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McIntosh MC275 MK VI Clone

Quad Shuguang KT88-T arrive. I have to said this tube so good. Sound become very please to enjoy.
I will put back the Telefunken 12AT7 and 12AX7 after the KT88-T have enought burin time.

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justbenice said:
I tried to replace the 3x12AX7 and 4x12AT7 in the clone MC275 with Mullard tubes and acctually the Mullard worse than the original tube come with the clone MC275, sound become very thin.
After fail with those Mullard tubes, i tried to replace those buffer and driver tubes with Telefunken tubes. The Telefunken tubes give a little bit better than the original tubes come with the clone MC275, but not enough to made me keep its, sometime i even think the original tube have sound suits my musical taste better. And the price of 7 Telefuken tubes cost half of the whole clone MC275 amplifier. So i don't think i need to replace the buffer and driver tube in this clone MC275, it was already very very good.
All the Mullard and Telefunken tube i tried have life metter at at least 95%. Like new!

Yesterday i order quad of Shuguang KT88-T Black Treasure Tubes, which i hear people said it better alot than Gold Lion. I will report back that if the Shuguang KT88-T Black Treasure can beast the 4 of original tubes come with the clone MC275.

As the seller said, those tubes come with the clone MC275 are custom made. I don't know if it was true because they re-print the label in the tube but as now, i am quite impressed with the quality of the tubes that come with the clone MC275.


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I would not put any thought on the Stock tubes as I tested each one and 4 had marginal values and 2 tested Bad (also the C22 clone ALL had bad stock tubes to which they also replaced (tested good), hence I only use these for burning in gear). I am using V1-V2 - NOS 12AT7 Long Black Plates Raytheon, V3-V7 NOS HP "Made by GE". NOS Telefunken, Mullard I would be careful (can get $$$) going down this road as it's real depends on circuit design. Maybe Asian tubes sound better in this unit. Looking forward to your testing.

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CohibaJoe said:
NOS Telefunken, Mullard I would be careful (can get $$$) going down this road as it's real depends on circuit design. Maybe Asian tubes sound better in this unit. Looking forward to your testing.
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Thank you for this adivce! I going to sale the Telefunken and buy a 12AT7-12AX7 Black Treasure version from Shuguang. I think they are pretty good as they have 1 year warranty from the factory. The original tubes come with my clone MC275 are "new version custom made" and i have to paid 30usd more for it.
 
dubai2000 said:
Having had great experience with a Dartzeel clone, I pulled the trigger on this one too - as I also prefer the classical McIntosh design, it is what they call Version V (upgraded). I am looking forward to receiving it soon.
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Let's us know when you get it! I love mine. Mine came with "Rucycan" main filter caps. :rolleyes: I swapped those out with the genuine article along with all the Chengxin electrolytics. I also swapped the bias voltage resistors with trimmers so I could get the voltages right on the dot.
 
I can't knock it aside from the name branding ..by by now I have two Chinese tube amplifiers (yaqin mc13s , yaqin mc100b) and they have been fantastic. It's a stand alone Chinese brand nonetheless fantastic gear at prices you just can't say no too once presented with it.

So I cannot imagine this being any less. Who knows in the near future I might score one of those McKung-tosh amplifiers they look incredible

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ellum68 said:
Let's us know when you get it! I love mine. Mine came with "Rucycan" main filter caps. :rolleyes: I swapped those out with the genuine article along with all the Chengxin electrolytics. I also swapped the bias voltage resistors with trimmers so I could get the voltages right on the dot.
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Will do so - apparently it has already been shipped. I plan on recapping as well, but first I need to move house next month. I am curious though: why did you remove the autobiasing function? Do you feel the amp sounds better this way?
 
dubai2000 said:
Will do so - apparently it has already been shipped. I plan on recapping as well, but first I need to move house next month. I am curious though: why did you remove the autobiasing function? Do you feel the amp sounds better this way?
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Didn't remove it per se. Someone brighter than me can explain how the bias functions works in this circuit. My feeble brain is pretty much maxed out by understanding the simple bias circuit of old Fender guitar amps. Some people got copies of that amp with trimmers installed already. Mine came with fixed resistors, but you can clearly see an outline of a trimmer on the board. Using a trimmer simply allowed me to nail the bias voltage to spec. More an OCD "me" thing over anything else.
 
None of the original nor replica McIntosh tube amps are "autobias". True automatic bias requires a sophisticated computer controlled circuit that none of these have.

All of the Unity Coupled amps, because of their unique design, are much less susceptible to aging and unmatched tubes than any other tube amp as far as I know. Because of that, there historically has been no way to adjust the bias other than actually replacing a fixed resistor with a different value. However, the newer Factory MC275s do have a trimmer on the board so the bias can be adjusted. Some (all?) of the newer replica MC275s have this feature. It appears the amp here for discussion was a transition amp with the trimmer outline on the circuit board but it still used fixed resistors.

I applaud installing a trimmer in the circuit for optimum performance. I've installed one on both old original McIntosh tube amps as well as one of the newer replicas.

I assume there is one trimmer per channel? Do you recall the value you used?
 
Auto bias used to mean a fixed resistor and maybe a bypass cap. I've had and have several amps like this. Either splitting the cathodes with a resistor and cap per pair of output tubes, or all four tied to the same resistor in PP amps.
I still have a couple SE amps like that also.
 
Lavane is correct in that some folks called the type of amp he described above as "auto bias". More correctly called "cathode bias". None of the McIntosh Unity coupled amps use cathode bias on the output tubes.
 
Earlier today I received a big, black case which seems to be a very good protection for the amplifier. I have not yet looked under the hood - I was too curious to see/hear if it works alright - and the first impressions are already very(!) favourable. I shall post more in a few days.
 
dubai2000 said:
Earlier today I received a big, black case which seems to be a very good protection for the amplifier. I have not yet looked under the hood - I was too curious to see/hear if it works alright - and the first impressions are already very(!) favourable. I shall post more in a few days.
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Burn-In 200hrs, and please Open the unit up for pictures.
 
No, unfortunately I don't. My listening session yesterday continued late into the evening: what I really like (so far) is the tonal quality of the amp - compared to the solid state amp I had used before it seems to be a bit more mid-centred and the bass is a bit less "structured" - but those things might change after some more listening time. The saga continues....
 
More impressions - the amp is really as good as already stated by others above. It's easy to listen to for hours without any listening fatigue - burn-in seems to balance to sound more - the initially perceived slight mid-hump seems to be gone (or my ears have adjusted). I still have not opened it up, but in pure sonic terms I don't feel any urgent need to change caps (I might only do so for the fun of it).
 
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