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John Curl's Blowtorch preamplifier
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Old 24th June 2008, 03:51 PM   #7111
MikeBettinger is offline MikeBettinger  United States
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Quote:
Originally posted by 1audio
While I think designing the circuitry for EMI resistance is important my experience points to layout and stability as being the dominant issues in emi/rfi resistance.
A good article in EDN about layout and the RF environment. A number of interesting comments.

<<http://www.edn.com/article/CA6515348.html>>
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Old 24th June 2008, 04:04 PM   #7112
1audio is offline 1audio  United States
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John Curl's Blowtorch preamplifier
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Originally posted by john curl
Up near Sutro tower, Damien?
How did you guess? I don't think you need to plug in the fluorescents to get them to light up on that hill.
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Old 24th June 2008, 04:15 PM   #7113
john curl is offline john curl  United States
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In 1973, I tried to make a Levinson JC-1 work there. I gave up and told the guy to use a transformer. I agree, it must not be healthy.
PS, any news on the Quantek?
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Old 24th June 2008, 04:46 PM   #7114
Steve Eddy is offline Steve Eddy  United States
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Quote:
Originally posted by john curl
In 1973, I tried to make a Levinson JC-1 work there. I gave up and told the guy to use a transformer.
A transformer!?

My God! You should have told him to take up residence in Sutro TUNNEL instead.
 
Old 24th June 2008, 06:08 PM   #7115
john curl is offline john curl  United States
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Demian, mail probs. can loan you IC card.
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Old 24th June 2008, 06:19 PM   #7116
dimitri is offline dimitri  United States
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Quote:
Go back an read the previous discussion on input stage gain and signal handling capability Vs VAS signal handling capability and compensation methods.
Dear Glen,

I'm appreciating your enthusiasm, but should admit that there are some gaps in your education. Please read some of these books http://www.hottconsultants.com/book.html to be able to talk about EMC issues.
 
Old 24th June 2008, 07:23 PM   #7117
LHMAudio is offline LHMAudio  United States
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I ordered the Toshiba JFETS 2SK170 and 2SJ74 from MCM. I received a partial shipment (the rest are due this Friday) and they appear to have a JP suffix. Earlier posts have suggested there are different quality parts and given the low price at MCM I assume these are not the high quality parts. I have three questions:

1. Is the JP in fact the suffix or a country abbreviation, and
2. If the JP is the suffix, what does that mean?
3. If the JP is not the suffix, how to ID the suffix?

Thanks.

Lindsay
 
Old 24th June 2008, 07:58 PM   #7118
Edmond Stuart is offline Edmond Stuart  Netherlands
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Default RFI

Quote:
Originally posted by dimitri
Dear Glen,

I'm appreciating your enthusiasm, but should admit that there are some gaps in your education. Please read some of these books http://www.hottconsultants.com/book.html to be able to talk about EMC issues.
Hi Dimitri,

I don't think Glen is completely wrong by just looking at the harmonic distortion. Suppose that under influence of a strong HF signal, both tops of that signal (i.e pos. and neg.) are equally compressed. In that case, no AM demodulation will detected, as the whole thing is symmetrical (i.e. no rectifying). However, the tops of an superimposed AF signal will also compressed (maybe even more), which is easily detected by a HD analysis.

Nevertheless, I will start tomorrow with sims of AM demodulation effects, by subjecting several front-ends to a 0.3V 10MHz carrier, 70% modulated with a 10kHz sine. Measuring of the demodulation products will be done by means of an FFT.

BTW and OT, what's the correct spelling: "an FFT" (130k hits on Google) or "a FTT" (55.7k hits) ?

Cheers,
Edmond.
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Old 24th June 2008, 09:40 PM   #7119
john curl is offline john curl  United States
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Dimitri is right, read up, fellow engineers!
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Old 24th June 2008, 11:57 PM   #7120
GK is offline GK  Australia
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Default Re: RFI

Quote:
Originally posted by Edmond Stuart

. Suppose that under influence of a strong HF signal, both tops of that signal (i.e pos. and neg.) are equally compressed. In that case, no AM demodulation will detected, as the whole thing is symmetrical (i.e. no rectifying). However, the tops of an superimposed AF signal will also compressed (maybe even more), which is easily detected by a HD analysis.

Thanks Edmond. And yes, that is EXACTLY why I proposed the alternative unmodulated carrier test (see my previous reference to symmetrical circuits).

Some symmetrical amplifier stages with wide bandwidth will readily behave as a limiting amplifier when over driven with an AM modulated RF carrier and contribute very little demodulation.

As a consequence a measure of the amplifiers demodulation performance will not necessarily indicate how badly an injected RF carrier will effect the amplifiers ability to linearly amplify audio signals.


Cheers,
Glen


Quote:
Originally posted by dimitri


Dear Glen,

I'm appreciating your enthusiasm, but should admit that there are some gaps in your education. Please read some of these books http://www.hottconsultants.com/book.html to be able to talk about EMC issues.

Oh, well if you say so.
 

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