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Old 25th November 2009, 09:30 AM   #1
Bertel is offline Bertel  Germany
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Default DAC -> Amp with parallelled E182CC and Lundahl transformers -> 8ohm headphones

I am about to finalize concept and design for basically a complete amp stage 'between' the balanced voltage output of my DAC (Wolfson WM8741 in dual mono config) and my headphones with 8ohm impedance (Ultimate Ears UE-10pro). Credtis for this go to Lars/revintage who has provided immense knowledge and support - thank you so much Lars!!

The specifics are:

- Lundahl LL1676 transformers (connected 2:1) for balanced-to-unbalanced conversion
- two parallelled E182CC/channel as in the attached schematic
- Lundahl LL1630 output transformers

What do you all think of this? I am absolutely thrilled by how 'simple' and straightforward this is, a purist and minimalist approach with highest-quality components - I'd appreciate your comments if you'd like to share

Best,
Robert
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Last edited by Bertel; 25th November 2009 at 09:32 AM.
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Old 25th November 2009, 10:53 AM   #2
Jaap is offline Jaap  Netherlands
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I would steal his powersupply: ecp.cc

Look also here: http://www.audiodesignguide.com/NewH...Amp/index.html

Last edited by Jaap; 25th November 2009 at 10:59 AM.
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Old 25th November 2009, 02:43 PM   #3
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Second thoughts about 1630, 14,4:1 . Zout will be quite high, in the ballpark of 8ohm. Maybe better with a 5k:8ohm with descent primary inductance. Have no suggestion. Think Dsavistk has done some work that showed that damping wasn´t so important.
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Old 26th November 2009, 03:59 AM   #4
Bertel is offline Bertel  Germany
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Hi Jaap,

many thanks!

I knew the ecp.cc article, shurely an interesting and integrating solution.

The audiodesignguide article was very interesting reading too, I could find additional thoughts on the Lundahls, and on many other aspects

Well, regarding power supply I was intending more to keep it 'external' - I was thinking of this: Z100A shunt Voltage Regulator in combination with this: CCS1A Constant Current Source Would this work - or is it blasphemy...?

Many Thanks,
Robert
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Old 26th November 2009, 07:16 AM   #5
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Hey Bertel,
Waste of money! With discrete components you can build a PSU for this amp at a fraction of the cost. One or two depletion MOSFETS and a voltage regulating tube(plus a few small components) is all that is needed. Two channels will draw 40mA plus the 10-15mA through the regulator.

Last edited by revintage; 26th November 2009 at 07:23 AM.
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Old 26th November 2009, 07:25 AM   #6
Bertel is offline Bertel  Germany
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Ok, got that

What do you think of the PSU which is pictured in the second link that Jaap had linked to (Hi-end headphone amplifier, bit down the page) ? I shy away a bit from "integrating" it as much as in the epc.cc example - or would this bring benefits not achievable with an "external" solution?

Thanks
Robert
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Old 26th November 2009, 08:29 AM   #7
Jaap is offline Jaap  Netherlands
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Quote:
Originally Posted by Bertel View Post
Hi Jaap,

Well, regarding power supply I was intending more to keep it 'external' - I was thinking of this: Z100A shunt Voltage Regulator in combination with this: CCS1A Constant Current Source Would this work - or is it blasphemy...?

Many Thanks,
Robert
I have done a 5814 (also D3A or E810F)/LL1630 pre-amp in the same style. First with 2 chokes in the psu and later with only one choke + 10M45s CCS + 0A2 gas tube returned to the cathode. This was a big step forward (more bass for instance). I had not enough room so I tie wrapped the 0A2 under the hood. It worked a long time but the thing started oscillating yesterday so I have to do some surgery.

I am also thinking of changing the PSU by adding a solid state regulator and perhaps taking the 0A2's out. If I remove two big oil caps I have room again on the chassis.

I have some boards from the Jan Didden (Janneman)/Elektor regulator. Take a look at the power supply forum. There is a choice these days. I saw for instance the simplistic Salas regulator. I even think that for a hobbyist a HV superregulator is not over the top. Provided that you are not ripped off by buying a too expensive kit
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Old 26th November 2009, 08:47 AM   #8
Bertel is offline Bertel  Germany
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Ah, so you had the 0A2 connected back to the cathode like in the ecp.cc example, right? I don't know, well sure I have no experience with tube-based PSUs, but I would really like to keep PSU 'out' and go solid state too.

And yes, good that you mention it - I am just about to start building two shunt regulators as designed by ikoflexer, this is further development based on the simple Salas reg
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Old 26th November 2009, 09:54 AM   #9
Jaap is offline Jaap  Netherlands
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I am certainly no expert on this subject, but I have the idea that regulators and long leads is not a good combination.
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Old 26th November 2009, 09:59 AM   #10
Bertel is offline Bertel  Germany
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Yes, you're absolutely right - the closer the regs are at the load the tighter they can manage the load, especially true for shunties! So if you can find some space in your chassis...
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