I'll be using a separate smps for each channel.
This is the schematic I'm using as a starting point: https://www.sound-au.com/tcaas/jlhupdate.htm (but with a cap in series with the feedback resistor R6)
The only DC demands on the virtual 0V are from the input resistor R2 (insignificant) and the current sources R11 and R12. I think a balancing resistor from 0V to -V will be necessary, to compensate for these. Or should I swamp them by putting 330 ohms(ish) across each series PSU cap?
Thank you all for you help. I'll contribute when I have some results to show; right now it's all on paper, soon to be veroboard and wonky metalwork.
R2 connect to the central contact of the balancing resistor between the tires (+ -). Ground through an electrolytic capacitor.
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Only the caps, no resistors. Input and feedback are connected to the center-point (floating ground) of the caps too. There is a small leak current to one side, so if no speaker is connected, there will be some DC-offset. This can be compensated with a large value resistor over one 'half' of the PS caps, but I have not bothered with that. Search 'sublimed JLH' here on the forum. My SMPS are HP laptop bricks, and they retry a couple of times before they have charged the PS caps enough, and then they work as they should.
Your design is amazing. Piece of art. Anyone built them?
I think if I just use a pair of series caps, then the two CC sources will pull the centre tap up via R11 and R12. So I'll either balance them with a resistor between centre tap and -v rail, or double the value of R11 and 12 and take them to -ve rather than gnd.
However, from what you say (quoted above) all works fine without modifying the circuit or adding the balancing resistor?
I'm away from home as we speak, and itching to get back to the veroboard...
Ok, you are building the beefy version? That one is already made for dual supply, so that's easy! I have a pair of them too, but I like the bootstrap version for simplicity and stability. Ok, maybe CCS for the input would be nice..
There will be some current going from positive rail to 'ground' via R11 & R12, so you cold probably have a high value resistor from 'ground' to negative rail to compensate for that. This is to prevent the small DC current going through the speaker. Easy to put in after it's built.
Keep in mind that the SMPS secondaries can't be connected to safety earth, they have to be floating, or you will have trouble..
There will be some current going from positive rail to 'ground' via R11 & R12, so you cold probably have a high value resistor from 'ground' to negative rail to compensate for that. This is to prevent the small DC current going through the speaker. Easy to put in after it's built.
Keep in mind that the SMPS secondaries can't be connected to safety earth, they have to be floating, or you will have trouble..
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Exactly so. Thank you for the reality check.
The safety ground will be where the input jacks join. Each channel will have its own star that's a stub off the junction of the two caps.
The benefit of the input CCS is that by keeping q5 and q4 close together, DC offset won't drift with temperature.
How much power are you burning with your beefy amps? I'm not planning on a huge output, just trying to give the output transistors an easy life by sharing the pain.Using TO3 devices without insulating washers on separate isolated heatsinks for each pair.
The safety ground will be where the input jacks join. Each channel will have its own star that's a stub off the junction of the two caps.
The benefit of the input CCS is that by keeping q5 and q4 close together, DC offset won't drift with temperature.
How much power are you burning with your beefy amps? I'm not planning on a huge output, just trying to give the output transistors an easy life by sharing the pain.Using TO3 devices without insulating washers on separate isolated heatsinks for each pair.
I don't use the one with double outputs, never built it into an enclosure. The 69 PNP is running on 19,5V 1A, very little heat, and very little power.. 🙂
The beauty of JLH 1969 design is no match requirement of the output transistors. Even two different models are used, as long as they have similar spec. The performance shows no inferior.
Did any ever tested the JLH1969 with a BC550C (or BC546 BC547) as the phase splitter transistor?
Any dissipation problem?
Why is the slower BC139-16 preferred?
Dissipation?
Any dissipation problem?
Why is the slower BC139-16 preferred?
Dissipation?
Replying to very old question...look at Nigel's avatar, the answer's right there ;-)
Hello,
I am finishing building my jlh amps (https://sound-au.com/tcaas/jlhupdate.htm) and I will start tests before connecting the speaker.
As both channel are independant (separate power supply), how I can I test and adjust a possible difference of output power?
regards
max
I am finishing building my jlh amps (https://sound-au.com/tcaas/jlhupdate.htm) and I will start tests before connecting the speaker.
As both channel are independant (separate power supply), how I can I test and adjust a possible difference of output power?
regards
max
If the power supplies are the same, and if you adjust quiescent current to be the same, then the maximum output power will be the same. Or is it the gain you're concerned about? If the feedback resistors are the same, happy days. It's not dependent on any components except these two pairs of resistors.
Good luck with the testing, remember not to let the magic smoke out- it's a bugger getting it back in.
Hi, thanks for your reply.
Actually, I have 0.4V differences between both power supply i could not fixed but i am not sure if it as impact.
And for quiescent current I measured the voltage accross the R10 resistor (0.330ohm) but as I could not be 100% sure of its value, the quiescent current could have 0.1 A difference (at maximum)
