The reddish orange plates took some getting used to as normally you don't want that. The pair that I worked were bought for some ridiculous amount, no more than $100 IIRC. Why I am never in the right place at the right time!!!!!
Don't know what the current rate is, probably couldn't afford them anyway. Last I heard he was scouring the earth for all of the 8005s he could find.
Craig
Don't know what the current rate is, probably couldn't afford them anyway. Last I heard he was scouring the earth for all of the 8005s he could find.
Craig
That model would be the MI-200. It was a four chassis rack mounted beast with potted output transformers about a cubic foot square. The transformer was quadfiler wound and included the driver stage. I think I read somewhere that the Grateful Dead used one for sound reinforcement. I've had a pair of these in my amplifier collection for years but have never turned them on. Maybe someday.
They also build an MI-350 monoblock (MC-3500 consumer version) that used eight 6LF6/6JE6 tubes in push-pull parallel. This was a single chassis amp and is also a monster in size. (I own one piece) The output transformer is pentafiler wound which includes the 6BL7 cathode follower and the 6DJ8 pre-driver plates and the 6DJ8 cathodes (crosscoupled). Have never fired this up either.
It has been said that when McIntosh went past bifiler primaries into tri and more, the sound quality suffered loss of detail. To what extent this is true or not I can't say for sure. But the other night I was at a friends home who uses an MC-240 and it was very nice sounding, at least to my ears.
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Yes... I think in the main this has already been said?
As I said it was also made as the K-104... you can find the schematic if you look, I expect.
_-_-
As I said it was also made as the K-104... you can find the schematic if you look, I expect.
_-_-
It is another way of saying what came first, which in this case is the McIntosh amplifier design versus the Electrovoice design.
The MC240 has one simple loop from a separate isolated secondary back to the input cathode.
McIntosh was the amplifier that introduced me to tube amplifiers, however my initial lust for them has declined over the years. These days, I tend to think of McIntosh as the 'Adcom of the vintage era'. Their amps are reliable, but not the greatest in hi-fi. Of course, this is debatable! I won't begrudge anyone and their Mac-love.
I run a vintage MC250 solid-state amplifier in my family-friendly second system and find it gets pretty close to the 'tube' sound.
I run a vintage MC250 solid-state amplifier in my family-friendly second system and find it gets pretty close to the 'tube' sound.
not really, depending on where/how you look.
these are audio adaptions, of radio circuits/schematics.
actualy, they are somthing special.
once the electrolitic caps, are bypassed, and or replaced,
with lower distortion types,
(plastic,or oil)
AND
mached with the proper speakers, the ones they were designed with,
they sound very good.
these amps have a low damping factor.
best to use highly damped, hi efficiency speakers.
'like the ones they were desgned with'.
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Ummm... exactly what speakers were they "designed with" right after WWII??
I think we are talking about older McIntosh designs - the original concept which is/was the unity coupled output stage, not the newer solid state (which has no relationship whatsoever to the earlier design, nor was it designed by the same person - afaik) - nor the later tube designs which similarly were adaptations whose benefits are not so clear.
_-_-bear
PS. what exactly are "highly damped" speakers?
A speaker with a low Qts would be "highly damped" and would likely benefit in sonics from a low damping factor amplifier, as a high DF amp would cause the Qts to be lower (more "damped").
I think we are talking about older McIntosh designs - the original concept which is/was the unity coupled output stage, not the newer solid state (which has no relationship whatsoever to the earlier design, nor was it designed by the same person - afaik) - nor the later tube designs which similarly were adaptations whose benefits are not so clear.
_-_-bear
PS. what exactly are "highly damped" speakers?
A speaker with a low Qts would be "highly damped" and would likely benefit in sonics from a low damping factor amplifier, as a high DF amp would cause the Qts to be lower (more "damped").
And here I thought that Les Paul was the only reason McIntosh was famous because he used them for guitar amps. YeahYeah I am a guitar player & a MC240 owner 😀
Really? I'd love to see an example of a unity-coupled transformer in an RF design pre-McIntosh. Can you cite one?
altec/ jensen /lansing/RCA/western electric
that was my understanding.
cross-coupled
agreed
There were quite a few designs that predate the McIntosh that were cathode coupled to the output transformer. At least half a dozen. I guess by definition they are all "unity coupled"??
