Re: 8038 way too much THD
The problem with an LC LPF is that you have to know the impedance it is going to work with, and every time --
The problem with switched cap filters is the "clock feedthrough" and other noise components -- even in the case of the lowest noise filters this is some tens of uV. You can use gangs of digital pots and make linear filters (on the Analog Devices website) but you will need to do the decade filtering by switching caps. Despite these limitations you can get a digitally filtered oscillator under 0.01% THD.
EBay really seems to have dried up -- if you see the Krohn Hite THD analyzer it has a very low noise, very low THD oscillator. Output is 5.1 V so you will need some attenuation.
thespeakerguy said:
The problem with an LC LPF is that you have to know the impedance it is going to work with, and every time --
The problem with switched cap filters is the "clock feedthrough" and other noise components -- even in the case of the lowest noise filters this is some tens of uV. You can use gangs of digital pots and make linear filters (on the Analog Devices website) but you will need to do the decade filtering by switching caps. Despite these limitations you can get a digitally filtered oscillator under 0.01% THD.
EBay really seems to have dried up -- if you see the Krohn Hite THD analyzer it has a very low noise, very low THD oscillator. Output is 5.1 V so you will need some attenuation.
eBay
As I said earlier if you wait they will appear. There is an HP 239 oscillator on eBay. Its not cheap however. Just keep looking.
The Tek 4084 is very good and should be used with a very low distortion oscillator.
I had to deal with a digitally synthesized LDO source a while back. Finally scrapped it and made an airplane PCB with an analog oscillator to replace it. The radiated noise made it unuseable. It was a turntable motor driver.
Soon (months) I will go through my collection of audio analyzers and see which I can part with. If there is interest I will post the list when I get to it. I have lots of other interesting stuff for audio DIY as well.
-Demian
As I said earlier if you wait they will appear. There is an HP 239 oscillator on eBay. Its not cheap however. Just keep looking.
The Tek 4084 is very good and should be used with a very low distortion oscillator.
I had to deal with a digitally synthesized LDO source a while back. Finally scrapped it and made an airplane PCB with an analog oscillator to replace it. The radiated noise made it unuseable. It was a turntable motor driver.
Soon (months) I will go through my collection of audio analyzers and see which I can part with. If there is interest I will post the list when I get to it. I have lots of other interesting stuff for audio DIY as well.
-Demian
Re: eBay
Sometime this winter I will take Crawford's IM Analyzer from AudioXpress and simplify it -- this is a project in need of DSP.
The 4084 is a ruggedized version of the AA501 (I think) -- I have the 4084 and it works very nicely.
I was also thinking that the SG505 oscillator could be modded pretty simply to reduce the distortion.
1audio said:
Sometime this winter I will take Crawford's IM Analyzer from AudioXpress and simplify it -- this is a project in need of DSP.
The 4084 is a ruggedized version of the AA501 (I think) -- I have the 4084 and it works very nicely.
I was also thinking that the SG505 oscillator could be modded pretty simply to reduce the distortion.
The SG505 is already very low distortion at .0008% or less. Improving this is very difficult.
As for DSP, the relatively simple analog systems used by Sound Technology and others get to less than .001% pretty easily. I would think the A to D would be the limit of performance for doing it digitally. Is it worth the effort?
And today there is an HP 339 needing knobs and ?? for cheap on eBay.
-Demian
As for DSP, the relatively simple analog systems used by Sound Technology and others get to less than .001% pretty easily. I would think the A to D would be the limit of performance for doing it digitally. Is it worth the effort?
And today there is an HP 339 needing knobs and ?? for cheap on eBay.
-Demian
Guess I will. Bummer. The HP 239 seems to be exactly what I'm looking for after doing some research. Not as cool looking as my old Waveforms tube gen, but small and low distortion. $200 does seem to be a bit high, but I need to replace the Waveforms badly...and patience isn't one of my virtues...
A Sound Technology 1700A just appeared on ebay and its cheap. John Curl uses one still with an opamp upgrade and finds that its performance is as good as it gets. (I don't know which opamps he switched it to.) Stock its oscillator is .001% or less. Not bad for a buck! Will probably end at less than $100.
