John Curl's Blowtorch preamplifier part II

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simon7000

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billshurv said:
Sorry, need to be monosyllabic
70dBa against what. top 40 pop music will have a DR of 4 or 5 so that will be around -6dBFS. Nice music might be -40dBFS. At your 70dBa what would 0dBFS give you without touching the volume knob?
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100 dBa SPL peaks with live symphonic music. 90 dBa SPL with most good program material and 75 dBa SPL with over compressed stuff.

At 85 dB/W and 2M listening distance that would require 85 + 25 (dynamic range) +3 (headroom) + 6 (inverse square law) -15 (desired level 70 dBa SPL) = 104 dBa SPL out of the loudspeaker or 80 watts.
 
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billshurv

billshurv

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simon7000 said:
100 dBa SPL peaks with live symphonic music. 90 dBa SPL with most good program material and 75 dBa SPL with over compressed stuff.

At 85 dB/W and 2M listening distance that would require 85 + 25 (dynamic range) +3 (headroom) + 6 (inverse square law) -15 (desired level 70 dBa SPL) = 104 dBa SPL out of the loudspeaker or 80 watts.
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Your edit goes from 70 to 85? Also why 3dB headroom with a digital source that can't go above 0dBFS?
 
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DPH

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SY said:
Daniel, congratulations in advance- you'll do fine. Just remember that you know more about the subject than anyone on your committee.
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Thank you, SY. There are some fringes of what I did which I'm not so sure about, but that's also expected.

simon7000 said:
Derfy,

It is a shame you can't tell when I am serious. SO WHEN I AM..... You really should consider letting Brad get a peak at your latest comic book. If he doesn't scream it may increase your confidence.

There is certain to be someone on your panel who is convinced they know more than you or your advisor and will want to be sure you know that.

Or as the advice given to the folks just before going to the firing squad, "Relax, doesn't matter how many guys are shooting at you, the only guy who counts has a whistle."

That should be your advisor.
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Oh, of course. Reality of theses today is that you really focus on papers and just glue them together, so the papers get the effort over the glued portions. :)

My advisor wants to graduate me, and I'm more worried about my committee falling asleep than lighting me up. No inter-committee rivalries to worry about, fortunately.

Okay, back to crest factors and sizing output capacity (I listen pretty quiet and near field, so attenuation is the name of my game). :)
 
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dvv

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gpauk said:
What difference does silver plated OFC make? Other than costing more...
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You know, the usual sales blurb, cut and paste here. They say more dtail and better current transfer. To be fair, I did go for it after investigating several similar products in its time and found this one to be better than others, even if marginally on occasion.

The price was comfortable, €30/m.
 
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dvv

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john curl said:
Again, the real problem is not voltage swing, but current output. Perhaps I should make a 32W amp and call it the Dauphine. '-)[/QUOT

Agreed. But because you don't need PSU rails as high as you do for a 150W/8 amp, you can use just two pairs of output devices per channel, now make those two pairs NJW 3281/1308, which are rated for 200W dissipation and watch them drive just about anything with PSU at +/-35V, quite enough for 50/8 .
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jcx

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except that JA review's fig 4 underbias seems inexcusable if it results in deadzone which many have pointed to as highly audible distortion - including the GedLee Metric

why wouldn't the fall back position be minimal (or is it Self's "optimal) Class B?
 
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