Studer 928 Story...

Off with the old damaged transformer...


...on with the new, annnnnnd...

Then there were two (fully functioning master summing modules...)


Yes, job's a good'un!
Must be high quality print. On lesser gear you would likely lose one or two of those plated through pads.

I know I could track back through the schematics but what are the blue trimmers for please? Level set? DC offset?

Yeah, Dave, the boards are really good lifting or other issues with the lands or traces even with the prolonged application of heat needed due to the 2-sided board; really nice to work on.

Those trimmers are in a number of places throughout all the module types...sometimes it’s for level calibration, other times it’s VCA distortion null the case of the two you see in the picture with the output transformer, those are the output level cal trimmers.
I have such a long sordid history of being obsessed with not actually using something until it’s all “perfect” and refurbished, and I usually drown myself into “improving” or otherwise modifying the device in the process...and my life being full and complicated like it is, guess what? Stuff never gets finished...projects sit...oh I do “finish” stuff but it’s usually the stuff I decide to sell.

I’ve reconnected with some old musician friends. I had to let go of a lot of friendships many years ago for the sake of my marriage. I’m not saying that’s “wrong” or “bad”, but it was incongruent with me, and it was one of countless incongruences; sacrifices that seemed to be deposited into a vacuum. Relationships *always* require sacrifices...give and take...always. But there needs to be a balance to it. My first marriage was out-of-balance. It’s not that way anymore...remarried and my wife has encouraged me to reconnect. Anyway, I walked away from a project that I think could have been *something*. Not huge, or even all that big, but something. My friends are absolutely brilliant musicians, and we really resonated together...they brought the best out of my drumming. It was hard to let it go. We had finally committed ourselves to getting into a local project studio to do some live multi-tracking...that was 1996. It was to ADAT. I stepped away before we mixed it. At some point during the last couple decades I got ahold of the ADAT masters and had somebody transfer stems to .wav files...I have all that stuff. I’ve always wanted to mix the stuff we recorded. So, my studio is far from setup...nothing is “finished”. The Studer is all scungey from its 20 years of service, the legs are all banged up, but I’m doing something very different for me...I’m throwing it together, soldering up some multicore snakes to the Tuchel connectors, loading a rack with a patchbay and only the gear needed to do some basic mixing and friends haven’t heard what we recorded in over 20 years and that was just a really bad rough mix to cassette...they are anxious to hear it...and I want to use the Studer. With the few repairs I’ve done on it it is 100% functional. I’m just doing it. It will still take some time to get all the stuff together, but my youngest son who has the audio production bug and is already pretty good with a soldering iron is jazzed about the project...we’ve made a to-do list...first up on the list was getting the console frame mounted to the legs. Done.

Hi all together,
it has been quite a while since my last post, but i have to tell some great news:
Besides one stereo and one master channel, that remain unchanged for a few more weeks as reference, i have finally finished the process.:guitar:
almost 3,5 thousand electrolytic caps, an other 3,5 thousand foil caps, about 650 opamps...
The power supplies started to get unreliable, so that I had to build an intermediate solution with some Mean Well modules. They are not too bad, but I will get sth better, probably with some low noise Daitron modules.
The next step for me is to calibrate the whole desk before i start soldering some cables to connect my new Antelope Orion HD Gen 3.
After this iI will probably get down to some cosmetic things, like repainting the legs and renewing the leather hand rest

Any news on your project?


