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Old 29th September 2012, 04:05 PM   #551
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Component changes? it's a good question, and the answers are not entirely able to be explained, but I can offer some thoughts about real physical effects that may be helpful:

1. Magnetic materials. Many resistors, including the normal wirewound (R1, R2) and carbon film (all the others in the standard kit) have steel in the end-caps or the leads. If the regulator is near any transformers in an amplifier, some heightened magnetic coupling is possible. If you have a very transparent system, and there are possibly some stray fields near the regulators (a densely packed design like the TRAM is a good example), then the chances are that using nonmagnetic wirewounds will improve the sound.

2. current noise. The sense resistors R1 R2 carry the filament current. But the filament current flows in the same conductor (the filament substrate) as the music signal, no noise in the filament current will directly impose on the music. The current-noise of resistors is well-known to vary between resistors of different constructions - see for example:

https://dcc.ligo.org/public/0002/T09...rent_noise.pdf

The crucial fact is that we are getting 1.25A-worth of current noise (300B filament) imposed on the few-mA of music signal current - so a small change might well be heard.

I think that most folk like the low DIY price of my regulators, so I prefer to ship them with types that sound good, if not the ultimate. Changes to resistors are system-dependent and very much a question of taste - so please experiment and try other parts - providing R1 and R2 have the same level of power handling.

The obvious choice for the small resistors would be Tantalum film - a nice nonmagnetic design favoured by Kondo-san, among others. I have not checked availability of these yet. It would be a very-high-resolution system that could pick out differences of that kind - the small resistors[ R3 .. R11 ] do not have a strong influence on the output current.

Summary: Try non-magnetic wirewounds at R1 as the most likely tweek. Then go after the capacitor. Try the Amtrans that Morten likes.
Tantalum for the other resistors is strictly for the adventurous...

.
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Old 29th September 2012, 04:59 PM   #552
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"But the filament current flows in the same conductor (the filament substrate) as the music signal, no noise in the filament current will directly impose on the music."

Rod - I think you are saying "so noise in the filament current" here, so the "no" is a typo?
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Old 29th September 2012, 05:01 PM   #553
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Andy yes!

I should have typed:

"But the filament current flows in the same conductor (the filament substrate) as the music signal, SO, noise in the filament current will directly impose on the music."
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Old 10th October 2012, 05:31 AM   #554
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Rod - how does one get a pair of your DHT heater boards? Mr. Larry D. Moore Esq. highly recommended them for his UltraFi 300b - I am eager to try.

Thanks!
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Old 10th October 2012, 07:18 AM   #555
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I'm pleased to hear that Larry enjoyed the 300B regulators!

The Regulators are available as a DIY (self-assembly) kit, on request (please click my name to send email). The kits are resistor configured to suit the type of DHT.
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Old 10th October 2012, 10:37 AM   #556
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Hi Rod

I thought I'd post this here instead of emailing as it might benefit some readers. I've got a couple of queries on the boards I'm using with sv572/sv811. I changed my original RS 2x9v 100va frame to a toroid as it was buzzing loudly. I changed to an airlink toroid 2x9v 120va. This allows best part of 9v@7A for each regulator.

It gets very hot, 60+celcius(by my rough dmm thermometer). As the transformer for sv572 was not mentioned in the app. notes I was kind of working in the dark, but correspondence with Rod enlightened somewhat. It seems I need 3 times the end current at the transformer to start with. In my case thats 12amps, for a 4 amp sv572. I hope I'm understanding this correctly. I'm currently looking at a 2x9v frame 200va.

Notwithstanding the transformer issue the results are superb as I've lost most of the noise from the amp. But.... the barrier diodes, MBR1045, are getting really toasty, 105celcius(by the same dmm as mentioned before). I don't have any experience with these so I'm wondering if anybody can offer thoughts. I'm not sure if this temp is ok, or whether I need sinks on the diodes or whether I should move to an external sink to get the heat out of the inside of the chassis. At the moment I do fear for the health of the adjacent caps.

Ed
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Old 10th October 2012, 10:55 AM   #557
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MBR1045 schottky diode forward voltage 0.57V (at 10A), at 4A ~0.45V.
0.45V*4A = 1.8W !! on each diode!

I think, need some (medium sized) heatshinks.
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Old 10th October 2012, 11:12 AM   #558
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Hi Ed,

We can look at a PSUD2 session to analyse the current.

The dc current of 4A translates into an rms current of about 8A in the secondary winding - hence the recommendation to use 9V 12A: it is best not to run a trafo at 100% full load for hours of listening time!

Best buy for UK DIYers is the JMS 150VA trafo, configured with 9V secondary, 240V primary:

150 VA

This should run quite cool.

The rms current in each diode is about 5.7A, so heatsinking may well be needed at this high level, or you could try MBR1645 for lower drop. Beware that the TO220 package tabs are not isolated -please use a Mica insulator and grease.

I am pleased that you like the sound!
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Old 10th October 2012, 11:29 AM   #559
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A much better supply can be made with a choke-input arrangement.

The transformer is 12V 6A trafo (eg Hammond 266M24) and a 10mH 5A choke e.g. Hammond 159ZJ.

The rectifier diode current drops below 3A, and the pulse-current drawn from the supply are much lower, meaning less chance of EM-coupling to other wires or trafos.
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Old 11th October 2012, 10:39 AM   #560
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Hi Rod,

I'm considering how to update my TRAM with your regs. I use 2A3s. I could do choke input similar to the above if I use a 2nd chassis attached under the TRAM. heatsinking will then be easy to organise. The trafo and diodes will need to be different. Have you spec'ed anything similar previously?

Cheers,

Clive
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