I recently started building the standard budget DIY measurement rig (i.e. Panasonic mic & pre-amp, Wallin Jig II and Speakerworkshop on a laptop) and cannot get more than .1V from the 'headphone' jack into an 8-ohm load. I assume the laptop soundcard amp is just not enough. Would the preferable option be to:
a) Use an existing receiver and the line-out from the laptop for external amplification
or
b) Build a gainclone or similar chip-amp for dedicated purposes.
I would prefer not to have to take one of my receivers into double duty, but am concerned about some of the possible issues with a gainclone, specifically oscillation and 'discomfort' with low impedance loads. As it is to be used for speaker testing, I would suspect it would see some low loads from time to time.
Any suggestions from someone with experience with this would be appreciated.
Sandy.
a) Use an existing receiver and the line-out from the laptop for external amplification
or
b) Build a gainclone or similar chip-amp for dedicated purposes.
I would prefer not to have to take one of my receivers into double duty, but am concerned about some of the possible issues with a gainclone, specifically oscillation and 'discomfort' with low impedance loads. As it is to be used for speaker testing, I would suspect it would see some low loads from time to time.
Any suggestions from someone with experience with this would be appreciated.
Sandy.
I have been using a non inverting OPA549 GC for about 7 or 8 months for small signal driver testing, with no problems at all. It runs off a little 15-0-15 30VA trannie and is perfect for the job. I used a Sfernice 5% pot for the input to give reasonable accuracy, and it's a great little tool.
Sandy you could build a small GC fairly cheap especially if you have a parts stash...or you could just get a used amp really cheap...it all depends on the time you want to invest in this....heck when I built my signal generator years ago before software was available I included a small LM386 amp and speaker to hear what the frequency sounded like..haha
DIRT®
DIRT®
Hello Sandy,
I've built a non-inverting gainclone for use with SW and it works great. Using the software becomes much easier when the jig consists of a power-amp, mic pre-amp, PSU and all signal switching built into one box!
Be aware that most gainclone-type chip amplifiers have a minimum gain of 10 - this means that the measured signal could be ten times the amplitude of the reference signal. I simply used a divide by ten attenuator on the input to the power amp to keep the signals of similar amplitude.
There are schematics, pics and a rough build description on my website but it's not linked from the main page. Someone wanted to see schematics before the article was finished so I just dumped it up there. I'll find the URL if anyone is interested.
Nice one,
David.
I've built a non-inverting gainclone for use with SW and it works great. Using the software becomes much easier when the jig consists of a power-amp, mic pre-amp, PSU and all signal switching built into one box!
Be aware that most gainclone-type chip amplifiers have a minimum gain of 10 - this means that the measured signal could be ten times the amplitude of the reference signal. I simply used a divide by ten attenuator on the input to the power amp to keep the signals of similar amplitude.
There are schematics, pics and a rough build description on my website but it's not linked from the main page. Someone wanted to see schematics before the article was finished so I just dumped it up there. I'll find the URL if anyone is interested.
Nice one,
David.
Thanks!
Sounds like the GC should be a good solution. I'll double check the National datasheet and probably build a very standard version.
In hindsight, I would have done better by building everything in one box, but I already completed the mic-pre and the jig. Another project for later. . .
Thanks for the help!
Sandy.
Sounds like the GC should be a good solution. I'll double check the National datasheet and probably build a very standard version.
In hindsight, I would have done better by building everything in one box, but I already completed the mic-pre and the jig. Another project for later. . .
Thanks for the help!
Sandy.
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