can't figure it out

[shooter]

'm ooglin schematics for my next build and I find this;

I'm looking at V1b
my guess is it's common grid , some sort of AGC

[kagliostro]

Also the OT winding at cathode is a bit odd to me
not the winding at cathode itself, but the intake that goes to pin number 5 of the connector .... 

Franco

[VMS]

Some kind of voltage regulator maybe   

[shooter]

Also the OT winding at cathode is a bit odd to me

If you look at the legend, they use that as the  70.7v type line out, inductors were once considered cool

I'm really only interested in a V1 phono preamp circuit that's odd

[shooter]

   I'm even more confused, I can't get B+ to V1a
I'm now leaning to some sort of PI???, I'm redrawing it so I can see better

[sluckey]

V1A plate current path flows through R8 to V1B cathode to V1B plate to C12C.

[VMS]

It's a voltage regulator, look at the schematic on this service manual:


http://www.vintagevacuumaudio.com/schematics-manuals/mcintosh/mcintosh-mc60-service-manual-parts-list-schematics.pdf

[shooter]

You folks are amazing, thanks

I also just sorta skipped over the "preamp" part of the connector and read "input"

I found the revised schematic that eliminates the neon's, then found type 125 that eliminates the regulator

[shooter]

ok, think I get it, maybe. I redrew V1, if I tweak R5/R31, I change V1a's plate voltage?

Is there something I'm missing if I feed my own "next" gain stage?  can I keep it DC coupled?  or is it better to cap couple?  I'm going for SE vs the PP

[PRR]

> SE vs the PP

??

Anyway--- That's a McIntosh. Mere Mortals are not supposed to understand. The killer detail is the unity-coupled OT, something NO other maker ever attempted. The flip-side is that it needs HUGE signal at 6550 grids. McIntosh was full of too-clever ideas. To sell them, he put every bell and whistle on. Great amps, but not for you.

That's not a suitable steal-point for a guitar amp.

[shooter]

That's not a suitable steal-point for a guitar amp.

this idea is a mono-block 10-20W.  I want a phono level in and something that can deal with 1-2vac in.  It's more about "that's unique", also, can I make it variable, if so, I can scope the effect of changing DC plate, on AC signal

I also found a meter circuit from one of my early hero's, Mr. Mims

[shooter]

here's the 1st draft pre-section.  the PA will be one I used before, QSE EL84's
not all the values are there yet, any that are, I'm open to recommendations

I named it, now I gotta build it, slowly, probably start with a new BB rev 3

[shooter]

It's 62degrees!!!  so I tore down the donor chassis.
3.5kw mod-sinewave invertor that I, um, forgot to switch out when the grid came back

[shooter]

finally found all the Iron
250v 200mA PS
10H 200mA choke
25W UL OT

now I need casters

[Willabe]

finally found all the Iron
250v 200mA PS
10H 200mA choke
25W UL OT

now I need casters

 

[shooter]

I bread boarded the panel meter last night, probably have a switch to monitor input, or output of the preamp.

[shooter]

got 2 many fires going so I took the Hammond 270HX and plugged it in, PT test into a 5K load gets 408vdc with a fullwave, ct grd.  I haven't had an amp since Christmas,  , and I'm not even a player
hopefully by the weekend