recapping console

[operator_tape]

I have a old studiomaster series 5 16/8/2 console and think it needs to be recapped. How can I know, if a console needs to be recapped?

[airloom]

How does it sound?
Is it noisy?
Do you want to improve the sound?
WHA?

[operator_tape]

I would like to improve the sound so I could mix with it, its a little on the noisey side. I don't know what it sounded like before I bought it, but I don't think anyone has changed anything in it ever.

[O_ellinas]

Hi

i have a Studiomaster Series 5 16-8-2 too and I have started doing the recap, I am glad I found another person who is mad enough to get into such a tedious job. Would be interested to know how you are getting on?

I have decided to change all electrolytic caps; they are 20 years old and not great quality to begin with. I found some had leaked and others were like swollen, so it pays to change them if you have the time and inclination to do it.

I started by the power supply caps; major improvement in noise and hum. I found out that most original caps were rated low, like 16 volts for a 15 volt power supply, so I used 25 volts throughout (except where the design called for higher voltage).

I have done four boards so far, Main L/R, Group/Monitor and Channel 16; I think the sound is a little bit cleaner.

I have also done other things which I would be glad to discuss if there is interest.

[sears]

If your board sounds noisier the longer you leave it on, is this a sign that it needs new power supply caps?

[Jim Williams]

Hum, yes. Hiss, no. If you have excess white noise, you have likely a defective opamp somewhere.

[roygbiv]

Ooh Ooh, let me get in on this thread!

I too have an older Studiomaster system that needs some repairs. Its a Studioamaster STAR system. Unfortunately, I can't find any schematics anywhere (as operator_tape knows - he's the only guy to respond with my earlier post pleading for help with this obscure board).

The problem I'd like to fix: the main output L/R faders cut in and out intermittently when set to ~ -5dB on the faders.

Does this sound like a cap problem, or a fader problem? I've already tried spraying a bunch of DeOxit into the faders, no luck so far.

[O_ellinas]

Hi all

Hum, yes. Hiss, no. If you have excess white noise, you have likely a defective opamp somewhere.

I agree. Try swapping parts.

The problem I'd like to fix: the main output L/R faders cut in and out intermittently when set to ~ -5dB on the faders.

Almost certainly a bad fader. Try swapping with a functional fader and see what it does. If your board is build like mine, the faders are japanese made Noble 100 mm faders, 10k log. OK build, nothing to write home about, but certainly a lot better than the cheap PCB mount Alps you find these days. At least they don't wobble about like crazy.

To replace bad faders I used the Alps RSAOK11; it is very good albeit a tad expensive, but make sure there is room for it. I had to cut protruding solder tags on the adjacent board to make them fit, but 100% worth it.

Generally speaking I found that the Alpha dual pots that Studiomaster used on their boards are terrible. They all went scratchy or intermittent on my board. All, or nearly all panpots and mid sweep EQ are affected. Curiously enough, single pots did a lot better. When I am done with cleaning and recapping, I am considering requesting a quote from Omeg for wholesale replacement of all bad pots.

roygbiv: I have the schems for the Model 5 18-6-2 if that can be of any help.

[operator_tape]

Glad to see someone answered the post. Where did you get your caps? How much have you invested already in the board? Have you done any op amp swaps?

[operator_tape]

do you have any pics of the boards after you re-capped them?

[roygbiv]

Hey O_ellinas

Thanks for the advice - maybe I'll pop it open this weekend and take a look at the faders, see if I can easily get them off (it seems pretty modular inside).

Also, thanks for the offer for schematics, but I need them for the STAR system, a odd looking unit for sure:
http://www.studiomaster.com/hp9.html

So far, I've only been able to locate the manual, not the schematics. Pity, because it's a pretty funky board (in a cool way), and I'd like to get it up to 100% working.

operator_tape - through some digging (or maybe you told me???) I found there is a guy who used to post on several audio sites as "pooh bear", or "eyeore", or something like that. He apparently used to work at Studiomaster for years. Unfortunately, I' haven't been able to track him down, but you may have some luck.

[O_ellinas]

I found there is a guy who used to post on several audio sites as "pooh bear", or "eyeore", or something like that. He apparently used to work at Studiomaster for years.

The chief engineer at Studiomaster back in the day posts sometimes in the Prodigy Pro forums under the AP nickname.

That STAR thing is really odd!

operator_tape: no I do not have any pics unfortunately, I have little time for my hobbies so it is really "PCB out-soldering iron-PCB in" as fast as possible.

But there is really nothing special to see compared to the stock board. What are you looking for?

I bought the caps on Ebay, got a good price buying in bulk. The most commonly used value in the board is 47?F, I bought 300 of them for like 20 euros.

