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05/26/22 at 19:44:03 




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Anybody installed input selector switch on zma? (Read 112 times)
Carlsbad
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Anybody installed input selector switch on zma?
05/11/22 at 02:44:05
 
I have a zma on the way.  I am currently very happy with a Rachel but went for the upgrade.  

The amp has XLR and RCA inputs.  I need 2 sets of inputs for my system.  I  use the digital preamp in my Dave DAC which is very sweet and the other set of inputs is my HT to the front speakers.  

I just figured out there is no switch and I can't have them both plugged in at the same time.  I saw "..but not at the same time" on the description and thought it was strange--who would want to play 2 sources at the same time.  

I'm not interested in having to swap cables when I want to watch a movie.

I guess I'll install a selector switch(es)--probably a toggle on each side to reduce wire length.  but it is pretty crowded.  

Has anyone here ever performed this mod?

thanks
Jerry
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Decware ZMA with 25th mods
Decware SE34.I5, Rachel (backup)
Chord Dave DAC
Tekton Encore Speakers
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mperdue63
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Posts: 102
Re: Anybody installed input selector switch on zma?
Reply #1 - 05/11/22 at 03:25:45
 
I have a ZMA and I keep my ZP3-Turntable connected to the RCA and my DAC connected to the XLR all the time with no negative impact. I just don't use them both at the same time.
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Carlsbad
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Re: Anybody installed input selector switch on zma?
Reply #2 - 05/11/22 at 05:16:30
 
Thanks.  I've read other reports of people having trouble with it. I'm glad it is working for you.
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Decware ZMA with 25th mods
Decware SE34.I5, Rachel (backup)
Chord Dave DAC
Tekton Encore Speakers
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Carlsbad
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Posts: 45
Re: Anybody installed input selector switch on zma?
Reply #3 - 05/17/22 at 14:43:14
 
Well, I'll post my results here in case others want to do the same.  Got the amp.  Sounds great.  Awesome balanced inputs with transformers.  

Steve filled up every square inch of the top of that amp with components:  4 transformers, 10 tubes, 4 gauges, 4 bias adjust pots, etc.  So I'm having trouble finding a place to put a switch.  I've given up on rotary switch and since there are only 2 sets of inputs, I'm going to try to find a place to shoehorn in a toggle switch someplace where it doesn't look crowded... gotta take the top off and look at it from both sides.  Manual says it can take up to 8 hours for the big caps to discharge.   I'm also toying with the idea of putting a switched resistor across the caps so I can flip a switch and dicharge them in 60 seconds...tube rolling is a bit more challenging if you have to wait 8 hours to switch tubes.

More to follow.
Jerry
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Decware ZMA with 25th mods
Decware SE34.I5, Rachel (backup)
Chord Dave DAC
Tekton Encore Speakers
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Archie
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Re: Anybody installed input selector switch on zma?
Reply #4 - 05/17/22 at 16:20:23
 
Quote:
Manual says it can take up to 8 hours for the big caps to discharge.


Before I open up my ZMA I let it "play down" with a music input and the amp turned off.  I think that discharges the caps but I've never touched the contacts to check!  The resistor across the contacts is a good idea.  Not sure of the resistor size though.

Oh, and I've never waited to change tubes.  Sometimes I don't even bother turning off the amp.  Just don't try that with the OA3s.
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ZLC
Technics 1200G TT w/ Ortofon Jubilee MC cart
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Carlsbad
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Posts: 45
Re: Anybody installed input selector switch on zma?
Reply #5 - 05/18/22 at 03:55:25
 
Thanks Archie. I tried this.  It only played a few seconds, similar to what I'm used to other amps playing down that don't have large caps.  Makes me think they probably didn't discharge so be careful.

Your experince swapping output tubes confirms my thought that it is really just the OA3s you have to worry about.

thanks for this.
Jerry
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Decware ZMA with 25th mods
Decware SE34.I5, Rachel (backup)
Chord Dave DAC
Tekton Encore Speakers
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Archie
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Re: Anybody installed input selector switch on zma?
Reply #6 - 05/18/22 at 06:24:33
 
I've pulled my OA3s after "playing it down" too without issue.  Over the years Steve may have posted more about this if you try searching his posts.
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ZLC
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)
Homemade Big Betsy Speakers (F15s)
Silver Cabling
DIY Isolation platforms under amps & TT.
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