Nothing new here unfortunately...the last 1-2 months have involved downsizing and moving and I'll be getting settled for awhile. But the new place has a small dedicated room for music/recording equipment, so, even though small-ish, I'll finally have a space again for the first time since 2013 where I can have gear permanently setup and there should even be room for a small workbench setup for continuing work on long term projects like the Studer desk and Ampex MM-1000 tape machine among others...for now, at least all the gear is in its own heated space, which I haven't had in all these years. We are doing renovations in the new place, plus there are honey-do lists for my wife and baby to take care of first, but inevitably I'll be getting back to audio projects and posting updates.
I wish you all the best with the moving and renovation!
I have done a few (quick) mixes with this new to me hybrid workflow (the Telefunken Live from the Lab sessions are great!).It's great to work with a physical desk. There is still tons of work left like building a patchbay, a siderack and such things, but it seems to move in the right direction.
Hello, I'm newbie here..
I just read your posts and experience about studer 928 console, I truely admire your vast knowledge!
I'm one who seriously considering about buying same desk.
Just want you to ask some questions about your experiences while running this desk.
Does it has good stability? I saw nice reviews about it but someone told me they have serious heating problem and lots of malfuctions. I know there is haters always but just want to check experience from real owner. Also.. is it require lots of costs to maintenance? I know this might be silly question but I'm having nightmare recap scenario for my current console now, so I just want to ask this anyway.
my concern is all about stability, I bought a console in bad condition before and had big serious issues with that and finally give up to restore it..
I don't care about just one or two channel become jammed or any other minor bugs, I just hope the console doesn't shut down too often or paralyze my entire system because of that.(it's what happening to me now)
Fortunately, the 928 desk I'm about to buy it seems in pretty good condition, rarely used, but I'm still concerned... am i just paranoid?
Sorry for my bad english, Any kind of your experience will very helpful to me,, thanks a lot!
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Please share more about what somebody told about heat issues with these consoles. What is their personal experience? There is a little warmth on the control surface that radiates from the opamps, BUT…

I’m telling you…

These consoles were built using extremely high quality components, high quality assembly standards, designed with reliability in mind…they were built for TV and radio broadcast…name another environment where a console must not go down…theatre. They were designed for that too. I have torn apart and rebuilt more mixing consoles than I care to remember at this point. I have definite opinions about what works and what fails after 10, 20, 30, 40, 50 years…both physically and electronically. If somebody told you a Studer 928 has reliability issues they do not know what they are talking about. Period. I’ve been all up in my 928. I fully expect it to keep working for decades. They did all kinds of things with the design to promote reliability AND good sound. I love my 928.
Hi, thanks for your kind reply.
About heat things, well..someone said because of 928's circuit design, each components are too close to each others. so they made hell of heat like SSL or Neve!(even more than both)also he said lifespan of components are very weak and short..
but I guess it was just trolling from someone who actually has no experience about the desk.

By the way, seems you recap all the circits by yourself.. wow. is it hard work? I can solder and built cables like XLR, Db25 connectors myself. so I'm wondering if recap work is like simple soldering or is it a completely another story?

Also I've heard it's hard to recap SMD components by hand.(correct me plz if i'm wrong)what about 928? are they built with SMD circits?

Sorry for too many questions.. ahaha
I really appreciate it.
I think that person did not know what they were talking about. Components on the 928 boards are no closer together than any other console I’ve worked on, but that’s only half the story. It’s also about the circuit design. The audio rails on the 928 are +/-15V. But they step down to about +/-12V on the boards. Less voltage means less heat and higher reliability. But it also means less headroom. Oh no! You say. But wait. Using parallel drivers and high quality hybrid opamp/transformer driver circuits, and balanced throughput audio circuits, the 928 achieves better than +6dBu nominal operating level at all stages. It has tons of headroom at its inputs and outputs, but with high reliability low voltage power rails. Smart. The output specs are telling. They don’t just give a dBu figure, but relative to the input impedance of the connected device; plenty of drive. There’s a lot more heat generated on the plug in amplifier boards on my Ampex MM-1000 tape machine. It’s 55 years old. They still work fine. The component density in terms of proximity is similar, and, again, there’s a lot more heat. And another thing, electronic components are DESIGNED to operate at temperature. You can look at the spec sheets. Typically opamps have a normal operating temperature range up to 125 degrees celsius! Is that ideal? No. But that’s hot enough to cook something. My control room doubles as my office for my day job since I work from home. I frequently have the console powered up for most the day so I can listen to music while I do busy work. It’s been hot here this summer and I don’t have AC in the control room. The console doesn’t get hot. It’s warm, but just warm to the touch. Like components don’t get over 45C. But, again, the opamps are rated up to 125C…resistors up to 155C. I could go on. That’s NORMAL OPERATING TEMPERATURE RANGE. For example. I think the person who was hating on the Studer needs to be more specific what SSL model they are comparing to so I can point out why it’s an unfair comparison. The 928, and I bet all period Studer consoles, are highly reliable. The most reliable I’ve ever operated or worked on. And the quality of the components on the 928 are high quality. All resistors are metal film for instance.