If you like to improve on the original design, you could consider 22?F non polarized caps instead of two back-to-back 47?F polarized caps; but they would probably be more expensive and you must make sure they fit in there.

Also there is one 47?F on the channel boards that you can simply get rid of and replace by a strap, it is located near the bus connector and couples the insert jack return to the fader. It is there to cater for the unlikely event that your outboard gear passes DC.

The question of investment is an interesting one. I thought about it long and hard. Is it worth putting any money in a board like this, considering that you will probably never recoup the cost by reselling the board? In my case I decided that I would go for it, for the following reasons:

- i got the board for cheap, like 100 euros;
- i like it, it's got lots of vibes; not clean, noisy but tough, warm sound and great EQ; good looks "a la Motorhead"
- i take this as a DYI project;
- the investment can be spread over time, as opposed to shelling out cash up front
- in that price bracket there aren't a lot of contenders anyway; here where i live I could probably get a Behringer or a Seck 18-8-2, or an older Soundcraft; but i cant' face the hassle of hunting for another board on ebay, pay more for something that may or may not work better. At least this board is very serviceable, i have the schems and I got to know it inside out.

So much for the economics.

Yes I did try Op amp substitution. It is actually the first thing I tried and it was a mistake because i realised it makes no sense to buy expensive chips when your pots are scratchy and your power supply hums. The caps, pots and faders have priority in the grand scheme of things.

But yes, if you want to know, I thought that replacing the TL071s in the mic preamp by something like a OPA134 would make my life better. Well it turned out it hardly made any difference, because the actual amplification resides in the transistor pair that is in front of the op amp, so swapping the humble TL071 for a fancy one does not do much and is actually a bad idea because it draws a lot more current for no real advantage. In theory the OPA134 has less distortion but I gladly admit I am tin-eared and did not hear any noticeable improvement.

Always remember that the number one problem with op amp substitution is (apart from price) power consumption. Pukka op amps always draw a lot more current that the TL071/72. The Studiomaster Series 5 was a modular design and its power supply could power up to 8 additional tracks. This means that you have some room for manoeuver for op amp substitution, but not too much of it either.

In my view, there is one place where a better op amp would make sense: the EQ. I think substituting OPA2134 for the TL072 used in the channel EQs is worth a try and would probably yield better results but I have not tried yet.
Another possibility is to use TL061/62 in the utility parts of the board, like the oscillator, and aux send/returns to optimise power consumption.

I have not considered other op amps because of the price. OPA604, AD797, etc. too expensive.

Sorry too long a post... I talk too much. I have to go. Next time I will tell you about the power supply in the Studiomaster Series 5.

[O_ellinas]

Hi operator_tape

I have found a cheap supply of drop-in, or near drop-in, replacements for the pots in Studiomaster Series 5 consoles!

www.futurlec.com

They stock the Alpha pots to the same specs as the original. Available values include the dual 10k lin (pan pots), single 10k lin and log (aux and eq pots)

Rev log is not available.

And the good news is that the dual pots sell for $0.90! The front - to back pin space is 0.5" instead of 0.75" though, so you may have to drill some additional holes in the PCB. The single ones look like they are perfect replacements though.

The not so good news: word of mouth over the net says its not a very reliable vendor. However for what its worth, I ordered just one pot as a test and it arrived after a dozen days straight from thailand.

they also stock suitable replacements for the crappy bus connectors.

[Jim Williams]

I went through a few of these around 20 years ago. Installing local .1 uf bypass caps on the power rails does help. All feedback loops need to have a small cap across, most stages had them. Use Wima FKP-2 or MKP-2 polyprop caps in the EQ, especially the hi mid and hi shelf. Opamps can be the older OPA 2134 BurrBrown stuff, the LT1358, the OP-275, the AD 8599 (with a brown Dog adaptor) or the National LME49720/LME49860, balanced outputs can use the National LM6172 for great output drive. Also check out the new AD8510 series, a BurrBrown fet input sub for the OPA134 series. Mic pre transistors can be 2SA1316 or 2SA1083's to lower front end noise and add some HF air. A nice big Power One HDD-15-5A will be a good power supply if you add the small 1/2 amp 48 volt supply for phantom. Then you can play with opamps all day long. The summing amps in the master should be the National LME part due to it's large open loop gain, = a clearer mix buss.

[O_ellinas]

Whoah thanks Jim! Great stuff!

Re power supply: much to my surprise I found out that it is probably the largest piece of electronic equipment I know of that does not have any power supply bypassing. None. Zero. Bugger all. So yes I definitely second adding liberal amounts of bypassing on all boards.