I have used the Maplin original circuit except for 390R gate resistors and ALF16N16W and ALF16P16W lateral mosfets. I also decoupled the power rails to the LTP and current mirror stages.
An externally hosted image should be here but it was not working when we last tested it.
I have started planning a second version.
This will have a constant current source instead of the 47K resistor on the first LTP.
I have removed the diode in the current mirror and used a transistor instead.
This will have a constant current source instead of the 47K resistor on the first LTP.
I have removed the diode in the current mirror and used a transistor instead.
Here is cct diagram of second version.
An externally hosted image should be here but it was not working when we last tested it.
There's this one on eBay which I believe uses the same circuit but with modern Lateral MOSFETS. 2SK1058 & 2SJ162. EBB 150 Mosfet Power Amplifier Module 125W RMS Audio Disco PA | eBay
Bone,
125W claimed for a single pair output stage cannot drive speakers.
The most you can expect is to be able to drive a test resistor to that level.
A single pair output stage using two 200W devices can reliably drive an 8ohms speaker to ~100W.
If those output devices are <<200W, then the power capability will be proportionately that much less.
125W claimed for a single pair output stage cannot drive speakers.
The most you can expect is to be able to drive a test resistor to that level.
A single pair output stage using two 200W devices can reliably drive an 8ohms speaker to ~100W.
If those output devices are <<200W, then the power capability will be proportionately that much less.
Maplin MOSFET Amp
I found copies of original tech specs. Appears that its performance was much better than I thought😱 though I had nothing to compare with at the time. I remember it had a fairly "bright" characteristic sound that was probably why many modules ended up in home-made disco-kit. I got tired of my ears ringing and sold the system to a workmate for £75, probably still going strong if it was as bomb-proof as claimed😀
I found copies of original tech specs. Appears that its performance was much better than I thought😱 though I had nothing to compare with at the time. I remember it had a fairly "bright" characteristic sound that was probably why many modules ended up in home-made disco-kit. I got tired of my ears ringing and sold the system to a workmate for £75, probably still going strong if it was as bomb-proof as claimed😀
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I built one for my mobile disco and it simply wasn't loud enough.
So I bought a Maplin 225WRMS bipolar amplifier kit.
That was much louder and worked well for many years on the road.
A few months back I got hold of an unbuilt Maplin mosfet amplifier kit.
I was amazed to find one still unbuilt from the 1980's.
I built it up and it worked first time.
So I bought a Maplin 225WRMS bipolar amplifier kit.
That was much louder and worked well for many years on the road.
A few months back I got hold of an unbuilt Maplin mosfet amplifier kit.
I was amazed to find one still unbuilt from the 1980's.
I built it up and it worked first time.
Hi Nigel,
The tech specs (third page) shows how to add paralleled transistors to output stage to increase the output power. Don't know if anyone actually developed this into a new product. I think your re-vamp with a sprinkle of Self and Cordell circuit up-dates will produce a nice sounding amp module.
Who knows, if we discuss it enough a ready-made clone might appear on eBay😉
steve
The tech specs (third page) shows how to add paralleled transistors to output stage to increase the output power. Don't know if anyone actually developed this into a new product. I think your re-vamp with a sprinkle of Self and Cordell circuit up-dates will produce a nice sounding amp module.
Who knows, if we discuss it enough a ready-made clone might appear on eBay😉
steve
Hi everyone, I'm new to the forum but have been given 4 each of 2SJ50 and the 2SK135. I was hoping to perhaps build a simple but quite good quality amp for home - I have a 200W toroidal transformer with 24VAC rails (a little light, but I'm not into flogging amps 🙂. I've heard various things about the Crescendo amp from way back - some good, some not; does anyone know of a decent, updated schematic for a low-to-medium powered amp using these transistors? I've no qualms about using them in pairs, so 4 transistors per channel - I'd rather put them to use as our home amp is about to die soon I suspect.
thanks!
much appreciated
Barney in NZ
thanks!
much appreciated
Barney in NZ
I built a pair of these into a rack case back in the 80's to use for theatre and PA work. Still going strong!
Save these for a later stereo (or two monoblocks) 2pair output stage.
Practice with a pair of MUCH cheaper modern equivalents.
Your original 50/135 will be almost impossible to replace and if you find some they will cost you a fortune.
Or
Sell them to the highest bidder who WANTS only Hitachi originals.
Best sounding amplifiers are those uses the 2SK, 2SJ, and example is the PPX amplifiers from CitroniC, Best ever
I just designed and built an amplifier using similar circuit as Maplin mosfet amp but using ALF16n16W/ALF16p16W dual lateral mosfets.
You could use the circuit here replacing the output lateral mosfet.s
http://www.ckp-railways.talktalk.net/maplinlateralmosfet_2.jpg
here is final ver of layout posted here for this amp.
25W Class A amp with Lateral MOSFETs
I didnt want to disturb that that thread further.
25W Class A amp with Lateral MOSFETs
I didnt want to disturb that that thread further.
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