Nice write up Dave. One thing that will eliminate hum is to use battery bias. Ever try different driver tubes? The JJ ECC99 works great there. RCA clear tops are good too, I've even used 12bh7's, as far as preamp tubes I've used the Sylvania 5751's and liked those very much. I also have some Sylvania 7025's that work really nice.
Ming-Da MC34-B
- Thread starter DanTana
- Start date
Yes, I'm using it on the driver/preamp position now, I haven't done it at the phase splitters because I believe they would require about a 22v battery for proper bias? The 12ax7 only needs about a 1.5v bias. I would definitely consider battery bias on the first stage and the 12v heater conversion for the second.
Andywardle
New Member
Ming Da 34b + KEFQ15
Hi there, great thread - looking forward to getting my mitts on the 34B and seeing what it'll do. I have just bought one (waiting deliviery) from Ornec.
I am to be driving KEF Q15's (6ohm), and wonder which Impedance seeting to run them on? Common sense says the 4ohm tap will work best. Am I right?
Which of the mods will reap the best reward the quickest?
Andy
Hi there, great thread - looking forward to getting my mitts on the 34B and seeing what it'll do. I have just bought one (waiting deliviery) from Ornec.
I am to be driving KEF Q15's (6ohm), and wonder which Impedance seeting to run them on? Common sense says the 4ohm tap will work best. Am I right?
Which of the mods will reap the best reward the quickest?
Andy
Andy,
The Q15 dips to about 3ohm at 8-9kHz, and the Q15.2 also at 200Hz - have a look at the curves at:
http://www.pcavtech.com/techtalk/wire_size/index.htm#Q15-mag-lo
Try both to see which you prefer, you won't hurt anything; I'd guess the 4ohm tap may be better.
Mods which most improved the amp for me were changing the output tubes to KT77 with triode connection, getting rid of negative feedback (if so, you must do the triode thing as well), and upgrading the coupling caps - I'd regard these as the mods with the best bang for the buck (sub EL34 for KT77 if you're nervous). If you go further and delve into battery bias, different input and phase splitter tubes etc you need to know more about what the circuit does, and you start getting into DIY territory. Once you cross that border, abandon all hope - you may become addicted to working out what's wrong with the MC34B circuit, and how it can be done so much better...
Cheers
David
The Q15 dips to about 3ohm at 8-9kHz, and the Q15.2 also at 200Hz - have a look at the curves at:
http://www.pcavtech.com/techtalk/wire_size/index.htm#Q15-mag-lo
Try both to see which you prefer, you won't hurt anything; I'd guess the 4ohm tap may be better.
Mods which most improved the amp for me were changing the output tubes to KT77 with triode connection, getting rid of negative feedback (if so, you must do the triode thing as well), and upgrading the coupling caps - I'd regard these as the mods with the best bang for the buck (sub EL34 for KT77 if you're nervous). If you go further and delve into battery bias, different input and phase splitter tubes etc you need to know more about what the circuit does, and you start getting into DIY territory. Once you cross that border, abandon all hope - you may become addicted to working out what's wrong with the MC34B circuit, and how it can be done so much better...
Cheers
David
Andywardle
New Member
My Ming Da arrived!!!
Hi folks,
I got my ming da
Sounds great, but now i'm getting a bit twitchy, and am going to insert some JJtesla e34l EL34s.
Anybody got a good Bias setting that I can start with for these new valves?
Going over the DIY threshold is one of the reasons that I got the amp! :thmbsp: but thanks for the heads up Davehanc!!
Andy
Hi folks,
I got my ming da
Sounds great, but now i'm getting a bit twitchy, and am going to insert some JJtesla e34l EL34s.
Anybody got a good Bias setting that I can start with for these new valves?
Going over the DIY threshold is one of the reasons that I got the amp! :thmbsp: but thanks for the heads up Davehanc!!
Andy
Andy,
Did you try any mods?
I am still sifting through the contents of this extremely-informative thread, planning to try one thing at a time, and take my time doing it. Need to draw up a plan first. I bought an MC34-B a couple of months ago and very happy with it out of the box (I'm no audiophile but might get converted one day). Sounds like there are many improvements to be made and I love tinkering. First thing I guess is to draw out a full schematic for the stock amp, building on Dan's schem that he thoughtfully posted. I am definitely hooked on the valve sound for the simple uncluttered music that I mostly like. Glad I gave the valves a go.
Ian.
Did you try any mods?
I am still sifting through the contents of this extremely-informative thread, planning to try one thing at a time, and take my time doing it. Need to draw up a plan first. I bought an MC34-B a couple of months ago and very happy with it out of the box (I'm no audiophile but might get converted one day). Sounds like there are many improvements to be made and I love tinkering. First thing I guess is to draw out a full schematic for the stock amp, building on Dan's schem that he thoughtfully posted. I am definitely hooked on the valve sound for the simple uncluttered music that I mostly like. Glad I gave the valves a go.
Ian.
Hi...i'm new to this forum. I'm intereted in modding and biasing the Ming da mc 34 B amp. Would like to ask some questions. Which pins should i measure when biasing the amp( Changing the original 6p3 tubes to EL34 tubes)? and can i use KT-66 tubes instead of EL34 tubes? Thank you very much.
