JLH as a first project
Hi,
I've build the 1996 JLH as my first DIY project in 2001.
In 2003 I built a second set using all the information gathered on this and other sites.
See my website
J-amp 2003
for circuit diagrams, pcb layout etc.
Jos
DJNUBZ said:
Hi,
I've build the 1996 JLH as my first DIY project in 2001.
In 2003 I built a second set using all the information gathered on this and other sites.
See my website
J-amp 2003
for circuit diagrams, pcb layout etc.
Jos
The input stage reminds me more of the Aleph-X than the JLH. The rest is very much like the output portion from the updated JLH from Geoff's site.
Have you built one?
Have you built one?
I have published a version I built about a year ago here, which was essentially an Aleph X (Mosfet) but with the Aleph current source replaced by a phase splitter. Now I am tempted to build a bipolar Xed JLH, having already build 2 1996-JLH's and ran them normally bridged but not X'ed.
Comments from experienced JLH builders still most welcome.
Patrick
Comments from experienced JLH builders still most welcome.
Patrick
JLH amp
Hello, I am a new member to this forum.
First of all I like to thank Mr. J.L.Hood to publish his Class A circuit. I did read a lot of very good comments to the sound, so I decided, that this will be my next amp, after my ex ruined my wonderfull 1976 Elektor Equa after the divorce.
I like to thank also all members of this page for their qualified contributions and keep this page going.
First of all I like to place some questions:
- reading so much about the transistors in the circuit, can I get a honest recommendation for a pure natural sound, regarding a power approx. 25 W on 6 ohms.
- does someone have some experience with MJ 11016.
- does someone has built a balanced input pair for this amp?
- does someone has built a CFP output for this amp?
I would be happy to find some answers
Michael
Hello, I am a new member to this forum.
First of all I like to thank Mr. J.L.Hood to publish his Class A circuit. I did read a lot of very good comments to the sound, so I decided, that this will be my next amp, after my ex ruined my wonderfull 1976 Elektor Equa after the divorce.
I like to thank also all members of this page for their qualified contributions and keep this page going.
First of all I like to place some questions:
- reading so much about the transistors in the circuit, can I get a honest recommendation for a pure natural sound, regarding a power approx. 25 W on 6 ohms.
- does someone have some experience with MJ 11016.
- does someone has built a balanced input pair for this amp?
- does someone has built a CFP output for this amp?
I would be happy to find some answers
Michael
> any plans to build it?
Yes, but quite a few projects with higher priority to finish. So won't be finishing this year.
> I would probably replace the input pair with jfets or mosfets.
Why?
In any case, I have already built something similar with MOSFETS. Sounds good, but no better than some other versions of Aleph X that I have built / am building. And I do like the original bridged JLH with BJTs.
Incidentally, I have measured some BJTs under operating conditions (Vce 20V, current swing from 0 to 3A, emitter resistor 1R, driven by a 10Hz sine wave at base). There are, surprisingly for me at least, substantial differences between MJ15003 and MJ21194 in terms of hfe linearity (or how much it changes with Ic). I guess I am going to try my luck with MJ21194 first.
I notice that at least one member here has built the JLH with Sanken 2SC2922. I wonder if they are willing to tell us how it compares with the On Semi output devices.
Patrick
Yes, but quite a few projects with higher priority to finish. So won't be finishing this year.
> I would probably replace the input pair with jfets or mosfets.
Why?
In any case, I have already built something similar with MOSFETS. Sounds good, but no better than some other versions of Aleph X that I have built / am building. And I do like the original bridged JLH with BJTs.
Incidentally, I have measured some BJTs under operating conditions (Vce 20V, current swing from 0 to 3A, emitter resistor 1R, driven by a 10Hz sine wave at base). There are, surprisingly for me at least, substantial differences between MJ15003 and MJ21194 in terms of hfe linearity (or how much it changes with Ic). I guess I am going to try my luck with MJ21194 first.
I notice that at least one member here has built the JLH with Sanken 2SC2922. I wonder if they are willing to tell us how it compares with the On Semi output devices.
