For trade: Set of Sansui 1000 (not 1000A) Transformers

[Shannon Parks]

I parted out a grotty Sansui 1000 a few years ago. It was just made in 1963 with the plate capped 25E5 tubes. The trannies are decent shape and I can post pix if anyone is interested. No UL taps and arcane PT hookup. Schematics are out on the web. Primary on the outputs tested at 1200 ohms or 1400 ohm, IIRC, which doesn't seem useful to me. But supposedly fantastic iron.

Looking for a pair of output trannies for trade. SE or PP.

Shannon

[EWBrown]

I have a definite interest in these (as if I don't already have enough iron weightting down the cellar floor around here)...

IIRC, 25E5 has similar op-chars to the EL36, and the somewhat similar 6BQ6GB / 6CU6 series. Which, just by a strange set of circumstances, are nearly identical to my favorites, 6AV5GA / 12AV5GA.

In that case the OPT is probably about 4K CT: 8 ohms (and the secondary of these trannies has 8, 16 and 32 ohm outputs. The B+ voltage would be between 300 and 325V depending if the stages are fixed or cathode biased. (Fixed bias G1 voltage would be approx -25VDC) This should be good for at least 30WPC judgng from a similar 6BQ6GA modulator in a 1960s ARRL ham radio publication.

Sansui 1000 output section schematic is located here



And this circuit was very similar to that of the 1961 vintage SM-80.
Which was rated at 33 watts per channel at less than 1% THD, 40W max.



/ed B

[Shannon Parks]

Coming your way, Ed. I did remeasure them this morning, and the outputs are weird. One is OPT-1 and the other is OPT-2. OPT-1 has an extra primary line. You might discern it from the schematic. I was thinking they were 4, 8 & 16 ohm secondaries, so your schematics make more sense. So I measure 2.5K on one and 3K on the other. The lams look different on the two outputs, too (originals though). I think the transformer company was Hashimoto, Tango or Tamura?

Shannon

[henniekuyper]

Hi Shannon

I could swop you for some Hammond SE transformers.

Regards
Hennie

[Shannon Parks]

Hi Shannon

I could swop you for some Hammond SE transformers.

Regards
Hennie

Thank you, Hennie, but I owe Ed some iron already. Shipping them to him in lovely NC.

Shannon

[EWBrown]

IIRC the Sansui 1000 used Tango OPTs or Hashimoto, tangos in the earlier product runs, hashi's in the later, before the 1000A was released.

The AU70 used an interesting approach with 7189s, note the individually adjustable fixed bias, and the cross-coupled cathode neg feedback using the OPT secondary. This circuit could readily be duplicated with modern (hammond, edcor) iron.



Their various amp designs all use the 6AN8 as the VA and PI stages.

/ed B

[ramkumar]

EWBrown's examples are worthy, thanks for sharing these scans Brown!

[EWBrown]

Some AC voltage "ratio testing" shows these to be approximately 3.2K CT, with 4, 8, 16 and 32 ohm secondary taps. I'm sure they could be "ratioed" to behaving like 6.4K CT into 8, 16, 32 and 64 ohms, at least the 8 and 16 would be useful, 32 and 64 ohms for really "deaf-people" headphone amps If the user isn't already hearing-impared, he will soon be...

I'm probably going to run the Sansui iron with PP triode strapped 6AV5GAs, and see (or listen carefully) how they sound. 2A3s / 6B4Gs in PP with fixed bias and 3K A-A OPT are good up to about 15 Watts RMS.

Maybe make them pentode / triode switchable, if I need more "juice"

These originally ran with 25E5s (PL36s) , which are the 25V filament version of EL36, which are similar to 6BQ6, which are nearly identical operating characteristics to 6AV5GA. I suppose, that if I use the original Sansui power trannie , I could try 25AV5GAs or series-connected 12AV5GAs, the possibilities are endless...

6BQ6GTB/6CU6s have a nominal 11 -12 W PD rating, but in Class A or AB1 amplifier duty, they can easily handle 18 to 20 W PD without getting all hot and bothered, and red in the plate

/ed B

[EWBrown]

Tamura F-2020 series Iron, pretty fancy stuff, details on this page, scroll down. I have two of these (previously used) which may become available on pre-bay for "adoption", soon.

http://www.eifl.co.jp/index/export/tamurat/f.htm

I know, the data "grid" doesn't "tabulate" well in this format...

F-2020 SERIES
Output transformers for push-pull exclusive use for output 50W. in combination with various kinds of vacuum tubes including 5-pole and 3-pole tubes, these can be used in many different circuits

SG taps are provided for cathode NFB winding and for UL
Wide band design for better phase characteristics are arranged through adoption of a special winding system.
0.25dB is marked for the lowest constant loss as the output transformer.

Stock
Mark Catalogue
No. Impedance Frequency
Range Output Primary Maximum
DC current Primary Inductance
Primary Secondary Balance Unbalance DC 0mA DC 10mA

o F-2020 3.5K
With UL tap 4,8,16
Cathode NFB winding 10-100KHz 50W 150mA*2 10mA 90H 60H



http://www.tamura-ss.co.jp/en/electroni ... 0-2020.pdf


The full Tamura Audio Transformer catalog, with more detailed technical specs:

http://www.tamura-ss.co.jp/catalog/pdf/C-1005-16.pdf

These are definitely NOT "budget iron"- the current price for new F-2020s is 51,480 Yen, and current (July 23 in Japan) rate of exchange is 78.16 Yen to the US Dollar.

Do the math... $658.65 EACH

/ed B