Oh boy - responses like that are why I spend less and less time on forums. I bought it because it uses a single rail supply, of which I already possess several so I don't need to mess around with a bulky enclosure and transformer and dc servo mods, etc. Unless I'm mistaken the large coupling cap is a prerequisite for the single supply design, as mentioned by the OP, ashok, in the early pages of this thread (the performance of which he mentioned as close to the dual supply you are talking about). As for the instructions, I've figured them out for myself, so I don't have anything further to say about this.
Fair enough. Actually, I didn't pay any attention to the single rail supply of that kit or the size of the board since so many other HA designs typically use dual rail supplies.
If responses like mine easily offend you, then perhaps you should spend less and less time on forums.
I was only curious why you had purchased that particular kit instead of one of the more popular ZERO ZONE kits.
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Just to follow up for posterity: I've replaced almost every cap on this board with good results. But the best mod was replacing the transistors with equivalent from Digikey. Maybe the ones it comes with are fake? At any rate, this amp now sounds really terrific. Even better after using a an LM317 to low noise LT3045 for 15v power supply.
A really nice, compact, cheaper option that allows greater flexibility with power supply with a couple simple mods. And based on what I can tell from the JLH single-ended schematic, this amp is very similar.
Glad to hear that you're pleased with the final results after replacing all the caps as well as all the transistors with transistors from DigiKey.
I've never found a LM317 to surpass the performance of a LT3045. Perhaps the off-the-wall single supply JLH circuit that you're using is some type of exception.
I've thrown all my LM317/337 supplies in the trash where they belong since they simply aren't up to the task of removing noise in higher gain applications, plus there are MUCHO better regulators out there.
I've never found a LM317 to surpass the performance of a LT3045. Perhaps the off-the-wall single supply JLH circuit that you're using is some type of exception.
I've thrown all my LM317/337 supplies in the trash where they belong since they simply aren't up to the task of removing noise in higher gain applications, plus there are MUCHO better regulators out there.
Interesting. Would you care to mention a better replacement for an LM317? Thanks.
I said I am using the LM317 TO the LT3045, not replacing. LM317--->LT3045--->headamp.
You've tossed your Salas headamp in the trash, LM317 in the trash. Forgot what else you've said you've tossed in the trash. Shame. Would be better off putting them up for sale to maybe benefit someone else...
LT3045 is THE replacement for LM317. LM317 can be of good use as prereg but I would not use it as main regulator anymore. It still is used by many as it is the ECC83 of regulators. People simply often have the habit to use what they know, not what is best. Then they try to improve performance with tricks.
LT3045 does not need tricks. A truly excellent regulator. I just wish a 1.5A version and a negative version would be made.
Cheap way of trying it out can be with this PCB that uses its brother LT3042. It can deliver 1.5A but it is not short-circuit proof.
Low Noise LT3042 Linear Regulator Power Supply Module For Amanero XMOS DAC Power | eBay
LT3045 does not need tricks. A truly excellent regulator. I just wish a 1.5A version and a negative version would be made.
Cheap way of trying it out can be with this PCB that uses its brother LT3042. It can deliver 1.5A but it is not short-circuit proof.
Low Noise LT3042 Linear Regulator Power Supply Module For Amanero XMOS DAC Power | eBay
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Yes, I love the LTs. The 317 was what I had laying around. Noise floor dropped like a stone once I added the LT.
Building this one... Almost finished... But can someone give me some instructions on the trimpots?
Where you measure?
Also it says 12V AC.. Think 15V also would be possible?
The trimpots theoretically control the DC offset at the outputs.
In the real word offset varies widely depending on the temperature of the output devices.
Having assembled 4 of these JLH HA kits, IMO a servo is the only to really control the offset of these amps.
You could use 15V, but the regulators will get even warmer than they do using 12V.
Even with 12V the regulators' heatsinks get pretty hot.
In the real word offset varies widely depending on the temperature of the output devices.