Attachments
Hello everyone,
I am new to the technical world of amp mods and I'm wanting to modify my MC34-A to triode. I have bought the 100 ohm resistors and I don't know which pins are #3 and #4. I feel that I shouldn't even attempt this because of my lack of experience. But I don't know of a local service that would preform this mod for me so I want to try it. It sounds easy enough remove #4 on all valves and connect 3 and 4 together with the resistor. My amp looks just like the picture in the previous post. I just cant see to follow the wires from the transformer to the output tube. There is a copper wire linkage that runs across 2 valves on one pin. Then there are 2 baby blue resistors that bridge between 2 valves on another pin. Please help, and forgive me for being so technically challenged. Cheers!
I am new to the technical world of amp mods and I'm wanting to modify my MC34-A to triode. I have bought the 100 ohm resistors and I don't know which pins are #3 and #4. I feel that I shouldn't even attempt this because of my lack of experience. But I don't know of a local service that would preform this mod for me so I want to try it. It sounds easy enough remove #4 on all valves and connect 3 and 4 together with the resistor. My amp looks just like the picture in the previous post. I just cant see to follow the wires from the transformer to the output tube. There is a copper wire linkage that runs across 2 valves on one pin. Then there are 2 baby blue resistors that bridge between 2 valves on another pin. Please help, and forgive me for being so technically challenged. Cheers!
Gentlemen, while there are numerous AK'ers who could probably answer your questions I know DanTana was quite familiar with this amp and the OP of this thread. He isn't online as often as in the past so I suggest you PM him referencing this thread and I'm sure he will respond the next time he signs in. Good luck.
Terry
Meixing MC34-A06
:thmbsp:Very very interesting mods from DanTana specially
I`m already ordering or purchasing (sory for my english)
MC34-B but after a careful look in their web page and receiving their
price list I came with conclusion why baying another tubes when the Chinese already put them in amp. EL34 x4(JJ)、12AU7 x2、12AX7 x2
and it is about Euro100 expensive than MC34-A
any suggestion?
Agron:yes::yes::yes:
:thmbsp:Very very interesting mods from DanTana specially
I`m already ordering or purchasing (sory for my english)
MC34-B but after a careful look in their web page and receiving their
price list I came with conclusion why baying another tubes when the Chinese already put them in amp. EL34 x4(JJ)、12AU7 x2、12AX7 x2
and it is about Euro100 expensive than MC34-A
any suggestion?
Agron:yes::yes::yes:
I agree with DanTana that Chinese audio has a stigma. Some of the quality seen in the Hi-Fi suffers, but not all. I think there are some (companies) that are having better QC and overall visibility on the manufacturing process than other companies who are letting counterfeit and stealing of parts take place.
Also I think that some Chinese companies are doing the same thing many Japanese companies were doing in the 1970's and 80's in the American auto industry. They see that they can make a quality product that can compete in the world market. Honda and Toyota starting making very good cars and very decent prices in America. I have an amp by Line Magnetic Audio and I like it more than a Cary I listened to for double the price!
It's also made to a very high standard.....
Also I think that some Chinese companies are doing the same thing many Japanese companies were doing in the 1970's and 80's in the American auto industry. They see that they can make a quality product that can compete in the world market. Honda and Toyota starting making very good cars and very decent prices in America. I have an amp by Line Magnetic Audio and I like it more than a Cary I listened to for double the price!
It's also made to a very high standard.....
Realizing this is a very old thread, I have searched for a schematic for the MC34-B, yet have had no success.
Reason: My amplifier had a catastrophic tube failure while playing: a right channel 6L6 lit up internally, and thankfully blew the fuse. After installing a matched quad of JJ 6L6's and adjusting the bias, the right channel is without a sound. Swapping preamp and output tubes does nothing.
Both my Vandersteen 1's are perfectly functional with a NAD test amp.
The outputs measure proper resistances through the ground, 4 Ohm, and 8 Ohm taps.
Power supply: I have good filament Voltage, and find myself wondering if the right channel plate Voltage is nothing. Not sure if I have no high Voltage there, or a blown output transformer.
I would like to test high Voltages, and of course the windings in the tube side of the output transformers, as well as trace the input circuits.
Thanks to anyone for assistance, I am profoundly appreciative in advance.
Jon
Reason: My amplifier had a catastrophic tube failure while playing: a right channel 6L6 lit up internally, and thankfully blew the fuse. After installing a matched quad of JJ 6L6's and adjusting the bias, the right channel is without a sound. Swapping preamp and output tubes does nothing.
Both my Vandersteen 1's are perfectly functional with a NAD test amp.
The outputs measure proper resistances through the ground, 4 Ohm, and 8 Ohm taps.
Power supply: I have good filament Voltage, and find myself wondering if the right channel plate Voltage is nothing. Not sure if I have no high Voltage there, or a blown output transformer.
I would like to test high Voltages, and of course the windings in the tube side of the output transformers, as well as trace the input circuits.
Thanks to anyone for assistance, I am profoundly appreciative in advance.
Jon
Sorry I've been very very busy lately and haven't had time to find the old schematic. I think I still have a copy of it somewhere and will upload as soon as I can find it. I think I wrote the makers of the amp to get the original copy from them, but I used some schematic program and made a nicer copy. Give me a a couple weeks to find it.
Thanks,
Dan
Thanks,
Dan