Patrick
Hi Michael,
For many, one of the big advantages that this amp has is it's excellent gain/phase charactoristics which means that no compensation is needed.
When JHL published his second version of the amp he had considered using a long tailed pair but decided not to, because this would impact on the gain/phase margins ( and would almost certainly need a compensation cap or network etc )
My guess is that using CFP as an O/P devise would have the same consequences. Distortion may be decreased but would it sound better ?
Graham Maynard has offered here a circuit that has has a LTP i/p plus other novel elements and says it sounds very good.
I would suggest building a known good design first as a reference before getting into ideas that would need to be subjectively substantiated.
http://www.tcaas.btinternet.co.uk/jlhupdate.htm
This might be a good starting point
good luck
mike
For many, one of the big advantages that this amp has is it's excellent gain/phase charactoristics which means that no compensation is needed.
When JHL published his second version of the amp he had considered using a long tailed pair but decided not to, because this would impact on the gain/phase margins ( and would almost certainly need a compensation cap or network etc )
My guess is that using CFP as an O/P devise would have the same consequences. Distortion may be decreased but would it sound better ?
Graham Maynard has offered here a circuit that has has a LTP i/p plus other novel elements and says it sounds very good.
I would suggest building a known good design first as a reference before getting into ideas that would need to be subjectively substantiated.
http://www.tcaas.btinternet.co.uk/jlhupdate.htm
This might be a good starting point
good luck
mike
> When JHL published his second version of the amp he had considered using a long tailed pair but decided not to, because this would impact on the gain/phase margins ( and would almost certainly need a compensation cap or network etc )
While I am aware that this is what he said, I could not quite figure out why that should be the case. Maybe you could help me out with a scientific explanation ??
Thanks,
Patrick
While I am aware that this is what he said, I could not quite figure out why that should be the case. Maybe you could help me out with a scientific explanation ??
Thanks,
Patrick
Patrick,
I would guess this is because in JLH's design, he used a singleton input stage, with output from the collector and feedback to the emitter. If he had used a long tailed pair, then the output would be from T1, yet the feedback would be to T2, thus interposing an additional effective device in the chain. The phase shift introduced by the second device is absent in his singleton configuration; the one device handles both input/output and feedback.
Cheers,
Hugh
I would guess this is because in JLH's design, he used a singleton input stage, with output from the collector and feedback to the emitter. If he had used a long tailed pair, then the output would be from T1, yet the feedback would be to T2, thus interposing an additional effective device in the chain. The phase shift introduced by the second device is absent in his singleton configuration; the one device handles both input/output and feedback.
Cheers,
Hugh
Hi Patrick,
I had a look at your design. I would say its gain/phase relationships would be excellent and it should not be necessary to introduce lag compensation or even phase lead. Then again, however, it must be said that amplifiers with compensation can be made to sound very good indeed, so that of itself this may be no real advantage.
Without building and hearing it, it's difficult to know how it will sound. You must remember that the JLH is an asymmetric design despite being pushpull, so it is likely to introduce some H2. This will confer warmth on the sound. Because of its balanced topology your circuit will cancel this H2, leaving only H3 and H5, and it may not be as euphonic. It will certainly sound very clean and free from intermodulation, but whether this is what you prefer is another matter. Lots of people like their women with stockings, after all...... It will sound demonstrably different to the original JLH, however.
Cheers,
Hugh
I had a look at your design. I would say its gain/phase relationships would be excellent and it should not be necessary to introduce lag compensation or even phase lead. Then again, however, it must be said that amplifiers with compensation can be made to sound very good indeed, so that of itself this may be no real advantage.
Without building and hearing it, it's difficult to know how it will sound. You must remember that the JLH is an asymmetric design despite being pushpull, so it is likely to introduce some H2. This will confer warmth on the sound. Because of its balanced topology your circuit will cancel this H2, leaving only H3 and H5, and it may not be as euphonic. It will certainly sound very clean and free from intermodulation, but whether this is what you prefer is another matter. Lots of people like their women with stockings, after all...... It will sound demonstrably different to the original JLH, however.
Cheers,
Hugh