------------------------------ From: billyee@vnet.IBM.COM Date: Thu, 9 Dec 93 16:53:45 EST Subject: McIntosh Amplifiers Since, I currently have an interest in buying a McIntosh amplifier, I was wondering if anyone knows anything about McIntosh stuff, history and status in the high-end audio world today. Reason I am asking? Because, I know they were a big BIG name in the 1950's to 1970's, but then it seems they kinda lost the edge, and mellowed off into a low profile operation. They switched from tubes to solid state, but retained the use of their output "auto-transformers" in their solid state designs. This I believe is what give them the so called "McIntosh" sound. (IMHO it's a nice sound). But in this new age of Krells, Levinson's, Audio Research's, etc. I do not see McIntosh amps being reviewed by the high-end rags. What gives? Only recently have I seen Sam Telig in Stereophile magazine speak some good words about a McIntosh MC275 Commemorative, Limited Edition tube amp. I would like to know how the MC2255, MC7270, MC7300 and MC7150 McIntosh solid state amps stack up against the other high priced, high-end amps tube or solids. Let me hear some feedback please. FYI, I've heard a MC2255 amp (production years were from 1981 to 1986) with my modified Aria-3 speaker systems with subwoofers and it simply was sweet. Just sweet. Yeah, you guessed it, I like sweet. I though that my Adcom GFA-585 and two GFA-565 monoblocks were doing a nice job until then. Now I'm spoiled and it makes me wonder why McIntosh amps are not on the Golden-Ear boys recommended lists. I hope some folks out there can enlighten me. ------------------------------ From: terry@austin.ibm.com () Subject: Re: McIntosh Amplifiers Date: Fri, 10 Dec 1993 16:35:33 GMT Bill, I have a MC7150 which I've been using for about 3 Years, and find it CONSIDERABLY better then the Adcom, Rotel, and Hafler Equipment, but still MUCH more affordable than the Krell, Rowland, and Levinson gear. Although I have listened to the High End, I find McIntosh to be the more reasonable compromise. You're right about there being very few Audio Magazines reviewing Mc hardware, they all seem to look at the extremes. I hope this helps. -- Terry Boylan AWS/Austin T/L 678-4755 ------------------------------ Date: Mon, 13 Dec 1993 16:20:00 +0000 From: "henry (h.) pasternack" Subject: 70W McIntosh Amplifier in Glass Audio. The new old stock McIntosh transformer Bruce Rozenblit mentions in this article is no longer available. Audio Classics now sells a replica transformer they have had made to original specs. The price is $125 each. I have a pair of these transformers, and may be inter- ested in selling them. Write for details. I wouldn't recommend using a pair of 6550s with these transformers as described in the "Glass Audio" article. Rozenblit is running very high B+ in this circuit. In this configuration, the 6550's are capable of putting out about 100W. The poor transformers were only designed for 35W service. A much better match would probably be a pair of Sofvtek 5881/6L6GC's with a B+ of around 450V. In pentode mode, this would give an output power around 50W. Rozenblit specifies a 1000VCT power transformer, which will result in 700V B+ with solid-state rectification. Bad idea. He was trying to apply the VTL design philosophy of high B+ and low bias current, but I don't think he fully understands all of the tradeoffs involved. It would be better to use the transformers as they were designed. Another example of Rozenblit's carelessness: He specified 1000PIV rectifier diodes for the power supply, but failed to consider that the diodes would see reverse peaks of 1300-1400V in his circuit. Better double up on the diodes for safety. I think a lot of the success of an amplifier design is in the details. Rozenblit had a nice project, but he screwed up, IMHO, and published a design that has real problems if copied exactly. The transformers seem pretty decent, though. There's no reason one can't use them to build a solid amplifier. -Henry ------------------------------ From: tech@aupair.cs.athabascau.ca (Richard Loken) Subject: Re: 70W McIntosh Amplifier in Glass Audio. Date: 14 Dec 93 17:30:08 GMT henryp@bnr.ca (henry (h.) pasternack) writes: > The new old stock McIntosh transformer Bruce Rozenblit mentions >in this article is no longer available. Audio Classics now sells a >replica transformer they have had made to original specs. The price >is $125 each. I have a pair of these transformers, and may be inter- >ested in selling them. Write for details. I suggest you use McIntosh's circuit with a minimum of clever tricks. McIntosh won by using a very solid conseervative design and a vastly superior output transformer (IMHO) and that design with modern components should sound very nice. Get a copy of the MC230 manual and clone it with modern parts and listen carefully before you start modifying. They don't pay all that money for Mac amps because they sound bad. The one problem you may have is if the 230 design uses a now rare output tube type (and I don't know the answer to that) in which case you are well advised to redesign it with an available type but do the redesign very conservatively. I would not be in a hurry to try to pull more power out of the output transformer then McIntosh did because you will shorten its life. >From 50 years to ten years:) You can get a lot of clues about my personality from this article. No? -- Richard Loken VE6BSV : "...underneath those Athabasca University, Athabasca, Alberta Canada : tuques we wear, our heads tech@cs.AthabascaU.CA : are naked!" {atha|aunro}!cs.athabascau.ca!tech : - Aurthor Black ------------------------------ From: KSTETSON@fair1.fairfield.edu Subject: McIntosh Amplifiers Date: 15 Dec 1993 07:46:49 -0600 I too have wondered why McIntosh equipment seldom sees mention in the audio press. Judging from the listings in Audio Classics catalogs, they certainly hold their value. I recently purchased an MC250 (50 watt/channel tranistor power amp) and an MX110 (tube tuner- preamp) from the original owner. These units are 25+ years old and everything works flawlessly. Within a week I had brought my Adcom GFA 535 power amp and GTP-500II tuner-preamp to the dealer for him to sell on consignment. I had been happy with this equipment for over four years, but the improvement with the Mac equipment was dramatic. (Other equipment in use includes Cambridge Soundworks Ensemble, Dual CS-5000, and Adcom GCD-500 CD-player -- YES, I KNOW this is not high end stuff, but it's pretty good...) The best way to describe the difference in sound is a broader soundstage, warmer but detailed, noticably tighter bass, and simply a much more musical sound. I have been listening to CDs lately that I hadn't played in months, having been playing vinyl almost exclusively before the Macs arrived. kstetson@fair1.fairfield.edu ------------------------------ From: wright@pioneer.uspto.gov (Dirk Wright) Subject: Re: McIntosh Amplifiers Date: Thu, 16 Dec 1993 14:18:47 GMT : But in this new age of Krells, Levinson's, Audio Research's, etc. I do not : see McIntosh amps being reviewed by the high-end rags. What gives? Only : recently have I seen Sam Telig in Stereophile magazine speak some good : words about a McIntosh MC275 Commemorative, Limited Edition tube amp. The reason Mcintosh isn't reviewed in the mags is because they don't "float" loaner gear amongst the reviewers. The way it works is that a manufacturer that wants his gear reviewed simply sends the equipment around to the magazine staff hoping to get them interested in reviewing it. It's kind of a Kiss-ass way of doing business. Also, Macintosh doesn't go to the electronics shows, where the mag reviewers find gear they want to review. Mcintosh simply believes in word of mouth, I guess. They put adds in the mags, but that's about it. Regards, Dirk ------------------------------ From: stuartz@sco.COM (Stuart Zimny) Subject: Re: McIntosh Amplifiers Date: Fri, 17 Dec 1993 21:36:48 GMT In article <2eskb0$22k8@introl.introl.com> wright@pioneer.uspto.gov (Dirk Wright) writes: >The reason Mcintosh isn't reviewed in the mags is because they don't "float" >loaner gear amongst the reviewers. I think another reason might be that MacIntosh does not issue new models very often and therefore does not conform to the "Amp of the Month" paradigm put forth by the mags with monthly publishing deadlines and pages to fill. Stereophile did review a Mac amp a few years back quite favorably, by the way. Another excellent company which follows this philosophy is Bryston which has not, until very recently, received coverage by the Mags. -- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Stuart Zimny Internet: stuartz@sco.COM SCO Technical Staff UUCP : ...!