I learnt the term as "bifilar" actually, probably from my father's ARRL handbooks, as a teenager long ago. It was and still is a mysterious and unique usage term to me, so I attempted to keep the terminology here a bit less opaque. I do appreciate the proper term being mentioned for its technical correctness and your really good rundown on manufacturing too.
For interest, my first job was as a cadet industrial chemist in plastics manufacturing. A neighbouring factory to ours produced E-I transformers and lighting ballast chokes by the ton, for national distribution so by making friends, I received some very cheap power transformers via the back door!
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;-)
The JLH also runs with 12 volt and < 1 amp. Is it not a SE;-?
In addition, you could simply set the input to the base of Tr3 or Tr1 (original schema). Then you lose voltage gain but you get clean sound gain;-)
I've got a question, maybe you can help me:
I built the Geoff Moss Version for ESL with four output transistors: https://sound-au.com/tcaas/jlhesl.htm
I use the MJ15003 as output transistors: https://cdn-reichelt.de/documents/datenblatt/A100/MJ15003_MJ15004_MJ15003_MJ15004#ON.pdf
Could I use the MJL21193G as a direct replacement? https://www.mouser.de/datasheet/2/308/1/MJL21193_D-2315974.pdf
I want to put the Amplifier into an active speaker, These MJL21193G would be much better to mount.
Didn't find much information about the use of MJL21193G as output transistor, but I think the specs shoulb be fine?
What is your oppinion about it? Is it worth a try?
Appreciate your help, and Thanks in advance!
I built the Geoff Moss Version for ESL with four output transistors: https://sound-au.com/tcaas/jlhesl.htm
I use the MJ15003 as output transistors: https://cdn-reichelt.de/documents/datenblatt/A100/MJ15003_MJ15004_MJ15003_MJ15004#ON.pdf
Could I use the MJL21193G as a direct replacement? https://www.mouser.de/datasheet/2/308/1/MJL21193_D-2315974.pdf
I want to put the Amplifier into an active speaker, These MJL21193G would be much better to mount.
Didn't find much information about the use of MJL21193G as output transistor, but I think the specs shoulb be fine?
What is your oppinion about it? Is it worth a try?
Appreciate your help, and Thanks in advance!
The main thing to watch is thermal resistance junction to case. This should be good enough on the ones you mention. Better than what was available in 69 etc. 0.7C/watt is similar to TO3 from memory. Some TO3 these days seem to be higher. Mica insulators still appear to be the best to keep this number as low as possible with a smear of thermal paste. Once warmed up they may need tightening down a few times - too much paste may cause that. Max junction temperature one plastic is still lower than TO types.
Performance is trickier. If stated ft gives reasonable idea about frequency. Gain may be more difficult, HFE behaviour can relate to hfe and both vary with current. Similar behaviour or better is a good idea but gain varies anyway. Min values are best but may not be given. Mr Hood may have ordered a matched pair and gain selection with his best pair of transistors as that service was available from a UK supplier. Just had to cross their palms with silver. There was a need for people who repaired the many amps that were around at the time not just DIY.
Hood mentions putting the highest gain transistor in the lower position. That is just a case of knocking something up to check it. Some one on this forum should have some simple ideas on how to do that. Gain will increase as they warm up. The heatsinks are needed anyway.
There are articles on the web concerning an entirely bipolar curve tracer. Might be fun to build but low current. This type is connected to an oscilloscope to obtain the display. People seem to be impressed. It uses a bipolar multivibrator. Those can produce very fast edges providing they are not swamped by stray capacitance. This helps get a clean display.
Has anyone actually looked at the supply current behaviour on Hood's amp? Higher band width probes for oscilloscopes are rather expensive but it can be done with a suitable shunt in the line to reasonable accuracy, Even Amazon stock some values,
Mr Moss tried the MJ21194 which is, I believe, the TO3 version of MJL21194 and rejected it as it oscillated.
Of course, your build will be different so who knows, might be fine.
It is not SE. or rather not the 1969 version. The bias is maintained by resistors and the voltage would drop across them as well, then the FB resistor would also follow with the output dropping. It is designed to keep Vout about at half rail under DC conditions. Many do not realize what an ingenious little design it was, even nowadays.
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The MJ21194 is a great audio transistor but the datasheet shows that its gain doubles between 25C and 100C, so if you use that in a JLH you will need big heatsinks to control the current. The MJ15003 gain is shown to vary by only about 25% between 25C and 150C. That would make it a better choice for the JLH I think, unless you use some sort of servo to control the current.
TIP35 is probably not the power transistor to choose if you want the best linearity in a plastic package. Its great for linear power supplies, UPS etc. but we usually build JLH '69 type amplifiers for their great sound quality. TIP3055 is the logical substitute for 2N3055 but neither may be what you'd call the best type for audio, in general. They're cheap though and ST Micro make a good version of TIP3055 so I'd start with their genuine product, test and then decide whether it meets your expectations.
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On a related topic, I was also searching for better TO3 power transistors and thought I had found something in MJ15015 which, according to the original spec, had an Ft 3 times that of 2N3055 or typically 8 MHz. Avnet/RS,Farnell, Element14 etc. are apparently selling said product but the datasheets for theirs and similar TO3 transistors are for Multicomp products which are relatively cheap but have much lower Ft specs than Onsemi's.
Assume nothing about discrete semis now. It seems fakes are now acceptable commercial products, part numbers are only generic and specs are just numbers for tempting us to buy junk.
Assume nothing about discrete semis now. It seems fakes are now acceptable commercial products, part numbers are only generic and specs are just numbers for tempting us to buy junk.
A little reading to go over the basics of this simple but complex diagram.
https://sound-au.com/tcaas/jlhoutput.pdf
https://sound-au.com/tcaas/jlhoutput.pdf