Recapping is not generally that hard with the right tools, but it is more challenging on the Studer with the double sided glass fiber PCBs. It just means more patience and skill with removing components and soldering in the new components. But don’t assume you have to recap everything. I’ve been over the top in the past. It’s preventative maintenance. It’s not always a given it has to be done.

There are no SMD components on the 928. It’s one reason I like it.
I know nothing of that Studer console save that Studer have a top reputation for superbly engineered audio equipment. However, as SB says, you don't usually need to go nuts and change every capacitor (or even any maybe!)
I shall repeat my usual advice. What is 'wrong' with the boards as they are? Degraded caps might give a worsened hum level and/or a loss of extreme LF performance (and possibly more distortion but most people won't have an AP system handy capable of showing it!) these quantities can be checked against specification IF you have the kit and know how to usd it. If you don't maybe think again before wading in?

But if you decide to change a goodly number of the capacitors it is worth making a 'form tool' to attach to a solder iron tip. This allows you to heat up both leads of the cap at the same time and it should then lift out with zero track damage. Clean the holes with 'wick'.

Recent updates..
I am happy to announce that I have finally joined the 928 Owner's Club after considering the opinions posted here and after a lot of searching and contemplation. As I did, I hope that my writing will be helpful to others, and I would like to leave my experience and impressions regarding this desk.
First of all - I was very lucky. Before I bought the desk, I heard from seller that it was in very good condition, but after a long testing, I found that my desk was in perfect condition. Literally - perfect. I didn't expect this level of condition, but all channels are perfectly normal and there are no leaks or malfunctions. The faders of all channels are in the zero position with little deviation from their nominal levels, and the group and master buses are perfectly calibrated. In general, 0.1db difference in the analog domain do not considered as error, but my desk does not have even that. LR of each master channels just perfectly matched!
This was great news for me, who suffered from a maintenance nightmare with an old Calrec, and I was very impressed. The interface is very user-friendly, even people who don't have much experience with these types of large consoles will be able to use it in no time. It's so intuitive. All functions are clear and designed to be easily understood by users. The power supplies are not noisy, but they are somewhat noisy (a little louder than the fan noise of pc), so I'll put them in the machine room. The psu itself almost generates no heat, so I don't think any other cooling device will need in the machine room. I've had experience working in a studio with a neve vr installed and the 928's power supply is very quiet compared to the heat and noise produced by neve.. The desk itself seems to be a little overheating than I expected.
The default leg position is a bit high for me, so I made a custom wooden side panel and a custom frame to mount the desk on it. -This is totally my personal taste because of monitoring

About sound - I haven't really put it into many sessions yet, and I'm talking after a light test, so it will take a while to fully understand the true character of the device. The only downside is that the headroom is a bit low. The texture when pushing the desk isn't bad, but it doesn't seem like a good desk to use that way. It felt like sweet spot is in little lower level, and it's basically clean and bit of a mid-forward sounding desk to my ears. EQ is pretty cool. It's a little bit of shame there is no LP filter and more detailed features, but basically, you can sculpt as much as you want. To be honest, personally I'd prefer 'mojo' of calrec little bit more.. However, the 928's EQ also seems to have an attractive enough character in its own way. The impression of HF is almost the same, but Studer sounds more transparent way. LF is also impressive..
The compressor/limiter on the GR channel and master limiters are also not bad. but little bit boring.. If I use it a little more, the impression may change, but I was expecting something more musical..serious stuffs but it doesn't feel that way, it feels more like a limiter for broadcasting. (sorry that i'm keep mentioning about my old desk, calrec's master compressor is fantastic though. nice solid ssl type bus compressor!)

It's only been about a week since I installed the console and started using it. so is my first impression. Overall a decent desk.. I'm very happy with it!
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Hi. Thanks for sharing your impressions!

