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Old 7th October 2009, 11:14 AM   #331
peranders is offline peranders  Sweden
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Quote:
Originally Posted by AKSA View Post
John,

I agree...... the diodes sure are simple, but the heatsink mounting is a PITA.

Hugh
Use a transistor which you can clue to the output transistors.
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Old 7th October 2009, 02:55 PM   #332
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by AKSA View Post
John,

I agree...... the diodes sure are simple, but the heatsink mounting is a PITA.

Hugh
I don't have a qualified opinion on diode vs. multiplier. But solving the mounting issue is trivial, in my opinion. It's a completely different matter than mounting a component that generates significant heat. In that case, heat transfer rates are important. Intimate contact with the heatsink or other part is essential.

In the case of mounting diodes, which are really just measuring devices here, the heat transfer rate in much less important. The sink won't heat instantly, and the diode thermal mass is low. All that has to be done is to have the diode next to the source it's measuring. Then just put a little insulation over the diode(s) to trap the air and heat radiating from the sink/output transistor and you're done.



Sheldon

Last edited by Sheldon; 7th October 2009 at 03:18 PM. Reason: more precise statement
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Old 7th October 2009, 04:10 PM   #333
Bigun is offline Bigun  Canada
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I wonder what the impedance of these things are ?
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Old 7th October 2009, 05:47 PM   #334
Nico Ras is offline Nico Ras  South Africa
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Hi guys
I support the LM317 configuration Hugh offered us to look at. It remains simple and almost everyone has had some experience with LM317. It is an overall a predictably good performer. Adding Hugh's common mode rejection chokes follows his ideas in keeping it with the AKSA "sound".

Since Hugh cannot accommodate all, I propose that I design the power supply as a snap-off section so those with other ideas can replace the standard version by simply snapping off the on-board PSU section.

At this point I am not sure Hugh should accommodate the old geysers needing HF boost but maybe Hugh would not mind offering a simple add on bass/treble control that can be placed in front of the amp as a separate item. Maybe this board could contain the cross-feed control and this become an add on for those who feel they need it.

The base design thus remains a simple no frills headphone amp as intended.

Kind regards

Nico
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Old 7th October 2009, 05:52 PM   #335
Nico Ras is offline Nico Ras  South Africa
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Quote:
Originally Posted by AKSA View Post
John,

I once did a comparison between the Vbe multiplier and the diode string.

Hugh
Hi Hugh,

here I can vouich for this, the diode bias string does sound "better" to me, almost all my designs bar a few earlier Vbe/BJT output one uses a diode string since I noticed the difference.
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Old 7th October 2009, 05:57 PM   #336
Nico Ras is offline Nico Ras  South Africa
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Quote:
Originally Posted by Bigun View Post
Diode's have to be soldered together in a string, their bare leads insulated (not so easy if you have to solder them first) and then all of them glued to the heat sink.
Hi Gareth,

In this design with its low power, the diode string is not needed to be on the heat sink, monitoring ambient is more than sufficient. So no need to do what you suggest. There will be no thermal runaway, I can assure you.

Nico
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Old 7th October 2009, 06:50 PM   #337
T in AZ is offline T in AZ  United States
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Quote:
Originally Posted by Nico Ras View Post
Hi guys
I support the LM317 configuration Hugh offered us to look at. It remains simple and almost everyone has had some experience with LM317. It is an overall a predictably good performer. Adding Hugh's common mode rejection chokes follows his ideas in keeping it with the AKSA "sound".

Since Hugh cannot accommodate all, I propose that I design the power supply as a snap-off section so those with other ideas can replace the standard version by simply snapping off the on-board PSU section.

At this point I am not sure Hugh should accommodate the old geysers needing HF boost but maybe Hugh would not mind offering a simple add on bass/treble control that can be placed in front of the amp as a separate item. Maybe this board could contain the cross-feed control and this become an add on for those who feel they need it.

The base design thus remains a simple no frills headphone amp as intended.

Kind regards

Nico
Here is my sim for the PS, Simple and low ripple, Check and see if I made any mistakes or forgot anything? The diodes on the regs aren’t supposedly necessary but I would rather be safe. Just change.txt to .asc
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File Type: txt PwrSup24.txt (4.0 KB, 18 views)
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Old 7th October 2009, 07:39 PM   #338
gaetan8888 is offline gaetan8888  Canada
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Quote:
Originally Posted by Nico Ras View Post
Hi guys

At this point I am not sure Hugh should accommodate the old geysers needing HF boost but maybe Hugh would not mind offering a simple add on bass/treble control that can be placed in front of the amp as a separate item. Maybe this board could contain the cross-feed control and this become an add on for those who feel they need it.

Kind regards

Nico
Hello Nico

As an old geysers, I've try few type of bass/treble control, passive type was not good, the treble booster I've post in another thread was good but I've redone a sim with this last bass/treble control circuit using an op-amp.

There is many op-amps who can be use, OPA627, OPA827, THS4031, LM4562, and OPA637 but you would need to boost the circuit gain to more than 5 for this last op-amp

My Tina simulator are easy to use but limited, so maby Hugh, nico, bigun or KT could come out with a better circuit.

So here is the schematic.

Bye

Gaetan
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File Type: gif op-amp-BASS TREBLE TONE CONTROL.gif (25.8 KB, 161 views)

Last edited by gaetan8888; 7th October 2009 at 07:56 PM.
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Old 7th October 2009, 08:19 PM   #339
Nico Ras is offline Nico Ras  South Africa
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Gareth this is your call,

If you agree and other geysers are interested, I am willing to make an add-on board for the headphone amp with this tone control and a simple cross feed.

Nico
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Old 7th October 2009, 08:32 PM   #340
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by gaetan8888 View Post
As an old geysers,
I think the word you want is geezers. Geysers spout water or steam. Geezers spout off.

As an old geezer with declining hearing, I actually set my stuff up fairly flat, or even rolled off a bit over 10k. True, I don't hear much up there, but then I don't hear much up there when I listen to live music. So a flat setting sounds most realistic to me - which is what I think Hugh was referring to when he said we compensate. Some day, I'll have to compensate with a hearing aid. At that point, headphones with boosted HF would allow listening w/o the aid to replicate everyday hearing.

I'm not arguing for or against tone controls here.

Sheldon
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