MOSFET! Could It Be A.... Sanyo?

MOSFET! Could It Be A.... Sanyo?

Next time you're sitting around talking trash with your MOSFETid friends, stump 'em with this one: "What '80s amp uses the classic Hitachi 2SJ49 and 2SK134 in TO-3 cases, two complementary pairs per channel, just like the Hitachi 8500 Mk II; dual transformers just like the Hitachi 8500 Mk II; bridgeable just like the Hitachi 8500 Mk II; 100 watts per channel just like the Hitachi 8500 Mk II; headphone jack just like the Hitachi 8500 Mk II-- but ISN'T an Hitachi 8500 Mk II? and doesn't at all resemble the otherwise similar Sherwood S-6040 CP? ..Ha ha! Give up?"


SANYO PLUS P55 MOSFET AMP

It's the circuitbreaker-equipped, LED-metered, surprisingly well-built Sanyo (yes, Sanyo, the folks who make those very reliable nickel-metal-hydride rechargeable batteries, who bought Fisher BITD and were in turn absorbed by Panasonic awhile back) Plus Series P55 MOSFET amp. About the same shape as the LED-metered Sherwood (which is also a twin-transformer design), inside they look nothing alike (nudesters to follow). In fact, the Sanyo is cooled with a heat pipe, a la Kyocera. You can hear the heat pipe gurgle when the amp's been running awhile.

Like the Sherwood, the Sanyo was on the US market for a disappointingly short time and came with a matching tuner (T55) and preamp (C55). Unlike the Korean-built Sherwood, the Sanyo was a product of the home country, Japan.

The sound? Glorious. Driving a Stax Lambda Pro with the Sanyo gives the lie to the old wives' tale that electrostatic headphones don't have percussive bass. The Ultrasone demo CD never sounded so good. On the other hand, it's not much different, so far, from being a smaller Hitachi HMA8500 Mk II with LED meters and less of a formal look. More details and impressions later. Oh, the photo shows the P55 driving a pair of damped Yamaha Orthodynamic headphones, model YH-1, with a lot of bass boost from a Yamaha C85 preamp.

The round speaker selector knob shown is not original.

I like!:yes:

Very cool looking in a sort of SAE way...

Can't wait to see the nudies!

Too cool!
Looks good, too.

You know, I've seen one of those in silver on CL. But the picture was so bad, I couldn't tell exactly what it was. Now I wished I had called....

wow

Wualta, Cant say I sit around with any friends discussing those topics, but that is a really nice looking amp.
Thank You for confirming that the output devices were also the same used in the Hafler DH200 (I think, anyhow), also from the early eighties.
I dont know, but I have heard somewhere perhaps just through electronic industry history, that there is (was) some connection between Sanyo and Kyocera. Not necessarily true, just heard at one time in the past.
The bridgeable feature seems to me to be way ahead of its time, I cant think of too many amps that had it.
Cant say I love the look, but what a combination of technology, guts, and features, surely this product had the stuff to convert non-believers.
Cant wait to peek under the hood.
Do You also have the matching tuner and pre ????
Very nice.

Damage,
Didnt think they made these in silver - that would be a surprise.

Nice find!!!

I am sure it sounds good,
not a pretty amp, but Mosfet sound is the BEST!!!

I have a few mosfet power amps, Perreaux, Hitachi, Hafler and a Kit Job that Really rocks.....

Nothing beats that Mosfet sound...
Enjoy!!

Mark

P55 photos as promised

I apologize for the flash-on-camera, but in this case there wasn't much choice. Note the nice even coating of dust made visible by said lighting technique. I don't think anyone except some long-dead weevils has been inside this thing since it came from the factory. The MOSFETs themselves hang upside down and are easily accessible from underneath, just like Sony's VFET integrateds.

Note also that while some of the parts resemble some in the Sherwood, the layout is entirely different. The heat pipe with its fins looks like something from the underside of a fridge ("WARNING: FREON GAS UNDER PRESSURE" says a sticker). Note too the unusual horizontal mounting of the power supply electrolytics (4x 10,000uF, 63v).Some of those resistors look awfully cheap and old. How old is it? This is one of those amps that turns up nearly unmentioned in Google, although it was tested [and reviewed] by Julian Hirsch in the August 1980 issue of Popular Electronics. Ads began to appear in audio magazines in the fall of 1979.