What size is your frame and what modules are loaded? Share some pics of it here? What serial number and manufacture date?

Headroom is a bit low?? It’s +6dBu nominal, and I think can handle +23dBu cleanly, and that’s without the optional input transformers…add another (I *think*) 6dBu to that with the transformers. What inputs are we talking about? My experience is it’ll take whatever you throw at it. Am I correct you have balanced sources connected to it? Don’t think of the 928 as a color box. Think of it as command central for whatever exists that is connected to it, clean or colorful, and it’ll not get in the way, no matter what buss or path you’re using, of whatever defines your sources or outboard gear. That’s the first beauty of it. But there IS opportunity for color with the 928, not on the input side, but on the output side on the master busses and/or mono groups with the hybrid output drivers. So setup your inputs for clean signal management, but on the summing and output side try really driving the output levels. It’s not crazy obvious, but to my ear when you push the summing outputs the LF and HF ranges stay clean but the midrange gets this bite on the edges of the transients and leading program material…a dirty bite that brings a nice presence to the LF and HF material. I absolutely love it. And it does it without breaking a sweat. It’s pretty sexy. The circuit design is pretty sexy too…high quality transformer output nestled in the feedback loop of a high quality opamp-based driver…it’s slick. And the EQ…right…it’s clean…I feel like the hi shelf filter has a nice sweetness to it though and what I really like about the EQ section overall is I grab the knob that should address what I want addressed, turn it and *boom* it does exactly what I expect and need it to do. No fishing around because the EQ doesn’t sound good…I hear the problem frequency or mash, I know (for instance) it’s in the low-mid filter range, raise the gain, sweep the center frequency…there it is…cut…done. Hey that sounds better…on to the next issue. No drama, no “well that didn’t help”…just boomdone. It’s one of the easiest most satisfying EQ sections I’ve used on a console. Yeah it could be more complex…but then it would probably be too much for me. 4 sweepable bands with hi and lo shelf and two mid peaking filters is enough for me, plus the fact the mono input modules add switchable Q settings on the mid bands, and both mono and stereo modules have the 70Hz switchable HPF. There are three film caps (six on the stereo modules) that set the frequency of the HPF. I bought a bunch of film caps and dip headers so I can make up plug-in cap arrays to easily change the cutoff frequency of the HPF. So at some point I’ll mess with that. No it’s not as convenient as a swept filter, but better than fixed. Regarding the group compressors and master limiters, yes this console was built for the broadcast industry, so the capacitors that set the attack time range make for an overall short attack range. This may, depending on the program or source content, make the processors seem less “musical” because of the fast attack. The attack timing is program dependent, using VCA circuitry. But those caps that set the range of that attack timing are what determines that range. At some point I want to mess with those caps to increase the attack time range and see if that makes the compressor/limiter more musical. I will say though, my first impression was like yours, but that was right after first-blush impressions and all I had available to test with was program material that was already through post production. It’s really a different story when working with raw sources. Maybe that doesn’t apply to your experience but I feel less urgency these days to mess with it. But I have spare modules so eventually I’ll mess with it. It’s a high quality dynamics processor, but it seems it gets a little bit of a bad rap because, in my opinion, it’s misunderstood. It may not behave as one typically expects because, I believe it was designed with the broadcast world in mind. I’ve come to like it better as I’ve gotten to know it better, and additionally I’ll see what happens when I mess with it a little and adjust the attack time range.
So it’s been awhile since I’ve updated this thread…I still have the Studer, I still love the Studer…and I’ve got a few things of questionable interest to share as far as the bits and pieces that have happened since the last update about 18 months ago.

