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Old 30th July 2012, 04:21 PM   #431
sonidos is offline sonidos  United States
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Jan,

Funds have been sent. Thank you.
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Old 8th August 2012, 06:19 AM   #432
RNMarsh is offline RNMarsh  United States
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how is the build going?
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Old 8th August 2012, 02:12 PM   #433
sonidos is offline sonidos  United States
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Default Warp speed? Nope...

I ordered those 10 cent jfets and they are all dogs. Jan Didden shipped the MJE's asap but they haven't arrived. Taking all the patience I can muster!

I am going over the layout of the board to be sure I haven't missed anything. It's coming together. I have about 90% of the parts now.
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Old 8th August 2012, 03:37 PM   #434
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Quote:
Originally Posted by janneman View Post
Javier, if this is the cap after the reg, you normally don't want it to be super-low ESR. The ESR part is required for loop damping to enhance stability.
Very high quality film caps are a no-no here.

I have a prototype 400VDC reg where I actually had to insert a 1 ohm R in series with the output cap to quiet it down - my electrolytic was simply too good

jan
Yup. One can do a back-of-the-envelope estimate of required ESR by looking at the regulator spec, inferring ESL from the output impedance curves, and setting R = ESL / C. The humble 7815 / 7915 parts come off fairly well by that measure, amusingly enough.
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Old 8th August 2012, 04:58 PM   #435
sonidos is offline sonidos  United States
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Originally Posted by DSP_Geek View Post
Yup. One can do a back-of-the-envelope estimate of required ESR by looking at the regulator spec, inferring ESL from the output impedance curves, and setting R = ESL / C. The humble 7815 / 7915 parts come off fairly well by that measure, amusingly enough.
I learn something every day from this forum!
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Old 8th August 2012, 05:25 PM   #436
sonidos is offline sonidos  United States
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Default general board layout

Here is what I've concocted. Funny, but after putting the rat's nest together, it all started to take shape just like Mr. Marsh's board.
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Old 8th August 2012, 07:09 PM   #437
Unomas is offline Unomas  Spain
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Originally Posted by RNMarsh View Post
how is the build going?
Hi, mine is going on step by step. Right now I'm concentrated on the PSU and later on I'll started the HeadAmp. I'll report on the evolution. As for the HA PCB, I'll be using Jack's design (after all he started this very wonderful and informative thread ).

By the way, I think you mentioned earlier on the thread that this design is optimized for low-Z headphones. Just in case we would need it adapted to higher Z ones (like the old AKG K340 or Sennheiser HD800, both of them around 300 Ohms), could you please give us some directions to adapt the design? Thanks in advance.

Javier.
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Old 8th August 2012, 07:16 PM   #438
sonidos is offline sonidos  United States
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Originally Posted by Unomas View Post
Hi, mine is going on step by step. Right now I'm concentrated on the PSU and later on I'll started the HeadAmp. I'll report on the evolution. As for the HA PCB, I'll be using Jack's design (after all he started this very wonderful and informative thread ).

By the way, I think you mentioned earlier on the thread that this design is optimized for low-Z headphones. Just in case we would need it adapted to higher Z ones (like the old AKG K340 or Sennheiser HD800, both of them around 300 Ohms), could you please give us some directions to adapt the design? Thanks in advance.

Javier.
Yes, I have Senn 300 ohm phones as well. I asked him before about adjusting resistor values but he warned me that I couldn't increase it that much more. It's in one of my previous posts somewhere. I believe it was R8.
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Old 8th August 2012, 10:53 PM   #439
Unomas is offline Unomas  Spain
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Originally Posted by sonidos View Post
Yes, I have Senn 300 ohm phones as well. I asked him before about adjusting resistor values but he warned me that I couldn't increase it that much more. It's in one of my previous posts somewhere. I believe it was R8.
Thanks Javier for your answer. Well it might not be the best option for this type of headphone, but anyway it may be helpful to know the limits for this little wonder:
- Maximum Vout for a typical +/-12v or +/-15v supply (considering the use of well matched pairs)
- Maximum Iout while working in class-A and absolute limit (considering the use of adequate heatsinks to avoid dangerous temperatures on the final TRT)

Javier
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Old 9th August 2012, 01:06 AM   #440
RNMarsh is offline RNMarsh  United States
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It all depends on the efficiency of the headphone driver; its max input before damage or gross distortion sets in. Give it a try first with 300 Ohm headphone as-is. then tell me.

The 30 Ohms just means it can drive lowZ without distortion. many amps cant do this and IC amps cant do it at all.... even with IC buffers. It's just takes too much current.

I didnt mean that it wouldnt do as well with higher Z. In fact, the thd is even lower into higher than 30 Ohms. I am having a hard time measuring the level.

All -- keep us posted on what you hear when it gets done or if there are problems or different power supplies.

The max power is about 10-12 W... heat sink dependant.

Thx, RNM

Last edited by RNMarsh; 9th August 2012 at 01:18 AM.
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