hi everybody,

this is my first post here after being just a guest for years now. i learned so much from this forum, a big thanks to all of you!!!!!

after soldering all of my cables and some stomp boxes, i wanna get deeper into the diy modding and building of mic pres.

i purchased a symetrix sx202 and i wanna do some tweakings to it, but i can't find any specific info about the mod or different mods.

all i know, is that monte mcguire postet his mod some years ago and it became quite famous, but i can't find any list or text from him.

all i know is that there was a txt document online, that has been removed
now.that's all i found out after googling the mod for hours.

i really hope anybody can help me!!!

thanks in advance,

alex

I think this is what you're looking for:

thanks man thumbsup

hi,

i finally received my sx202 and i compared it to the mod list of monte mcguire.

i can't find the 'retrofitted resistor' with 511 ohm - can anyone show me ?

as i have no problems with the understanding of the first two mods ( opamp change and ssm 2015 compensation ) i don't know what really to do with the coupling between the 2015 and output stage.
can anyone explain in simple, nearly tech-free words?


btw, i searched a few days for the lt1469 opamp here in europe, couldn't find one single dealer.i ordered now directly from linear technology, hope it works out. does anyone have a dealer of the opamp here in europe, if my order should be refused?


hope, anyone is willing to help a stupid rookie

Just wanna ask how is the outcome of your Symetrix sx202 mods? Sure wanna hear from you...

You have an older model that does not have the 511 ohm series resistors into the 4560 opamp stages. You can add them by cutting the trace and soldering the resistor across the cut. Also, there are better choices for the 4560's, I use National LM6172's. I replace the .01 uf psu bypass caps near these parts to .1 uf mono ceramics. That seems to tame some stability issues.

Jim Williams
Audio Upgrades

well, it's been some time, since i've done this and to be honest, i'm not completetely concinced with the result.

i replaced the opamps with the linear ones ( 50 euros with tax for 6 opamps dfegad) and compensated the ssm2015.
the first channel is fine, but better ?! - might be a wee bit better, it sounds ok now.
the second channel had a buzz on it in stock mode, and still has a buzz, when pushing the gain, so i decided to not use that channel.

maybe someone has a clue, what it might be?

i bought another 202, right after i finished the first one, to check where the missing 511 resistor should be.

it turned out to be a rev. b board , so no resistor here, as well.
and i had to damage the whole body and the xlr connectors on the board to open the body to finally reach the board, really frustrating.

i changed the opamps here, as well and did the ssm compensation.
the opamp change turned out to be ok, but the ssm compensation resulted in distortion on both channels, and so i went back to stock caps.

basically, the second 202 has just the opamp changed and the rest is stock.

i have a stock 302 and my (half)modded 202's and i like the 302 a bit more.
it has slightly less noise and phase reverse on both channels, but that's it.




thanks for your response jim, can you show me where the trace is (are) to the opamp(s).
btw, soldering the reistor is better on the back of the board, right? never done this before.

thanks for your time and effort.

best,

alex

Ummm, there's a slot inside the XLR's designed as a locking screw, use a greeny and give it a 1/8th turn to the right to losen the lock, then you can slide out the pcb without damage. If in doubt, get help.

Jim Williams
Audio Upgrades

Jim, can you PM me on the cost to do a full upgrade of an SX202?
Mine is Rev G, 1991 with BA4560s.

I know this thread is old but I just picked up a used SX202. Not sure if I would trust myself to do the mod. Is there some any one that charges a fee to do the mod?

The SX202 performs well and sounds good stock. The point of modifying it is to learn something, and also to get a higher-performance preamp without spending real money. Paying somebody else to do it would defeat the purpose. There are several new preamps out now that will out-perform the SX202 for less than the cost of buying and paying somebody to modify the SX202. In particular, the Shinybox SI excels at what the SX202 was trying to do, and the price is very reasonable.

Rather than paying $Lo.ts or €Ma,ny or even £Cra,zy for the hard-to-find LT1469, there are plenty of other chips out there that are much more readily available and affordable (but still very high performance) you could try instead. The single most worthwhile mod is to replace the 4560s with good machined-pin sockets so you can drop whatever you want in there without soldering the IC directly. I would probably start with an OPA2134 if I were doing it today. I would also replace all the electrolytic capacitors with Panasonic FM or Nichicon HE parts of the same voltage rating and package size (which will result in a decent increase in capacitance).

alex79: The hum in your right channel isn't normal. There's not a power transformer in the box radiating to one side more than the other. These units are known to be susceptible to EMI especially with longer input cables and certain types of microphones, but look for faults elsewhere too. Bad solder joint on a ground connection, or even something as simple as physical proximity to another device with a tendency to radiate mains-frequency EMI. In any case, it can be fixed and in doing so you'll probably learn more than you learn upgrading op amps and capacitors. Not to mention getting another nice preamp channel for your efforts. I'm sure the damage you did to the chassis trying to get it apart isn't helping the hum/shielding situation, so I'd start by cleaning that up.

