Higher Power Low TIM Leach

[wahab]

you can also make a good amp using the hitach that are sill
alive, with a lower voltage transfo??...though, less powerfull..
50W/pair...

 

[Stormrider]

you can also make a good amp using the hitach that are sill
alive, with a lower voltage transfo??...though, less powerfull..
50W/pair...

Yes, I am going to test the channel that looks OK, and keep it as a back up for my working FET 500, or salvage the Hitachi's for a smaller amp. I'm sure all the fet's in the blown channel are dead, but they will be saved until I can confirm either way (need to make a tester).

 

[taj]

Stormrider,

Here's an archive of Jens's 10-pair Leach amp.

http://web.archive.org/web/20080510170113/delta-audio.com/Leach-Clone.htm

I have all the files archived myself if you need any of them. If I remember, Jens used it up to 70v rails, but I'm sure it's simple to push it the extra distance to 80v. 5 pairs of MJ21194/93 (to-3) would be good I think.

The boards are not shaped well for your heatsink, but you could reconfigure the output section with your layout.

..Todd

 

[alex mm]

Low TIM Leach .... 2 pairs

Hi ,
Another variant ,of Low TIM power amplifier with only 2 pairs finals transistors

An externally hosted image should be here but it was not working when we last tested it.

Maryy xmas !

 

[Ultima Thule]

TO-3 and TO-3P are physically compatible

Interesting solution. But, I think converting the amp to use the TO3P packages would be as much work as retrofitting it with the Leach PCB's and, I already have the MJ21193/94's. I still don't understand why Hitachi discontinued the TO3 lateral. Seems like every mosfet amp from the 70's and 80's used it.

Stormrider,

FYI TO-3P are drop ins for TO-3!
You just bend the outer legs (G & D) on the TO-3P package 90 degrees backwards, the middle leg (S) isn't used in case the flange is connected directly, otherwise you just solder a wire from the middle leg, all other holes and leg spacing are exactly the same as TO-3, it's not for nothing the package got the name TO-3P.

Cheers Michael

 

[Eva]

TO-3 Plastic

 

[Ultima Thule]

Yes Eva that's right!
Long time no see, nice to see you (and your eye?) around!

Cheers Michael

 

[Stormrider]

Stormrider,

Here's an archive of Jens's 10-pair Leach amp.

DELTA AUDIO - Leach Amp Clone

I have all the files archived myself if you need any of them. If I remember, Jens used it up to 70v rails, but I'm sure it's simple to push it the extra distance to 80v. 5 pairs of MJ21194/93 (to-3) would be good I think.

The boards are not shaped well for your heatsink, but you could reconfigure the output section with your layout.

..Todd

The heatsinks only have space for four pairs.

I think I will hold off on this until I can do it right. Correct transformer (for +/-70Vdc), my own PCB for these heatsinks, etc... or if I decide to rebuild the amp with new mosfets.

 

[wahab]

change the transformer for a 2 X 35V AC, and use four devices/channel...
it s the cheaper..

 

[scott wurcer]

wow, i've never seen hitachi mosfets blown up like that!
speaking of letting out the magic smoke ....


mlloyd1

Wow, we had a customer in China that tried to tell us that they had "holed" some DSL amps but over the phone it was not clear what was being said, we didn't get it till we saw the FA.

 

[TonyTecson]

Good to hear some hope for this. Can you elaborate?

for the to-92's, you can use mpsa42/mpsa92
for VAS, mje340/350
for drivers, mje15032/15033
for output, mjl21193/21194, if TO3, mj21193/21194

 

[fooeywuffle]

I just bought a set of 16 of the MOS-FETs from an Ashley, they were all bad, acted like 5 volt power zeners! K135. J50

 

[AndrewT]

who or what are "Ashley"?

 

[llwhtt]

Pro audio manufacturer in New York.

Craig

 

[djk]

Ashley is a furniture retail chain, Ashly Audio Inc. is an audio manufacturer.