tchgtr
Well-known member
I just acquired one of these for not very much from a local Craigslist sale. There isn't a lot of info on the web about them, so I thought I'd start a thread here and see what happens. Fortunately, this one came with the manual and schematics.
This is a UK-made mixer from around 1990. The designers went on to Midas and Audient. The S Series is designed for live work, according to the DDA website (ddaconsoles.com), but I'm finding that it works and sounds great in my home studio. The one I have is a 24-channel version, but it's in a frame that can hold 32 channels, so the search is on for more channel strips. Schematics can be found at the website, but I will post some here for convenience.
PSU
The biggest problem with the mixer was the power supply. I took a chance on it when purchasing, as the PSU was obviously fluctuating quite a bit when I first examined the board. Meters were swinging about and the V+ and V- indicators on the PSU would go on and off. P48 seemed solid. First thing I did was recap the PSU.
Opening it up, I found one 12,000uf and one 10,000uf cap in the +- section of the supply. I'm no genius, but this seems to me to be asking for trouble, since we want the +- voltages to be consistent. The schemo calls for 10,000u in this place, but good ole' All Electronics had some 15,000uf Panasonics in stock, and in they went, as well as replacing all electrolytics in there with slightly larger values.
However, the voltages were still fluctuating wildly, and it took some more poking and prodding to discover that the problem was merely that the 2N3055/PN3055 transistors were not bolted down to their heat sinks properly. Perhaps the insulation between them and the heat sinks had shrunk over time. It was amazing to me that a light tightening of the nuts immediately solved the PSU problems, and ever since it has been rock solid.
It has a fan, which was not working, so I vacuumed it out and sprayed it with contact cleaner. Sure enough, with some coaxing it slowly started to rotate and get up to speed. Seems reliable now. I'm glad, because it was glued in place at the factory, and was going to be quite an ordeal to get loose. I imagine I will have to do this at some point in time...
Voltages are now @ + and - 17.3V. All good, except P48 is up around 51V!
MASTER CHANNELS
The obvious problems I found were that the left side of the headphones was much quieter than the right, and the Monitor output was strangely putting out mono on one side (into both channels!).
The schematics were a time saver here. A simple recap of the phones amp fixed the headphones imbalance, and for some reason the wiring from the Monitor out XLR jacks to the card connectors was all wrong. Mix out was OK, and I can't imagine why someone wired the Monitor out the way it was. Once these items were fixed, the Master channels were working fine, and I have since replaced the electrolytics with Panasonic FCs, using stock values everywhere, except in the signal path coupling between stages, where I upped the values to 220uf.
No bypass caps on the signal path yet, but thinking about trying it. I like the balance on the mixer now and the high end is present, but not strident, so I'm leaving it alone for the moment.
GROUP CHANNELS
The groups had few problems, other than dirty faders. They have now been recapped, again with 220uf in any stage coupling caps. The schematic calls for 68uf in most coupling caps, but the original coupling caps in the board were mostly 100uf.
However, these caps had some discrepancies from the schematics.
C31 was 22uf on all 4 group channels, but the schemo called for 100uf. I installed 100uf.
In the group and master channels, there are sections labeled EBO 1, 2, 3,...etc.. I assume this means Electronically Balanced Output. On the group channels one cap in EBO 1 (going to the Matrix 1 output) was consistently backwards from the PCB printing as well as the other 3 caps in the EBO section. on all 4 cards. This was perplexing, to say the least. I ended up matching the other caps polarity and PCB labeling, and so far everything seems fine. I'm using Matrix 1 as a send for parallel drum compression, and it works.
INPUT CHANNELS
All 24 input channels are working great. So far 16 have been recapped with 220uf for coupling between stages. Most mic input caps were 33uf or 47uf axials. I replaced with 47uf radials. I left the line inputs at 100uf as they came with the board, tho I tried 220uf on a few.
The improvement is noticeable when comparing two-channel material between new and old caps.
