JLH 2005 my first measurements
I have now done my first measurements on the JLH2005 class A amplifer.
Only the first channel, so far and with Power from lab Powersupply.
The result so far is very good I think ! PDF attached.
I use the Mj15003, but perhaps also test with 2N3055 as I have lots of them.
Also interested if someone has used other BJT !
/Christer
I have now done my first measurements on the JLH2005 class A amplifer.
Only the first channel, so far and with Power from lab Powersupply.
The result so far is very good I think ! PDF attached.
I use the Mj15003, but perhaps also test with 2N3055 as I have lots of them.
Also interested if someone has used other BJT !
/Christer
I used mj 15003 mj15024 mj21194 2n3055 2n6459 BD130 on all the generations of jlh, mj gives me better results has the listening.
the 2N are listening no bad,just "grey" and little flat
the BD are too slow and very flat
the MJ are bright ,punchy and very smooth on bass,An iron fist in a velvet glove
the 2N are listening no bad,just "grey" and little flat
the BD are too slow and very flat
the MJ are bright ,punchy and very smooth on bass,An iron fist in a velvet glove
Yes, My Email is jane@siliconray.com
Could you please tell me your Email address? I would like to send detail picture and product informtion to you.
Could you please tell me your Email address? I would like to send detail picture and product informtion to you.
Hi Jane,
I sent you an e-mail at jane@siliconray.com, did you receive it ?
I'm looking for the price for a set of JLH headphone PCB + shipping.
Please send me a PM.
BR,
Eric
I sent you an e-mail at jane@siliconray.com, did you receive it ?
I'm looking for the price for a set of JLH headphone PCB + shipping.
Please send me a PM.
BR,
Eric
Anybody have problems with fuses blowing whilst 'running in/adjusting?
I have 2 fuses between the transformer prior to the PSUs, both rated at 4 Amps - Type T.
Fuse holders are rated to 20A.
Transformer is 15-0-15 at 160W giving around ±17V on the PSU outlet.
Each channel has it's own PSU with 2 banks of 2 by 10,000 uF caps rated at 50V
Quiescent current is set at 1.8Amps [600mV across R10 (0.33 ohm)]
The heatsinks on the output run up to around 45°C (ambient circa 17°C). After a few minutes both fuses blow (circa 30 minutes after switch on).
Any ideas?
Secondly, the BD 140's (Q8) run at around 65°C even with small LED heatsinks on them (space limitation of the PCB).
Not sure if the original design suggested Q8 (and Q3) should be mounted on the same heatsink as the power transistors rather than on the PCB? Perhaps this could be the problem?
Right now I'm running each channel separately to see what happens.
Your thoughts would be appreciated.
I have 2 fuses between the transformer prior to the PSUs, both rated at 4 Amps - Type T.
Fuse holders are rated to 20A.
Transformer is 15-0-15 at 160W giving around ±17V on the PSU outlet.
Each channel has it's own PSU with 2 banks of 2 by 10,000 uF caps rated at 50V
Quiescent current is set at 1.8Amps [600mV across R10 (0.33 ohm)]
The heatsinks on the output run up to around 45°C (ambient circa 17°C). After a few minutes both fuses blow (circa 30 minutes after switch on).
Any ideas?
Secondly, the BD 140's (Q8) run at around 65°C even with small LED heatsinks on them (space limitation of the PCB).
Not sure if the original design suggested Q8 (and Q3) should be mounted on the same heatsink as the power transistors rather than on the PCB? Perhaps this could be the problem?
Right now I'm running each channel separately to see what happens.
Your thoughts would be appreciated.
Secondary fuses before the capacitors are almost worthless.
They have to be rated to survive charging the capacitors from zero and become so big to meet that duty, that they will rarely ever blow during overloads.
A close rated primary fuse, which will require a soft start, will blow when an overload occurs.
They have to be rated to survive charging the capacitors from zero and become so big to meet that duty, that they will rarely ever blow during overloads.
A close rated primary fuse, which will require a soft start, will blow when an overload occurs.
Thanks for your reply Andrew.
I actually have a 2 amp in the power inlet drawer (which doesn't blow).
There's also a soft start C/B installed (should have mentioned that) prior to the in-line fuses which, together with the '30 minutes to blow', lead me away from any switch on type of phenomenon.
The last 2 fuses that went seemed more to have 'melted' than blown (the fuse wire had sagged rather than ruptured).
Have now run the amp one channel at a time and the fuses didn't blow so using 4 amp might be problematic.
Take your point on the usefulness of secondary fuses. Just some literature recommends using them.
Do you recommend I leave them there and uprate to maybe 5 Amp or take them out?
I actually have a 2 amp in the power inlet drawer (which doesn't blow).
There's also a soft start C/B installed (should have mentioned that) prior to the in-line fuses which, together with the '30 minutes to blow', lead me away from any switch on type of phenomenon.
The last 2 fuses that went seemed more to have 'melted' than blown (the fuse wire had sagged rather than ruptured).
Have now run the amp one channel at a time and the fuses didn't blow so using 4 amp might be problematic.
Take your point on the usefulness of secondary fuses. Just some literature recommends using them.
Do you recommend I leave them there and uprate to maybe 5 Amp or take them out?
Check what your amplifier does if it loses one supply rail and check if it is different when it loses the other supply rail.
If your speakers are safe when the amplifier loses one supply rail, then consider using supply rail fuses AFTER the main smoothing bank.
If your bias is 1.8A and your front end draws 0.04A then the total draw for two channels is 3.68A
That is getting close to 4A, but a fuse should still pass for ever. Unless it has been fatigued due to starting surges.
It would be better to use F2.5A for each amplifier. Then if one amplifier gets abused there is more chance the fuse will rupture.
If your speakers are safe when the amplifier loses one supply rail, then consider using supply rail fuses AFTER the main smoothing bank.
If your bias is 1.8A and your front end draws 0.04A then the total draw for two channels is 3.68A
That is getting close to 4A, but a fuse should still pass for ever. Unless it has been fatigued due to starting surges.
It would be better to use F2.5A for each amplifier. Then if one amplifier gets abused there is more chance the fuse will rupture.