Toshiba Ouput Tranistors 2SD424 & 2SB554 (many Adcoms)

fredv

Hi Ben,

Yes, I prefer a match set. It is really a good question whether they were pre-matched
from Toshiba. I doubt it was the case; however, if the transistors were from the same
batch, then they can be very close.

I will send you email later.

Thanks!!

heiney9

I'd have to say NO they weren't pre-matched from Tosh. Plus by now there is no way to tell how many "runs" are mixed together in the bundle you have. Perhaps at one time when they were still in production they were sent to Adcom as matched sets. But by now this many years later I'd match them all again to be sure.

H9

ben62670

heiney9 wrote: »

I'd have to say NO they weren't pre-matched from Tosh. Plus by now there is no way to tell how many "runs" are mixed together in the bundle you have. Perhaps at one time when they were still in production they were sent to Adcom as matched sets. But by now this many years later I'd match them all again to be sure.

H9

So cynical:p
These were shipped directly to an Adcom repair shop 250 each in one box(I have 500 total), they came with the screws, and the insulators:D The box was still sealed with the Toshiba tape. The guy I bought them from had to cut the Toshiba seal to take pics:D:D:D

heiney9

ben62670 wrote: »

So cynical:p
These were shipped directly to an Adcom repair shop 250 each in one box(I have 500 total), they came with the screws, and the insulators:D The box was still sealed with the Toshiba tape. The guy I bought them from had to cut the Toshiba seal to take pics:D:D:D

Well you didn't tell me that . One thing I learned from Nelson Pass in reading about his designs is that no matter what, he always hand matches his components. It only makes sense if you have the ability to match them to go ahead and do it to get the best possible result.

Looks like maybe you might try your hand at building an amplifier. The trannys are the least expensive part however

H9

fredv

You are absolutely right. The other tranny (toriod), chassis (good looking), and heat sink can easily make up 80% of a DIY amp unless the parts are all exotic production!!! Heat sink is the killer if it is a pure class A.

ben62670

heiney9 wrote: »

Well you didn't tell me that . One thing I learned from Nelson Pass in reading about his designs is that no matter what, he always hand matches his components. It only makes sense if you have the ability to match them to go ahead and do it to get the best possible result.

Looks like maybe you might try your hand at building an amplifier. The trannys are the least expensive part however

H9

I am thinking of building a super amp. I'm thinking a 220 volt range outlet (50amp) type transformer to an output of around 90v. I would have the transformer mounted away from the amp (another room)connected by welding cable. I would have a huge mounting pad for the output transistors that is water cooled. I would like to use a car type radiator mounted outside in the summer, and inside in the winter(free heat). With this design I could run my custom SDA's, surrounds, center, and subs from one unit. I am figuring about 1k watt each channel for the fronts, 500 wpc centers, surrounds, and 750x2 for subs. I know this sounds insane, but I am trying to get decent output in full class A to about 25-50wpc all channels except sub(full class A/B is fine for a sub). The grand total would be 5k watts clean in one amp chassis. I figure clipping would occur around 8k watts( I would never ever do this to my ears)The biggest killer of this project would be the capacitors. 100volt caps of sufficient capacity would be big dollars!

ben62670

I left out another important component problem. Bridge rectification of that magnitude would be on a level I have never seen. I would also like to use Darlington input configuration like the GFA-585/565 style, and DC offset protection would be imperative.
Any thoughts?

Ben

fredv

ben62670 wrote: »

I am thinking of building a super amp. I'm thinking a 220 volt range outlet (50amp) type transformer to an output of around 90v. I would have the transformer mounted away from the amp (another room)connected by welding cable. I would have a huge mounting pad for the output transistors that is water cooled. I would like to use a car type radiator mounted outside in the summer, and inside in the winter(free heat). With this design I could run my custom SDA's, surrounds, center, and subs from one unit. I am figuring about 1k watt each channel for the fronts, 500 wpc centers, surrounds, and 750x2 for subs. I know this sounds insane, but I am trying to get decent output in full class A to about 25-50wpc all channels except sub(full class A/B is fine for a sub). The grand total would be 5k watts clean in one amp chassis. I figure clipping would occur around 8k watts( I would never ever do this to my ears)The biggest killer of this project would be the capacitors. 100volt caps of sufficient capacity would be big dollars!

