Hi,
I'm embarking on a project to overhaul my Studiomaster 16-16-2 mixing desk (actually 20 channel with a four channel expansion). I think it's a decent sounding desk and I've made some good recordings on it (https://ditto.fm/cowboy-films if you're interested) but the pots and faders are all scratchy, despite efforts to clean them, and there's too much noise/hum for my liking. I overhauled the PSU about two years ago, replacing all the electrolytics, and that went some way to reducing the hum but I'd like to do a full overhaul now.
Firstly, information on this desk is scarce. I can't find any schematics online so I suspect I'm going to end up having to trace the circuit from the PCBs. If anyone has any information on it, that would be fantastic.
This is the desk in question:
It has 20 channels, 16 busses and tape returns, three band EQ with swept low and mid, two post-fade sends and one pre-fade.
The construction is semi-modular, with individual channel cards linked together by push-on connectors. One long connector carries power and busses/auxiliaries and the lower smaller connector carries 8 more busses. There is a separate ground wire soldered to bus wire on the faders. There is a lot of room under the channel cards at the back if anything needed adding.
The channel cards look like this:
The design seems very basic:
So far, my plan is:
I am also considering the following:
I've also been semi- considering some 'advanced' modifications:
Any help/suggestions would be greatly appreciated. I'm in no rush to get this done so while I've got it apart, I might as well do as much as possible within reason.
Thanks,
James
I'm embarking on a project to overhaul my Studiomaster 16-16-2 mixing desk (actually 20 channel with a four channel expansion). I think it's a decent sounding desk and I've made some good recordings on it (https://ditto.fm/cowboy-films if you're interested) but the pots and faders are all scratchy, despite efforts to clean them, and there's too much noise/hum for my liking. I overhauled the PSU about two years ago, replacing all the electrolytics, and that went some way to reducing the hum but I'd like to do a full overhaul now.
Firstly, information on this desk is scarce. I can't find any schematics online so I suspect I'm going to end up having to trace the circuit from the PCBs. If anyone has any information on it, that would be fantastic.
This is the desk in question:
It has 20 channels, 16 busses and tape returns, three band EQ with swept low and mid, two post-fade sends and one pre-fade.
The construction is semi-modular, with individual channel cards linked together by push-on connectors. One long connector carries power and busses/auxiliaries and the lower smaller connector carries 8 more busses. There is a separate ground wire soldered to bus wire on the faders. There is a lot of room under the channel cards at the back if anything needed adding.
The channel cards look like this:
The design seems very basic:
- The mic preamp looks like it's four BJTs into a TL071 op-amp.
- The three-band EQ uses a single TL072 (I don't know how).
- The line input just feeds into the mic preamp via a pad.
- There are no other op-amps on the board. The insert send it driven directly from the EQ op amp, the return drives the fader.
- There is no post-fade amp, the fader connects directly to the pan-pot which then drives all 16 busses, the stereo bus and the auxiliaries.
- The clip indicator is hidden under that switch board on the right.
- There is a single mylar decoupling capacitor between the power pins on each op amp.
- There are no mute switches.
So far, my plan is:
- Replace all pots and faders.
- Replace all electrolytics.
- Modify pre-fade send to be post-fade.
I am also considering the following:
- Is there any point replacing any of the mylars? (the consensus seems to be no so far.)
- Could mic preamp performance be improved by replacing the 5% carbon films with better matched metal films?
- Could hum be improved by replacing the bus grounding with a star-grounding arrangement?
- Are there any other modifications that could be made to improve things.
I've also been semi- considering some 'advanced' modifications:
- Adding a PCB with a separate line-input amplifier instead of the padded-down mic input.
- Adding mute switches
Any help/suggestions would be greatly appreciated. I'm in no rush to get this done so while I've got it apart, I might as well do as much as possible within reason.
Thanks,
James
way cool...i'm a 16/4 owner myself and yes info on these is hard to come by
have a look here https://www.florian-anwander.de/studiomaster_16_4/
have a look here https://www.florian-anwander.de/studiomaster_16_4/
I've now traced out the schematic from the channel strip PCB, minus the clip indicator which I haven't had time for yet. I've attached it as a PDF.
