OK-- so I got the thing calibrated, I think, and I just bought this motherfather, so I should be set for testing. Some questions concerning connectors, however.
My BNC connectors for the probe have a clip on them, but it appears to be just to ground the probe to the scope. Can I attach other alligator clips to the probe so I can test without killing myself? Also, I know I need a connector between the function generator and the scope and I've looked, but can't seem to find a BNC to BNC connector for a function generator-to-probe connection.
I'm probably making this too hard, but any help would be appreciated.
Kofi
My BNC connectors for the probe have a clip on them, but it appears to be just to ground the probe to the scope. Can I attach other alligator clips to the probe so I can test without killing myself? Also, I know I need a connector between the function generator and the scope and I've looked, but can't seem to find a BNC to BNC connector for a function generator-to-probe connection.
I'm probably making this too hard, but any help would be appreciated.
Kofi
You're making it harder than it is.
Function generator -> amp. If your function generator has an RCA output, you're set; if it's a BNC, you can grab a BNC-to-BNC coax from Radio Shack, cut it in half, and terminate with an RCA plug (you can make another with the other half or turn it into a different kind of adapter). Handy wire to have around.
Amp to dummy load- that's plain old wire.
Scope to dummy load- that's your 10x probe.
If you want to monitor the input using the other scope channel, use your 1x probe clipped to the amp's input plug and its ground clip connected to the star.
Function generator -> amp. If your function generator has an RCA output, you're set; if it's a BNC, you can grab a BNC-to-BNC coax from Radio Shack, cut it in half, and terminate with an RCA plug (you can make another with the other half or turn it into a different kind of adapter). Handy wire to have around.
Amp to dummy load- that's plain old wire.
Scope to dummy load- that's your 10x probe.
If you want to monitor the input using the other scope channel, use your 1x probe clipped to the amp's input plug and its ground clip connected to the star.
You can also buy two flavors of BNC to RCA adapters from Radio Shack, so there's no need to chop up a BNC to BNC cable. Just use an adapter on the RCA inputs of the amp, and you're ready to go, as the Wavetek function generator has BNC outputs. What you'll want will be the male RCA to female BNC adapter. If you have RCA cables, but no BNCs, you can use a male BNC to female RCA adapter on the Wavetek, then you're ready to go with a standard RCA cable.
I go through this rigamarole all the time when I lug my stuff in to work to check it on our gain-phase analyzer.
I go through this rigamarole all the time when I lug my stuff in to work to check it on our gain-phase analyzer.
Yes, pretty much that’s all you’ll need for a dummy load. For routine tests, you don’t need anything too fancy. You can use a series/parallel combination of several 2 watt carbon composition resistors for something quick and dirty. There are many possible combinations that would work. As just one of many possible examples, for a forty watt load, you could buy twenty 39-ohm, 2 watt resistors. Make two banks of ten resistors in parallel (3.9 ohms) and then place the two banks in series for 7.8 ohms (per channel). Stray wiring resistance gets you close enough to 8 ohms for routine work. Leave some air gaps between the resistor bodies for cooling - and remember, these will get hot even at 10 watts or 20 watts. It is tempting to find a pair of single large 4-ohm or 8 -ohm wirewound power resistors. Unless these are specially designed to be non-inductive, there will be an inductive component (not unlike most tweeters, coincidentally). For all but very precise measurements, this option is going to be OK too.
If you want to get fancy, solder either end of that load across a ten-turn pot and an RCA female jack from wiper to load ground. Instant sound card return. Then use something like this - http://www.ne.jp/asahi/fa/efu/soft/ws/ws.html - to investigate the ugly secrets of amplifier outputs.
While we're talking about dummy loads, I'll show you what I just bought at a ham fest: seven (all they had) NOS 225-watt non-inductive resistors by Dale. These are 8.5 ohms, so I'll need to parallel a 136-ohm resistor (20W) across each to put them right at 8 ohms. If you look closely to the picture, you can see the criss-cross Aryton-Perry windings which cancel the inductance. I got all seven for $5. I can't recommend ham fests enough for buying audio parts.
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OK, so Kofi finally has some test equipment!
I ran what I believe to be a 10KHz square wave through the Bevois Valley amp and I come up with a wave that looks COOL-- kinda like kanji. But I'm just betting this ain't so cool.
Take a look and tell me why I should just throw it in the trash and start over.
Kofi
I ran what I believe to be a 10KHz square wave through the Bevois Valley amp and I come up with a wave that looks COOL-- kinda like kanji. But I'm just betting this ain't so cool.
Take a look and tell me why I should just throw it in the trash and start over.
Kofi
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Kofi Annan said:
Can't help you on the scope part, cause I haven't got mine up and running yet. But no, don't chuck the amp. Get it working well (you will, and by then you will have learned lots of new stuff), enjoy it for a while, then when you hanker for a little more exercise maybe convert it to gingertube's little variation, the Baby Huey - http://www.diyaudio.com/forums/showthread.php?s=&threadid=72536&highlight=
Sheldon
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