Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on January 18, 2011, 01:51:28 am

Title: Adding a VVR to 18w amp
Post by: TIMBO on January 18, 2011, 01:51:28 am

Hi guys,I got a spare VVR and i'm wanting to add it to a 18w amp. I looked through all the schems i have and can't find one thats been added to one. Help please, thanks

Title: Re: Adding a VVR to 18w amp
Post by: tubenit on January 18, 2011, 04:36:08 am

I added three 18w versions here in ARCHIVES:


http://www.el34world.com/Forum/index.php?topic=6899.0


With respect, Tubenit

Title: Re: Adding a VVR to 18w amp
Post by: TIMBO on January 18, 2011, 01:30:58 pm

Thanks Tubenit, I have about 150 schems in my file and it takes forever to search through them to find info, there must be an easier way to search them. Anyway i have updated the schem. Thanks

Title: Re: Adding a VVR to 18w amp
Post by: TIMBO on January 22, 2011, 01:49:54 am

Hi guys, Just doing some last checks on this build and i was thinking that the circled filter stage is not necessary in this circuit. Any thoughts. Thanks

Title: Re: Adding a VVR to 18w amp
Post by: tubenit on January 22, 2011, 06:20:25 am

I think you need it so there is filtering prior to the VVR. And it certainly won't hurt anything.

Tubenit

Title: Re: Adding a VVR to 18w amp
Post by: TIMBO on January 22, 2011, 02:20:40 pm

Tubenit, I was wanting to have the option to switch between fixed and cathode biasing as per Sluckeys Nov Project, but from what i am reading to use a VVR i don't think this can be achieved and to use a PPIMV won't sound as good. Will it be a case of choosing a fixed or cathode bias  :sad: Thanks

Title: Re: Adding a VVR to 18w amp
Post by: sluckey on January 22, 2011, 03:30:36 pm

Quote

I was wanting to have the option to switch between fixed and cathode biasing as per Sluckeys Nov Project

The idea of switching sounds cool and I flipped that switch many times for the first week. But I gotta tell you, it's just a waste of a good switch. I don't have that switch in my stuffed Vox (which is the same circuit) and my orig November has long since been converted to a Matchless Lightning.

I would be very happy with VVR in a cat biased EL84 amp. I bet you would too.

Title: Re: Adding a VVR to 18w amp
Post by: TIMBO on January 22, 2011, 04:58:26 pm

Thanks sluckey, I think i am only trying to get the best of both worlds.The end result i would like to get ( i am thinking that the fixed bias will achieve this) is to be able to dial the power amp to be cool or pushed. The VVR i have is for a cathode bias. From what has been posted the power amp will perform this way at any level of the VVR (bedroom use only) so can this line of thinking be achieve another way as i would have to make another VVR unit or order one from the US.Thanks

Title: Re: Adding a VVR to 18w amp
Post by: jojokeo on January 22, 2011, 05:09:29 pm

Quote from: sluckey on January 22, 2011, 03:30:36 pm

The idea of switching sounds cool and I flipped that switch many times for the first week. But I gotta tell you, it's just a waste of a good switch.
I would be very happy with VVR in a cat biased EL84 amp. I bet you would too.

sluckey, does this mean you only use the cathode bias setting?

Title: Re: Adding a VVR to 18w amp
Post by: sluckey on January 22, 2011, 06:50:16 pm

Quote

does this mean you only use the cathode bias setting?

No. It means I don't have switchable bias in my November amp.

Title: Re: Adding a VVR to 18w amp
Post by: jojokeo on January 23, 2011, 12:07:37 am

 :rolleyes: - sorry I asked