Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Shack on October 04, 2016, 05:47:45 pm

Title: this years project
Post by: Shack on October 04, 2016, 05:47:45 pm

I could easily build a champ, vibrochamp....or single ended plexi, or....I could do a remodel of my blues jr, like I was intending.

I see lots of plexi pedals that run upwards of 250.00 to buy, if I built a plexi preamp what would be the best way to run it into like, say a HRD....in front or through the power amp in.....the line out on my tweed deluxe didnt work on the power amp in jack, probably a phase issue....and havent pursued it further.


I would like to make a single ended plexi, with a preamp out jack, to use as a preamp for the HRD somehow and see how it works


Is that worth the effort?   wish I could just try all projects

Title: Re: this years project
Post by: jjasilli on October 04, 2016, 06:12:22 pm

If I understand, you wish to build a low power SE Plexi amp, with the option to run its preamp into a more powerful amp, like the HRD.  Sounds like a good idea.  In the Schematics Section Tubenit has schematics for preamp line out.  If you make the preamp line out adjustable with a pot, you should be able to feed it, at your option, into the bigger amp's input jack or line in.  (Be prepared to address possible hum issues.)

Title: Re: this years project
Post by: Shack on October 04, 2016, 09:04:08 pm

perfect, thats exactly what im thinking  :icon_biggrin:

Title: Re: this years project
Post by: Paul1453 on October 05, 2016, 05:18:33 pm

I have not used any send and return FX jacks on my builds yet, but I have done this.

I have a 6V6 Plexi build that I made my own component board for.
It was basically a board with just the pre-amp components on it.

So I was working on designing an EL86 PP output section.
When I thought I had that worked out,
I snipped the wires to the tubes on my 6V6 Plexi's pre-amp board.
I then removed the whole circuit segment, pots included, in one big piece.

I wired up 3 12AX7 sockets in my new design,
and connected the Plexi's pre-amp circuit board with longer wires just laying outside the amp on my wooden bench.
It worked perfectly on the 1st try.   :icon_biggrin:

I don't see any reason why what you are proposing wouldn't work.
Only issue I think you might encounter is hum/noise from connecting two separate power supply circuits.   :icon_biggrin:

Title: Re: this years project
Post by: Tone Junkie on October 05, 2016, 06:43:28 pm

use 1/4 inch jacks.
 On the pre amp put a ground lift switch so it runs on the ground of the power amp. if there's still hum use Merlins ground lift also. on pre amp grounding with a cap and resister.
Bill

Title: Re: this years project
Post by: Shack on October 06, 2016, 10:02:33 pm

thanx for the replies...im thinking I may just start with the preamp and if all works well for me I will add the power section.....will build power supply for the whole thing and experiment as I go....the preamp is what I want the most, I dont use the practice amps I got now lol

but I love the low power Hi gain amps ive seen on you tube ....so one never knows