First of all I *finally* got to the point I had some time and could prioritize rehabbing the smallish 8’ x 10’ space I had off the garage for music/home office purposes…some budget carpet tile and trim, electrical work…the room was previously bare concrete and used for storage, and only had minimal power available on a shared circuit. Here’s the Studer after getting the carpet and trim done, adding a dedicated power circuit, adding receptacles, and moving it in:


I’ll cut to current day for a second…I got that all accomplished with the music/home office space, and then several months ago…we moved again. But it’s been a good move and we hope to stay put for a long while. The new music/home office space is a bonafide room inside the house with about 50% more space plus a closet and some interesting ceiling facets…and a window…second floor. It’s an upgrade for sure. It was interesting getting the Studer moved in…even with the legs and all the modules removed the frame is still heavy, and big…even with both me and my brother-in-law it was a challenge to move. Don’t even ask me about the Ampex MM-1000 2” 16-track. Anyway, we’ve been steeped in home improvement projects, and the day-to-day family and work demands for many months…so this is how the Studer looks at the moment:


Sigh. BUT, the future looks bright for finally getting things operational…I have all the patchbays, multicore wire, connectors, racks, etc., and I’m slowly getting closer to the point when I can focus a little attention in getting things setup. In the meantime I’m doing some work on a modification to the mono input channels that will replace the fixed HPF with a swept filter.


I did a bunch of stuff after getting the console moved into the space at the last house and before the move. More on that in the next post.
So if you look back in post #71 you’ll read about problems with the power supply umbilicals that came with the console. The frame of my console is made up of three “buckets”, two 16-slot bucket and one 12-slot bucket, and there is one multi-rail power supply per bucket. To summarize, the guy I bought it from obtained the console from a university auction. The console had the power supplies but no umbilicals when he bought it…misplaced when the console was decommissioned at the university broadcast studios. So he made some up. He had a hard time finding the right components, mainly because I think he didn’t know where to look. So the cable was the wrong type (too heavy a gauge, too stiff, overall OD too big), and the result was the solder joints to the connectors had poor integrity (they were coming loose), and it wasn’t possible to fit the locking hoods for the Tuchel connectors at the console backplane…the seller said he couldn’t find the hoods anyway. So it was just two 30-pin Tuchel connector housings held in place by the friction of the pins and sockets, fighting the pressure of three large stiff cables. I was always either reaching back there and pushing them back in as they slowly tried to back out, or finding some crazy non-conductive way to wedge and hold them in place. And the circular connectors at the power supplies? He was never able to source the locking rings, and one of the three connectors was also missing the strain relief. So in all truth, the umbilicals were *super* sketchy, not really safe…not long after I got the console in January of 2019 I acquired all the parts and materials to make a proper set of umbilicals, but I hadn’t put the parts to use…until last year. But there was a related parallel project also summarized in post #71 regarding…power supplies.

There are basically two generations of Studer 928s…an early and a late. Production of the 928 started in the mid-1990s and the transition to the second generation happened sometime in the year 2000 I believe. There were no changes to control features or cosmetics, it was all PCB refinements, some changes to some components for better noise floor and isolation with the talkback system among other things…and changes to some of the ground scheme…all of those changes were detailed in TSBs for retrofitting to the 1st generation consoles. The other major thing that happened was a complete change in the power supplies. Studer designed and manufactured the power supply backplane PCB assembly on both versions of the power supply, which includes the low voltage logic power supply, but for both early and late generation versions the rest of the guts were farmed out. And so there are no technical documents included in the Studer documentation outside of the backplane PCB. I originally thought the complete tech docs for the later generation power supply were included with the Studer docs, but they are not. There’s a note that refers the reader to manufacturer of the guts for the tech docs. Well the guts of the early generation supply, as I noted in post #17, were made by a company called Delaire, Inc, which was acquired and dissolved by another company about 20 years ago…no tech docs to be had there anywhere. I tried. And I don’t like that because if repairs are needed in the future it’s more difficult without the docs. And both versions of the power supply are switching instead of linear type, which means they are more complex to troubleshoot and work on. At least for a guy like me. So at some point I learned the later generation supply, rather than a monolithic PCB housing the +/-15V and +48V power rails like the early generation Delaire supply, was made up of high quality TDK Lambda modular power supplies…high-performance, highly-regarded off-the-shelf power modules…so cool. You can still find modules NOS for cheap…I figured it would be easy to get ahold of schematics, layouts, parts lists, etc. for the Lambda modules, and I had an opportunity to buy a set of three later generation supplies…quieter cooling, nicer chassis, higher power, easier to service…more on-par with the console. So I bought them. I then discovered it wasn’t as easy as I thought to get the tech docs…but after some reasonable and congenial persistence with TDK, and signing a hold-harmless agreement with a number of conditions, they provided the docs. So I now have a full set of tech docs for the later generation supplies. I also found a pair of the 15V modules online NOS for $60 shipped for the pair. So I have backup. The later generation supplies have a slightly different pinout at the supply end, so it was a decision to make if I was going to build up the new umbilicals with the pinout for the supplies that came with my console, or use the set of later generation supplies and build the cables up for those supplies. I chose to do the latter. But before that I had a couple things to do first.