I removed and jumpered C36, as it seemed redundant to me, and so far I'm not hearing any noise or clicking from the EQ switch, which is the only reason I can see for that cap being there.
Another interesting thing about the input PCBs is the option of an input transformer in the mic pre, but no one on the net seems to be able to find any info about what transformer might be used. There is some discussion of it in a GroupDIY thread (http://groupdiy.com/index.php?topic=30240.msg366794#msg366794). Naturally, this is something I would like to try, at least on a few channels, though I am mainly using the board for mixing, and using the line inputs at this point in time.
AUX/FOLDBACK MASTERS
There are 4 AUX and 4 FB sends from each input channel (and 4 FB sends from the Group channels), and there are two channel strips on the board to control these. This is a nice feature, especially since each send has it's ow EQ, as do the returns on the group channels. All have been recapped.
METERS
All 6 SIFAM meters seem to work, but the R output meter does not rest fully at 0, nor can it be adjusted there.
The manual mentions changing the bulbs in them, but gives incomplete instructions. None light up on this board, but when I try to open them up, I'm afraid of damaging them, as they don't come apart easily, so I've left them alone until I have a better idea or maybe find some info in the archives. I see on the web that other folks have pondered this also.
OTHER WORK
All knobs and fader knobs were removed and cleaned with a gentle mix of water and hand soap.
All (ALPS) faders were removed, dismantled, and had years of sound tech grunge and hair painstakingly cleaned out. The rails were then lubricated with silicone oil after being cleaned and blown out.
Armrest was cleaned and treated with Armor All. It's in amazingly good condition with only one small tear.
There are two DIY channels on the board that seem to have been for injecting two-channel info into the main mix. I have disconnected them, but they nicely have P&G faders, which I have cleaned and might put on the Master channels.
CONCLUSIONS
I got this board for $150, which is amazing to me, but it's a good thing I could solve it's problems The sound is a big improvement over the modded Studiomaster Mixdown I have been using, though the design and age of the two mixers is similar. It's full of TL072/74 and 5532/4 chips, which are soldered to the PCBs so I don't have any plans to swap chips at the moment, based on my experience with the Studiomasters (I've restored three of them), which seemed to benefit more from cap replacement and bypass caps than any chip swaps.
The DDA sounds more transparent and less beefy than the SMs, and the EQs seem very nice with good film caps already in place. They are a pleasure to use, and I don't feel the need for cap upgrades, which were a big improvement to the SMs.
The board is a pleasure to work on compared to the SMs, since all channels can be easily removed, instead of the need to dismantle the whole mixer to work on it.
There are no direct outs on the DDA, but I have lots of pres in the studio so I don't plan on using the board for mic inputs, but the pres do sound good after the recap.
Each channel has FX send and return, but they are unbalanced, which is fine for my current studio set up. I now have them hooked up to a patch bay, and the mixer interacts well with all my compression and FX so far.
There are various arguments online as to the quality of these mixers related to other DDA models, but a quick look at the schematics shows me that basically they are all modeled after the same design, especially the S, M, Q, and D series. Routing and flexibility is different from model to model, but the basic design of each segment of the mixers seem to be based on the same circuits.
My manual came in what appears to be the original DDA notebook cover, and has a page indicating 1990 prices for the various models and options. This mixer was just over 13K USD at the time.
QUESTIONS/COMMENTS?
1. Can anybody suggest a mic input transformer to try? The PCB cards show it replacing two axial caps (33uf in some of my channels and 47uf in others).
In the GroupDIY thread, someone mentions trying the Neutrik NT4, but says it doesn't work. Schematics show all models of this era DDA having the transformer option, and it's hard to believe they would use a different transformer for each model. Any info here would be gratefully accepted from anyone ho's opened up their S, M, Q, or D series mixer.
2. Snatchman, are you still around? You started an S Series thread in GroupDIY, but didn't follow up, as far as I can find. Any more info you might have discovered would be a welcome addition here.
