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Mezmerize DCB1 Building Thread
Mezmerize DCB1 Building Thread
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Old 12th June 2018, 11:52 AM   #2061
nzlowie is offline nzlowie  Australia
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Quote:
Originally Posted by Salas View Post
9.88 & 9.87 are not low rails in dcb1 practice and 16.6vdc rectified from 12v taps indicates strong mains so all is well. 15v taps would give more heat to the input Mosfet due to higher dc drop across but less Ciss capacitance. Try those taps also since you got the sinking but keep them in use only if you find the result bit more open in the treble. Else its just a waste in heat that it will be felt after you push the mA to high hot-rod.
Cool, thanks for that. I was just a bit concerned when the voltages weren't over 10v as mentioned. Didn't think there could be too much wrong as it's doing everything right.


Still evaluating but from what I'm hearing I'd say it's added more accuracy to the music, placement is more precise and there seem to be more micro details coming through which adds a lot of nouonce to vocals ect. Hasn't really done much to the sound stage, this was already very good.

Happy so far.

Thanks to everyone for making this available.
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Old 12th June 2018, 12:42 PM   #2062
nzlowie is offline nzlowie  Australia
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Only minor issue is a small amount of hum, I've got 95db bass speakers and it's just audible right up close. The transformer is well away from the board so I don't think placement is an issue.
Is a toridal better than a normal"box" transformer?
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Old 19th September 2018, 12:37 PM   #2063
nlgbo1 is offline nlgbo1  United Kingdom
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Default High left channel offset?

Just managed to get around to building the mezmerize board.
All seems ok so far, I get +10.39V and -10.13V at the DC test points on the board, with a 15v transformer.
Right channel has offset of -0.5mv
Left channel has offset of -5.3mv

Is there any way to reduce the left channel offset, or is this acceptable?
Thanks,
geoff.
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Old 19th September 2018, 02:19 PM   #2064
Salas is offline Salas  Greece
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Mezmerize DCB1 Building Thread
Mutually exchange places between the higher offset channel's JFET pair, maybe you will get lucky and they will reduce. Else you can't do anything more than finding a better pair to replace them or accept their now mV figure. 5mV is not the end of the world but that depends on the power amplifier too. If its DC input coupled and has high voltage gain it may amplify that to a level that is going to change its output bias somewhat. Usually its either blocked by an input capacitor in the amp or its inconsequential.
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Old 19th September 2018, 03:07 PM   #2065
nlgbo1 is offline nlgbo1  United Kingdom
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Thanks Salas,
I tried swapping the JFETs over (as per post 1945), I now get:
Left +2.8mv
Right -2.3mv

Sounds fine on test, not hooked it up to my main system yet for a proper listen.
Thanks,
geoff.
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Old 19th September 2018, 03:17 PM   #2066
Salas is offline Salas  Greece
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Mezmerize DCB1 Building Thread
Not bad at all. What is the power amp you will use with it?
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Old 19th September 2018, 03:22 PM   #2067
nlgbo1 is offline nlgbo1  United Kingdom
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Err, good question!
At the moment, it's going to be a Neurochrome Modulus-86 (lm3886 composite), but looking to build a F5-Turbo in the near future.
Thanks for the great build, I learned a lot from this!

geoff.
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Old 19th September 2018, 03:40 PM   #2068
Salas is offline Salas  Greece
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Mezmerize DCB1 Building Thread
You are welcome. Just look to have enough voltage gain in the system for your speakers sensitivity to express alive dynamics, since a buffer preamp won't add to that, the source and the amp will contribute all signal voltage there is.
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Old 8th December 2018, 11:14 AM   #2069
Ralphien is offline Ralphien
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Salas, your suggestion was pure genius and showed uncanny intuition. Many thanks and take a bow. You saved me from dismantling the board. You were right I had not put in the earth link in the middle of the board! It is the old Mesmerize Black version by crt. From the beginning I somehow got the idea it was an optional connection if you got earth hum. Maybe the blue version?
Anyway the picture shows it just works now to specification and I need to try it with music.
Dropbox - Black Mes works!.JPG
Thank you
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Old 8th December 2018, 02:06 PM   #2070
Salas is offline Salas  Greece
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Mezmerize DCB1 Building Thread
In blue boards you may enhance those links with wire for lowest resistance, especially the long one associated with the AC rectification area, but there is copper film already underneath those two white linking lines because blue are double sided so its just optional and not that important. But the old black board is single sided so to actually make the links with wire jumpers on it is necessary.

Congratulations for completing your build and let us know your impressions with music.
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