John Curl's Blowtorch preamplifier part II

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#38,341
godfrey said:
Made up from 2200uF caps - you definitely bought them all!
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They come in bags of 250 so there's well under a single bag's worth in this contraption. I haven't shown the ones I bought most recently which exploded - you just can't trust these Taobao sellers to tell you the correct working voltage...😛

BTW, is that a spark plug sticking out the side? How'd that get in there?
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I had to go back to the amp itself to work out what that was - its the post of the 4mm binding socket to connect to the speakers.

@SE - I'm not quite as much a bass freak as that 😀 Don't tell JC but the input coupling caps are actually much, much smaller 1206 X7Rs 😉
 
#38,344
chris719 said:
You'll use 150000uF of rail capacitance but won't spring for PP or C0G coupling caps? 😛
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I've already sprung for them - have plenty reels of NP0, just too lazy to solder them all up as I wanted at least 1uF and the biggest NP0s are 100nF 🙂

I don't even think RocketScientist would use X7R for coupling 😉.
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Probably coz he was much more concerned about distortion (X7R comes with substantial voltage coefficient) than I. After all he'd invested a considerable amount in test gear. To me, if I can't hear it (and so far, I haven't) it don't matter 😀
 
#38,347
Yes, I agree it seemed extreme at first. But then I listened, added more caps and listened again. It made a difference to the LF dynamics - previously I could hear more low-level details on headphones, but with the extra caps the speakers have caught up a lot.

The amp'll play maybe 20s or so after I pull out the plug, depends on the music playing and the volume.

<edit> There's a way you can check if your current amp has enough capacitance, so long as you have a reasonably high impedance set of 'phones (or a trafo). Listen with the phones connected via resistive attenuator which presents a much higher impedance than a speaker. Then attach an 8R dummy load and listen again - if you hear the loaded amp gives poorer bass 'slam' you've just discovered your amp is undercapitalized 🙂
 
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#38,348
john curl said:
PMA, please, it is 'complicated' for most who look in here. They are not necessarily professional audio designers, like you, me, Nelson, Cordell, etc.
If I had a simpler complete schematic (proven to more or less work) I would have posted it. Even YOU PMA are somewhat confused by the schematic, or you would not have asked me about the asymmetrical loading.
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John, that is just so disingenuous. Where do you pull this stuff from?

OK, no need to answer - we are in polite company.

😀
 
#38,349
Abraxalito,
I assume you are using those caps after a smpsu, do you think that is making up for a too small power supply side there?

Today has been a recovery day from the Blue Screen of Death, Microsoft got me again with one of their critical updates. no way to fix the mess they made! I'll talk to you offline later Richard.
 
#38,351
I think, sometimes, that many here should try to understand a circuit, before they criticize.
It is a FACT that PMA found a problem in the switching logic years ago. After he informed us, we fixed it and I personally thanked him for his input.
Now, he talks about the 'UNEQUAL' LOADING of the -/+ outputs, respectively. Why would I do such a thing? Am I crazy? Please note that one side has a trim pot. Maybe, that will help. Yet PMA asked me about this within the last 24 hours, so I suspect that he too has not thought the circuit through completely.
 
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