Hee hee, I didn't even dream of 50% size of this beast. My other half will kill right from the get go. Since half of my life is gone, I need to preserve my brain cells for projects that I can bring to live

ben62670

Fred could you recommend a good book? I have Slone's book on high power audio amplification, but it doesn't cover a lot of things I need to know. Like driving that many output transistors. Also I would like to be able to get full output from a one volt signal input instead of the almost 2 volts the 565's, and 585 require. A low voltage tube input stage would be pretty neat.

Phasearray

how much for a pair?
I have a busted Toshiba SA 725 that I accidentally connect Output of SpeakerA to the input of Speaker B....Not sure what model those transistors are on the Toshiba though..

ben62670

Phasearray wrote: »

how much for a pair?
I have a busted Toshiba SA 725 that I accidentally connect Output of SpeakerA to the input of Speaker B....Not sure what model those transistors are on the Toshiba though..

Do you need a pair of complimentary transistors, or 2 of the same. You really need to know the model of the transistors,
Ben

fredv

I spend more time on DIY tube projects than SS and haven't read too many SS books. I like the Art of Electronic, http://www.amazon.com/Art-Electronics-Paul-Horowitz/dp/0521370957, which covers a lot of good topics; however, not quite specific to amp building. Why do you want such a sensitive input? I built an amp (only 35 mighty tube watts per channel) that has 0.75V full power sensitivity. While it sounds good, it also picks up all sort of noise that irritates me big time.

ben62670

fredv wrote: »

I spend more time on DIY tube projects than SS and haven't read too many SS books. I like the Art of Electronic, http://www.amazon.com/Art-Electronics-Paul-Horowitz/dp/0521370957, which covers a lot of good topics; however, not quite specific to amp building. Why do you want such a sensitive input? I built an amp (only 35 mighty tube watts per channel) that has 0.75V full power sensitivity. While it sounds good, it also picks up all sort of noise that irritates me big time.

Most pres are rated at 1 volt out. I am thinking that a lower sensitivity on the inputs would be a good , and I could bump up the gain on the driver stage?

Phasearray

ben62670 wrote: »

Do you need a pair of complimentary transistors, or 2 of the same. You really need to know the model of the transistors,
Ben

DOH!
NVM, it uses a single STK463 Stereo amplifier.....

ben62670

I just checked out that book. I think I may go used on this one:)

Face

Will these fit in our Accurians?

ben62670

Face wrote: »

Will these fit in our Accurians?

With a slight mod yes.

heiney9

ben62670 wrote: »

Fred could you recommend a good book? I have Slone's book on high power audio amplification, but it doesn't cover a lot of things I need to know. Like driving that many output transistors. Also I would like to be able to get full output from a one volt signal input instead of the almost 2 volts the 565's, and 585 require. A low voltage tube input stage would be pretty neat.

Hey Ben you have stone nads . Building an amp from scratch is very very tough. There are so many variables. I'd find a good design that's already been tried and tested rather than trying to build something right from scratch since you really need to know ALOT to do it right right out of the gate.

Good luck to you and if you want to build an Aleph clone let me know because I'll take it off your hands when your done :D

H9

ben62670

What is this Aleph clone you speak of?

heiney9

ben62670 wrote: »

What is this Aleph clone you speak of?

See the Pass forum on DIYaudio. I haven't really looked into it too much because I don't have the skill/patience to build one. But I do know they have been/are popular and there have been many of them done and lots and lots of posts about them.

I believe the other popular Pass DIY is the Zen amplifier. That's the cool thing about Nelson Pass, after a certain amount of time he will share his circuit designs and advise how to build his stuff. I know of no other major player that does this as consistently for the DIY crowd as he does.

Those Tosh's were excellent trannys for the day and actually would hold their own today. They were the transistor of choice for a long time for many manufacturer's. Tosh had an excellent rep for quality and they are high quality parts. I'd say from a repair/amp builders POV you have a mini goldmine there for the right crowd.

