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Old 15th June 2003, 11:07 AM   #1
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Default PS auditions

I finally got around to trying the 4-transformer low-flux PS Kuei proposed. The GC in question is 3875 inverted with just 2 resistors and no input cap. Initially a 160VA toroid was used per channel. The transformers i ordered are 100VA EI with dual secondaries which feed dual bridges. I compared the toroid to a single EI (not very fair powerwise) and to two EIs per channel with primaries and secondaries connected in series. Still haven't included dc blocking in the primaries.
The results in my system are a bit controversial. The toroid, as in past experience, produces the fastest and clearest mids, good dynamics but obvious congestion at higher volume and weak and inconsistent bass. The single Ei doesn't give the impression of being less powerful even at higher volumes (my transformer winder claims he's very conservative with the ratings); the sound is a bit slower with a nice deep bass and good depth layering and probably more listenable long term. The combination of two series connected transformers initially showed promise with its ability to efficiently move air. It has slightly overblown bass with good depth, a nice and steady soundstage but very distant mids and generally slow and uninvolving sound. This may have something to do with the low flux but previous experience shows this often to be the result of going over the top with the VA rating.
I also tried 4x12v/7ah batteries and while sounding great with acoustic music, on a wider selection the bass sounded disjointed and lagging from the rest, seriously screwing PRAT. I think the problem is not inherent in batteries but relates only to acid batteries, or even to particular makes, as i use NiMH in my MC stage with great results.
Incidentally my 'normal' amp is a way-over-the-top PX25 SET with 3 PS per channel.

peter
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Old 15th June 2003, 03:40 PM   #2
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Default Re: PS auditions

Quote:
Originally posted by analog_sa

I also tried 4x12v/7ah batteries and while sounding great with acoustic music, on a wider selection the bass sounded disjointed and lagging from the rest, seriously screwing PRAT. I think the problem is not inherent in batteries but relates only to acid batteries, or even to particular makes, as i use NiMH in my MC stage with great results.
What make batteries were you using ?

were they new or fairly new ?

how large were the bypass caps ?

and excuse my ingorance but what is PRAT ? my guess would be precise rhythm and timing but this abreviation is new to me.

cheers

mike
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Old 15th June 2003, 04:44 PM   #3
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Hi Mike

Relevant questions indeed. The batteries are out of my UPS, fairly used but charge up to full capacity. Sorry, forgot the make, certainly not Yuasa or Panasonic. The bypass caps are simply the caps i use with the mains PS - 2x1000uF/chip BG. The character of the sound with batteries is slightly reminiscent of what you get if go overboard with the supply caps. Smaller batteries might sound better. Make no mistake though, the sound with batteries may be stunning on simple acoustical music, especially vocals. If girls with guitars is what you listen to mainly, batteries are great.
You're very close on PRAT - Pace Rhytm and Timing - a popular term in turntable-talk.

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peter
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Old 15th June 2003, 05:12 PM   #4
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I understand you are talking about this PS. Which diodes did you use? From what you mentioned, it seems like using transformers separetely may actually produce better sound than series connection?
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File Type: jpg ps.jpg (16.8 KB, 1851 views)
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Old 15th June 2003, 05:57 PM   #5
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Peter

That's the circuit which started me. I used MUR860 in a bridge as i didn't want to experiment with too many variables at the same time. Surely full rectification wil sound different to bridge - less switching noise from the diodes but more stress on the caps - may well be better. I might try it first in a preamp as it seems to make more sense with less current. My observations about the sound may only be relevant in the context of the particular transformers i use. Kuei seems to recommend this circuit with toroidal transformers and the results may well be different. All this is pretty inconclusive...sorry.

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peter
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Old 15th June 2003, 06:05 PM   #6
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I also have 4 EI transformers and I might try it one day too. Although I did not try batteries yet, I got the feeling it may not be the ultimate solution either. The 4700u electrolytics in a pic above are low voltage, 10V or so should be fine, right?
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Old 15th June 2003, 08:26 PM   #7
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The diodes limit the voltage across the caps to 1.4v. I still haven't tried this circuit. It will probably have a more pronounced effect on toroids than on EI and while some of this effect will no doubt be beneficial you'll have to cope with an extra cap colouration. it will be great if you give all this a try.

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peter
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Old 15th June 2003, 09:22 PM   #8
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Quote:
The 4700u electrolytics in a pic above are low voltage, 10V or so should be fine, right?
Not AC line rated?
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Old 16th June 2003, 01:05 AM   #9
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Quote:
Originally posted by leadbelly


Not AC line rated?
If the caps would have to be AC line rated, there would not be enough voltage for transformers to run.
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Old 16th June 2003, 01:12 AM   #10
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Quote:
If the caps would have to be AC line rated, there would not be enough voltage for transformers to run.
No, I was thinking along the lines of safety regs (CSA). Don't they need to be AC rated as long as they even touch AC line, in case a short/part failure dumps the full line voltage across them?
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