If there are any Czechs following this thread, I’d ask them about the KD503 (Tesla) devices. Are these any good for the latest versions of the JLH amp in comparison to the MJ15003? I have some of them around but I don’t have any specs.
I have a 1969 version of the amp with Toshiba 2SC3280 devices. These work fine in the old version but maybe 35 mHz transistors will not go well together with the last version.
Thanks
I have a 1969 version of the amp with Toshiba 2SC3280 devices. These work fine in the old version but maybe 35 mHz transistors will not go well together with the last version.
Thanks
Re: 28,5V
May I humbly share this experience with the JLHs that I have built? There is no change with the rest of my system except the amps.
There is a track on one of my favorite CD that the intro was sounding like some sha/hiss noise in the background with the JLH 1996 using 22V Iq at 2A supply.
But with the JLH for ESL using 20V at 4A the intro was discovered and can be heard that it was actually a live recording of a distant sandy beach with gentle waves.
That recording (the intro) I always use now to evaluate how a system sound and perform. I am surprised that a low level sound of a sea wave is so difficult to reproduce in a sound system. I guess the sea wave sound for it to sound real must need to have a substantial low frequency power.
Just my 2 cents
Chris
ralf said:
May I humbly share this experience with the JLHs that I have built? There is no change with the rest of my system except the amps.
There is a track on one of my favorite CD that the intro was sounding like some sha/hiss noise in the background with the JLH 1996 using 22V Iq at 2A supply.
But with the JLH for ESL using 20V at 4A the intro was discovered and can be heard that it was actually a live recording of a distant sandy beach with gentle waves.
That recording (the intro) I always use now to evaluate how a system sound and perform. I am surprised that a low level sound of a sea wave is so difficult to reproduce in a sound system. I guess the sea wave sound for it to sound real must need to have a substantial low frequency power.
Just my 2 cents
Chris
Just completed the 1969 version of JLH 10W.
Fitted it with a 5k linear volume control and found that there is an increase in tisss noise when it is at minimum position. When at max position, the tisss noise disappears. Marantz CD63II with output impedance of 200 ohms is use as source.
Should I use a higher value volume control pot (100kohm)?
or
Should I built another pre-amp with a higher input impedance to act as a buffer to the volume control?
Thank you.
Fitted it with a 5k linear volume control and found that there is an increase in tisss noise when it is at minimum position. When at max position, the tisss noise disappears. Marantz CD63II with output impedance of 200 ohms is use as source.
Should I use a higher value volume control pot (100kohm)?
or
Should I built another pre-amp with a higher input impedance to act as a buffer to the volume control?
Thank you.
Why 28,5 V @ 2.8 Amps?
Let me lead you through my thoughts.
Currently I run a 1996 JLH 22V @1,8 Amps Iq.
Sound wise I have no ability to describe "flaws" like Tim A.
My 1996 JLH however provided me a significant better low than did the Denon set.
As I'm planning in a future to build myself speakers to upgrade from my current JM Lab's I decided to build an JLH version which
1: could be more "tuned" to speaker loads. (The 1996 version is set to run for 8Ohm)
2: could produce some more output as sensitivity of future speakers might easily be lower than the 92dB/W produced by the JMLab's.
The 2003 ESL version can be tuned this way. As my psu is fully regulated and adjustable in a wide region (from 17V upwards) and is able to supply continuous over 7Amps, the amp can be run even at 5A bias (although a low rail-voltage should be used (<18V).
As it in the mean time will replace the 1996 version I just decided to start with a higher railvoltage and a higher Iq. (roughly 50% plus)
Bottom line; I just picked two values which looked fine. Nothing more than that
However, as I have to take into respect the overall power produced (cabinet restriction, as two of them will heat up a same cabinet) I've lowered Iq to 2.1 A in the finalized version and start comparing it with the 1996 version within a week or two.
This is one completed amp:
The other one is still "under construction"
Let me lead you through my thoughts.
Currently I run a 1996 JLH 22V @1,8 Amps Iq.
Sound wise I have no ability to describe "flaws" like Tim A.
My 1996 JLH however provided me a significant better low than did the Denon set.
As I'm planning in a future to build myself speakers to upgrade from my current JM Lab's I decided to build an JLH version which
1: could be more "tuned" to speaker loads. (The 1996 version is set to run for 8Ohm)
2: could produce some more output as sensitivity of future speakers might easily be lower than the 92dB/W produced by the JMLab's.