Those D-series Neutrik XLR connectors are a pain in the ass. I've got several bent screwdrivers from trying to lock and unlock them. We don't use them in our products for this very reason. But don't thrash on the chassis trying to get it apart. All the magic happens inside that 4th hole in the XLR connector, and that's where you should direct your attention. Counter-clockwise to unlock, clockwise to lock.

This is my first post here even if I read here in this really prof forum from a long time.

I would like to draw your attention on PSU of the SX202 at 220v, it is not the same given to the domestic costumer of symetrix and it is rated at 19Vac, I never get importance to it but when last week I bought a used 2 unit here in Italy, reading about how US user paid attention on the PSU that nowday is rare to find because of the importance to have exactly 16Vac of output, I do some mesure on it, and I come out "disturbed", why?

The export PSU send out 23Vac!!! (against the 16Vac of US PSU and this could be a good new for US owner that need to find a replacement to the hard to find original PSU) but what I found not serious from the guys of symetrix is that with this extra power the 78M15 and 79M15 after few seconds become already untoucheable because of their hot temperature!

Here I quote an old post from ulysses on rec.pro.audio:
-----------------------------------------------------------------------
Looking at the schematic, I can see that all of the pre-regulator
filter caps are conservatively rated such that an input voltage up
around 25VAC would not destroy them. If there was any detrimental
effect from increasing the power supply voltage by a few volts, it
would be increased dissipation in the 78M15 and 79M15 voltage
regulators. They would run a little hotter and die a few days sooner.


I'm sure any quality AC transformer in the 15-20VAC range and capable
of at least 200mA will be fine.
ulysses

------------------------------------------------
Only the range sometimes is few mA more than 200 so at least 250mA will be preferable, (mine , the export PSU is rated at 500mA that means that is possible to run 2 units with it).

What I note too was that even the LT1469CN8 run hot but the 15v they receive is still less than the max 18v they are rated so I dont care to much about, or I must care?

At the end my question is: I know a factory that does PSU on specific if I ask them to have one at 16Vac and at least 300mA I will have some benefit other than longer life of 78M15 and 79M15 ?

So, I'm going to piggy back on this thread. I'm doing my best to acquire an SX202. I'm rady to mod if as soon as I get it. asically, I'm going to do the first 2 mods he recommends (output amp changes to an OPA 2134 and SSM 2015 compensation capacitor changes) and see where that gets me. It seems to be the low-hanging fuit.

Has anyone revisited the SX202 and updated some recommended upgrades?

Hoping to get either some specific recommendations or a true revisit of the McGuide mod list.

Thanks in advance.

I have 3x SX202, one modified (different revisions).

they are ok stock. I paid 30$ each. better then any smpro-audio stuff. but great.. no.

Depending on condition that sounds about right, I would never pay more than $100.00, they need TOO much for what they are, and a wall wart with NO real ground is a huge issue with me..I would mod a Mackie first..or at least USE the supply from a Mackie...
My.02 cents.

And 16VAC in is about right, would NOT go higher, I would add heat sinks to 7815 IF not already present..

And the SX202 is RIPE for mods, needs EVERYTHING...

I've made several wonderful-sounding albums using stock SX-202s. They're good preamps. You can beat them handily with what's around today (try the Shinybox SI if you want my biased recommendation) but they're no slouches by any means. Reasonably clean, and musical. Susceptible to RFI with long mike cables and/or certain microphones.

Deltec, did you measure your 23VAC under load or open circuit? The AC transformer will put out some extra volts when there's no SX202 plugged into it.

Heatsinks on the regulators are one solution. Or (after consulting the data sheets of all the parts inside), you might could replace the 7815 and 7915 with 7818 and 7918. That'll kill some dissipation, and increase your headroom slightly. But is the 2015 rated for 18V? Idunno.

maybe that's the reason you design gear and other people record

I use the sx-202 on drums.. (toms mainly.. and mostly for the trigger pad). heh

I had some good success on cookiemonster vocals with them. better then mackie. (I was young.. so sorry)

That AC won't drop much, those chips draw very little current.
The rectification is half wave, so that reduces the DC input voltage a little.

Those use 78M15 and 79M15's. I would replace them with the 1 1/2 amp versions, the 7815/7915. An 18 volt wort will give a 22 volt DC to the reg's. Higher will stress the heat on them. There is not enough room insides to mount heatsinks so forget that. A 16 volt AC wort works great. I use a 2 amp version to provide some extra current. I buy them for $4 from All Electronics in Van Nuys, CA.
All Electronics | Electronic and Electro-Mechanical Parts and Supplies at Discount Prices

Back in the "good 'ol days" we would place a sleeve of heat shrink tubing around a regulator that had no heat sink and no room for one. That helps spread the heat around the entire die to help prevent hot spots from frying the regulator.
It was an old 70's trick.

Jim Williams
Audio Upgrades

Jim (or anyone),

I managed to heatsink the regulators in mine by attaching to the front of the them, though I'm not sure how much good that does with just the top half in contact.

