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Old 21st October 2011, 11:01 AM   #351
regal is offline regal  United States
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Quote:
Originally Posted by Dr.H View Post
Hi fellas,

Patrick you mention that you use SEN for PCM1704. I currently use Spencers D1 IV on a PCM63 (Balanced) DAC. Did you find the SEN better than the Spencer D1?
I did not like the spencer D1 for PCM63k, easily beaten by a simply 50 ohm i/v resistor plus quiet (ccs/led/shunt PS) 6n6p anode follower where I actually had a switch to compare the two side by side level matched (which isn't saying much for the spencer d1 at all.) This was a case where the tube (hybridish) had lower THD than SS!

I guess Spence D1 and the Zen predudiced me against I/vs's. I mean if the input impedance is as high as a passive resistor I/V, and the linearity is worse than a tube?


The best performing I/V for the PCM1704 I have is a BJT with 27db nfb followed by a diamond buffer all dc coupled (its commercial.) And I do think that a minimalist concept like the CEN is worth a serious look (but again the PCM1704 hates an I/V with input impedance over 10.)

But the Cen certainly demands a try for me with the Jfets (especially the ouput transformer option.)
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Old 21st October 2011, 03:23 PM   #352
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Thanks guys. Regal, please share your views once built. I've been wanting to build SEN for the pcm63 for a while, but alas, other priorities are pressing!
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Old 22nd October 2011, 12:23 AM   #353
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Hello,


If one wanted to use a regulated power supply, would that be a problem? My dac already has one available at 15v (see image but 15v zeners). Or is this circuit so sensitive that battery power is mandatory? (asking since I'm still waiting for my Linear Audio issue ordered a while ago)

Thanks
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Last edited by mfrimu; 22nd October 2011 at 12:28 AM. Reason: 15v
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Old 22nd October 2011, 01:05 AM   #354
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See posts from #150 (this thread) onwards, about the floating supplies, batteries, etc.
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Old 22nd October 2011, 01:31 AM   #355
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I have read the posts #150 on regarding floating supplies. I'm a newbie in regards to floating supplies.

I suspect that even if my supply was isolated from the rest of the circuit ground and I used only +15v and 0v there would be leakage to ground via the mains transformer. Is that so?
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Old 22nd October 2011, 01:52 AM   #356
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I too, looked at the idea of floating supplies, shunt regs, etc and considering that you need a dedicated 18v supply for each Cen/Sen stage, it quickly became a problem in itself

And, I wasn't happy with the voltage developed across the Riv also being superimposed on the supply lines, regulator, caps, transformer secondary, etc - just asking for signal degredation

Take a look at the world of batteries, particularly those Li-ion ones intended for remote controlled cars, helicopters, etc (Patrick himself uses a system of the 9 volt block batteries with isolating relays for recharging ) - this appears a simpler, possibly better, supply solution.

..... just my 2 cents, mind you.
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Old 22nd October 2011, 02:14 AM   #357
regal is offline regal  United States
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Lithium batteries, especially the ones with unmeasureable output impedance and noise (LiPO4 and other variants) are a huge untapped new frontier for DAC's, both on the digital and analog side. But setting up the automated charging circuit is a PIA I've found one of the biggest problem with dealing with low level signals is the power company and rectifiers, take a scope to your wall outlet and study it over the course of a day, its amazing we get any quality audio at all from household mains. I work with robots and vfds in my real job and you wouldn't believe all the issues from poor quality mains.

So taking the jump into the new battery technology is well worth the trouble, just don't make them explode
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Old 22nd October 2011, 04:22 AM   #358
EUVL is offline EUVL  Europe
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With a PCB and all parts ready, you'll get this going within an hour using 8x 9V alkaline batteries for two balanced channels. They will give you more than 10 hours listening. And when after 10 hours, you are still pleased with the results, then it's the time to start worrying about charger circuits, filtering caps, regulators, ..... But then again you may enjoy the music so much that you won't want to bother with regulators and what not any more.

So why worry about it now ?


One step at a time,
Patrick
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Old 22nd October 2011, 01:34 PM   #359
qusp is offline qusp  Australia
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yeah i called for a GB on A123, i don't have enough for this many supplies. I have a FMA cellpro 10XP charger that will work fine, just need to set up 2 sets of batteries perhaps for continuous play, not keen on having the charger connected to the dac.
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Old 23rd October 2011, 02:31 PM   #360
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regal,

With due respect and my limited knowledge I fail to grasp how power supplies would be a problem in a digital circuit. My PC has a 50$ 500w supply and has not missed a single 'bit' ever running at 3Ghz 24hrs/day for 2+ years now, hence I would say the power supply is ample able to deal with mains noise etc.

In low level analog circuits, that is a different story.
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