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ZMA - comperhensive upgrade complete (Read 2617 times)
BAndrade
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Re: ZMA - comperhensive upgrade complete
Reply #50 - 06/11/19 at 01:26:02
 
Wondering if any of you folks have experienced this.

It seems to me that different periods - 15 minutes to 45 minutes - before starting to play music makes a difference in quality of sound output v/s background noise.

Playing music immediately after powering up was the worst scenario. It took about 2 hours to get that exquisite sound. So the shortest period to run the ZMA idle is about 15 minutes.

Looks to me that if the ZMA is left powered up but silent for about 15 to 20 minutes before beginning to play music caused the background noise level to be pitch black and music to be fabulous straight off the bat.

Interestingly if the ZMA was charged up for 45 minutes or more before starting to play music, the background appears to be ever so slightly less black than those experienced at the above shorter time. But now the speed increased to perfection and the music playback is better than fabulous – floating and realistic.

I have been deeply thinking why this is so. My thinking is that it is because there is no dedicated noise filter arrangement in the power supply of the ZMA but there is reliance on noise damping instead, in those large capacitors. So at the 15 -20 minute mark the massive caps are still not fully charged as yet and any ripple riding on the power supply after the rectifies get absorbed by the capacitors because there is slack in the capacitors to dampen the noise riding on the power supply. Where as at the 45 minute mark onwards the caps are fully charged and so some of the power line ripple simply bypass the fully charged caps and move on further down the circuit but now the fully charged capacitors far more readily supply current.

My preference is the fully charged state as it produces music that is just fantastically timed and detailed, the very minor increase in background level is not at all normally perceptible unless highly concentrating on it only with single mindedness, blocking all else.

I would imagine for stock ZMAs without massive amounts of capacitance the times would be proportionally less but in any case leaving the ZMA powered up for at least about 5 to 10 minutes before starting to actually play your music would yield the best results. Otherwise depending on how hard and what is being played it would take longer to reach that optimum point.
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Archie
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Re: ZMA - comperhensive upgrade complete
Reply #51 - 06/11/19 at 01:31:10
 
Are you saying that NOT playing music is required?  Or will it catch up eventually if music is played from the start?
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Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
HR1s (Upgrd - top & bass drivers & X-ovr)
Silver Cabling
DIY Isolation platforms under everything.
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BAndrade
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Re: ZMA - comperhensive upgrade complete
Reply #52 - 06/11/19 at 03:45:01
 
I mean just turning the ZMA "ON" without actually driving the speakers. i.e. the source e.g. DAC etc is paused or off. Driving the speakers causes a draw  of power from the amp delaying the large capacitors from being fully charged.
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Archie
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Re: ZMA - comperhensive upgrade complete
Reply #53 - 06/11/19 at 15:53:13
 
Got it.  Thanks.
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Technics 1200G TT w/ Ortofon Jubilee MC cart
ZMC1
ZP3 (25th A Mods)
ZR2 (25th A Mods)
CSP3 (25th A mods)
ZMA (25th A mods)
HR1s (Upgrd - top & bass drivers & X-ovr)
Silver Cabling
DIY Isolation platforms under everything.
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BAndrade
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Do it once, do it
right. Repeat for
quality life.

Posts: 65
Re: ZMA - comperhensive upgrade complete
Reply #54 - 06/16/19 at 12:20:43
 
Just for fun I decided to add the original 2000 uF Red capacitors for a total of 13500 uF per side. As a quic experiment I did the connections with alligator clips as shown in the picture.

Folks if you doubt music with such a drastic change from the humble beginnings of only 2000 uF per side has no effect, you are mistaken. You’ll think your ears have undergone a tune up – everything is even more crisp and clean.

Background is getting blacker more and more as there is now lesser and lesser dependence on the electrical grid for immediate power gratification. This background thing b.t.w. is not fathomable. Until it is moved further down you realize there is this lower level. Every time it is lowered the sound becomes more and more clear like more and more shine is being produced by constant buffing on chrome metal.

I probably reached the limit of these input transformers' start up current. I could hear the electrical flux building up in the transformers when I toggled the power switch to "ON". However running current through the input transformers seems to be lower based on the running temperature of the transformers being 10F lower than normal – 99 F vs 110F. However I have been only running like this for an hour now. I’ll take more readings further along and report here if the temperature drastically increases.
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BAndrade
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Do it once, do it
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Posts: 65
Re: ZMA - comperhensive upgrade complete
Reply #55 - 06/23/19 at 18:58:41
 
Something huge in the works.

My drive to achieve more and more perfection or OCD in modern parlance has compelled me to place an order for input and output transformers made by the same manufacture as the original ones  on the ZMA but of substantially higher output.

Rationale:

My calculations and discussion with the manufacturer of the transformers viz. Hammond Manufacturing have led me to believe if driving higher wattage, lower efficiency wide frequency speakers the original transformers are close to their "core saturation" point at mid/high volumes levels. Definitely using KT88 tubes at higher outputs will exceed the manufactures specs for the transformers (even though the ZMA owners manual has listed KT88 as an alternate) entering the region of saturation of the transformer core. BTW the stock ZMA will easily drive speakers that are 90 dB or more efficient and that do not go lower than say 30 Hz or so. In this case these and all earlier posted upgrades will yield proportionally less results as the speaker demands on the amp are far less.

Thing is these new transformers are physically larger in size,I have no idea how I am going to fit them on the amplifier base. As with all the upgrades done so far if things do not work I have the option of going back.

While I am at it I decided to include a filtering section so also ordered a couple of 5H chokes and 47 uF Mundorf Tube caps. These definitely will have to be external to the ZMA base unit.

Both looking forward to it as well as not for the amount of work involved. Might be far more than I have done so far for any single upgrade task. To gain access to shoulder points I expect to remove a lot of the work already done and re-fixing it all back.

No rest for the wicked ...
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