3. Glad to hear from anyone who has experience with the mixers or sees errors with any of the info above. I'm here to learn, and always grateful for any added knowledge from the folks here on this wonderful forum.
This is a UK-made mixer from around 1990. The designers went on to Midas and Audient. The S Series is designed for live work, according to the DDA website (ddaconsoles.com), but I'm finding that it works and sounds great in my home studio. The one I have is a 24-channel version, but it's in a frame that can hold 32 channels, so the search is on for more channel strips. Schematics can be found at the website, but I will post some here for convenience.
PSU
The biggest problem with the mixer was the power supply. I took a chance on it when purchasing, as the PSU was obviously fluctuating quite a bit when I first examined the board. Meters were swinging about and the V+ and V- indicators on the PSU would go on and off. P48 seemed solid. First thing I did was recap the PSU.
Opening it up, I found one 12,000uf and one 10,000uf cap in the +- section of the supply. I'm no genius, but this seems to me to be asking for trouble, since we want the +- voltages to be consistent. The schemo calls for 10,000u in this place, but good ole' All Electronics had some 15,000uf Panasonics in stock, and in they went, as well as replacing all electrolytics in there with slightly larger values.
However, the voltages were still fluctuating wildly, and it took some more poking and prodding to discover that the problem was merely that the 2N3055/PN3055 transistors were not bolted down to their heat sinks properly. Perhaps the insulation between them and the heat sinks had shrunk over time. It was amazing to me that a light tightening of the nuts immediately solved the PSU problems, and ever since it has been rock solid.
It has a fan, which was not working, so I vacuumed it out and sprayed it with contact cleaner. Sure enough, with some coaxing it slowly started to rotate and get up to speed. Seems reliable now. I'm glad, because it was glued in place at the factory, and was going to be quite an ordeal to get loose. I imagine I will have to do this at some point in time...
Voltages are now @ + and - 17.3V. All good, except P48 is up around 51V!
MASTER CHANNELS
The obvious problems I found were that the left side of the headphones was much quieter than the right, and the Monitor output was strangely putting out mono on one side (into both channels!).
The schematics were a time saver here. A simple recap of the phones amp fixed the headphones imbalance, and for some reason the wiring from the Monitor out XLR jacks to the card connectors was all wrong. Mix out was OK, and I can't imagine why someone wired the Monitor out the way it was. Once these items were fixed, the Master channels were working fine, and I have since replaced the electrolytics with Panasonic FCs, using stock values everywhere, except in the signal path coupling between stages, where I upped the values to 220uf.
No bypass caps on the signal path yet, but thinking about trying it. I like the balance on the mixer now and the high end is present, but not strident, so I'm leaving it alone for the moment.
GROUP CHANNELS
The groups had few problems, other than dirty faders. They have now been recapped, again with 220uf in any stage coupling caps. The schematic calls for 68uf in most coupling caps, but the original coupling caps in the board were mostly 100uf.
However, these caps had some discrepancies from the schematics.
C31 was 22uf on all 4 group channels, but the schemo called for 100uf. I installed 100uf.
In the group and master channels, there are sections labeled EBO 1, 2, 3,...etc.. I assume this means Electronically Balanced Output. On the group channels one cap in EBO 1 (going to the Matrix 1 output) was consistently backwards from the PCB printing as well as the other 3 caps in the EBO section. on all 4 cards. This was perplexing, to say the least. I ended up matching the other caps polarity and PCB labeling, and so far everything seems fine. I'm using Matrix 1 as a send for parallel drum compression, and it works.
INPUT CHANNELS
All 24 input channels are working great. So far 16 have been recapped with 220uf for coupling between stages. Most mic input caps were 33uf or 47uf axials. I replaced with 47uf radials. I left the line inputs at 100uf as they came with the board, tho I tried 220uf on a few.
The improvement is noticeable when comparing two-channel material between new and old caps.
I removed and jumpered C36, as it seemed redundant to me, and so far I'm not hearing any noise or clicking from the EQ switch, which is the only reason I can see for that cap being there.
