Studiomaster Mixdown PSU bypassing, recapping & mods help

[PaulRich]

Latest(17/10/08)
After drowning all pots and switches in Servisol Super 10 I have gotten rid of intermittentness on the channels i have tested
I am still getting, what sounds like to be white noise and maybe 50hz spikes at 50, 150, 200, 250, 350, 450 & 650hz
Ive knocked up a crystal earpiece contraption my friend told me about and on 2 of the channels ive traced the noise, which starts at the collector of the 1st transistor(http://www.toshiba.com/taec/components2 ... 0/6451.pdf) from the line input. My friend said that I should check the caps around it to see if thats the problem as the transistor should either work or not. No in between.
Paul

[ef37a]

Yes Paul, check the caps but I fear your friend knows jack about transistors. Silcon transistors can go intermittant all ways up from christmas, noisy? You would not believe how noisy they can go!

Germanium transistors are inventions of Beezlebub, horrid things. Get a hair dryer and a can of freezer spray.

Dave.

[PaulRich]

Hey ef37a,
hope youre having a good weekend
Get a hair dryer and a can of freezer spray?
Is this some kinky game thatll coax it into sounding nice
Just kidding
How does that work?
thanks
Paul

[ef37a]

Thermal stress laughing boy, thermal stress!

You warm the general component area up and this often initiates or worsens the symptom. Zap each "infallable" transistor or susupect cap' in turn.

Sometimes it works better the other way. Cool something down then warm it up (you CAN use a solder iron but takes years of practice not to bugger everything you touch!).

Happy thermal stressing!

Dave.

[PaulRich]

Hey ef37a,
not quite sure i understand
so i power up channel, spray freeze at component(transistor, cap), then what am i doing, looking for, testing?
thanks
paul

[mu7et]

Hi! It sounds like you have a good idea of what you want to do with your Studiomaster mixer. Recapping and modifying it can certainly improve its performance and reduce noise. Here are some additional tips and suggestions:

1. When you're recapping, make sure to use high-quality capacitors with a low ESR (Equivalent Series Resistance) and a high voltage rating. This will help ensure that the capacitors perform reliably and don't introduce additional noise into the circuit.

2. In addition to adding bypass capacitors to the power rails, you may also want to consider adding a separate regulator circuit to provide clean, stable power to the audio circuits. This can help further reduce noise and improve performance.

3. Upgrading the opamps can make a significant difference in the sound quality of your mixer. The ones you listed are all good choices, but there are many other options available as well. You may want to experiment with different opamps to find the ones that work best for your particular application.

4. When upgrading the mic preamp transistors, make sure to use high-quality, low-noise transistors. The 2SA1316 and 2SA1083 are good choices, but there are also other options available.

5. When modifying the EQ, you may want to consider adding additional frequency bands or changing the frequency response curves to better suit your needs. Just make sure that you are careful not to introduce additional noise or distortion in the process.

6. Finally, be sure to take your time and carefully document your modifications.

[Mike Stranks]

Welcome mu7et!

I suspect the person with the problem has long ago fixed it, binned it or moved on...

... the thread is 15 years old...

[Wonks]

And I have no idea how you’d manage to add extra EQ controls to a mixer that’s already got as many controls on its fascia as it’s possible to cram in.

[James Perrett]

The original Mixdown also has extremely quiet mic preamps so I can't see any need to modify them.

[Hugh Robjohns]

I suspect mu7et was really only posting to promote his own website... a link I removed.

[zenguitar]

I suspect mu7et was really only posting to promote his own website... a link I removed.

Ahh... And I thought that his post reeked of ChatGPT too.

Andy

[Hugh Robjohns]

Yes, it does seem to repeat a lot of earlier comments in a GPT kind of way.