Readers of Greek will be glad to hear that the magazine Hxos Eikona (Sound Vision) tested the living daylights out of the P55, also in the August 1980 issue. And those are the only two reviews I've been able to find so far.

Interestingly, the back of the amp has no convenience outlets, nor does it have binding posts, just some good-quality spring clips. There's a single set of RCA inputs next to the stereo/strapped-mono switch, the reset buttons for the two 3.15A circuit breakers, and that's it.

Here's a flash shot of the fascia. Note the red anodizing of the front panel.





This is what the speaker switch originally looked like:


It's hard to know what to make of this amp. It's certainly decent quality. The looks... well, you get used to the meters jumping around (they can't be turned off) and the graphics surrounding the LEDs are.. umm.. But it's certainly an alternative to the look of the Hitachi amps of the period, though on eBay the selling prices are about the same for the Sanyo and the Hitachi HMA-8500 Mk II. As for the Sherwood, I suspect that it was an attempt to build a P55 inexpensively in Korea using the later plastic bodied MOSFETs, a conventional heat sink and simpler chassis construction.

Oh, why not one more. And the Sherwood's interior, for comparison:

I have been inside so many vintage Sanyo receivers, I cant help but add some meaningless observations.
The horizontal mounting of the filter caps is a hallmark of how they made use of internal space, and in observation could be a consideration of the somewhat low profile of the chassis. The shields on the transformers are seen on all the plus series units I've seen, and also on pics of big Fisher receivers we've seen.(RS1060/80) However, these transfo's are Rex and all of the others I've seen on Sanyo gear have been Matsushita.

The finned bridge rectifiers are exactly the same as used in the JCX2900K and the Plus 130(also in pairs). The combination dual emitter resistors (or in this case drain resistors) are exactly those used in the plus 130's amp.
The heat exchanger (as I call it) is also exactly like the plus 130, except it is combined into one long unit on the P55. Wualta, Please give us an indication if You can heat this thing up at all,(?) that is some impressive cooling area for a 100 watt/ch amp.

Based on what I've put together on the plus series receivers, this amp should have been introduced in 1980. Service manuals from the first "JA" series amps from Sanyo are dated 1981, which came after the Plus series. I think if You search the online auctions, You will be able to find a service manual for this unit, I know I've spotted them from time to time.

The circuit breakers were used on the earlier JCX-2600K and 2900K, but not on the Plus series receivers interestingly. ( back to internal PCB mounted fuses, but cant vouch for the plus 200). They work in the event both polarity outputs short(main rails shorted), and prevent fire, but do nothing to protect the outputs themselves.
The convienience outlets were most likely placed on the C55 preamp, and the P55 and T55 could be plugged into it and switched on/off. (just a guess)...
The speaker terminals are the same used from the JCX series receivers on thru to all plus series units. They hold up very well and are some of the better ones used, but I still dont like spring clips, cant be alone there. Those LED's can be shut-off, but then what would You have to look at ????. One of the few Sanyo's that I dislike the cosmetics of.

Thanks very much for the internal pics, best of luck with the unit, chances are because of this thread, the P55 is little more sought after now, and the reasons are pretty clear.

Orion sez (replace the '7' with '8' in the years!):

SANYO
PWR, P-55 PLUS

Manufacture Years: 1971 - 1974

Power: 100

Retail
MSRP: $400.00
USED: $41.00
Wholesale
Mint: $24.00
Average: $14.00

Also listed are other members of the 'family':

SANYO
PWR, P-33 PLUS

Manufacture Years: 1982 - 1984

Power: 33

Retail
MSRP: $250.00
USED: $36.00
Wholesale
Mint: $21.00
Average: $12.00

========================

SANYO
PWR, P-75 PLUS

Manufacture Years: 1981 - 1984

Power: 75

Retail
MSRP: $450.00
USED: $62.00
Wholesale
Mint: $36.00
Average: $21.00

==============================

SANYO
PRE, C-55 PLUS

Manufacture Years: 1981 - 1984

Retail
MSRP: $300.00
USED: $32.00
Wholesale
Mint: $19.00
Average: $11.00

==========================

SANYO
SGNPRO, N-33 PLUS NOISE REDUCTION

Manufacture Years: 1981 - 1986

Retail
MSRP: $300.00
USED: $27.00
Wholesale
Mint: $16.00
Average: $9.00

=========================

SANYO
TUNER, PLUS T-35

Manufacture Years: 1980 - 1982

Retail
MSRP: $200.00
USED: $78.00
Wholesale
Mint: $45.00
Average: $26.00

===========================

SANYO
TUNER, PLUS T-55

Manufacture Years: 1980 - 1982

Retail
MSRP: $250.00
USED: $130.00
Wholesale
Mint: $76.00
Average: $44.00

Njoy!

