Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Glennjeff on July 09, 2016, 06:01:10 am

Title: All in One Preamp - THOUGHTS
Post by: Glennjeff on July 09, 2016, 06:01:10 am

Would anyone care to comment.

In particular, would I really need to do that switch trick with the TOS / PLEXI section.

Title: Re: All in One Preamp - THOUGHTS
Post by: John on July 09, 2016, 08:46:47 pm

I dunno about the switch trick. I try to get away with as few as possible.


Since I'm dim at this stuff, can you explain the mixer stage? At first I figured each stage would just go to your PI tube. Are you wanting to also mix each preamp nugget  if you want?

Title: Re: All in One Preamp - THOUGHTS
Post by: Glennjeff on July 09, 2016, 09:56:18 pm

Hi John,

I do want to mix each nugget, plus the active tube mixer is known to generate it's own harmonic content and some people claim the active mixer stage has super special magical rainbow unicorn properties.  :laugh:

This was just the basic sketch, will need to be refined a little. There will also be a couple of overdrive sections later on.

Title: Re: All in One Preamp - THOUGHTS
Post by: John on July 10, 2016, 06:25:52 am

Ahh yes, the unicorn properties!!  :icon_biggrin:


I was thinking more about that switch. I'd say if you're doing all this heck yeah use it. Be a good way to A/B the difference in tone, IMO.

Title: Re: All in One Preamp - THOUGHTS
Post by: HotBluePlates on July 11, 2016, 02:43:03 pm

You may want to export your .sch file to a .gif so folks without the program can view it.

Title: Re: All in One Preamp - THOUGHTS
Post by: uki on July 11, 2016, 02:46:04 pm

Quote from: HotBluePlates on July 11, 2016, 02:43:03 pm

You may want to export your .sch file to a .gif so folks without the program can view it.

I got a program that can generate .sch but I can't open yours, .jpg have good quality, and .pdf is also good.

Title: Re: All in One Preamp - THOUGHTS
Post by: Glennjeff on July 11, 2016, 09:59:05 pm

Apologies, thought the sch was a freeware program.

Here are the GIF's

Title: Re: All in One Preamp - THOUGHTS
Post by: PRR on July 11, 2016, 10:20:50 pm

That form of mixer has very low maximum output level.

Suggest adding separate plate resistors and three 220K mix-resistors. Or even skipping the gain here, just mix 1 2 3 with 220K, and add make-up gain behind.