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In Reply to: RE: Take a look at this. posted by totosooner@yahoo.com on June 26, 2016 at 01:51:15
"Based on Mac's brain trust why would you question their choice of tubes."
Because they used the cheapest phase splitter that was a pin-pin match with the rest of the tubes they use. As to this glass thickness, you have noticed something successfully; some new tubes have thicker glass than their Original Era counterparts made domestically.
As to this claim on McIntosh selecting criteria, do provide some proof, I'd love to see it.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Follow Ups:
I own Mac 12ax7's (as an example) and have owned, or currently own Sylvania, GE,RCA, Tele's , Mullard, Sugaung, Mataushita, EH, JJ, and I am guessing others over the years. The Macs are the heaviest..and its very noticeable.
By the way....When I test THD and frequency response it is ALWAYS at the rated power......in the case of an MC275 MK IV that would be 75 w/ch, not 1 watt. The frequency response is like nothing I have ever seen.......completely flat from 20 to 20Khz.
In all seriousness, tell me how to post the print out and I will. It is just freaky to see what these guys build.
Peace
Stewart
Nobody made special tubes so McIntosh could select them...OMG, I don't think you have any idea how ridiculous that is.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I am afraid you are wrong in a number of ways.
First it is is very common for firms to specify specific characteristics they want in a product they sell under their label. As an example when you buy a a tire, many other things at Walmart it may say Goodyear so and so, but it is Walmarts version. They tell the vendor what price point they have to hit,what physical characteristics must be there and what can be ignored. The vendor then comes back with a product that they can build to meet Walmarts directives. Its the same with anyone else.
Somethings in tubes (which are easy to build with the right tooling) may be as simple and binning ( taking only those which test in the top 10%). It may be using certain conductors, it may be the top 10% of glass qhality,it may be who knows what. Money buys anything.
Stewart
You are right in that the tube manufacturer doesn't make a different structured tube for an audio manufacturer however,it was very common for high end audio manufacturers like Fisher and Mcintosh to get better testing tubes to their specs for overall data,especially when the tube company puts the Mcintosh or Fisher logo on the tubes..Mcintosh doesn't personally go to the JJ or SED factory and hand select tubes,they do however get the best testing tubes and they pay extra for this especially when their name is going on it. JJ no doubt hand picks the tubes to meet the specs McIntosh requested before they print the logo on them. All in all they are still selected from same batches of production tubes,they just test better.
I was surprised to learn a few years back there were were A and B stock tubes..It sort of reminds you of when the auto industry rejects millions of tires each year from the tire companies because they don't meet the car manufacturer's standards,even tho they are perfectly good tires.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 06/27/16
"it was very common for high end audio manufacturers like Fisher and Mcintosh to get better testing tubes"
That's absolutely correct. I've always been disappointed by the section-to-section and tube-to-tube variation in RCA 'SN7s. However, a few years ago I bought some of these that no one else seemed to want because they were labeled "Zenith." The matching on those tubes was unlike any I've ever seen, so good I wouldn't hesitate to just pull them out of the box and install them in an amp as-is. After seeing that, I went back to the seller and bought all he had. :)
--------------------------
Buy Chinese. Bury freedom.
Back in 2005 on Ebay,a gentleman was selling these NOS/NIB Fisher branded EL37s.Of course these are Mullards but anyway these tubes came from a Fisher warranty service center back in 1968 and he worked there and had them all that time..He was selling for them for 90 dollars each and I bought the last two he had.He didn't sell these as matched tubes but when I got them I had noticed the number 946 at the bottom and being they both had this number,I thought I would throw them in my Heath TT-1 and they both tested identically on mutual conductance and emission and I mean to the number.I then put them in my maxi-matcher I made up out of a 475vdc power supply and biased thru 10 ohm resistors.I tested the tubes at 425vdc and minus 46 on G1 and the current draw was around 48ma as I recall but it was identical for both tubes. I then put them in my Fisher 80AZs which I have several and I measured plate temperature and even that was identical on both tubes when put them in the same socket and i measured at several different points.
Ten months later to the day almost I found another vendor selling some of these same tubes but he was in Parsipinni NJ where the other guy was in Chatsworth CA.I got two more of the same type NOS/NIB branded Fisher EL37s for 190 for the pair this time..I got these tubes a couple days later only to find out these tubes also have that same 946 code..That made me put all four of them in a friend's real Maxi-matcher and all four drew identical amounts of current at the 400vdc voltage..These four tubes were perfectly matched in everyway from mutual conductance,emission,plate temperature,and in even the maxi-matcher.
That's when I realized why this had to be.Being these were factory replacement tubes,the Fisher amps that use EL37s have no bias adjustment, so these tubes had to be matched and ready to go when you dropped them in.
Since I don't have a curve tracer,I match my tubes in a more primitive manner but it at least tells you they possess very similar characteristics.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 06/28/16
By the way....When I test THD and frequency response it is ALWAYS at the rated power......in the case of an MC275 MK IV that would be 75 w/ch, not 1 watt. The frequency response is like nothing I have ever seen.......completely flat from 20 to 20Khz.I think you were addressing me on that question but nobody denies the specs that Mac amps are able to produce because they are absolutely marvel in design with their output trafos and overall execution of the driver,voltage amp, and nested loop FB. The early reissues didn't make rated power but I blame that on govt regulation because they were running a lower B+ so they could meet UL specs and they wanted to keep the original look..After customers started complaining about not making rated power,they made a change to where they put part of the output tube bases below the chassis and then put heat venting holes around the tubes and then raised the B+ up accordingly.
McIntosh, like other commercial designs,would often cut corners in some areas even back in the early days.I own six Mc60s and one of the amps was born without a choke and yet,the holes are there for a choke to be installed.They did have a few iterations of this amp so maybe this particular one was setup for a background music system in a commercial application..I ended up putting a choke in so it matched the other five but also,Mac used to used to use copper lined chassis in many of their earliest Mc30 and Mc60s and that was done away with as well. The Mc30s all should have had a choke installed by the mere fact of the amount of current the amp draws at or near full power. Mac also used bias windings on some Mc30s and Mc60s and some they didn't.They would take the AC off one half of the high voltage secondary,put in a dropping resistor.and then rectify it..It's ok to do this but it is kind of cheezy when you think about it. My point is,even the best companies are not immune to the bean counters.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 06/26/16
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