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#21 |
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diyAudio Member
Join Date: Sep 2003
Location: GuangDong China
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the 4th page(the last)
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#22 |
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diyAudio Member
Join Date: Nov 2004
Location: Illinois, USA
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I also have a Ming-Da MC34-B amp. Basically it's exactly the same internally as the MC34-A, albeit a couple features and the 6.3v heater setup for the preamp and input tubes. I wired my preamp tube to 12v and use 12ax7 tubes in that position. Simply remove the wire off pin 5, remove pin 9 from the gound, take the wire from pin 5 and route it to pin 9, and jump pins 4 and 5 together. I've also used 6DJ8 in the input tube spot, but wasn't as happy with the sound as the 6N1, i'm considering the 6h30 tube next in that spot. I've also replaced all the 6P3 tubes with the "new" Mullard reissued EL34's. After biasing them and the new preamp tubes, the sound is incredibly improved now. I would like to know if anybody has successfully replaced the 6N1 with the 6H30 yet. Otherwise, I'm going to wire it for 12v and try some other input tubes.
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#23 |
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diyAudio Member
Join Date: Jun 2004
Location: Cool end of a soldering iron NW of Toronto
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Dantanna, All,
I am using vintage Mullard EL34's in my Ming Da MC34B. Cathode current is set at 35 mA idle per valve with the grid bias pots. I have placed 6BK7B's in the long tailed phase splitter socket and use the supplied 6N2 input amp tubes as I have so far found nothing else that sounded as good stuffed in the sockets as wired. The power output is now 28 watts RMS per channel, both channels driven instead of 18 watts with the originally supplied 6P3P's. The amplifier sounds fantastic!!!! What is all this about re-issued Mullard EL34's??? How can a long defunct company reissue something? If this is like RCA, or Altec then only the name is being obtained, being disparaged by no talent charletains working for the shareholders for profit in exchange for substandard modern c r a p which sells only because it is badged with a once famous and respectable name. |
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#24 |
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diyAudio Member
Join Date: Nov 2004
Location: Illinois, USA
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Great to hear from other happy Ming-Da MC34-B owners!! I'm curious to hear more about your choice of driver tube, rcavictim. I have put the 6DJ8 in there and it wasn't bad, just not as good as the 6N1, try rewiring the preamp socket where the 6n2 was and put a JJ Tesla 12ax7 in it's spot.
As far as the "new" Mullards go, SED bought the rights to use their logo and trademarks. Supposebly, these reissues are copies of the yf-4 version of the EL-34's. I bought them for a couple reason, I had read they were good, the Mullard logo looked kewl, and if I didn't like them I'm sure I could sell them easier. So far, I'm really happy with them, I also strapped them into triode mode and "sweet" is probably the best way to describe them. |
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#25 |
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diyAudio Member
Join Date: Jun 2004
Location: Cool end of a soldering iron NW of Toronto
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DanTanna,
I played with various 6DJ8's and 6922's (in both holes) but was not impressed. I considered trying a 6CG7 (excellent driver tube) but haven't. I was totally surprised by the 'air' added by substituting the 6BK7B for the 6N1P. Regarding the Mullards. "Is that a Mexican poncho or a Sears poncho?" You tell me it's a Sears poncho. Good luck with them. Where might someone find these and how much do they set one back? This question coming from someone who is not at all impressed yet with EH offerings based on experience with only the 6CA7 fat bottle. I think the old Mullards I have are 2nd design circa early 60's. They have seen a lot of use and still with emission like new are fantastic reliable valves. I should add that I also had purchased a MC34A amp when I bought three MingDa's for evaluation. I and others who heard a-b comparisons all agreed that as supplied, with Chinese valves, the cheaper MC34B sounded noticeably better. I kept the MC34B for my personal use (it is now driving the Ultor-X speakers in my Avatar creating a 3D soundstage that betters anything I'd heard before or since), and sold the MC34A. I sold a new MC34B to a customer in the US who was blown away by it's sound quality and power when compared to quality brand SS 100w/ch equipment. |
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#26 |
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diyAudio Member
Join Date: Nov 2004
Location: Illinois, USA
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I bought the EL34's from Triode Electronics for $77.00 a matched quad. I have them in triode mode and they sound very good.
Another update on my project, I wired the driver socket, formerly the 6n1 to 12v heater, and put in an ECC99 and am very happy with that tube, I was disappointed with the 6DJ8 myself. I also tried some clear top RCA 12AU7's in that spot, not quite as dynamic as the ECC99's. |
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#27 |
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diyAudio Member
Join Date: Jun 2004
Location: Cool end of a soldering iron NW of Toronto
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DanTanna,
The 12AU7 is quite a high distortion tube. That is why I often rewire the filament pins and shove in a 6CG7 which is close to the 6SN7, demonstrably in testing the lowest distortion triode commonly available. $77 for a matched quad of EL34's is very affordable if they are decent. |
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#28 |
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diyAudio Member
Join Date: Nov 2004
Location: Illinois, USA
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rcavictim, I bought all the tubes from Triode, the ECC99's are available there too, very reasonable and after about two weeks of running it that way, I'm pretty happy with them. Seems with the ECC99 in there, it has become more sensitive to the changes of the preamp tube. Meaning I can hear the differences more clearly now than I could before. I was thinking of trying an 12AT7 in the preamp socket. I'm using the JJ Tesla and EH's in the preamp socket, both sound good but in different ways. Next I was considering putting in some higher quality coupling caps, and trying instead of .33uf ones, some .22uf ones.
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#29 | |
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diyAudio Member
Join Date: Jun 2004
Location: Cool end of a soldering iron NW of Toronto
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Quote:
That amp makes great bass. Reducing the size of the coupling caps may screw that up. I have had no urge to go inside my amp at all except to adjust bias. As for changing already pretty good quality coupling caps (Solen) to some boutique jobs that could cost what the entire MingDa amp wholesales for in China, you would probably get more improvement for the dollar in room treatments or loudspeaker upgrades IMO. As far as tube rolling, I only tried about four different types and stuck to only those that required no changes of filament pin wiring at the sockets. Let us know how the 12AT7's sound in the preamp socket. |
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#30 |
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diyAudio Member
Join Date: Oct 2004
Location: Adelaide South Oz
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I have a preamp which has a cathode follower output.
I have found that I can drop 6DJ8, 6N1P, 6922, 6ES8 into the socket and they all work nicely at very similar operating point. So which do I prefer? Depends on which power amp I'm driving - with most of my valve amps I like the 6DJ8 best. With my good solid state power amp I definitely like the 6ES8 best. This is definitely a variable mu tube and you get a SET like characteristic that as you increase the volume (signal level) you get increasing asymetrical distortion (due to the variable mu) and the sound "warms up" or "wets" or whatever description you like to use with increased signal level (as 2nd Harmonic distortion is added). This despite it being in a cathode follower (ie 100% feedback). For those MANY of you who say you don't like the sound of a cathode follower in your preamps - bung in a 6ES8 (ECC189) and have a listen. Cheers, Ian |
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