Another interesting thing about the input PCBs is the option of an input transformer in the mic pre, but no one on the net seems to be able to find any info about what transformer might be used. There is some discussion of it in a GroupDIY thread (http://groupdiy.com/index.php?topic=30240.msg366794#msg366794). Naturally, this is something I would like to try, at least on a few channels, though I am mainly using the board for mixing, and using the line inputs at this point in time.
AUX/FOLDBACK MASTERS
There are 4 AUX and 4 FB sends from each input channel (and 4 FB sends from the Group channels), and there are two channel strips on the board to control these. This is a nice feature, especially since each send has it's ow EQ, as do the returns on the group channels. All have been recapped.
METERS
All 6 SIFAM meters seem to work, but the R output meter does not rest fully at 0, nor can it be adjusted there.
The manual mentions changing the bulbs in them, but gives incomplete instructions. None light up on this board, but when I try to open them up, I'm afraid of damaging them, as they don't come apart easily, so I've left them alone until I have a better idea or maybe find some info in the archives. I see on the web that other folks have pondered this also.
OTHER WORK
All knobs and fader knobs were removed and cleaned with a gentle mix of water and hand soap.
All (ALPS) faders were removed, dismantled, and had years of sound tech grunge and hair painstakingly cleaned out. The rails were then lubricated with silicone oil after being cleaned and blown out.
Armrest was cleaned and treated with Armor All. It's in amazingly good condition with only one small tear.
There are two DIY channels on the board that seem to have been for injecting two-channel info into the main mix. I have disconnected them, but they nicely have P&G faders, which I have cleaned and might put on the Master channels.
CONCLUSIONS
I got this board for $150, which is amazing to me, but it's a good thing I could solve it's problems The sound is a big improvement over the modded Studiomaster Mixdown I have been using, though the design and age of the two mixers is similar. It's full of TL072/74 and 5532/4 chips, which are soldered to the PCBs so I don't have any plans to swap chips at the moment, based on my experience with the Studiomasters (I've restored three of them), which seemed to benefit more from cap replacement and bypass caps than any chip swaps.
The DDA sounds more transparent and less beefy than the SMs, and the EQs seem very nice with good film caps already in place. They are a pleasure to use, and I don't feel the need for cap upgrades, which were a big improvement to the SMs.
The board is a pleasure to work on compared to the SMs, since all channels can be easily removed, instead of the need to dismantle the whole mixer to work on it.
There are no direct outs on the DDA, but I have lots of pres in the studio so I don't plan on using the board for mic inputs, but the pres do sound good after the recap.
Each channel has FX send and return, but they are unbalanced, which is fine for my current studio set up. I now have them hooked up to a patch bay, and the mixer interacts well with all my compression and FX so far.
There are various arguments online as to the quality of these mixers related to other DDA models, but a quick look at the schematics shows me that basically they are all modeled after the same design, especially the S, M, Q, and D series. Routing and flexibility is different from model to model, but the basic design of each segment of the mixers seem to be based on the same circuits.
My manual came in what appears to be the original DDA notebook cover, and has a page indicating 1990 prices for the various models and options. This mixer was just over 13K USD at the time.
QUESTIONS/COMMENTS?
1. Can anybody suggest a mic input transformer to try? The PCB cards show it replacing two axial caps (33uf in some of my channels and 47uf in others).
In the GroupDIY thread, someone mentions trying the Neutrik NT4, but says it doesn't work. Schematics show all models of this era DDA having the transformer option, and it's hard to believe they would use a different transformer for each model. Any info here would be gratefully accepted from anyone ho's opened up their S, M, Q, or D series mixer.
2. Snatchman, are you still around? You started an S Series thread in GroupDIY, but didn't follow up, as far as I can find. Any more info you might have discovered would be a welcome addition here.
3. Glad to hear from anyone who has experience with the mixers or sees errors with any of the info above. I'm here to learn, and always grateful for any added knowledge from the folks here on this wonderful forum.
