B15 preamps with 6SL7 and 12AX7

[bnwitt]

Hello everyone!  I hope all is well.  It has been a while since I've been here.  Been traveling non stop with my job and not much time for amping.  But now I may have a project.  A local music equipment dealer wants me to build a prototype dual channel bass guitar pre-amp circuit to go into his already designed chassis with one channel being an early 60s 6SL7 B15 preamp version and the second channel the early 70s 12AX7 B15 version.  The circuit is supposed to have a US/UK switchable power input, individual channel control and channel blending capability as well as balanced, unbalanced and headphone outputs.  Sounds like a fun project.  Has anyone every done anything like this in here?


Barry

[shooter]

here's a good example of individual channel controls and blending;
http://sluckeyamps.com/phoenix/phoenix.pdf

look to Marshall or Fender for 120/220 "international" input power

the line out stuff, google up pre-made XLR - line out modules

[sluckey]

Sounds like a neat project Barry. You may want to locate that 6 pole 3 position rotary switch before you dive in too deep.

[shooter]

I started thinking again 
what if you had 2 "EIA" type recepts; US version wired inside 120, EU version wired 230?
match the power cord to the hole, maybe need a lockout switch?  Definitely need a universal PS

[bnwitt]

Steve,
Good to hear from you buddy.  Which version has the rotary switch?  I met with the dealer and he handed me the prototype unit which he tells me is noisy and not fully functional.  Everything is crammed into a pretty small chasis and the wiring lead dress is poor.  I'll post some photos later.  Shooter, I think I'll see what Marshall does.
Edit:  I see the 15S is the one with the rotary switch.  The prototype I received doesn't have one.  I think mine will.
Barry

[bnwitt]

Here is a Dropbox link to some photos of the unit as is.  I think I am going to have to start from scratch.


https://www.dropbox.com/sh/f9wx8ermrswzxw8/AACQrFMK_HsV5YIYpfFmGfMTa?dl=0


Barry

[kagliostro]

Ciao Barry

https://www.ebay.it/itm/COMMUTATORE-ROTATIVO-6-VIE-3-POSIZIONI-/311783587437





Franco

[bnwitt]

Thank you for the link to the switch Franco

[kagliostro]

At the moment I have no intention to build something like that 12ax7 preamp

but as that rotary switch isn't so common ..... I ordered one for my stock

Franco

[bnwitt]

Well I'm back on this project.  I finally have some time to work on it.  I'll post my progress as I go.
Barry

[kagliostro]

You may want to locate that 6 pole 3 position rotary switch before you dive in too deep.

 

No, I don't remember which was the reference schematic that used that 6 pole 3 position rotary switch

(I got one of those and I had it under hand yesterday)

Please someone can refresh my memory, Thanks

--

BTW bnwitt, did you go further with taht project ?

And more than all, I hope you and your family are all well

Thanks

Franco

[kagliostro]

Is this the schematic ?

https://el34world.com/charts/Schematics/files/Ampeg/Ampeg_b15s_revd.pdf



Franco

[tubeswell]

FWIW, I posted a pic of an original 1961 B15 schematic in the Schematic forum a couple of weeks back.

[kagliostro]

Thanks Tubeswell

Franco