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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Re: Question for John Curl...Please! posted by Nelson Pass on October 21, 2004 at 14:54:11:
Thanks for the reply. That was posted a while ago. The problem turned out to be a ground loop between my HP TVM's (400E) and the function generator at the input. Just as you suggest. I should have thought of that myself. Lifting the grounds cured the problem nicely. I am a retired engineer and have a lot of instrumentation experience, so I should have caught that sooner. Mea Culpa.Once I got that straightened out, I obtained results generally close to the factory specs in most cases. I typically test each unit at 50 Hz and 1 kHz and have found a fair amount of difference at the two frequencies.
I have referred a number of people to your web site for your 1980 paper on cable measurements. I later used some of your measurements in a couple of papers I wrote. One was on the "voltage divider" effect between the source impedance of the amp, plus the cable impedance interacting with the spekaer's impedance to form a frequency dependent voltage divider, thereby reflecting the shape of the speaker's impedence curve into the speaker's frequency response. The second was a set of computations of the cable impedances for different lengths and gauges and constructions. The data is in tables rather than curves as in your paper. The values are then compared to the 5% rule of thumb for audibility. I give your paper and site full credit. If you'd like, I'd be happy to e mail you a copy. I think it's a real crime that after all these years, your 1980 paper is one of the very few on the subject.
I was also quite interested in the article you wrote on constant current amps and full range speakers. Are you familiar with Tomcik's 1954 paper on using series resistances to adjust the Q on E-V speakers? (Tomik was E-V's Chief Electronics Engineer at that time) In many of his cases, the resistances are quite large and approach constant current. I was struck by the similarity. I can provide a link if you're interested.
Again, that you for responding. I had no idea you visited that site.
Best Regards,
Jerry Crum
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Follow Ups
- Re: Question for John Curl...Please! - Bold Eagle 16:55:30 10/21/04 (0)
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