Having assembled 4 of these JLH HA kits, IMO a servo is the only to really control the offset of these amps.
You could use 15V, but the regulators will get even warmer than they do using 12V.
Even with 12V the regulators' heatsinks get pretty hot.
If measuring DC-offset, you'll simply connect a DVM across the left and right outputs and set your meter to the 200mV scale.
Very simple to measure, but you'll find trying to adjust the trimmers to get the lowest reading will be a tedious and to no avail process since the offset will always be fluctuating by a wide margin because of the design.
My JLH amps would have anywhere from a headphone frying 2V! DC-offset when cold to 40-50 mV when trying to use the supplied trimmers and no servo.
It was kinda like a dog chasing his tail when trying to adjust the supplied trimmer. Just when you think you have the trimmers set where it's the lowest, it goes up considerably when you first apply power to the amp.
That's why I designed a small DC servo PCB that keeps the offset within a few millivolts.
Be careful! You can easily fry a nice pair of headphones without a servo to control the DC at the outputs.
Good luck with your build.
Very simple to measure, but you'll find trying to adjust the trimmers to get the lowest reading will be a tedious and to no avail process since the offset will always be fluctuating by a wide margin because of the design.
My JLH amps would have anywhere from a headphone frying 2V! DC-offset when cold to 40-50 mV when trying to use the supplied trimmers and no servo.
It was kinda like a dog chasing his tail when trying to adjust the supplied trimmer. Just when you think you have the trimmers set where it's the lowest, it goes up considerably when you first apply power to the amp.
That's why I designed a small DC servo PCB that keeps the offset within a few millivolts.
Be careful! You can easily fry a nice pair of headphones without a servo to control the DC at the outputs.
Good luck with your build.
Hahaha that last comment is very reassuring...If measuring DC-offset, you'll simply connect a DVM across the left and right outputs and set your meter to the 200mV scale.
Very simple to measure, but you'll find trying to adjust the trimmers to get the lowest reading will be a tedious and to no avail process since the offset will always be fluctuating by a wide margin because of the design.
My JLH amps would have anywhere from a headphone frying 2V! DC-offset when cold to 40-50 mV when trying to use the supplied trimmers and no servo.
It was kinda like a dog chasing his tail when trying to adjust the supplied trimmer. Just when you think you have the trimmers set where it's the lowest, it goes up considerably when you first apply power to the amp.
That's why I designed a small DC servo PCB that keeps the offset within a few millivolts.
Be careful! You can easily fry a nice pair of headphones without a servo to control the DC at the outputs.
Good luck with your build.
I bought this one to drive my Audeze Sine Planars.
I will finish the build this evening and investigate how to implement a DC Servo.
Pretty new to all this. So thanks for your help.
I agree that would be a low-cost solution, but in my opinion the best output coupling cap is no cap at all.
Others here can disagree with that statement all they want, but I prefer DC-coupled designs when possible.
A simple servo takes care of the JLH's excessive offset without one having to resort to the old adage "which brand and type of coupling cap sounds best".
If someone is looking for a simple servo PCB for the JLH HA, shoot me a PM. I'm pretty sure that I still have a few left.
DC Offset
Using the resistor changes proposed by Miles Campbell way back in this thread and leaving the trimmers in place, my JLH 1969 has a DC offset at switch on of about 70mV. That drops to c. 30mV in less than a minute and is down to zero plus/minus a couple of millivolts in a couple of minutes.
A servo would solve this problem, but I just wait a few minutes before plugging in the headphones using the amp !
I don't know if a dummy load plug in the headphone socket would get the offset down faster.
Using the resistor changes proposed by Miles Campbell way back in this thread and leaving the trimmers in place, my JLH 1969 has a DC offset at switch on of about 70mV. That drops to c. 30mV in less than a minute and is down to zero plus/minus a couple of millivolts in a couple of minutes.
A servo would solve this problem, but I just wait a few minutes before plugging in the headphones using the amp !
I don't know if a dummy load plug in the headphone socket would get the offset down faster.