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In Reply to: RE: How can I get the magic of McIntosh MI-200 amps posted by bcguitar on October 23, 2014 at 08:42:35
Buy speakers that are 100 times more efficient?
Seriously, it's very hard to compare a 200-watt push-pull high feedback amp with a 2-watt single ended zero feedback amp. Kind of like a locomotive vs a moped.
What factors are important to you in terms of the "magic"?
Follow Ups:
great highs, mid and bass...overall excellent sound. I thought this was gonna be easy.
OK, I see elsewhere that you have 100dB speakers so a 45 SET will do the job unless you're a real deaf headbanger!
I'd say for really wide range sound you must find a really good output transformer. If you liked the MI-200 with it's enormous headroom, then you probably want pretty low distortion, so keep the OPT impedance on the high side and use a driver stage with lots of headroom. (I like current source plate loads, but a really good plate choke or interstage transformer will give you low distortion with even greater headroom. For total over the top, a regulated power supply might help.
Thanks Paul, that helps some. Does someone make an amp with these attributes that you know of?
"Does someone make an amp with these attributes that you know of?"
Not really - though I am not familiar with everything on the market!
John Tucker once made a shunt-regulated parafeed 45 using the Magnequest TFA-2004 output transformer, which will handle 20 watts at 30Hz - seems like overkill but it sounded fantastic. But that's a 3K impedance which is too low for the low distortion I was thinking about; I'd want 5K or so.
When I suggested a plate choke, it was to enable a high plate voltage - the power supply for a 45 will be around 350vDC. The 5842 (also mentioned) is not suitable because it has an absolute maximum of 200 volts.
Frankly I have not heard an interstage that sounds good enough, but in theory it does allow for the higher driver plate voltage.
Someone mentioned the design I am (slowly!) working on; it will not meet all the criteria I have suggested above - my comments were just a theoretical exercise to address the specific interests of the OP.
Someone also mentioned direct coupling, which does indeed sound wonderful. However, the difficulty in achieving and maintaining the operating points is so great a problem that I am avoiding it these days; I'd rather spend some money on really really good caps.
~!
The Mind has No Firewall~ U.S. Army War College.
Finally an actual answer, thank you cleantimestream!
Paul gave you an excellent answer of design goals that will net the 'traits' you made mention you favor... is quite difficult {in Paul's position as a manufacturer} as even an altruistic answer 'may' be construed as a ploy for his own wares. Paul {so far as I am concerned} possesses dignity incapable of such unscrupulous behavior. I, however am just another DIY lughead out there having fun.
The Mind has No Firewall~ U.S. Army War College.
one of my posts in one of the other forums about the same topic.
Paul is working on one, but we've been trying not to bug him too much :)
http://bottlehead.com/smf/index.php?topic=3000.msg67512#new
Better be a Moped capable of lapping Laguna Seca with a Formula One Car!
At the request of the Moderators,
This space has been deleted
So, what amp is that and does it sound good??????? Moped? wth
An 845 amp or a GM70? They are pretty ballsey for SETs. But really listen to what Paul said. You're really talking about a PP amp. You might try a class A NFGB PP DHT(45 or 2A3)tubes or triode-wired pentode with KT88/6550A tubes. The latter will sound less SETish, compared to 45 or 2A3.
On the other hand, with a 100 dB efficient set of speakers, you may have noise problems unless you can get low gain versions.
Observe, before you think. Think before you open your yap. Act on the basis of experience.
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