{uunet}!sco!stuartz "We walk right foot, left foot, not right foot, wrong foot" --B.Fuller-- ------------------------------ From: /S=Booth/G=T/I=G/OU=MSMAIL/O=DEN.MMAG/PRMD=MMC/ADMD=TELEMAIL/C=US/@x400.den.mmc.com (T. G. Booth) Subject: Re: McIntosh Amplifiers Date: Wed, 22 Dec 1993 00:58:09 GMT In article <2en6c8$2aie@introl.introl.com>, KSTETSON@fair1.fairfield.edu wrote: > > I too have wondered why McIntosh equipment seldom sees mention in the > audio press. Judging from the listings in Audio Classics catalogs, > they certainly hold their value. > For those interested in McIntosh equipment, you might want to get a copy of the November 1993 Hi Fi News & Record Review. A subjective review of the "new, limited edition" version of the MC275 power amplifier by Ken Kessler is presented therein. The amp is also featured on the cover. Just thought folks would want to know... Regards, TGB ------------------------------ Date: Tue, 28 Dec 93 14:43:46 EST From: jas@proteon.com (John A. Shriver) Subject: Re: McIntosh Amplifiers For those who might want a slightly less fawning review of the MC275 than Ken Kessler's, there was also a review in Stereophile in the last few months. Still, the Stereophile reviewer bought his own (two, in fact), so he honestly admits a certain bias. McIntosh has just reversed a long-standing policy of not loaning equipment for review. The Abso!ute Sound has reviews upcoming. Maybe other magazines do as well. Not that there is real any point in reviewing the new MC275, the production run was sold out before it started. Instant speculators' piece. In these days where the relative prices of tubes and transformers has changed so, McIntosh's design, which requires a compilcated bi-filar output transformer, and a driver transformer (Class B, grid current, requires this), is not as impractical as it once was. McIntosh could only pull it off (financially) by making their own transformers. It sure gets a lot of power out of one pair of tubes, with very low plate dissipation at idle. Using transformer coupling for the driver stage probably also leads to very stable overload, which has major sonic benefits. No onset of grid current leading to capacitor blocking. (As Tom Holman noted at a BAS meeting over a decade ago, he found designing the 1.2 watt output stage in the Advent 400 table radio a major challenge. He had to design it to sound good in constant clipping and overload. All amps should sound good in overload.) ------------------------------ From: gilmore@casbah.acns.nwu.edu (Kevin Gilmore) Subject: >Mcintosh 275 power amp Date: 30 Dec 93 02:26:14 GMT The person who said that the mc275 has an interstage coupling transformer is mistaken. It uses a 12bh7 as a phase splitter. I have the schematics to all of the macintosh tube amps, and none of them, not even the mc500 use interstage transformers. They all do however use bifilar wound cross cathode coupled output transformers. ....kg.... I got rid of my mc275 about a year ago. compared to the KSA-250, well no contest... ------------------------------ From: "Roy S. Morgan" Subject: Re: >Mcintosh 275 power amp Date: Mon, 10 Jan 1994 17:38:11 GMT On 3 Jan 1994 09:29:08 -0600, Kevin Gilmore wrote: >The person who said that the mc275 has an interstage >coupling transformer is mistaken. ... Kevin, I, too read the post about driver transformers in McIntosh amps, and remembered working on an MC-275 having no driver transformer. I knew that they were not used in the MC-40, MC-60, or MI-75's that I have, and thought that McIntosh may not have used them at all. There is some precedence in earlier history, however. Over the weekend I was given a copy of a few pages of the Radiotron Designer's Handbook, 1953 Edition, edited by F. Langford Smith. Section 8, Class AB2 Amplifiers (pp 593-596), includes a discussion and diagram for the "50-watt McIntosh Amplifier". The model number is not given in the pages I have, although