John Curl's Blowtorch preamplifier part III

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Well in the spirit of JC’s subjective side i’m gonna tell you about my latest endeavors with my nemesis of the last year or so.....the halo integrated.

After sending it back to be checked under warranty and it returning with the ‘it’s all in spec’ and still sounding the same.......weak transient response, as in leading/trailing edge was lacking making it appear ‘slow’.
While it was gone (a few months) I had plenty of time to research what I could try without actually changing anything internally (don’t trust myself in that capacity as of yet) and found that....

A) the Furman power conditioner may be part of the problem (throttled current?)

B) High capacitance speaker wire.....cardas 101 (278 pf/ft) that works well with my Yamaha might not be jiving with the Hint.

C) A change of fuse material (main in) could possibly make subtle changes in perception of speed/sharpness

So in a last ditch effort before trading it I picked some Belden 1313a (23.2 pf/ft, lowest C I could find with similar L and R) in the same length as the cardas.

Also the fuse with the most reports of ‘quicker’ and ‘sharper’ that was still reasonably priced.....turned out to be hi if tuning supreme black.

In the past couple days of testing with these I’ve found some interesting things....

A) the Furman had absolutely nothing to do with it and in my opinion sounds a bit smoother (all be it subjective) when in use compared to plugged straight to outlet.

B) tried the Belden wire (w/stock fuse) and while maybe a bit better it wasn’t the revelation i’d of hoped for.

C) tried changing the fuse alone with the original cardas 101 and again there didn’t seem to be any noticeable difference (tried back and forth a few times)

D) tried together and noticed things were coming around, not quick by any means but not slow anymore......acceptably relaxed is how i’d describe it.

So I played around with my test tracks and fiddled for a couple days I came to the conclusion that although prat was now at acceptable levels it still lagged behind the Yamaha on satisfaction level.

This morning I tried the coax spdif out of my elac discovery streamer directly to the Hint and was kindly shocked because before the dac in the elac was much smoother than the Hint, now the Hint is clearly superior than the Yamaha but only when using the on board dac.......I gotta tell you I was seriously underwhelmed by the Hint dac before.

Although these findings are all subjective, the changes were based in research to the best of my ability......I have no proof or even measurements for that matter (going off manufacturers spec on the wires) and strictly user consensus on the fuse.

My biggest question would be why such large improvement in the Hints dac? I mean it’s a big difference.

Also tried up and down on output gain of the streamer, both analog and digital were best in their original setting.

Flame away!
I’ve gone back and forth a few times and it is repeatable.

Bob
 
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The advice often given, even by experts, designers and sellers, about speakers is that you have to listen to them yourself to tell what you like, there seems no reason to assume that the same can't be said about any other component in your system. It's advice that cannot be argued with, of course it is utterly useless because it is utterly impractical for the vast majority of people.
 
Yep, and fuses ain't one of them

Really! And what do you think the effective AC power line resistance is from the power plant to your wall outlet? What is the cold resistance of say a 1 amp 3AG fuse?

(Answer typical power line .18 ohm, worst case .36 ohms per NFPA 70 electrical code. Fuse 1 amp slow blow .375 ohms cold and double that warmed up without failing.)

Now for Pavel and many others where the line voltage is 230 volts he would need to have a fuse rated 4 amps slow blow to better the line resistance.

More importantly the fuse resistance varies with current the power line resistance does not.

Next an amplifier drawing a mere 120 watts from a 120 volt AC power line does not draw 1 amp peak current (what the fuse responds to!) It easily will see a minimum of 10 times that. So the simple fuse resistance will make a 12% difference in maximum power output. A level that would be considered perceptible by most.
 
So the simple fuse resistance will make a 12% difference in maximum power output. A level that would be considered perceptible by most.

Listening near clipping (no disagreement please just asking)? My 110W amp had 7A 3AG mains fuses and 5A 3AG on each supply, I usually short all the fuses in my amps anyway, never had a problem I don't like loud music. BTW re: AP next time you see Bruce Hofer say high for me, he always sent his regards via our AP sales rep.
 
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Next an amplifier drawing a mere 120 watts from a 120 volt AC power line does not draw 1 amp peak current (what the fuse responds to!) It easily will see a minimum of 10 times that.

Absolutely not x10. You are again making up things to your convenience.

You are grossly exaggerating the fuse cold resistance (0.375ohm). https://www.socfuse.com/wordpress/wp-content/uploads/MCF3_datasheet.pdf an 1A fuse has under 0.1ohm cold, 1.25A is 0.06ohm cold. A factor of x4 to your number.

Each and every fuse rating is calculated based on (watts/volts) x 1.25 (125% of the normal operating current, watts are here not speaker power!), so 4A for a 100W 230V consumer is a hazard. Another factor of x3 in your numbers, x12 so far.

It is the filter capacitors that are seeing large current peaks, those are limiting the bandwidth, so the mains doesn't see large current spikes (perhaps except for the power on inrush current). This is the I^2t parameter and has little to do with the fuse rating, but with the fuse material/construction. If one needs a fuse to accomodate x10 current peaks, then the power supply is a disaster waiting to happen.
 
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Blame your twisted assumption, I have nothing to do with it.
Prime example of twisted assumption -->"However, a mole who works against the forum will call perfectly normal human ability as extraordinary to justify his behavior. He would spread lies telling everyone that he is not able to hear any difference on any difference being discussed, of course without any proof. He may even provide forged proof when somebody ask for it. We know falsifying ABX test to show inability to hear a difference is trivial for those who can hear."
 
Absolutely not x10. You are again making up things to your convenience.

You are grossly exaggerating the fuse cold resistance (0.375ohm). https://www.socfuse.com/wordpress/wp-content/uploads/MCF3_datasheet.pdf an 1A fuse has under 0.1ohm cold, 1.25A is 0.06ohm cold. A factor of x4 to your number.

Each and every fuse rating is calculated based on (watts/volts) x 1.25 (125% of the normal operating current, watts are here not speaker power!), so 4A for a 100W 230V consumer is a hazard. Another factor of x3 in your numbers, x12 so far.

It is the filter capacitors that are seeing large current peaks, those are limiting the bandwidth, so the mains doesn't see large current spikes (perhaps except for the power on inrush current). This is the I^2t parameter and has little to do with the fuse rating, but with the fuse material/construction. If one needs a fuse to accomodate x10 current peaks, then the power supply is a disaster waiting to happen.

Wow do you really not understand something so simple. A miniature fast blow fuse rated for 12.5 volts AC as you referenced is not even close to the types used to fuse the AC power line of an audio amplifier. Try an appropriate data sheet.

313 Series - 3AB_3AG 6_3x32mm Fuses Cartridge Fuses from Fuses - Littelfuse


Next you don't have a clue as to what the current into pretty much any audio amplifier looks like. It doesn't draw any current until the charging voltage from the transformer diode combination voltage exceeds what is stored on the filter capacitors. Very rarely do you see even a 5% sag on those capacitors. A 10 times surge is actually quite low for peak power but not unreasonable at a moderately loud listening level. I and many others have published this data and you are too freaking lazy to even look at what is out there.

The transformer does some some effective internal equivalent resistance, but a transformer would be useless if the efficiency in the power supply was 10%, the amount needed to drop the peak level to the average level!

Pretty obvious to most anyone, a short on the secondary of the transformer, power supply or even output transistors will cause the primary fuse to blow.

Attached is a simple shot showing the current peaking more than 10 times above the average current on a small transformer suitable for a pre-amplifier. Power transformers have much lower effective internal resistance.

Lets see any data you have measured!
 

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