Actually, there are quite a few commercial power amps using these as they ARE very rugged and reliable (as long as they are Motorola / ON brand).
Peavey CS series (CS800, CS1000 etc) use these, although they are restamped with Peavey's in house numbers. Here in Australia, many Jands amplifiers use them.
If you were considering these, then go right ahead - but beware of inferior brands and fakes which are lower rated.
Cheers
Peavey CS series (CS800, CS1000 etc) use these, although they are restamped with Peavey's in house numbers. Here in Australia, many Jands amplifiers use them.
If you were considering these, then go right ahead - but beware of inferior brands and fakes which are lower rated.
Cheers
I suspect the main reason you don't see then too often in DIY amps is that the drilling the holes mounting them to heatsinks is viewed as something of a pain in the posterior comparred to TO-247 packages. That, at least is my main reason. On of these days I'm going to build something with them just to I can stop being a TO-3 sissy.
The MJ15024/25 pair have been standard equipment in a lot of PA amplifiers for a longtime.
They are close to indestructable and are not seriously expensive.
The mounting/connection arrangement (TO-3) is the best thermally, but as mentioned is a pain for the diyer.
These are slower transistors compared to the best modern examples, but are still pretty fast.
Now that they are available, many (most ?) modern PA amplifiers nowadays run faster output transistors like 2SA1302/2SC5200.
The MJ outputs are a perfectly fine transistor.
Eric.
They are close to indestructable and are not seriously expensive.
The mounting/connection arrangement (TO-3) is the best thermally, but as mentioned is a pain for the diyer.
These are slower transistors compared to the best modern examples, but are still pretty fast.
Now that they are available, many (most ?) modern PA amplifiers nowadays run faster output transistors like 2SA1302/2SC5200.
The MJ outputs are a perfectly fine transistor.
Eric.
mrfeedback said:
Okay, I must be a smart***. I can't resist.
As an E.E. and medical equipment designer...I avoid TO-3's too. They are a pain for pretty much everyone. I use D-Paks, D2Paks, TO-220 and TO-247's whenever possible. In fact it's usually cheaper to put down two or three TO-220's than to do the physical mounting of the TO-3 can.
Scott
I'll risk exposing my flakey memory yet again... 
I had an APT 1 Power Amp some years ago. It was well built and sounded pretty good for it's day and (I beleive) used these output devices. The schematic was pasted to the underside of the amp. I always thought it was fairly clever at the time. As mentioned in another post, I don't think I've seen a Baker Clamp circuit in an amp since then.
Anyway, I lost the amp to a very potent lightning strike that took out many electronic devices in my home. The power supply parts and those Motorola output devices were the only survivors in the amp. I later used the output devices (since they were matched) in a Leach-like design that, last I heard, was still going strong
I had an APT 1 Power Amp some years ago. It was well built and sounded pretty good for it's day and (I beleive) used these output devices. The schematic was pasted to the underside of the amp. I always thought it was fairly clever at the time. As mentioned in another post, I don't think I've seen a Baker Clamp circuit in an amp since then.
Anyway, I lost the amp to a very potent lightning strike that took out many electronic devices in my home. The power supply parts and those Motorola output devices were the only survivors in the amp. I later used the output devices (since they were matched) in a Leach-like design that, last I heard, was still going strong
mrfeedback said:
With respect to: TO-3's
Yes, they are a pain to mount, and either you kludge wires soldered directly to the pins or use marginal TO-3 sockets. But the big reason I still use them is surplus heat sinks. there is roughly a metric ton of to-3 heatsinks at every electronics surplus store. The heat sinks are dirt cheap (hard to find un-beat-up ones though), and are already pre-drilled. Hard to beat.
Sheldon
Yes, they are a pain to mount, and either you kludge wires soldered directly to the pins or use marginal TO-3 sockets. But the big reason I still use them is surplus heat sinks. there is roughly a metric ton of to-3 heatsinks at every electronics surplus store. The heat sinks are dirt cheap (hard to find un-beat-up ones though), and are already pre-drilled. Hard to beat.
Sheldon
The TO-3 may be a pain to mount, but it does have it's own advantages. Like Eric mentioned earlier, the mounting for thermal transfer is superior compared to plastic flatpacks with single screw type. It also is able to withstand higher working temperature (>150C). A bonus, Sheldon rightly brought up, is cheap used surplus heatsinks, which is great for diy.
For myself, eventhough I've used newer power transistors, the MJ15024/25 still remain one of my favourite outputs. The main reason is I've yet to come across any transistors that can beat these in the bass region. It has that full-bodied, tight bass that faster transistors seem to lack. Very manly and muscular. The difficulty is getting it to sound right in the mids and highs. It can easily give you that mid "glare' and brittle highs that so characterise solid state amps. If these are engineered away, you can have a very nice sounding amplifier with the MJ15024/25.
This is how I like to mount TO-3s
For myself, eventhough I've used newer power transistors, the MJ15024/25 still remain one of my favourite outputs. The main reason is I've yet to come across any transistors that can beat these in the bass region. It has that full-bodied, tight bass that faster transistors seem to lack. Very manly and muscular. The difficulty is getting it to sound right in the mids and highs. It can easily give you that mid "glare' and brittle highs that so characterise solid state amps. If these are engineered away, you can have a very nice sounding amplifier with the MJ15024/25.
This is how I like to mount TO-3s
So many replays...
Hello everyone,
Thank you for your advices. In case that for me is not problem with TO-3 mountig (some time ago I made a stencil), I think that I shall use them. It’s a little bit sad that I can’t get MJL*** series transistors for some experiments.
Best Regards For Audio profs
Hello everyone,
Thank you for your advices. In case that for me is not problem with TO-3 mountig (some time ago I made a stencil), I think that I shall use them. It’s a little bit sad that I can’t get MJL*** series transistors for some experiments.
Best Regards For Audio profs
I worked on a QSC power amp once that had those devices paralleled per channel. Too bad the amp is an "ear bleeder", but--it is pretty rugged. I'm sure those transistors would sound respectable if they were driven by a well designed circuit.
Another popular transistor from Motorola/Onsemi is the MJ21193 and 21194. They are used in a multitude of products.
Another popular transistor from Motorola/Onsemi is the MJ21193 and 21194. They are used in a multitude of products.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.