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PA Systems A forum for discussion of all parts of a sound reinforcement or DJ system: loudspeakers, mixers (desks) etc.

soundcraft spirit folio SX Psu improvememnt
soundcraft spirit folio SX Psu improvememnt
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Old 6th April 2020, 01:18 PM   #31
turk 182 is offline turk 182  Canada
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so what? they are designed with higher max ratings, it doesn't mean they are running at max!!




yes it does qualify that it "may" be a problem source but until that is qualified with testing who can say...it could well come down to part cost vs performance being marginal but without more information what your describing points more to a circuit fault....so i would be more inclined to finding and fixing the fault rather then modding the supply on the assumption it's badly designed.


re use of "foreign language" in the public part of the forum, the forum rules are clear, no?
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Old 6th April 2020, 01:46 PM   #32
rozzilla is offline rozzilla  Italy
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my poor man testing procedure is:
- listening to my working track to monitors connect to master out at decent level,
- crank heaphone out to high level,
- unplug headphone from socket abruplty

this reveal a slightsonic improvement on master output. might be the right time to pull the trigger and collect a scope to testify rail activity on this procedure

in the meanwhile i am trying to finish my mix with channels biased at -9db and everything is ok
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Old 6th April 2020, 02:19 PM   #33
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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You need an accurate DVM and a Phillips screwdriver.
That is all you need at this stage.

My question again; have you got +-17volts?
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Old 6th April 2020, 02:40 PM   #34
rozzilla is offline rozzilla  Italy
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@ jon i cannot say about static rail voltages since i am not able to unrig the mixer and probe anything at moment
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Old 7th April 2020, 08:02 PM   #35
rozzilla is offline rozzilla  Italy
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how much rubbish i have to expect from it ?
https://shopee.com.my/%F0%9F%94%A5%F...274.2627865447
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Old 8th April 2020, 09:36 AM   #36
turk 182 is offline turk 182  Canada
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it's a transformer isn't it?
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Old 8th April 2020, 04:44 PM   #37
rozzilla is offline rozzilla  Italy
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yes it is
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Old 16th April 2020, 12:27 PM   #38
Xoc1 is offline Xoc1  United Kingdom
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I had a quick look at the schematic of the mixer and it seems to have very minimal decoupling of the op amps with just 100n capacitors used and minimal electrolytics.
The decoupling scheme may work but is obviously done to a budget.
I have had good success with using low ESR caps like Panasonic FC series - which come in a good range of sizes which makes it easier to substitute where space is tight.
I would replace the 2 PSU caps C104-C105 with low ESR caps and with an uprated size if possible.
I have only spotted 2 electrolytic caps on the voltage rails these being C37 & C38 on the master section and these are only 2.2uF - I would be tempted to substitute 100uF for these. I would probably look around the PCB to see if there were places where extra decoupling caps could be added to the mixer PCB and distribute these along the voltage rails, taking care to physically space them, especially from the regulator outputs. The difficulty is often finding how to connect any capacitors to the voltage rails and a decent ground.
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Old 22nd April 2020, 01:55 PM   #39
rozzilla is offline rozzilla  Italy
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thank you for your suggestions Xoc1
I still have not accessed internals to see how to improve caps, but i tested a new trafo. While the old ones have +/- 21.5V (no load) outs , new one have +/- 19.7V (no load) with a beefier 60VA rating.
Here it is FFT response of a short same audio snippets of house track i am working with, taken first with old trafo, then with the new one with very same desk setting (and room temp etc.)


I can hear a noticeable improvement on bass drum which sound tigher, maybe due to better response on midrange or less overall compression. Possible higher noise floor is not such a big deal since the music i used to work with.
I have concern to share those audio snippet on pubblic, but if somebody is interested i can send him on pvt link
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Old 22nd April 2020, 02:01 PM   #40
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Quote:
Originally Posted by rozzilla View Post
thank you for your suggestions Xoc1
I still have not accessed internals to see how to improve caps, but i tested a new trafo. While the old ones have +/- 21.5V (no load) outs , new one have +/- 19.7V (no load) with a beefier 60VA rating.
Here it is FFT response of a short same audio snippets of house track i am working with, taken first with old trafo, then with the new one with very same desk setting (and room temp etc.)


I can hear a noticeable improvement on bass drum which sound tigher, maybe due to better response on midrange or less overall compression. Possible higher noise floor is not such a big deal since the music i used to work with.
I have concern to share those audio snippet on pubblic, but if somebody is interested i can send him on pvt link
The +-17volts is the same. Have you got an over furtive imagination ... how can there possibly be an 'tighter' sound.
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