H9

ben62670

Thanks H9. My amp project is not something I am going to just jump into. I have been doing some studying, and I think it will take about a year+ to realize a completed amp. Its not going to be a 5000 watt amp, but basically a bunch of amps in one case. Mostly I am going to be copying the 585 topology, but I just need to figure out how to up the watts a bit.

hearingimpared

heiney9 wrote: »

#1 stupid thing is allowing the speaker cables to touch each other when the amp is powered up. Sometimes it just blows the fuse and other times it takes out the fuse and some tranny's. As long as one is absolutely careful when doing things like that.

A friend of ours accidently touched negative and positive bananas on the amp and it took out the whole Left channel. Too quick for the fuse to blow and enough current to take out the caps, transitors, and fuse the circuit board.

ben62670

hearingimpared wrote: »

A friend of ours accidently touched negative and positive bananas on the amp and it took out the whole Left channel. Too quick for the fuse to blow and enough current to take out the caps, transitors, and fuse the circuit board.

Guilty, and I know someone else who did it to their adcom:o

heiney9

ben62670 wrote: »

Thanks H9. My amp project is not something I am going to just jump into. I have been doing some studying, and I think it will take about a year+ to realize a completed amp. Its not going to be a 5000 watt amp, but basically a bunch of amps in one case. Mostly I am going to be copying the 585 topology, but I just need to figure out how to up the watts a bit.

FYI, there are simpler topologies than the 585/565. That design by Victor Campos and Walt Yung is considered to be overly complicated and could be simplified with the same and in many cases better results. That's why they are such a **** to work on. At the time it was a balls out approach to showcase what could be done on (for lack of a better word) a budget compared to the heavy hitters of the day.

It's a great sounding design but has a lot of parts and is a very complicated topology. Good luck and as always keep us posted.

H9

Systems

Ben here is your home work.This Mr Selfs books are excellent and cover every aspect of amplifier design. http://www.dself.dsl.pipex.com/ampins/books/book.htm and for further reading http://www.dself.dsl.pipex.com/ampins/ampins.htm

fredv

ben62670 wrote: »

Most pres are rated at 1 volt out. I am thinking that a lower sensitivity on the inputs would be a good , and I could bump up the gain on the driver stage?

What pre amp do you have? Is it a Rotel or a buffer? I found Rotel pre (based on only one Rotel preamp I ever owned) seemed to have very small gain. Most of the active preamps have at least 10db gains, so a 2V CDP output can easily send 10V into the amp at max. If you need a high gain tube pre, just let me know :-)

Systems

heiney9 wrote: »

That design by Victor Campos and Walt Yung is considered to be overly complicated and could be simplified with the same and in many cases better results.

So Jung helped in the amp designs as well?I thought he just did the pre amps (565?)being he is the op amp guru.

fredv

GV, good reading links, thanks!!

heiney9

GV#27 wrote: »

So Jung helped in the amp designs as well?I thought he just did the pre amps (565?)being he is the op amp guru.

To my knowledge he was involved only with the 565/585 amps. Those amps were designed exclusively by Yung and Campos. As you probably know they are entirely different animals than the 535, 545 and 555's.

I've never been clear how much involvement they had (if any) with the next generation Adcom's 55xx series. I know the 5800 and 5802 were a Nelson Pass design or atleast the framework for the design was NP's. Later on Adcom's engineering dept. had a knack for complicating things. NP gave them a simple basic design and they added things until it was unrecognizable (to paraphrase Nelson Pass).

One of the main reason's the 555 II was changed and Darlington output stage was added as well as a beefier tranny and larger heat sinks was solely so they could boast it's ability to drive a 2 ohm load continuously. No other reason as it didn't really improve on the original 555 beyond that goal.

Not a bad deal or marketing ploy but they made the design more complicated (compared to the original 555) that it needed to be (IMO). The Stereophile review of the day did indeed feel the series II had a few improved sonic characteristics. My self personally I prefer the original series but either is still great, IMO.

ben62670

Thanks guys. I am in and out here. My buddy needed some help building a sub box. Its a monstrosity with 15" Kicker Solobaric L7's. He doesn't want to brace it. Its going to be one of those loud boomy things.