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Old 19th June 2017, 04:08 AM   #371
ammel68 is offline ammel68  United States
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Thank you for posting the circuit, Tony. That really clarifies things.

By the way, what's the purpose of the BC560s connected to the Adj. pins?
Why this configuration for adjusting the voltage vs. say a 2k trimmer with a 20uF cap in parallel?
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Old 19th June 2017, 04:13 AM   #372
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The original source of the bc560 idea is here Improving the LM3x7 regulator circuit

I originally had a 4.7uF on the adjust to ground (and is what I implemented in the real circuit), but recent sims seem to indicate increasing to 15uF has some benefit, past that there are diminishing returns. Note that there have been many other proposed "better" lm317 circuits. This was just what I decided to implement.

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Last edited by wintermute; 19th June 2017 at 04:16 AM. Reason: add comment on adj cap
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Old 19th June 2017, 05:36 AM   #373
ammel68 is offline ammel68  United States
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Quote:
Originally Posted by ammel68 View Post
What is the regulator bake-off?
Never mind. I didn't realize "jackinnj" and "John Walton" are one and the same:
https://linearaudio.net/authors/353

I've already purchased and read John's Linear Audio regulator "bake-off" article where the Jung/Didden regulator came out on top.

I'm in the process of assembling my Jung/Didden boards from the DIY Store to see how they sound compared to my '317/337 boards I'm currently using for op-amp circuits.
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Old 19th June 2017, 10:40 AM   #374
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Mark, I don't know if it is important or not I tend to subscribe to the, "if it might make a difference, and isn't difficult/expensive to do then why not have a go camp".

I used LT317A's as supposedly they are a premium version with tighter tolerances... you pay for it though! They are more than 4 times the price of the cheapest LM317's but still at around $4.50 it isn't that expensive.

This thread has piqued my interest again, and I might actually make a proper pcb for my circuit rather than the verro board prototype I'm still using at the moment.

I wish I had the measurement gear to do lots of tests but unfortunately I only have rudimentary equipment.

Tony.
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Old 19th June 2017, 12:07 PM   #375
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Instead of the LM317 or LT317A, why not just go with LM337 for both neg and pos, and JBau's circuit aiming at low and flat impedance and phase?
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Old 19th June 2017, 01:12 PM   #376
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Certainly an option (or one of the newer LT series chips) (although I'm pretty sure the early thoughts around the LM337 superiority turned out to be measurement error, something to do with a 10000uF cap that was being swapped from one circuit to the other and not discharging properly from memory, but I can't find the post...) .

I found with the bc560 in play (in the sims) the impedance flattening that jbau used doesn't seem to have much effect, so an other wise bog standard LM337 circuit doubled up should do the trick, but as I said I'm not sure that the 337 was any better than the 317 other than it matched well in jbaus measurements with the LT1085.

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Last edited by wintermute; 19th June 2017 at 01:27 PM. Reason: add comment on measurement error.
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Old 19th June 2017, 02:17 PM   #377
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Originally Posted by wintermute View Post
I found with the bc560 in play (in the sims) the impedance flattening that jbau used doesn't seem to have much effect, so an other wise bog standard LM337 circuit doubled up should do the trick, but as I said I'm not sure that the 337 was any better than the 317 other than it matched well in jbaus measurements with the LT1085.
That's interesting, can you unpack that slightly? You mentioned that your measurement gear is 'rudimentary'. So does that mean you listened to a JBau-based PSU and found that it sounded no better than the Dieckman rec'd bc560 circuit, or what are you referring to?
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Old 19th June 2017, 04:16 PM   #378
ammel68 is offline ammel68  United States
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Originally Posted by wintermute View Post
This thread has piqued my interest again, and I might actually make a proper pcb for my circuit rather than the verro board prototype I'm still using at the moment.
If you do decide to make a board, I hope you can post it here for myself and others to view.
There are some people here that are very good at board layout and may offer some constructive criticism.

If I'm not mistaken, you're one of the people that helped me with my '317/'337 layout a while back.
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Old 19th June 2017, 09:20 PM   #379
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brucew268, no I haven't built jbau's version. I have just simmed some of the mods he did (both on the standard reg configuration and on the dieckman version. On the dieckman version the adjust pin mods have very little effect on the output impedance, I also wasn't able to get much effect using the LR on the output either, though that may require more experimentation.

What I have built is an earlier version of the circuit I posted above. Main differences were I had 3.3 ohm resistors in both the supply and return lines, recent sims show that the resistance in the return lines makes the lower half very sensitive to small resistance in the output, with output inpedance increasing significantly below 100Hz. So as was questioned at the time it wasn't such a good idea!

The other difference is I dropped the output caps from 1000uF (with a 470nf parallel) to 330uF. With the 1000uF the sim was not stable unless I added the 470nf in parallel. That should have told me something The sim is stable with the 330uF and the output impedance is almost identical to with a 1000uF.

One other interesting thing of note. The impedance peaks that jbau talks about with the LM317, do not occur with the dieckman circuit provided there is some series resistance in series with the output cap (again in simulation as I can't measure the output impedance in the real circuit).

edit: it seems from jbau's comments that the mods in his experience, have an effect on the imaging (ie soundstage). So regardless of measurement equipment available the final test will be a subjective one.

Tony.
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Last edited by wintermute; 19th June 2017 at 09:23 PM. Reason: add comment on imaging.
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Old 19th June 2017, 09:34 PM   #380
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Originally Posted by wintermute View Post
brucew268, no I haven't built jbau's version. I have just simmed some of the mods he did (both on the standard reg configuration and on the dieckman version. On the dieckman version the adjust pin mods have very little effect on the output impedance, I also wasn't able to get much effect using the LR on the output either, though that may require more experimentation.

What I have built is an earlier version of the circuit I posted above. Main differences were I had 3.3 ohm resistors in both the supply and return lines, recent sims show that the resistance in the return lines makes the lower half very sensitive to small resistance in the output, with output inpedance increasing significantly below 100Hz. So as was questioned at the time it wasn't such a good idea!

The other difference is I dropped the output caps from 1000uF (with a 470nf parallel) to 330uF. With the 1000uF the sim was not stable unless I added the 470nf in parallel. That should have told me something The sim is stable with the 330uF and the output impedance is almost identical to with a 1000uF.

One other interesting thing of note. The impedance peaks that jbau talks about with the LM317, do not occur with the dieckman circuit provided there is some series resistance in series with the output cap (again in simulation as I can't measure the output impedance in the real circuit).

edit: it seems from jbau's comments that the mods in his experience, have an effect on the imaging (ie soundstage). So regardless of measurement equipment available the final test will be a subjective one.

Tony.
Very helpful, thanks!
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