The parts are labelled as follows:
I think it's all correct as it all seems to make sense but if there's anything odd you notice, let me know.
My main observation is that there is no post-fade amplifier - the pan pot, all busses and auxiliaries are driven directly from the EQ output so there's potential room for improvement here.
There are also back-to-back electrolytics in a couple of places, also of quite small value compared to others in the circuit, so I wondered if replacing with non-polarised electrolytics would yield any improvement.
I'm going to analyse it all more closely and look for potential places to improve but I thought I'd post it now, since I've finished it.
The parts are labelled as follows:
I think it's all correct as it all seems to make sense but if there's anything odd you notice, let me know.
My main observation is that there is no post-fade amplifier - the pan pot, all busses and auxiliaries are driven directly from the EQ output so there's potential room for improvement here.
There are also back-to-back electrolytics in a couple of places, also of quite small value compared to others in the circuit, so I wondered if replacing with non-polarised electrolytics would yield any improvement.
I'm going to analyse it all more closely and look for potential places to improve but I thought I'd post it now, since I've finished it.
I haven't looked at those boards yet, but judging by available schematics of similar desks, I'm assuming so.
I used to maintain a seemingly identical mixer to the one you have - many years ago and have a complete set of schematic diagrams dated 1986. Also have a colour brochure showing the range of Studiomaster mixers, including the 16:16:2 - which was probably their 'flagship' model, featuring MIDI automation!
Do you have the EP3 power supply?
The microphone amplifier is roughly similar to the one you have created, but with some differences (which might be errors in your drawing?). The schematic I have is issue 3 dated March 86 drawn by P Almond.
The drawings are A3 sized, so tricky to scan - but I will be happy to let you have them if they will be of help to you?
Do you have the EP3 power supply?
The microphone amplifier is roughly similar to the one you have created, but with some differences (which might be errors in your drawing?). The schematic I have is issue 3 dated March 86 drawn by P Almond.
The drawings are A3 sized, so tricky to scan - but I will be happy to let you have them if they will be of help to you?
Hi,
I've had a chance to work on this a little bit more after being busy with work etc. It's not the EP3 that I have so I wonder if the mixer you worked on was a later model. This one doesn't have MIDI automation.
I've been trying to track down replacement pots but it's a seemingly impossible task. I can find the correct values but finding them with D-shafts or with the correct sized thread is the difficult bit. Smaller threads isn't too much of a problem as the sockets and switches should keep the cards in position and then I can use washers on the pots. The shafts are more of an issue, though, as it will mean that I have to replace the knobs as well.
The faders are also a problem. Finding 100mm 5k slide potentiometers is easy, but I can't find any with the correct spacing for the mounting screws. Everything I find has them spaced by 120mm but the ones on the desk are 110mm.
I've had a chance to work on this a little bit more after being busy with work etc. It's not the EP3 that I have so I wonder if the mixer you worked on was a later model. This one doesn't have MIDI automation.
I've been trying to track down replacement pots but it's a seemingly impossible task. I can find the correct values but finding them with D-shafts or with the correct sized thread is the difficult bit. Smaller threads isn't too much of a problem as the sockets and switches should keep the cards in position and then I can use washers on the pots. The shafts are more of an issue, though, as it will mean that I have to replace the knobs as well.
The faders are also a problem. Finding 100mm 5k slide potentiometers is easy, but I can't find any with the correct spacing for the mounting screws. Everything I find has them spaced by 120mm but the ones on the desk are 110mm.
Last edited:
Actually, I've just found that they're 90mm, rather than 100mm faders. I'm not having any luck finding these at all.
Not many mixer manufacturers used 90mm slide faders (thank goodness) - I don't think I could get them 25 years ago.
Cleaning the ones you have might be the only option I'm afraid?
Cleaning the ones you have might be the only option I'm afraid?