John Curl's Blowtorch preamplifier part II

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#50,882

I am not expecting to see a resurrection of Kuba consoles - different aesthetics today- but you are correct on the validity of the utilisation/looks concept (besides, we all know that at home, women rule and this for a reason).
In Europe, the ‘system’ concept was adequately explored in Germany, Holland and went full power in Denmark.
With systems of ~ 1965 one can see and study the most advanced all-tube implementations/matched speakers.
As my heart goes to radio reception (all bands), there is no further real progress since then, save for the IF section implemented in DSP

Scott, I think that for analog synth circuits, there was nothing that Moog hadn’t explored.

George
 
#50,886
john curl said:
So that Scott Wurcer's question is answered: What the reviewer what trying to relate was that I followed Ed Simon's advice to put a 50-100 ohm resistor at the INPUT of the IC to remove some difficult to fix oscillation, yet I bypassed it with a coil of wire to BYPASS the resistors noise at audio frequencies. Too bad I had to resort to this input resistor, because it would potentially reduce the S/N by 3dB or more. This is a 'flaw' in the IC design, in my opinion.
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These amplifiers are often designed for RF applications and as I have said in the past the self damping of the base (rbb) is to low for RF stabilty with audio interconnects and random hookup wires on the input. If you parallel up enough low noise high ft transistors they can and will often oscillate. Would you prefer the 100 Ohm inside the chip?
 
#50,887
I have 2 identical Borbely Millenium stereo amplifiers. 1 dual channel version uses a Hafler DH 200 chassis with 62 VDC rails, 600 va toroid, and 54,000 uf and the other pair sit in a Krell chassis with 700,000 uf of caps and 2 x 600va EI core transformers and 50 volt rails. Passive components are identical and all active components have IDSS matched within 0.1 ma. The front ends use regulated rails.

The larger power supply version despite it's lower voltage is more dynamic, smoother sounding, and the bottom end extends deeper.
 
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#50,888
PS Audio, are the first ones I heard of to say that a much larger transformer sounded better. How much does the size of the first filter cap play into this? Would a large transformer sound better with any size of filter cap, or does a large cap need a big transformer, to sound best, due to the higher current charging pulses?
 
#50,890
Rick Miller said:
PS Audio, are the first ones I heard of to say that a much larger transformer sounded better. How much does the size of the first filter cap play into this? Would a large transformer sound better with any size of filter cap, or does a large cap need a big transformer, to sound best, due to the higher current charging pulses?
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From What I remember it was the thought of lower impedance secondary ps audio first spoke of with small current requirments so the current pulse was small.
 
#50,893
Rick Miller said:
PS Audio, are the first ones I heard of to say that a much larger transformer sounded better. How much does the size of the first filter cap play into this? Would a large transformer sound better with any size of filter cap, or does a large cap need a big transformer, to sound best, due to the higher current charging pulses?
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What happens when secondaries are snubbed correctly.
Does that reduce/remove the subjective differences noted ?.

Dan.
 
#50,896
hitsware said:
The affect of overbuilding power supplies
is one of those mysterious things that can
be heard but not measured. I.E.
There is an audible differance between a
1000 Watt P.S. and a 100 Watt P.S. ......
Both supplying the same 1 Watt through
the same 10 Watt amplifier ........
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Overbuilding is just one way of making a conventional power supply work a bit better than they normally do - no mystery in it at all. It's very easy to hear PS problems in most amplifiers, typified by the quality degenerating into classic "hifi" sound ...
 
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#50,897
Max Headroom said:
What happens when secondaries are snubbed correctly.
Does that reduce/remove the subjective differences noted ?.

Dan.
Click to expand...

There are transformers that will give more volts if the secondary isn't snubbed or bypassed with a large cap, because it rings and this boosts the voltage.

I've found that snubbing the transformer often makes a big difference, but more in the treble and midrange than the bass.

I think in some cases resonances cause a "loud" sound and so the volume is turned lower, and then you wonder where the bass and everything else went. All the women sound like they're screaming at the top of their lungs. My objective as of late is to get this fake loudness as low as possible so all the details can be heard at any volume setting. The joke may be on me here though because I've measured the THD in these cases and nothing is different before or after the effect is removed.
 
#50,898
keantoken said:
The joke may be on me here though because I've measured the THD in these cases and nothing is different before or after the effect is removed.
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And this is where a better way of measuring is needed - I've used snubbing on various cheap components, and the audible improvement is obvious, yet I'm sure that conventional testing approaches would have picked up little.

That "fake loudness" is the giveaway, even a cheap chip amp can be pushed well into soft clipping territory without that intruding, if the right measures are taken ...
 
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