John Curl's Blowtorch preamplifier part II

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~50 year old power transistors, a DIY museum ?
(care for a glimpse of a page in a NEC databook)

No it`s not some aparatus from museum , but actual DIY creation from far Japan , where even today Japanese DIY people use those rare vintage parts to made power amps following that very specific retro style ,
No PCB`s use (or very little use of them) , everything is connected using PTP (point to point) technique ,
Actually I think that those amps are mechanically designed as some old tube amps , but instead of tubes , tube sockets , we can see vertically stacked heatsinks , main transf. , and filter caps ,
all in all it is my favorite DIY style , easy for assembling and connection and very easy for maintenance and eventual repair ,
and the best thing is that I can`t see nowhere those fancy ugly LCD function front panels with blue LED back illumination . :)
 

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diyAudio Member RIP
Joined 2005
Copper would be even worse at low frequencies. The only way copper provides any significant magnetic field shielding is at higher frequencies due to eddy current losses from skin effect.

If you don't understand it, then go to Magnetic Shield Corp's website and show me their copper shielding that you guys are claiming is better than high permeability ferromagnetic materials. Go on, show me. If copper is better, these people should know. Maybe you can email them and set them straight on the matter as they've obviously been doing it wrong all these years.

ae
No one is saying (or at least I'm not saying) that copper is better per se. But make it thick enough and the low frequency cutoff improves, ditto with Al or Ag. What one does lose are saturation effects with wonderful substances like mu metal.

When Aguiar engineered the Ap AUX-0025, Hofer thought the case would be steel, and Duke cautioned that the steel would cause distortion. He was right, and the case is Al.
 
diyAudio Member RIP
Joined 2005
No it`s not some aparatus from museum , but actual DIY creation from far Japan , where even today Japanese DIY people use those rare vintage parts to made power amps following that very specific retro style ,
No PCB`s use (or very little use of them) , everything is connected using PTP (point to point) technique ,
Actually I think that those amps are mechanically designed as some old tube amps , but instead of tubes , tube sockets , we can see vertically stacked heatsinks , main transf. , and filter caps ,
all in all it is my favorite DIY style , easy for assembling and connection and very easy for maintenance and eventual repair ,
and the best thing is that I can`t see nowhere those fancy ugly LCD function front panels with blue LED back illumination . :)
I hope there are some good gate stoppers with those FETs.
 
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We're talking about shielding against magnetic fields. And absorption loss is the primary mechanism here. That's really the only way materials like copper can provide any real shielding at all of magnetic fields. It is the absorption loss due to skin effect that copper can be effective at higher frequencies.

se

You were doing fine up until that last sentence.


THx-RNMarsh
 
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Gentle men;

Now here you have my version of wretched excess. But that is about right for me. Each mono-block weights in at around 550 pounds ! Huge C-core transformer. CFA design (of course). >450v/usec. Distortion? What distortion? Power output? Cost? Don't ask. Yes, thats a class-A N.Pass amp dwarfed in the background.... and you thought That was a big size amp. These are in the listening room of Dr Kung down in Trang, Thailand (near the Malasia border).


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Well, someone had to do it.



THx-RNMarsh
 
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diyAudio Member RIP
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All three amigos have a K1000 as reference.
Those are still pretty nice headphones IMO, although I am not a headphone connoisseur. I am looking forward to auditioning Alex Rosson's top-of-the-line, and he just loaned a pair to my friend so he could evaluate them (although he has now parted ways with Audeze). Alex told me he started doing planar magnetics for loudspeaker line arrays, but moved into his acclaimed headphones after the arrays didn't look to be a winning strategy for sales.

A former friend (just one too many egregious slights and offenses over many years) used to have a prototypical exchange in which he would deride me for failing to do something or other, often knowing that it was a significant expense (for him he would just call his rich mother and beg, and she'd send a check). He touted the K1000 phones and said, as an apartment dweller, he simply couldn't understand why I didn't get a pair, and went on to mention that a retailer had a couple of show samples at a substantial discount. I said (for a change) Alden, you're right. I'm going to order a pair. Long silence on the line.

Well errrr if you call them tell them I am about to order a pair. I said (with clear intent of instilling paranoia, I confess) What if I get the last pair?

I had been loaned his Roland electronic harpsichord, and was told I could buy it from him. So towards that purchase I bought both show sample pairs of K1000 and told him I would send him his.

This evoked a storm of dismay, tax records/expenses no no no this shall not stand. So I called the retailer and said Sorry, etc. and just got the one pair for myself.

Eventually he reneged on the harpsichord and had to have it back. Of course by then they were no longer available. I considered disassembling it and sending it back as a kit, part by part :gnasher:
 
But you could achieve the same thing with a lot thinner steel chassis.

se

I understand and agree, but my points were raised in support of Brad's original point that a solid hewn chassis made out of Cu would have pretty darn good magnetic shielding as well. The fact that such a proposal was patently ridiculous and a waste of material was, well, immaterial to the discussion. :D

The high-end ($$-wise, at least) of audio has spoken and they like their massive chassis--might as well get take advantage of the aesthetic in an attempt to benefit other aspects, no?
 
diyAudio Member RIP
Joined 2005
I understand and agree, but my points were raised in support of Brad's original point that a solid hewn chassis made out of Cu would have pretty darn good magnetic shielding as well. The fact that such a proposal was patently ridiculous and a waste of material was, well, immaterial to the discussion. :D

The high-end ($$-wise, at least) of audio has spoken and they like their massive chassis--might as well get take advantage of the aesthetic in an attempt to benefit other aspects, no?
And a hogged out silver chassis could always be gutted and melted down, if one needed money :D
 
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