.

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: PRR on December 11, 2017, 12:44:31 am

The 0.02u cap could go on the other side of the 3.3Meg.

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: TIMBO on December 11, 2017, 02:09:37 am

I'll give it ago. :thumbsup:

Title: Re: STINGER BY DENIS CORNELL - ROMANY PLUS
Post by: TIMBO on December 11, 2017, 03:42:35 am

WORKS GREAT!!!!!!
(https://i.imgur.com/GcvyZXh.jpg)

PRR, was this insertion point your original thought?