Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Big_Mike on October 04, 2018, 08:08:31 pm

Title: 6V6 Plexi Build
Post by: Big_Mike on October 04, 2018, 08:08:31 pm

I am going to start on a Hoffman 6V6 Plexi build over the next few weeks.  I am using a Heyboer 18 watt PT and a Trainwreck 30 watt OT. 

I am going to build it stock per the Hoffman layout, then might make a couple of tweaks to add a PPIMV as a substitute for the pre-phase inverter master.  I also am going to add a pot to the rear of the chassis to allow for variable negative feedback.

Really excited for this project.  Any suggestions on which 6V6 tubes to use to sound most like an EL34?  I have read that JJs sound a little different than other brands.

Title: Re: 6V6 Plexi Build
Post by: sluckey on October 04, 2018, 08:43:52 pm

I have JJs in mine. They match my JJ 5AR4. My amp sounds exactly like every 6V6 Plexi I've ever heard.  :wink:

Title: Re: 6V6 Plexi Build
Post by: Vlada on October 06, 2018, 05:55:58 am

I think you wouldnt hear much diference between new production tubes, except that JJ 6v6 sounds closer to 6l6. JJ 6v6 is great tube, it can handle higher plate voltage, hotter bias, built like tank. I have built jcm type circuit with JJ 6v6 tubes, it sounds great. My opinion: those are the best new production 6v6 tubes. Wish you good luck and happy building

Title: Re: 6V6 Plexi Build
Post by: dude on October 07, 2018, 09:28:46 am

I've tried all different brands of used American made 6V6, subtle  differences. The tonal differences JJ6v6's and used old stock 'to me" are the JJ's seem to be cleaner, louder and closer to a 6L6, could be because my old US 6V6 are used...?
If I were gigging with the amp, JJ would be my first choice, it's all a matter of your ears, IMO.
As far as the PIMV, I would use it, has a major effect on the loudness of the amp much more slower response then the PPIMV. I'd ditch the the NF pot (turning down PPIMV you lose the presence control) and put the PPIMV on the back with the front pre-MV. Blending the two gives much better control over break-up and loudness, of course that my opinion. I've tried both, alone and together.


But it's your amp, experiment  :icon_biggrin: .
al

Title: Re: 6V6 Plexi Build
Post by: Big_Mike on October 07, 2018, 10:11:35 am

Thanks for all the input, much appreciated.  I am going to build it first stock per the Hoffman schematic, and then tinker.  I want to experiment with the different master volumes.  A PPIMV reduces negative feedback, so adding a negative feedback pot to adjust resistance helps to dial back in NFB.