The set of later generation supplies I got originally powered a 928 operated by an Israeli broadcast company…television I think. What I know for sure is it was not in a clean environment. Here is what each of them looked like inside:


So I did my thing and cleaned them out, pulling the Lambda modules out, vacuum, brush, air duster, microfiber cloth and window cleaner where needed…got them all to look like this:


By comparison here’s the inside of one of the early generation Delaire power supplies…monolithic PCB…not so easy to remove, certainly not replace…if for some reason a Lambda module goes down, with a motorized screwdriver and one bit I could have the module swapped and back in service in less than 5 minutes easy…but here’s the inside of the Delaire supply:


It’s not a “bad” supply…powerful, clean, etc. It’s just nothing like the later generation.

Then the next thing I wanted to do was replace the fans. They were all working, but when executing a cold startup one of them would do a little whale song for a few seconds on, so that told me it was time to replace all of them. I purchased some fans that, on paper, where quieter than the original fans, with comparable airflow. I bought them, installed them, and it turned out they were louder…it all depends on the measurement parameters…the new fans may have produced less dB in sound pressure level, but the nature of the sound, including a resonance with the three fans together, made them more intrusive with mixing. So, back to the drawing board…I ended up getting some Noctua fans…they are much better than the factory fans, with even some improved air flow…a win-win.



I then noticed something odd with the output and redundant supply link connectors on the backplane of one of the supplies…two of the 10 sockets each on each connector are supposed to be linked via the PCB to which they are mounted…sockets for the +/-15V rails. So there are supposed to be two sockets for each rail. On one of the three power supplies there were no traces between the two pairs of sockets on each connector…everything else looked the same between all three of the PCB assemblies, it’s just on one of the power supplies there were two sockets not connected to anything; only one socket per 15V power rail. I didn’t like that. It’s easy to access the back of the sockets on the backside of the PCB, so to bond each pair of sockets I found some solid core copper wire that fit just perfect in the back of the sockets, and fashioned some pieces into short links:


There. That’s better:


So with the three power supplies tested, cleaned and polished up, with new fans installed, and the one backplane PCB revised to match the others, it was time to make the umbilical cables.

Here’s what a parts kit for this looks like to make a 4 meter set of the three umbilical cables for a Studer 928:


Note the way it is setup on the Studer, two power supplies merge into one Tuchel connector at the frame, so there are three of the 10-pin circular Hirose connectors at the power supplies, but only two 30-pin Tuchel connectors at the frame.

I started by soldering the circular connectors to one end. This was a little bit of a challenge because the size wire specified was *just* the right size to slide into the solder cups on the connector, and the wire being 16AWG had some stiffness to it…so trying to manipulate the conductors into the cups in sets, because the length of wire inside the connector housing was short…not much flex was available to manipulate the conductor ends and in order to access the solder cup to solder the wires in you can’t just shove them all in at once…you have to do it in rows…anyway it was a little bit of a challenge, but came out well:




Then it was on to the Tuchel connectors, which was a little bit of a puzzle, because of the different pin configuration between the two connectors. And there are groups of pins that are bonded in the connector. So that was step one…each solder lug on the Tuchel connector has two holes, one for the conductor and the other for strapping lug to lug. Here’s an example of one of them all done having respective pins strapped according to the diagram under the connector:


And then from there it was just careful and strategic work…this is the first set of Tuchel connectors I’ve worked on…learned as I went:





Finished product:


Then it was on to the cable for the third supply…