There are a lot of great discussions
on the board right now, but I haven't
had a lot of time to get on - there are
some more "life" things happening here.
There are a lot of great discussions
on the board right now, but I haven't
had a lot of time to get on - there are
some more "life" things happening here.
However, I'm going to pose this question.
I know that any answers to this question
that you give will give me some distraction
and comfort.
I have been working on my Gates Studioette
board again. It's from about 1962. Although
I had it partially running, I have taken
it apart again, because I didn't like the
way it worked. (I gutted the original inside, by
the way.)
Radio Shack makes some great little self contained
300 mW audio amplifiers. Each one is enclosed in
a little gray colored case. These amps run off of
9 volt batteries. They look like a little AM
radio, in a way.
I was planning to use one to drive the board VU
meter and one to drive the cue monitor/air monitor/
line monitor speaker. Trying to run 2 of these
amps off of the same supply is a weird thing.
They get unstable and start making screeching
noises, etc. The amps will run on just about
any voltage from 3 to 12, or so. But I don't
understand this instability. I do have a few
theories, though.
Any ideas on this one? I am working on a shoestring
budget here, but the outside of the board does
look quite good. Much better than when I pulled
it out of the dumpster years ago.
On another subject, if you haven't
checked out Carl's latest Low Power Hour, you
will want to do that. I thought it was great.
There was cool info and a lot of humor.
I have listened to it 3 times.
Best Wishes,
Bruce, W 60 HZ, Etc.
It sounds like not enough isolation between the two amps when powered from one battery.
Maybe just adding a 10uF or 100uF electrolytic will prevent the cross-talk.
I'll check out that No. 68. Sounds like it might be fun to hear.
Sounds to me like you got DC level coupling from that old board into those RS amps, and it's probably shifting as well during audio.
Use a .1uF ceramic cap..NOT an electrolytic!!! That electrolytic will pass that fluctuating DC right through itself and not solve anything. The ceramic cap will block that DC and let the audio signal pass through while not affecting frequency response.
RFB
I run into that all of the time around here. Amps don't like the same ground on the input and many times, as mentioned above, the input (positive) is passed through electrolytics to the circuit that can pass D.C. (Which is usually the issue)
I install 600-600 ohm transformers on the input(s) and all is cured. It isolates both ground and any chance of things sneakin' back through the hot lead of the input. Most all of these transformers will pass good audio fidelity. Rad Shack used to sell some nice, small ones but not no more.
I do alot of stereo audio, operating from a central battery. I must install these to keep from fryin' stuff! Some amps also have a floating ground and ground isn't always ground..
I fried a really nice TV and it took a week for it to happen. I took the earphone output to a small amp to push some external speakers I had mounted to the ceiling. Smelled smoke and the TV was smoking big time, an so was my amp! I noticed that the audio was somewhat muffled when I first connected it but I didn't think it was a big deal. It sounded better than the speakers in the TV. Had a few other issues after that before I figured it out..
The transformer also adds a load to the curcuit on both ends which could help with any noise around the cabling. Causes two loaded, isolated circuits..
http://www.talonix.com/shop/item.aspx?itemid=7510
I did a quick search. I'm sure you can find something leaded..
Another grounding issue to consider is if those amps operate from a separate power supply, especially if its a cheap switching supply. Your board is going to have a totally different power supply system, and often the old with the new don't quite mesh well not without some serious modification to one or the other.
Try powering those amps from the console power supply via a voltage regulator if your powering them from an external supply.
RFB
Thanks guys, I appreciate it very much.
I hope to have this Studioette console
done by the time a human lands on Mars.
Crud. I'll be old.
Very Best Wishes To You All,
Bruce, W 60 HZ, etc, etc.