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Bertel 25th November 2009 09:30 AM

DAC -> Amp with parallelled E182CC and Lundahl transformers -> 8ohm headphones
 
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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

Jaap 25th November 2009 10:53 AM

I would steal his powersupply: ecp.cc

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

revintage 25th November 2009 02:43 PM

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.

Bertel 26th November 2009 03:59 AM

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

revintage 26th November 2009 07:16 AM

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.

Bertel 26th November 2009 07:25 AM

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

Jaap 26th November 2009 08:29 AM

Quote:

Originally Posted by Bertel (Post 1993261)
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 :cannotbe:

Bertel 26th November 2009 08:47 AM

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 :)

Jaap 26th November 2009 09:54 AM

I am certainly no expert on this subject, but I have the idea that regulators and long leads is not a good combination.

Bertel 26th November 2009 09:59 AM

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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