Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Baguette on December 16, 2010, 02:33:40 pm

Title: Reverb implementation. Would this work?
Post by: Baguette on December 16, 2010, 02:33:40 pm

Hello folks,

I'm thinking about doing an amp with the Matchless Chieftain type reverb. It uses a regular // 12AX7 as the tank driver, and then amplify the wet signal with 2 12AX7 triodes in series, and then feeds one side of the LTP PI.

I'd love to free one triode in my circuit, so I'm wondering if I could replace the 2 reverb recovery 12AX7 triodes with just a single one, and still have a strong enough reverberated signal (see the 2 drawings below).

The thing is the Matchless reverb recovery stage:
- has it's first gain stage with a really low plate resistor (22k);
- none of the gain stages have its cathode bypassed;
- there's a big voltage divider after the 2nd gain stage.
All these things tend to reduce the gain considerably... which leads me to think it could be replaced with a single 12AX7 gain stage set up for maximum gain (220k plate load resistor, bypassed cathode, no voltage divider before the PI).

- Would my simpler 1 gain stage recovery arrangement work nicely?
- Would the reverb stilll be strong?
- Also, would this reverb implementation (the wet signal feeding one side of the PI) work with a different LTP PI (Fender Tweed style or BF style)?

Thanks a lot for your help!

(http://i151.photobucket.com/albums/s134/victor_denance/reverb_implement.jpg)
   

Title: Re: Reverb implementation. Would this work?
Post by: phsyconoodler on December 16, 2010, 06:03:58 pm

Tubenit will be along shortly to chime in,but a one tube reverb is totally doable.It just doesn't have the 'surf' sound that Fender style two tube reverbs have.I have installed one tube reverb in everything from a champ to a JCM800 and with Tubenit to help out,they all worked just fine.
  I always opt out for the most gain and the largest reverb pot so I can get as much reverb as possible.You can always turn it down but if it's not there to begin with there is nothing to turn down.
  The insertion point is pretty critical as well as the size of the mix resistor.It can work in a few locations but some work better than others.

Title: Re: Reverb implementation. Would this work?
Post by: tubenit on December 16, 2010, 07:14:15 pm

One tube reverb from the ARCHIVES:

http://www.el34world.com/Forum/index.php?topic=7957.0

If you need alot of reverb, take a look at the 6Bm8 reverb idea. I haven't built it myself but it's an interesting approach.

With respect, Tubenit

Title: Re: Reverb implementation. Would this work?
Post by: Baguette on December 17, 2010, 02:26:21 pm

Thanks for the replies guys,

The 1 tube reverb is pretty neat, but I find it weak.
The Fender type 2 tubes reverb is neat too but I never run it past 4 on the dial.

I want a 1.5 tubes reverb  :grin:

Seriously, something as deep as the Fender reverb sound, but less surfy and less extreme would be the ticket for me.

Title: Re: Reverb implementation. Would this work?
Post by: Willabe on December 17, 2010, 03:02:09 pm

Baguette,

Want your cake and eat it too?     :laugh:     Me Too!

I had a BFSR for years (played a lot of gigs with that amp), and still have a BFPR, but they were to my taste a little "splashy".  Never ran either one past 3, 3.5. Also had (years ago) a Mesa M II C, that had a one tube verb, which I didn't like.

I wonder how much the verb can be tweaked (the "splashyness") just by using a different tank? They have short, med. and long delay tanks, also 2/3 spring and long/short tanks. I've never tried this, but I'm wondering now? I never gave it a second thought before, I always used the longest delay, and when the 3 spring units came out I went to using those, also agine with the longest delay.

I wonder what others here have found out on this from trial and experance?    :icon_scratch:


   Thanks,    Brad       :smiley: