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Symetrix 528
Old 5th June 2013
  #1
Lives for gear
 

Symetrix 528

This is a mod I did to the Symetrix 528

first i bought it "modded" and it had the daughter board for the mic pre and a single BB opamp on the output actually that's not true they added 1 in the wrong spot the hf section of the eq. which I moved to the line input.






added a that 2180 to the compressor



added 5532 opamps to the entire eq section and to the gain opamp after the ina217 pre chip. swapped the ina217 for a that 1512

the filter caps are on sockets and I've been testing my favorite curves in q clone as well as sound files.
Old 4th April 2014
  #2
Hi Doulos, I have 2 528 that I would like to mod myself, is there a way you can guide me on what I should do to them, is there any mod instruction available, I know these guys are doing it for $99 Modifications - Revive Audio

would that be a better option, it's just that i'm in Canada and I don't want to ship those all over.

best and thanks for your picture, look very DIY

jy
Old 21st April 2014
  #3
Lives for gear
 
hymenoptera's Avatar
 

Cool thread.

I have a pair of these I scored cheap because their mic channels were dead. Still haven't tried to diagnose what's the problem, but I suspect a total recap will reveal something when I get around to it. EVerything else works in it, if it's not murky sounding and kinda dull, but I plan to eventually bring them both back to life, and then some.

I was wondering how the OP likes the 5532s, Panasonics and lemon drop mylars in the filter section?
Old 24th April 2014
  #4
Lives for gear
 

I like them alot. I spent a long time measuring the filter response when tuning it. I had to take the frequency to 28khz to get a nice slope.
Old 6th May 2014
  #5
Gear Head
 

Here are some pics of one I recaped last year

I'm waiting for some ssm2015>ina217 socket converter from revive audio, I was thinking of putting a THAT5012 as well
Didn't look carefully at the data sheet for now, did you had to increase caps value around the THAT5012?
I'd be interested in more pics of yours especially your opamps choices, after some tests I settled on JRC4560D for some instead of the original BA4560, strangely a nice improvement.
Old 30th December 2014
  #6
Quote:
Originally Posted by mecano View Post
Here are some pics of one I recaped last year

I'm waiting for some ssm2015>ina217 socket converter from revive audio, I was thinking of putting a THAT5012 as well
Didn't look carefully at the data sheet for now, did you had to increase caps value around the THAT5012?
I'd be interested in more pics of yours especially your opamps choices, after some tests I settled on JRC4560D for some instead of the original BA4560, strangely a nice improvement.
Hi mecano, would you mind to post the schematics of your mod in here, I like to try it on one of my 528, I already did the rivive audio burr brown INA217 chip mod and I would like to try changing other part now.

cheers!
Old 8th January 2015
  #7
Hi, so I decide to order some parts for my two pre-amp, here the list so far.

2X WIMA MKP2 0.01uF 5% to replace 103M pre-amp sec.
8X WIMA FKP2 1000pF 2.5% to replace 102 pre-amp - compressor
2X WIMA FKP2 330pF 2.5% to replace 331 pre-amp sec.
8X WIMA FKP2 150pF 2.5% to replace 151 de-ess - compressor - eq mid
4X WIMA FKP2 2700P 2.5% to replace 272K de-ess
2X WIMA MKP2 0.047uF 5% to replace 473J de-ess
4X WIMA FKP2 4700P 2.5% to replace 472K eq mid
4X WIMA FKP2 2200P 5% to replace 222K eq hi
2X WIMA MKP2 0.1uF 5% to replace 104 eq hi
14X LT1469CN8 op-amp
Old 8th January 2015
  #8
Gear Head
 

Hello blacky,
on Mids I used WIMA FKP2-5% 2200pF, 250V and WIMA FKP2-5% 4700pF, 250V,
on Low Xicon MPP 0,1uF
for the Deesser I used WIMA MKP4 0,047uF-LS7,5 250V and some FKP
C4 : FKP2 330 pF 630 V/DC 20 %
C13 and C14 : FKP2 470 pF 630 V/DC 20 %
C100, C101, C96, C16 : FKP2 150 pF 630 V/DC 2.5 %
I also used some silver micas around opamps.
Of course changed all electrolytics.
I replaced some ceramics because they were going to dust, I used COG and as I had some leftovers some mkt on input.
Depending on your model you can change R188 and R191 with 3K65, here I had to switch back ; it had an undesirable "swosh" when changing freq.

Are you sure to go with the LT1469CN8? Why this one? If you are going to remove opamps put some socket and perform some tests, I myself found the JRC4560D a huge improvement over the BA4560 and it is more likely to behave nice with the design without having to compensate.
Old 17th January 2015
  #9
Hi mecano, thanks for all your tips and mod information, as for the idea of using a LT469 I took it from Monte McGuire mod of a SX202, he describe the mod and the sound result pretty well and since both are of similar design 528 vs 202 perhaps that is the way to go, of course I will put some sockets and test them one by one a see the difference. In any case I will put my finding in here, if no one mind ;-)
Old 17th January 2015
  #10
Gear Head
 

Quote:
Originally Posted by blacky123 View Post
Hi mecano, thanks for all your tips and mod information, as for the idea of using a LT469 I took it from Monte McGuire mod of a SX202, he describe the mod and the sound result pretty well and since both are of similar design 528 vs 202 perhaps that is the way to go, of course I will put some sockets and test them one by one a see the difference. In any case I will put my finding in here, if no one mind ;-)
Would be great to have your feedback
Old 7th April 2015
  #11
Here for the gear
 
daveobieone's Avatar
 

Wow, what a great bunch of info in this thread...thanks guys!!!

I have my 528 on my bench now. I find it a delightful processor for my bass guitar. I wasn't as crazy about it for normal (voice-over) mic processing in my studio though. The reason for this was the speed of the gate release. I find it a bit slow. This allows a bit of a noise tail after words before it closes.

Have any of you made the determination of which cap controls the gate release? I'm thinking a smaller cap might allow the gate to close more quickly, and eliminate the noise tail.

BTW, my 528 has the Valley People VCA's in it...which I like very much.

I've installed an FET buffer (switchable) for the bass instrument input installed on the front panel of mine. This gives me a 1meg input impedance for nearly no load on the passive pickups on my basses, which brightens them up considerably. Switching out the FET buffer puts things back to stock on the mic preamp.

I have ordered the 2015 conversion socket to switch it out with a few other mic preamp chips I have on hand...including THAT1510, and SSM2019. I believe those are pin-compatible with the INA217 chip. I also socketed the output chip...currently running a 5532 in that, but may change to a Burr Brown of some sort.

It doesn't take much processing for the 528 to really shine on bass BTW. Only a touch past 2/1 ratio, and just a little gain reduction is plenty. I find the stock EQ frequencies / bandwidths to be fine for bass.

If I could just get the gate time constant to where I'm happy with it, I think I'd be using it more as a voice processor as well.

Thanks again,
Dave O.
Old 22nd January 2019
  #12
Quote:
Originally Posted by daveobieone View Post
Wow, what a great bunch of info in this thread...thanks guys!!!

I have my 528 on my bench now. I find it a delightful processor for my bass guitar. I wasn't as crazy about it for normal (voice-over) mic processing in my studio though. The reason for this was the speed of the gate release. I find it a bit slow. This allows a bit of a noise tail after words before it closes.

Have any of you made the determination of which cap controls the gate release? I'm thinking a smaller cap might allow the gate to close more quickly, and eliminate the noise tail.

BTW, my 528 has the Valley People VCA's in it...which I like very much.

I've installed an FET buffer (switchable) for the bass instrument input installed on the front panel of mine. This gives me a 1meg input impedance for nearly no load on the passive pickups on my basses, which brightens them up considerably. Switching out the FET buffer puts things back to stock on the mic preamp.

I have ordered the 2015 conversion socket to switch it out with a few other mic preamp chips I have on hand...including THAT1510, and SSM2019. I believe those are pin-compatible with the INA217 chip. I also socketed the output chip...currently running a 5532 in that, but may change to a Burr Brown of some sort.

It doesn't take much processing for the 528 to really shine on bass BTW. Only a touch past 2/1 ratio, and just a little gain reduction is plenty. I find the stock EQ frequencies / bandwidths to be fine for bass.

If I could just get the gate time constant to where I'm happy with it, I think I'd be using it more as a voice processor as well.

Thanks again,
Dave O.

dave,
is there a way to recognise versions of 528 from the outside?
afaik, there is a black one, and grey one with colour knobs. which one has valley vca?
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