Hello DIYers!
I’d like to start playing with my first DIY Amplifier, I know they’re outdated and there are more efficient packages out there but I love the looks of TO-3 power transistors.
So with that being said I’m wondering if you knew about a design that could work with low voltage high current transistors that I may modify the output stage a bit to make it work, it could be Class A or Class AB either Complementary or Quasi.
I want to use it as a learning experience and if possible, and that’s why I mentioned low voltage high current transistors, I’d like to use the transistors I have 2N5302, and I have a TON!!!, my understanding is that its complementary is the 2N4399.
And please if you think those transistors just won’t work I’d understand but please provide details about why, remember I'm trying to learn 🙂...
Thanks in Advance!
I’d like to start playing with my first DIY Amplifier, I know they’re outdated and there are more efficient packages out there but I love the looks of TO-3 power transistors.
So with that being said I’m wondering if you knew about a design that could work with low voltage high current transistors that I may modify the output stage a bit to make it work, it could be Class A or Class AB either Complementary or Quasi.
I want to use it as a learning experience and if possible, and that’s why I mentioned low voltage high current transistors, I’d like to use the transistors I have 2N5302, and I have a TON!!!, my understanding is that its complementary is the 2N4399.
And please if you think those transistors just won’t work I’d understand but please provide details about why, remember I'm trying to learn 🙂...
Thanks in Advance!
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You can select the transistors with the maximum Hfe for the amplifier JLH 1969, 1996, 2003 class A.
You can build a quasi-complementary amplifier class AB with power supply up to 45 V (+ -22 V): Leak30, Sinclair30, Apex6, etc.
With a complementary transistor 2n4399 in class A Hiraga, JLH1970 and various class AB amplifiers (with limited power supply). The output transistors are desirable to include an emitter follower according to the scheme.
You will also need a PCB, various parts or kits, a transformer, radiators, a box ...
The project cost can be significant and time consuming.
You can build a quasi-complementary amplifier class AB with power supply up to 45 V (+ -22 V): Leak30, Sinclair30, Apex6, etc.
With a complementary transistor 2n4399 in class A Hiraga, JLH1970 and various class AB amplifiers (with limited power supply). The output transistors are desirable to include an emitter follower according to the scheme.
You will also need a PCB, various parts or kits, a transformer, radiators, a box ...
The project cost can be significant and time consuming.
Thanks [mention]OldDIY [/mention]!!
The PLH article from Mr. [mention]Nelson Pass [/mention] was a very interesting 4:00 AM reading 🙂
I will continue doing my research about the other designs you mention, one thing that I couldn’t understand after reading the article is why you suggest choosing the transistors with high Hfe for this particular design?
Thanks again!
Alex
The PLH article from Mr. [mention]Nelson Pass [/mention] was a very interesting 4:00 AM reading 🙂
I will continue doing my research about the other designs you mention, one thing that I couldn’t understand after reading the article is why you suggest choosing the transistors with high Hfe for this particular design?
Thanks again!
Alex
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JLH1969 uses single transistors (not darlington) at the output. Reading for a long time 🙂
JLH 10 Watt class A amplifier
JLH 10 Watt class A amplifier
Hi Alex,
Those 2N5302's would make excellent series-pass transistors for a fairly substantial bench supply -- 0 to ~35V, 5 amps -- more if you design-in some over-current limiting or pair them up. Might be an easier starter project than an amp.
For audio outputs they're a little slow, and low hFE, by modern standards. Also, the 5mA cutoff current is kinda high.
How'd you score those beauties, anyway? (-- providing you don't mind saying ..😉)
Cheers
Those 2N5302's would make excellent series-pass transistors for a fairly substantial bench supply -- 0 to ~35V, 5 amps -- more if you design-in some over-current limiting or pair them up. Might be an easier starter project than an amp.
For audio outputs they're a little slow, and low hFE, by modern standards. Also, the 5mA cutoff current is kinda high.
