Did McIntosh make any improvements to MC-30 circuits over later edition?
I know my MC240 had a few minor changes

My local Mac retail guy, a tubehead, tells me that there were 'at
least five' versions of the MC-30 circuit. The only ones that I can
account for are with and without the use of 1/2 of the 'first' 12AX7
as a regulator for the input stage. In MC-30s that I have worked on I
have encountered 2 different values of coupling caps from bh7 to ax7.
I have not found schems with other versions of the circuit, so maybe
later variations were documented in service notes rather than redrawn
schematics. Mcintosh stayed remarkably loyal to the basic MC-30/60
circuit during the long production run of these pieces. The only
significant differences that I see are parts suppliers for passive
components, and they used ordinary consumer grade materials there.
FYI, some people say that the earlier version of the input circuit,
using the 1/2 12AX7 as a regulator is 'better'. I discerned no
difference.
If you're going to tinker in there, take a look at the HT voltages.
I found them 5% - 8% high with our 121V line voltage, which might be
enough to make a difference in wear on tubes and heat sensitive parts.
Switching to the '125V' primary tap on the PT brought them down
closer to spec.
According to Roger Russell
(http://www.roger-russell.com/amplif1.htm#mc30), there was a variable
damping kit available, presumably for use with loudspeakers requiring
a low damping factor to optimize the bass.
I have a rare MK-30, a kit version of the MC-30 of which a few
hundred were sold in '60 - '61. The only differences are screws
instead of rivets on the chassis and different transformer stickers.
Oh, and the soldering is neater.

Ross Hershberger
The Ballroom
Bauhaus Corners

"john s" wrote in message news:iaDsb.185124$Tr4.524662@attbi_s03...
Did McIntosh make any improvements to MC-30 circuits over later edition?
I know my MC240 had a few minor changes

I found one schematic online but it is not legible.
Found a 116 schematic which looks different than what I have.
"john s" wrote in message
news:iaDsb.185124$Tr4.524662@attbi_s03...
Did McIntosh make any improvements to MC-30 circuits over later edition?
I know my MC240 had a few minor changes

Hi John,

I'd be glad to email you the scans I have. Is the yahoo address OK?

Raymond

john s wrote:

I found one schematic online but it is not legible.
Found a 116 schematic which looks different than what I have.
"john s" wrote in message
news:iaDsb.185124$Tr4.524662@attbi_s03...


Did McIntosh make any improvements to MC-30 circuits over later edition?
I know my MC240 had a few minor changes