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Sakuma's bleeder tubes and series connected transfomers

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
 
:eek:

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
 
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? :scratch1:

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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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.
 
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I'm sure he has his reasons, and not all of us who question his approach are ignorant idiots. :D 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.
 
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.