How'd you score those beauties, anyway? (-- providing you don't mind saying ..😉)
Cheers
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Thanks Rick!
Well I've had alerts on eBay for a couple of years now, I'm receiving alerts for MOSFETS, Transistor Lots, TO-3, etc. That because I've been waiting for an opportunity to buy Original IRF244 and IRF9240 MOSFETs which I have fortunately found a few too 🙂.
Long story short that's how this opportunity popped up and I was attracted by its High Power Handling etc but as a Newbie in the Amplifier design I Ignored the facts that you just mentioned, Thanks for that!
And well when I said I have a TON yes I have a TON, I have 8 of those sets so 400 in total....
So what should I be looking at when selecting them?
How do I know they are slow vs fast, what are the parameters I should be looking at and the ideal values for Audio?
For the output stages of amplifiers, the selection of pairs is performed according to Hfe at several currents: 0.1a; 1a; 5a.
Figure 9: https://ru.mouser.com/datasheet/2/308/2N5302-D-1801588.pdf
Suitable for class A amplifiers.
Selectable by voltage (current limited).
Figure 9: https://ru.mouser.com/datasheet/2/308/2N5302-D-1801588.pdf
Suitable for class A amplifiers.
Selectable by voltage (current limited).
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Well the mosspec datasheet says Ft is 2 mhz, which isn't that slow. First generation 2n3055 was 200 khz and those did cause a little distortion on high frequency musical instruments like bells & pianos. The 1966 amp designs did clean up high freq distortion a lot when epitaxial transistors became available about 1972 & were substituted.
Hfe doesn't matter a lot for emitter follower outputs, which are the most common use of TO3 packages. Drivers can be TO220 up to 3 output pairs if well heat sinked.
I've built AX6, which sounds really nice IMHO on speakers, and has an output capacitor to prevent speaker damage from DC voltage caused by wiring errors or bad solder joints. Retro Amp 50W Single Supply - Page 22 - diyAudio Both typical newbie mistakes. You need a quasi comp amp to use only npn outputs, which is inferior in the 3rd digit of harmonic distortion to complimentary outputs. Not IMHO audible distortion on speakers, which have 1-40% HD typically.
I built AX6 on bare board with point to point wires, but there is a TO3 artwork in the thread if you have a way to etch copper boards.
If you have enough heatsink on the drivers, and use high freq high gain ones like mj15028/29 or 31/32, you could drive three output pairs. I just used one pair, and my AX6 will put out ~70 W for 5 seconds on 8 ohm speakers. Not very often of course. The 2n5302 has more soa @ 60 v than the MJ15003 equivalents I used. My version had single regulated supply 70 v, no center tap transformer, which puts about 35 v on each output transistor.
No center tap transformers can be cheap. I found 44 v 7 amp ones on ebay for about $60 from vermont transformer. Quoted transfomer rating is at full current, so that will rectify out to about a 60 v rail (1.4 full power voltage - 2 diode drops).
I built in a blown 1966 amp chassis with ruined boards & shorted output transistors, so my transformer+case+fuse+switch+powercord+feet cost was $55.
Blown up amps can be bought on ebay. Blown PA amps rejected by bar bands because transformers are too heavy to carry & set up every night, are especially cheap. Don't buy class D or T by mistake, those are not easily repaired and the voltages are too low for class AB.
Other quasi comp outputs are TGM8, basic50 by john ellis, G amp by sakis, 60 W 2n3055 by bilbo of sydney.
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Thank You indianajo, this is great information, I certainly have a bunch of options to consider now and what you suggest for getting cheap transformers, heatsinks, etc. is definitely the way I've been looking at 🙂 its incredible how cheap those amps go for right?
I'll finish a couple of repairs I have in my bench and then get started with my first DIY, really looking forward to it!
I'll finish a couple of repairs I have in my bench and then get started with my first DIY, really looking forward to it!