_-_-bear
PS Spread, I think you meant to say AF, not RF?
_-_-bear
PS Spread, I think you meant to say AF, not RF?
@ bear
Only if the ratio of primary plate driven windings and cathode driven windings are 1:1, and I am not aware of any that predate the McIntosh.
General thoughts below:
The original McIntosh design dates back to around WWII so I cannot think of many designs that even used global feedback let alone cathode feedback in that era. Some clear examples of precedents would be nice to see.
There is a reason why the original transformer design was patented, and that's because the approach was novel and original to Frank McIntosh. Driving a unity coupled output stage required some very clever engineering like the boot-strapped driver stage for the extreme voltage swings required. (IIRC some of the circuitry design was also patented) These amplifiers also were the first to utilize relatively high levels of global feedback and maintain stability into all sorts of loads. (Yes I am aware that the Williamson also used rather a lot of feedback, but wasn't unconditionally stable into every load.) Ever wonder why tube rolling results in little if any discernible change in the sound of most models of these amplifiers?
Why denigrate the considerable accomplishments of this outfit? They must be doing something right since they are the only surviving company from the dawn of hifi that I can think of.. 😀
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kevin,
I'm not disparaging the original design. I like it.
Obviously no one else used the same topology, since it was patented.
If you go back to Terman, (iirc) there are multiple examples of cathode coupled and maybe even partially plate and cathode coupled output stages. Probably some are illustrated and/or referenced in Radiotron.
As far as loop feedback is concerned, I do not think that is unique to McInstosh, nor do I consider that a significant element of the patented design at all.
Fwiw, other designs that have other merits and flaws were also patented in that period of time... McIntosh was just more sucessful commercially so it is remembered now, of course it is a superior design which is part of the reason for sucess.
_-_-bear
I'm not disparaging the original design. I like it.
Obviously no one else used the same topology, since it was patented.
If you go back to Terman, (iirc) there are multiple examples of cathode coupled and maybe even partially plate and cathode coupled output stages. Probably some are illustrated and/or referenced in Radiotron.
As far as loop feedback is concerned, I do not think that is unique to McInstosh, nor do I consider that a significant element of the patented design at all.
Fwiw, other designs that have other merits and flaws were also patented in that period of time... McIntosh was just more sucessful commercially so it is remembered now, of course it is a superior design which is part of the reason for sucess.
_-_-bear
No, tomtt's contention was that "these are audio adaptions, of radio circuits/schematics." I just wanted to see the radio circuit/schematic that Frank copied from before he filed his patent.
Personally, I love the elegance of the transformer design in the unity-coupled amps. Driver design is not trivial, but I am getting about 1.2% distortion out of some 6SN7s at 200Vrms for an amp I am working on with similar voltage drive requirements. No feedback to this stage at all, just CCS on plate with high supply voltage and light load from the following stage bias resistor. We'll see what overall open-loop distortion on this amp will be at the output when all is done, but I think its going to be pretty low.
not contention, as such.
was an observation .
doesn't seem like frank copied so much, as he recognized the potential.
seen a picture, of frank, at the bell labs, tweaking some radio equipment,
in this series of books -
'A History of Engineering and Science in the Bell System'
An externally hosted image should be here but it was not working when we last tested it.
also -
"Frank H. McIntosh began his career with ten years at Bell Telephone Laboratories in Murray Hill, New Jersey.
He then became a broadcast sales representative for the Graybar Corporation on the West Coast.
During WWII he was head of the radio and radar division of the War Productions Board. "
from here -
McIntosh Laboratory Part 1
other stuff -
McIntoshAudioAuctions.com - Frank McIntosh - McIntosh Audio - McIntosh History - Audio Equipment
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That's definitely what sound you get with too much gNFB. I equipped one project with variable gNFB: from none at all to about 13db(v) of gNFB. Turn that gNFB knob all the way up, and the sound does indeed become solid statey. Keep it set about 6.0db(v) of gNFB, and that's enough to take care of woofer damping, and to take just enough edge off the 6BQ6 finals (operated as pentodes with active screen regulation, fixed bias, and grid drivers). Less gNFB tends to sound overly "edgy" or "aggressive".
except this is not the original circuit, sounds like one of the later high power circuits??
_-_-bear
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