Yes, I have heard of Ming-da actually. Nice look to them, but I have never had a chance to audition one.
The schematic would be of use as it saves a lot of time when trying to figure out any of the calculations like how much +B voltage is going through. The iron if it is what they say it is, is what is preferred for iron in a transformer.
Other than that, we'll have to wait and see (kind of like being on Suhkumvit Road on a busy morning).
The schematic would be of use as it saves a lot of time when trying to figure out any of the calculations like how much +B voltage is going through. The iron if it is what they say it is, is what is preferred for iron in a transformer.
Other than that, we'll have to wait and see (kind of like being on Suhkumvit Road on a busy morning).
The bit about the EL34 being the only pentode where you can get at all the screens separatly is interesting in that it was Steve himself who popularized the SV83/6π15π.
dave
But does that actually make it bad or just not ideal... I realise they may be using wording that sells to some but seems fake to others, but how much effect does it have, and if lots is thins something I should be looking to upgrade?
Bare in mind this is not a top of the range amp... I can't afford one like that but for the money I spent it I think it sounds really very good...
I have a copy of 'valves amplifiers' on order, as it does look to be very good. and I have now got a copy of the schematics if anyone would care to take a look and tell me what they think... constructive critism is prefered though.
Attachments
Except for exact values, and valves this is one of 2 "standard" Chinese EL34 schemas. The other configures the 1st tube as an SRPP. (different BTW from the schema i found -- i guess for an earlier variation of the MC34)
I affectionately call these pre-built kits. Decent performance for the entry price but room for a whole lot of improvement.
Without getting radical (is it on a circuit board or point-to-point?), 1st thing i'd do is put a lower gain, higher transconductance tube in the front, balance the LTP and put a CCS on the bottom.
The 1st stage has the same topology as the Bottlehead Foreplay -- you can get some ideas on improving that from all the work done on that circuit.
dave
Regards the DECware article,
I only posted it to show the different triode set ups, saving long descriptions.
The SV83 is interesting...
There is a (Sound) difference between the two triode set ups. Yes OK the circuit and values will have an effect...
I also agree there is a large portion of snakeoil in the article so perhaps a bad choice...
Regards
M. Gregg
I only posted it to show the different triode set ups, saving long descriptions.
The SV83 is interesting...
There is a (Sound) difference between the two triode set ups. Yes OK the circuit and values will have an effect...
I also agree there is a large portion of snakeoil in the article so perhaps a bad choice...
Regards
M. Gregg
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Poor choice of tubes, topology, and operating points. Other than that... It's cut-and-paste "engineering."
Briefly, the input stage is run in a configuration that drops the open loop gain while (in contrast to negative feedback) actually reducing linearity. The cathode follower does almost nothing to increase the drive capability or moving a critical pole higher in frequency. This is followed by a poorly balanced inverter which uses a tube that, under the large signal swing needed, has high distortion (of high order as well). The feedback is implemented badly- the "designer" has paid almost no attention to optimizing the open loop gain and the HF poles, and as a result, the feedback loop only achieves a small reduction in lower order distortion at the expense of increasing higher order. Depending on the output transformer, stability will likely be marginal- ironically, given the lack of attention to compensation, a poor quality transformer might actually be MORE stable in the circuit.
The same basic circuit is done competently (if not ideally) in the old Eico amps- HF-87, for example. That may be worth looking at for a comparison.
Briefly, the input stage is run in a configuration that drops the open loop gain while (in contrast to negative feedback) actually reducing linearity. The cathode follower does almost nothing to increase the drive capability or moving a critical pole higher in frequency. This is followed by a poorly balanced inverter which uses a tube that, under the large signal swing needed, has high distortion (of high order as well). The feedback is implemented badly- the "designer" has paid almost no attention to optimizing the open loop gain and the HF poles, and as a result, the feedback loop only achieves a small reduction in lower order distortion at the expense of increasing higher order. Depending on the output transformer, stability will likely be marginal- ironically, given the lack of attention to compensation, a poor quality transformer might actually be MORE stable in the circuit.
The same basic circuit is done competently (if not ideally) in the old Eico amps- HF-87, for example. That may be worth looking at for a comparison.
Ming-Da amps can be used as good donors of chassis and transformers for real amps, including output transformers that are surprisingly good. I would rather call them expensive DIY Kits than Hi-End amps.
My Pyramid amps would fit in that 845 monoblocks that I repaired; instead of that 2x845, 2x300B, 2x1AU7 and 1x6SL7 I would fit 2xGU-50, 2x 6P15P, 1x6F1P, even 1x6E1P indicator and VR-105 VR tube. The same chassis, transformers, holes for tubes, but much better sound.
My Pyramid amps would fit in that 845 monoblocks that I repaired; instead of that 2x845, 2x300B, 2x1AU7 and 1x6SL7 I would fit 2xGU-50, 2x 6P15P, 1x6F1P, even 1x6E1P indicator and VR-105 VR tube. The same chassis, transformers, holes for tubes, but much better sound.
I hope I'm not falling into the saying"the higher a monkey climbs, the more it shows its ****" but I've been following this thread and just ask a probably silly question; if one was to change tubes as suggested, is there a difference between the input valves and output valves as to which would have the greater effect on the final sound?
When people talk of tweaking their hi fi gear to alter, subjectively, the sound, they pay huge sums for amplifiers or cartridges or expensive interconnects when the item most likely to alter the sound will be speakers. So if one wants to alter the sound by tube rolling, is it better to upgrade the input rather than the output tubes to get a subjective difference? Hope I've been clear enough in my naive question. Bear with me; I'm as green as they come valve wise.
When people talk of tweaking their hi fi gear to alter, subjectively, the sound, they pay huge sums for amplifiers or cartridges or expensive interconnects when the item most likely to alter the sound will be speakers. So if one wants to alter the sound by tube rolling, is it better to upgrade the input rather than the output tubes to get a subjective difference? Hope I've been clear enough in my naive question. Bear with me; I'm as green as they come valve wise.
I can't understand how you could follow the thread but still don't understand that it's not a brand, or type of tubes, matter in this particular case? Tubes in Ming-Da are already selected for better look and fame. What is wrong, the schematic that no matter which tubes you use will be still the same.
When you have a well designed and balanced amplifier like this one: http://diyaudioprojects.com/Tubes/KT88/ Which is built around Mikael Abdellah's KT88 amp, you tube roll the power tubes to get a warmer sound with EL34 Mullards or GEC KT88 or something with a little punchier sound with a more modern KT88 in SE mode. The gain tubes can have a similar effect depending in the brand. Most times I've seen people roll the output tubes with noticeable difference.
I have heard a marked difference with tube rolling the power tubes in a Marantz 8b, but that was comparing well worn tubes versus very new not even burned in vacuum tubes.
However, this is only something i would suggest doing with a well designed amplifier.
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