CUlater, thanks for digging all that up! You're right, Orion's fulla baloney on the dates for the P55. MOSFETs didn't even appear until the very late '70s, and the P55, C55 and T55 were all supposed to be a matching set, like luggage. So '80-'81 for the P55 should be about right.

Now, the funny thing is, Sanyo was making classic silver-face amps before they went nuts with the P55. Do a search on eBay using just <sanyo> and <amp> to get a look at what's on there now. One of 'em looks just like old Pioneer/Kenwood.

Sanyofreak, thanks for your useful comments. You identified some new (to me) heatsink styles and what they're attached to. Speaking of heat, I've been running electrostat headphones with lots of bass boost to give the amp a real phase-angle dutch rub, and it does get warm, but not as warm as the Hitachi 8500 does just sitting there. After everything's warmed up, you can hear a faint buzzing or sizzling sound coming from somewhere and you can hear a faint glug-glug sound from (I presume) the heat exchanger [Sanyo's term for it]. Tonight I'll vacuum up the dust and the dead weevils and try to pinpoint the source of the buzz/sizz.

Does your heatsink work properly? The coolent is still in the tube?

ModernClassic said:

Does your heatsink work properly? The coolant is still in the tube?

Click to expand...

If the gurgling is any indication, yes.

I suppose I should flip the amp over and check temps directly on the TO-3s. Has anyone here had trouble with the old Freon heat-pipes in these old amps? How about heat pipe cooling of CPUs in computers?

The buzz turns out to be from one of the power transformers or from its immediate vicinity. The heat-exchanger cooling system seems to be working properly, although the trickling/gurgling sounds can be a little unsettling in a quiet room. Nice gutsy typical early MOSFET sound. Drives the big Stax electrostats to ungodly volumes with startling clarity and unbelievable (for electrostats) bass.

If you had a choice between the Hitachi HMA-8500 MkII, the Sherwood S-6040 CP and the Sanyo, and assuming roughly similar selling prices, which one should you buy? Grab the Hitachi if only for the timeless styling, heavy construction, big power supply caps, big meters and servo circuits that make adjusting offset a thing of the past. Pick the Sanyo if you need something smaller and the stark aesthetics don't bother you. If you don't need the bridging feature, pick the Sherwood, which is the easiest to work on, looks good and sounds great.
.

I had a p-55 years ago. It performed very well. It did run a bit hot so I had a fan mounted on one side so it would draw cool air in. I miss it and wish I still had it.
c-ya
ToddG

Have you tried tightening the mounting bolts/screws for the transformers. Can help quiet the hum. Nice looking amp. Sanyo made one of the first high-end switching amps about ten years ago. Still considered to be one of the best around. About 18" square and 2" tall. As with most companies, when they put their mind to it, they can make some nice gear.

matching C55 preamp arriving

FedEx should be bringing a breathed-upon C55 preamp. The seller says he tests and adjusts if necessary, so perhaps this one has a better than average chance of performing as it did when new (although recapping wouldn't be a bad idea, since I don't think he did that). Here's the photo from the auction of the viscera:


I'm not sure which material the PCB is made of, since in the original photo it was an eye-stabbing fluorescent Tang orange.

The only thing it lacks, besides a headphone jack, is a suite of controls for phono cartridge loading. Other than that, it looks to be a good basic preamp of the era. I wonder if there are any FETs in the signal path?
.

I just picked up a Plus P-55 the other day. It needs a little tinkering, but it works.

I am sure it sounds good,
not a pretty amp, but Mosfet sound is the BEST!!!

I have a few mosfet power amps, Perreaux, Hitachi, Hafler and a Kit Job that Really rocks.....

Nothing beats that Mosfet sound...

Click to expand...

I as well find the mosfet sound appealing---especially the hitachi/renesas lateral mosfets 2SK1058 and 2SJ162..

Dave