The 2003 ESL version can be tuned this way. As my psu is fully regulated and adjustable in a wide region (from 17V upwards) and is able to supply continuous over 7Amps, the amp can be run even at 5A bias (although a low rail-voltage should be used (<18V).
As it in the mean time will replace the 1996 version I just decided to start with a higher railvoltage and a higher Iq. (roughly 50% plus)
Bottom line; I just picked two values which looked fine. Nothing more than that
However, as I have to take into respect the overall power produced (cabinet restriction, as two of them will heat up a same cabinet) I've lowered Iq to 2.1 A in the finalized version and start comparing it with the 1996 version within a week or two.
This is one completed amp:
An externally hosted image should be here but it was not working when we last tested it.
The other one is still "under construction"
quote:
Originally posted by Cheong
Just completed the 1969 version of JLH 10W.
Fitted it with a 5k linear volume control and found that there is an increase in tisss noise when it is at minimum position. When at max position, the tisss noise disappears.
quote:
Originally posted by Mike
this sounds to me as if the cct is just begining to oscillate at very low i/p impedance - ie pot turned to zero volume.
you could try a 100/200ohm resistor between the wiper of the pot and the i/p
Thank you Mike, it works!
Our first impression is that the JLH amp gives lots of detail and much better control on the Bass notes compared with a 2A3 push-pull tube amp. But subjectively, the tube amp vocals are better.
Originally posted by Cheong
Just completed the 1969 version of JLH 10W.
Fitted it with a 5k linear volume control and found that there is an increase in tisss noise when it is at minimum position. When at max position, the tisss noise disappears.
quote:
Originally posted by Mike
this sounds to me as if the cct is just begining to oscillate at very low i/p impedance - ie pot turned to zero volume.
you could try a 100/200ohm resistor between the wiper of the pot and the i/p
Thank you Mike, it works!
Our first impression is that the JLH amp gives lots of detail and much better control on the Bass notes compared with a 2A3 push-pull tube amp. But subjectively, the tube amp vocals are better.
Cheong said:
great
re the subjective sound - I don't know what kind of power supply you have but any measures that you can take to reduce noise should improve things.
e.g. cap / choke / cap regulation
schottky or other low noise diodes
also a very simple mod would be to put a 4.7uF film cap directly across each secondary of the transformer.
each of these mods should improve the subjective sound, together they could could make a big difference
good luck
Originally posted by Mike:
re the subjective sound - I don't know what kind of power supply you have but any measures that you can take to reduce noise should improve things.
e.g. cap / choke / cap regulation
schottky or other low noise diodes
also a very simple mod would be to put a 4.7uF film cap directly across each secondary of the transformer.
each of these mods should improve the subjective sound, together they could could make a big difference
Currently using a C-R-C supply (10000uF-0.5ohm-10000uF).
For C-L-C, was thinking of trying a 0.33mH air core.
Will report findings after trying your recommendations.
Thanks!
re the subjective sound - I don't know what kind of power supply you have but any measures that you can take to reduce noise should improve things.
e.g. cap / choke / cap regulation
schottky or other low noise diodes
also a very simple mod would be to put a 4.7uF film cap directly across each secondary of the transformer.
each of these mods should improve the subjective sound, together they could could make a big difference
Currently using a C-R-C supply (10000uF-0.5ohm-10000uF).
For C-L-C, was thinking of trying a 0.33mH air core.
Will report findings after trying your recommendations.
Thanks!
Cheong said:
When using chokes it's good to be carefull at turn on
If the chokes have a very low resistance there can be potentially damaging overshoot and ringing.
it's good to simulate if you can to get an idea of what will happen
otherwise if you make the first cap after the bridge half the size of the one following the choke ( eg 10,000uF & 22,000uF ) this should help to avoid this problem.
well worth the effort though
cheers
mike
JLH Cl A
Nice work X.G ! Neat layout. Most of my projects start off neat but after changing components, messing about with the circuit etc it becomes a mess. In Audio Amateur years ago, Nelson Pass had a photo of a project ( 40 watt Cl A ?) in the prototype stage, being a heap of components in space soldered together ! Maybe he could post it if he still has it. Maybe someone in touch could raise this with him.
Cheers T
Nice work X.G ! Neat layout. Most of my projects start off neat but after changing components, messing about with the circuit etc it becomes a mess. In Audio Amateur years ago, Nelson Pass had a photo of a project ( 40 watt Cl A ?) in the prototype stage, being a heap of components in space soldered together ! Maybe he could post it if he still has it. Maybe someone in touch could raise this with him.
Cheers T