Hi!
I just browsed Sakumas website and found some of his latest works. Sakuma is known for his unconventional circuits. He added some new twists to his latest builds.
There are 'bleeder tubes' added to provide some load to the power supply. Probably for stabilisation. But why use tubes instead of a plain resistor? He even uses expensive DHTs for this purpose like a WE300B here:
12AT7 / 841 SE phono preamplifier
There is even a transformer added as a load to the tube, with the secondary just grounded on both ends.
Here he uses a 50:
5691 / WE-102D SE phono preamplifier
This time even with an input transformer.
There is probably some reasoning behind it, did anybody read the MJ magazines in which these circuits got published? Was there an explanation why this was done?
Also quite interesting the use of several transformers connected in series as a load to enable transformer coupling of high rp tube like the 841:
841 SE Tone control and buffer amplifier
Best regards
Thomas
I just browsed Sakumas website and found some of his latest works. Sakuma is known for his unconventional circuits. He added some new twists to his latest builds.
There are 'bleeder tubes' added to provide some load to the power supply. Probably for stabilisation. But why use tubes instead of a plain resistor? He even uses expensive DHTs for this purpose like a WE300B here:
12AT7 / 841 SE phono preamplifier
There is even a transformer added as a load to the tube, with the secondary just grounded on both ends.
Here he uses a 50:
5691 / WE-102D SE phono preamplifier
This time even with an input transformer.
There is probably some reasoning behind it, did anybody read the MJ magazines in which these circuits got published? Was there an explanation why this was done?
Also quite interesting the use of several transformers connected in series as a load to enable transformer coupling of high rp tube like the 841:
841 SE Tone control and buffer amplifier
Best regards
Thomas
Reasoning? An unusual circuit with expensive components used in non-standard ways must surely sound better than a bog-standard circuit that any competent engineer/DIYer could design.
😱
Seems like a good way to boost Tamura's sales.
Any affiliation?
I see it as a consequent further development of "tube amps" with tubes that have only the heater connected (usually they come in bundle with many blue LEDs).
Including DHTs and transformers seem like a naturally "step up" from these designs.
No other idea that I could provide...
Martin
Seems like a good way to boost Tamura's sales.
Any affiliation?
I see it as a consequent further development of "tube amps" with tubes that have only the heater connected (usually they come in bundle with many blue LEDs).
Including DHTs and transformers seem like a naturally "step up" from these designs.
No other idea that I could provide...
Martin
I can think of far better circuits to use rare vintage tubes in which they would actually be amplifying an audio signal.
Surely there is an alternative explanation to this. The arrangement is too elaborate to be designed to simply increase the ps loading. Let's not jump to conclusions and speculate how silly Sakuma is.
My only non-cynical explanation that I can come up with is that these are parts of possible "upgrades" for the future. Everything already wired in the amp, just connections to the outside world have to be added.
This way, an additional line stage could be added to the existing (and already paid) amp fast and at low costs.
Too weird to be true?
Martin
PS: Is the schematic actually correct? Shouldn't the left PS diode also be connected to choke and first cap?
This way, an additional line stage could be added to the existing (and already paid) amp fast and at low costs.
Too weird to be true?
Martin
PS: Is the schematic actually correct? Shouldn't the left PS diode also be connected to choke and first cap?
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I think Sakuma's finally gone off the deep end. Although I have seen UTC transformer primaries used as a delay line in a preamp to compansate for transition speed when used with SS power amps. Seems bizarre to me.
Hi!
My intention was not to give any judgement about these circuits. I'm interested if Sakuma wrote anything bout this, probably in MJ mgazine. Anybody read about this who can post a translation?
Thomas
My intention was not to give any judgement about these circuits. I'm interested if Sakuma wrote anything bout this, probably in MJ mgazine. Anybody read about this who can post a translation?
Thomas
I guess if you feel like burning money why not? Didn't he write something about using WE 212s for lamps at his cafe tables?
12AT7/841 Phono Stage
Looks like a very expensive active quasi constant current load on the power supply. I think one could safely dispense with the transformer which now looks like nothing more than the transformer leakage inductance in series with the plate of that 300B. I would say it might make a wee bit of sense if the supply were a choke input and the intent was to make sure the load current was always above the inductor critical current with a sanely sized input choke, but this is not the case here.
Sakuma is looking for a very specific sonic experience and his focus is on mono, and full (limited) range speaker systems. It is hard to say what the intent is exactly except to provide an interpretative performance based on what Sakuma himself prefers.
One of my friends has actually been to the cafe at my behest, sadly I no longer remember what he had to say about the experience which in itself is interesting.
Looks like a very expensive active quasi constant current load on the power supply. I think one could safely dispense with the transformer which now looks like nothing more than the transformer leakage inductance in series with the plate of that 300B. I would say it might make a wee bit of sense if the supply were a choke input and the intent was to make sure the load current was always above the inductor critical current with a sanely sized input choke, but this is not the case here.
Sakuma is looking for a very specific sonic experience and his focus is on mono, and full (limited) range speaker systems. It is hard to say what the intent is exactly except to provide an interpretative performance based on what Sakuma himself prefers.
One of my friends has actually been to the cafe at my behest, sadly I no longer remember what he had to say about the experience which in itself is interesting.
Sakuma san is having his own reasons ; whatever he made , it's very different from common mistakes made by ignorant idiots or , even worse , ignorant sellers , all over the web
I'm sure he has his reasons, and not all of us who question his approach are ignorant idiots. 😀 I'm extremely interested in what Japanese hobbyists are doing, much more vibrant scene than here for the most part, and they have a knack for identifying worthwhile trends.
I'm a little concerned about the placement of fuses and power switches on the primary of the power transformers in all designs.
I'm a little concerned about the placement of fuses and power switches on the primary of the power transformers in all designs.
kevin , I didn't address you with my comment ;
thing I wanted to highlight is that Sakuma is representing entirely different world and approach
whoever is having thoughts about his ignorance is certainly not familiar with his work
I completely agree, and I take his work and that of a number of other noted Japanese designers very seriously.. 😀
One of the things that I find fascinating about the Japanese scene is the almost obsessive attention to detail, something I am trying hard to emulate in my newer designs.
One of the things that I find fascinating about the Japanese scene is the almost obsessive attention to detail, something I am trying hard to emulate in my newer designs.
One hopes (and in my case, I know) that YOUR attention to detail includes not using noisy rectifiers, properly loading the secondary of SUTs, and not running SUTs backward to use as output transformers handling signals at least an order of magnitude bigger than they are designed for.
Ouch.. 😱 Last time I checked your suspicions would be correct about what I am / am not doing.. 😀
I am wicked good at not soldering things as you might have heard.. 😀
I am wicked good at not soldering things as you might have heard.. 😀