-Demian
-Demian
The 1700A went for a bit under $200, which would have been OK, but I threw in a max bid of $180 and lost it. There was also a very nice 1701A that I was going for, but again, my max bid wasn't enough, and it sold for well over $300. I would have bid higher for it, but could not be at the computer for the end of the auction.
There's another 1701A on the 'Bay for a starting bid of $450 (!!). However, it's beat to hell, and 'tested to power up only'. Not a chance I'm bidding on that one.
However, it appears that I have found a SG505 with opt-2 for $300. The last few that have sold on eBay went for well over this amount, and they did not have the balanced output option. Funny that the prices for these SG505's varies all over the map...this is the cheapest, and I've seen them offered at test equipment resellers for as much as $1100. What a scam!
Now I need to find a TM power module...
PITA, and getting expensive, but hopefully this will end my search.
There's another 1701A on the 'Bay for a starting bid of $450 (!!). However, it's beat to hell, and 'tested to power up only'. Not a chance I'm bidding on that one.
However, it appears that I have found a SG505 with opt-2 for $300. The last few that have sold on eBay went for well over this amount, and they did not have the balanced output option. Funny that the prices for these SG505's varies all over the map...this is the cheapest, and I've seen them offered at test equipment resellers for as much as $1100. What a scam!
Now I need to find a TM power module...
PITA, and getting expensive, but hopefully this will end my search.
Thje Sound Technology stuff goes for prices all over the map. The details to look for are on the analyzer side- Auto Set Level is very useful. And the IM analyzer is also very good. The ST1700A doesn't have some of the features of the B and the 1701 is very similar to the B. I have a 1700B and a 1710 that has 15V output to meet some GSA specs.
The SG505's are always expensive for what they are. You can also look for the SG5050, the same with programmability. I have lot looked intot he cost of a TM frame for a long time. I don't need more holes for Tek stuff. I already have too many (7 scopes at last count).
-Demian
The SG505's are always expensive for what they are. You can also look for the SG5050, the same with programmability. I have lot looked intot he cost of a TM frame for a long time. I don't need more holes for Tek stuff. I already have too many (7 scopes at last count).
-Demian
1audio said:
there is nothing wrong with having more than 2 or 3 scopes ! -- I use an old 5XXX (A D13 -- both traces work great) with a 5L4N specturm analyzer and a 5A22N differential amp all the time -- I bought a spare 5XXX just for the parts!
The less expensive TEK SG502 etc. have a well matched dual pot for frequency control -- could be the basis of a nice mod.
Your right, but I have more. . . A 7854 that I use the most w/ 7A26, 2X7A22 diff amps, 7A13 comparator (almost impossible to overload) 7L5 lf spectrum analyzer, 7S11, 7T11, 7S12 samplers for looking at cables and a 7844 dual trace, 2 7603s, one for the Wavetek FFT plugin and a 5110 w/ misc plug-ins for the distortion analyzer. I like the 5000 stuff because its so cheap I don't bother to fix any of it. I just get another.
I also have 2 547's in storage. I just don't need them. If anyone local to me is interested in them let me know, I would really like to pass them on to good homes.
-Demian
I also have 2 547's in storage. I just don't need them. If anyone local to me is interested in them let me know, I would really like to pass them on to good homes.
-Demian
D --
at one time I had a 5223, but gave this to a biochemist friend who has used it quite a bit. These low freq scopes were used in the automotive and medical industries for their low noise.
I use a new TEK DSO, and a 2465 and the 5XXX series -- I just bought a bunch of plug-ins just to cannibalize the cabinets -- as I have decided to standardize most of my test equipment into TM5000 and TM500 chasis. When I go into the lab I automatically turn on the two scopes and my sig gen to let them warm up a bit (it's not a quiet lab!).
It get's pretty bad when you ask your kids if they would like a scope for Christmas !
at one time I had a 5223, but gave this to a biochemist friend who has used it quite a bit. These low freq scopes were used in the automotive and medical industries for their low noise.
I use a new TEK DSO, and a 2465 and the 5XXX series -- I just bought a bunch of plug-ins just to cannibalize the cabinets -- as I have decided to standardize most of my test equipment into TM5000 and TM500 chasis. When I go into the lab I automatically turn on the two scopes and my sig gen to let them warm up a bit (it's not a quiet lab!).