I also switched the regulator types as you suggested, but my 202 now has an issue which has been driving me nuts over the past day. I tracked it down to the positive supply not showing up on power up for unknown reasons. I've triple checked and resoldered everything in sight and am now guessing either the type of regulator I chose or the AC supply is causing it. Sometimes if I power down, then right back up, the +15 shows up and is fine.

The ones I'm using are an L7815CV and an LM7915CT. I'll go look for info on the CV/CT designations. Also, my 16VAC supply reads 18V with no load and I do indeed get about 23V at the input pins to those regulators. I'll see if I can find something closer to 16.

Thanks!

The thread that wouldn't die...

I've picked up an SX202 and am gradually modding it. I've replaced the op amps and now I'm sourcing parts to compensate the SSM 2015 as per the instructions listed.

If anyone has any leads on where to pick up the 7.5 pF and 56 pF capacitors recommended, I'd greatly appreciate the help. I've found some possible sources for the caps, but I haven't found any information regarding the desired voltages for the capacitors. Is that a critical value or can any cap from 100V to 1000V work?

Thanks in advance for the assist.

-Rick

The voltage rating isn't critical. Anything over 50V will be fine. The important thing is that you get the right physical size and shape, and NPO or COG dielectric.

Search for Capacitor at Digikey.com and then click on the "ceramic" selection. You'll get a parametric table that lets you narrow the selection based on parameters you care about. I would look for the package style you need, and choose the "COG, NPO" dielectric. You'll find that 7.5pF caps in NPO/COG radial package are not stocked, so you'll have to settle for 7.0 or 8.0pF, or you could put two 15pF caps in series (in which case you might choose axial-lead caps). 7.0pF is probably close enough. I've used caps from BC, Vishay, Murata, Panasonic, Epcos, and others, but I generally buy Kemet or NIC ceramic caps for production, depending on who I'm buying them from.

Maybe you listen with your eyes instead of your ears. Suits you for selling gear rather than using it.

I'll stand by the recordings I've made using stock and slightly modified SX-202s. I wasn't trying to impress anybody with what I could buy, I was just making records I like. Sure, I have plenty of other preamps to choose from now, but if I ever found myself with nothing but a rack of these, it wouldn't stop me from making great recordings. I've made good and bad recordings on a wide variety of equipment, and I know which is which.

hi,

How the@$%^^&*()!@ do you open this box up? Ive read that you need to unscrew the 4th screw in the xlr but%^&*(. i can't seem to do it tonight.

also......(im already pissed with this box and ready to trash it)
my adaptor makes it light up but it doesnt work...i dont think i have the exact ratings -its a 16v 400ma, is it the ac or is the box messed up. I just bought it without a psu.
would an exact psu make it work?

pardon my french
and thanks in advance

Asrvegas-

I feel your pain. That XLR lock thing is a b*%#h.

From what I remember, it only turns a few degrees to one side to unlock it (90 at the most). It also takes a really narrow screwdriver bit. I had to take one of those little jeweler's screwdrivers and file the corners down so it was sort of spade shaped to get into the slots. It may help to shine a flashlight or something into that hole and look in to see which way the slot is facing so you'll know what you're trying to grab. Remember, it just turns a tiny bit to get the little tab to move over to one side.

And yes, I would guess that supply may be too weak. I think mine is over an amp (maybe an 1100mA).

Hope that helps!

Grow some spherical dangly bits. And pull out your warn and dull cutters.

(observe attached pic).

And now, for what the internet hype has been clamouring for:

Yetihunter's Super Yeah Extensively Tested Best Mod For The Sx202 Ever

Step1. Order a pair of solder lug panel mount female xlrs.
Step2. Order Wire.
Step3. Solder
Step4. Hand hammer case so it somewhat resembles what it looked like before.
Step5. Screw together.

Mod Complete.

Je plaisante!
Mon ami et j'ai bu quelques bières. heh
We got a little out of hand.

Be very careful. And my suggestion is as bad
as the D series ("d" right?) connectors.

I just bought one of these. Rev-C board, in very clean, stock shape. Given the time since the 'McGuire' notes were done on mods for these units, has there been any real change on the suggested opamp changout? Mine has the BA4560's in it. Is the LT1469CNE (available from Linear Tech for about $5.50 from their website) suggested still, or the JRC or Fairchild 5532?

I noticed one of the earlier comments in this thread suggested a Shinybox SI for 'about the same amount of money' - Darn, I just looked them up... $500! each for a single channel... I'm sure they are nice, but I'm hoping this will be a nice upgrade from my Soundcraft Compact mixer pre's which aren't too bad...

Mine had some bending of the lid where someone had tried to remove the cover without releasing the XLR locks... those are ok once you figure it out, but a real pain until that moment!

Also, does anyone have a copy of the schematic for the Rev-C board?

Thanks

Hi,

I'm considering picking one of these up and am wondering how it would compare to my DMP3?

Is there a really easy mod I could do the the SX202? Would it be possible to just swap out the opamps?

I am currently selling a pair in the classifieds.