a reference is included in the book. The amp has 2 12Ax7's as pre-amp and inverter-amp, and a pair of 6J5's as drivers working into an interstage transformer. The final tubes are 6L6-G's. The specs of the amp are given as "... has a typical harmonic distortion of 0.2% from 50 to 10 000 c/s, rising to 0.5% at 20 c/s and 0.35% at 20 000 c/ s, at an output level of 50 watts. The frequency response under the same conditions, measured on the secondary of the output transformer, is level from 20 to 30 000c/s, -0.4 db at 10 c/s and -0.3 db at 50 000 c/s." These numbers are quite respectable for a pair of 6L6's, especially being driven by a transformer. The book also says, "The driver transformer ... makes use of the same bifilar winding method adopted in the output transformer." If anyone has experience with these "50-watt McIntosh" amplifiers, please post your impressions of them. --Roy Morgan Tech A-266 NIST, Gaithersburg MD 20899 301-975-3254 Fax: 301-948-6213 morgan@speckle.ncsl.nist.gov -- ------------------------------ From: dlkerl@cmack.b11.ingr.com (Dan Kerl) Subject: Re: >Mcintosh 275 power amp Date: 12 Jan 1994 19:32:22 GMT McIntosh and Gow's paper on the original design can be found in the Audio Engineering Society journal, December 1949. It describes the design of the 50-watt amp in question, including the reason a driver transformer was incorporated into that design. The wide bandwidth of the design is attributed to the elimination of lekage reactance effects between the halves of the output transformer primaries, plus a 4-to-1 reduction in the primary end-to-end impedance, made possible by the fact that the signal is applied accross the entire primary winding(s) at all times. It's quite a testimony to these gentlemen's design skills that these amps were routinely used in instrumentation applications requiring large bandwidths, and that the distortion performance was as good as it was with the output stage being biased so close to class B operation. (that's why those output tubes last so long) Schematics for several of the later Mcintosh tube amps can be found in Pittman's Tube Amp Book, volume 3. (Mc 40, 60, 75, 240 and 275). I don't see driver transformers in any of those units. -Dan Kerl dlkerl@cmack.b11.ingr.com ------------------------------ Date: Fri, 14 Jan 94 15:17:49 PST From: wws@renaissance.cray.com (Walter Spector) Subject: Re: 50 Watt McIntosh with driver transformer In article <2h110s$etr@introl.introl.com> you write: |> I think that this was the early McIntosh 50W2, which was a two chassis |> gry Hammertone job put out in the early fifties. They also made a 1 |> chassis 20W2 (20 watts) and before that a 20W1 and a 15W1. The 20W2 |> had the transformers inside the chassis which was then filled with |> potting compound (repairperson's dream!). :-( I have a 20W2 which needs a new power cord as the insulation is crumbling. This potting stuff inside stopped me the one time I tried disassembling it. (Anyone know what the proper way to deal with this stuff was?) |> I have a 20W2 that I've |> never put through its paces, so I can't remark on the sound. Mine didn't sound great by mid-70's standards. (Rolled off high-end.) But it has questionable tubes in it and hadn't been treated well before I came across it. I haven't hooked it up in several years (see above comment on power cord.) McIntosh sent me the schematic for it a while back. If anyone has questions about the transformer configuration I'd be happy to look it up. Now that you've piqued my interest, I guess I should replace that power cord this weekend. Walt ---- Walt Spector It usually takes more than three weeks (wws@renaissance.cray.com) to prepare a good impromptu speech. Sunnyvale, California Mark Twain _._ _._ _.... _. ._. ------------------------------ From: M18361@mwvm.mitre.org Subject: For sale: McIntosh MI-200 Tube Power Amp Date: Wed, 10 Aug 94 15:04:26 EDT I have a very rare McIntosh MI-200 Tube Power Amp (no power supply). The amp uses a pair of 8005s in push-pull for the output stage to provide 200 watts output. The output impedance can be matched for 4, 8, 16, or 600 ohms. I am looking for someone who might have an extra MI-200. I will consider either selling mine or buying yours.