It get's pretty bad when you ask your kids if they would like a scope for Christmas !
You remided me that I also have a THS720 and a Picoscope. Both of which are good digital scopes and fine for documenting things but not as easy or quick for general troubleshooting as an analog scope. And not useable past the frequency limit. Where I can tell what is happening at 500 MHz with the 7A24 200 MHz plug-in the DSO just ignores the input. But the THS720 is portable and useable. Its still a lot of scopes.
-Demian
-Demian
Good Lord!! What a collection!
I've got two basic scopes...a 2236, and an old 454 that needs some TLC (I ain't got the time to fool with it and should give it away for parts). Besides that, the ancient Waveforms 401B tube oscillator that had started giving me trouble at low frequencies (<100Hz) and precipitated my search for a low-distortion replacement, and the DA-4084. Also a couple of Nixie tube freq. counters and multimeters that are cool to look at but seldom get used, and a Tek CFG253 function gen with a few minor problems that I'd love to fix, but no one has any manuals for (wouldn't have any ideas, would you??)
I don't mind paying a little bit more for the SG505, as the only analyser with lower distortion that I could possibly come close to affording besides it was some of the Krohn-Hite units that are apparently rare as hen's teeth and sell for even more than the 505's.
I've got two basic scopes...a 2236, and an old 454 that needs some TLC (I ain't got the time to fool with it and should give it away for parts). Besides that, the ancient Waveforms 401B tube oscillator that had started giving me trouble at low frequencies (<100Hz) and precipitated my search for a low-distortion replacement, and the DA-4084. Also a couple of Nixie tube freq. counters and multimeters that are cool to look at but seldom get used, and a Tek CFG253 function gen with a few minor problems that I'd love to fix, but no one has any manuals for (wouldn't have any ideas, would you??)
I don't mind paying a little bit more for the SG505, as the only analyser with lower distortion that I could possibly come close to affording besides it was some of the Krohn-Hite units that are apparently rare as hen's teeth and sell for even more than the 505's.
2 EchoWars
No, that's not a scope collection -- when you have more than 20 working scopes for your own, then you might start talk about a collection. Everything else is child's play & kidding
))
To the cfg253: Well, that's not easy to get a servicemanual. The sethingys were made in Taiwan (I think serial starts with an HK and then a 5 or 6 digit number). You might try
http://www.teknetelectronics.com
But I could not find such a manual online, so you might request a quote for a service manual.
No, that's not a scope collection -- when you have more than 20 working scopes for your own, then you might start talk about a collection. Everything else is child's play & kidding
))To the cfg253: Well, that's not easy to get a servicemanual. The sethingys were made in Taiwan (I think serial starts with an HK and then a 5 or 6 digit number). You might try
http://www.teknetelectronics.com
But I could not find such a manual online, so you might request a quote for a service manual.
tekman said:2 EchoWars
No, that's not a scope collection -- when you have more than 20 working scopes for your own, then you might start talk about a collection. Everything else is child's play & kidding
There is a guy at Rutgers University in NJ who collects Tektronix scopes!
For those looking at Krohn-Hite -- the 1kHz, 5.1V oscillator in the KH 6900 THD analyzer measures 0.001% to 0.002% THD when examined on my other analyzers (HP, TEK and Boonton). My 6900B was seriously out of whack when I purchased it, but it was dirt cheap and came with a manual ! FWIW, the oscillator in my HP339 is always around 0.0023% THD., but the darned thing will totally conk out when range switching.
hi jackinnj,
yes, the website is nice t o at rutgers.
There is/was a guy in france, two large garge filled with 5xx boat anchors and 7xxx mainframes. Well, this gives a bad back when you have to do the cleaning every spring)
The hp339 is really nice, but terribly searched here in Europe. No chances on ebay, etc. here now. Well, I have to take time.
2 echowars: If I come over a cfg manual, I'll mail it to you.
yes, the website is nice t o at rutgers.
There is/was a guy in france, two large garge filled with 5xx boat anchors and 7xxx mainframes. Well, this gives a bad back when you have to do the cleaning every spring
)The hp339 is really nice, but terribly searched here in Europe. No chances on ebay, etc. here now. Well, I have to take time.
2 echowars: If I come over a cfg manual, I'll mail it to you.
