Impact of power supply upgrade for Pimeta
Nov 30, 2007 at 2:18 AM Thread Starter Post #1 of 8

slowpogo

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I have a Pimeta w/ Sjostrom diamond buffers, which are pretty power hungry. It's being powered with a Tread and printer power supply right now.

Do you think it would be worthwhile, in terms of SQ, to upgrade to a STEPS or Sigma11? My amp has plenty of capacitance, but seems a tad bit shy on the bass. I'm wondering if a better supply could make the bass punchier, or affect the sound noticeably otherwise.
 
Nov 30, 2007 at 9:36 PM Post #2 of 8

slowpogo

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I have searched but cannot find a topic for this particular question. Maybe I ask too many questions and you're all sick of it
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But I would love to hear some opinions...is a Pimeta not worthy of a STEPS or Sigma11? Or will those better supplies make it a better-sounding amp?
 
Nov 30, 2007 at 10:01 PM Post #3 of 8

balou

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I'd say no.
Have a look at Power Supply Tests
STEPS and TREAD are awfully close performance-wise. and modern opamps have quite some power supply rejection. and a pimeta is also not that much of an uber-amp.
a sigma11 might have a lower output impedance than a STEPS/TREAD, but again, will it matter? the pimeta and the diamond buffer just use relatively power-unhungry JFET and BJT components, no tubes, mosfets or other very power hungry things. so the lowered output impedance will likely have close to nil advantages. or what is the current power consumption of your pimeta?
 
Nov 30, 2007 at 10:08 PM Post #4 of 8

MASantos

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well, I noticed a bit less of bass when I changed the steps for a tread in my pimeta. It was very subtle though. What OPAMPS are you using?

Maybe changing for a more bass oriented opamp will give better results.
 
Dec 1, 2007 at 12:55 AM Post #5 of 8

slowpogo

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I am currently using AD744 for L/R, and AD829 for Gnd, all using compensation pin for output. I'm not sure how to measure the power consumption of the amp.

Anyway, it normally irritates me when someone suggests a major upgrade to me (not that you guys are doing it), but I'm actually starting to think that way myself.

I think rather than worrying if a better power supply will upgrade the Pimeta, it's about time to build a new amp. I'm enjoying my newish K701s with the Pimeta, but I'm aware that while the Pimeta will drive them OK I'm not hearing anywhere near the potential of these headphones.

Edit: the rest has been put in a new thread
 
Dec 1, 2007 at 10:13 AM Post #6 of 8

NelsonVandal

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AD744 is a bit shy on the bass, especially comp pin out. Using the normal output, this opamp is neutral but boring - still bass shy, undynamic, unclear. I have a LISAIII clone (without bass boost) with this setup AD744/829. I've tried it with comp pin out vs standard pin out, and I've tried it with other opamps. AD829 is warmer and less harsh compared to AD744, and I think they're a good blend. The final result is just a little bit leaner than neutral. You can get a warmer sound by rolling opamps to OPA134. I've never heard OPA627 or AD797, but they would probably give you the sound you want. Or why don't you add a bass boost circuit like in PPA or LISAIII and have the best of both worlds - details, soundstage and mucho bass.

I don't think the power section will alter the sound. I've tried adding/changing caps - no difference, going from battery to wallpower to battery - no difference, rolling opamps - major difference, rolling output transistors - audible difference (BD137/138 warmer than MJE243/253). I think it's the active parts (and caps in the audio path if used) that makes all the difference in a 3 ch amp.

I've built a 3 ch 2x9V battery powered amp with AD8599/AD825, BTW utterly neutral, and at first I only used 0.1 uF ceramics from rail to rail in close proximity to the opamps. Later I've tried adding electrolytics - 100 uF Sanyo OS-CON, 330 uF Panasonic FC, 2200 uF ELNA RJH - both from rail to rail and from rails to ground. I've done this "live" while listening, and there's no audible difference adding them! Not to my ears. I have HD650 and use an old H/K CDP and a modded iRiver IHP120 as source. Maybe there would've been an audible difference with better phones and source, but I doubt it would've been siginificant. Power caps = overrated?
 
Dec 1, 2007 at 10:43 AM Post #7 of 8

majkel

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Agreed to most above. In a topology with an active virtual ground there is hardly any impact of the power supply. In the other words, the power supply has got to be pretty bad to hear the deterioration of sound. All of that because the ground channel acts as another supply filter and voltage equalizer, and finally, when you use good electrolytic capacitors, all the ripple remainings from the supply voltage get lost in the electrolytics.
 
Dec 4, 2007 at 10:59 PM Post #8 of 8

mono

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Tread is fine but get rid of the printer power supply before it if it is switching type which produces far higher frequency noise which is harder to remove and more significantly effects the opamp PSRR.
 

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