John Curl's Blowtorch preamplifier part II - Page 2100 - diyAudio
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Old 1st March 2012, 05:26 PM   #20991
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Quote:
Originally Posted by SY View Post
Since the source impedance is ten times lower, the frequency response variations will be ten times lower.

I did not design my amp to drive 0R5 loads. The Wavac is sold to drive (more or less) 8R loads. That's the target of my design as well.
I suppose according to measurements I've seen here that Wavac was designed to drive horns. And it is quite adequate for that. I would ever did not consider testing it in terms of how well it would drive 87 dB/W/M 3-way speakers with chocking crossovers.
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Old 1st March 2012, 05:43 PM   #20992
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Quote:
Originally Posted by Wavebourn View Post
I suppose according to measurements I've seen here that Wavac was designed to drive horns. And it is quite adequate for that.
If horns have varying impedance with frequency, then it's a tone control. And a tone control with high distortion. Some may prefer that, but it would be easy to duplicate the effect for about 0.5% of the cost.

edit: Actually not a tone control, a fixed and uncontrolled EQ. Sorry for the sloppy terminology.
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Old 1st March 2012, 05:49 PM   #20993
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Quote:
Originally Posted by SY View Post
If horns have varying impedance with frequency, then it's a tone control. And a tone control with high distortion. Some may prefer that, but it would be easy to duplicate the effect for about 0.5% of the cost.
Yes, if you sense directly voltgages on speaker binding posts instead of listening to sounds.

I did that when I was a kid and did not have a voltmeter. I checked such a way batteries. The sourer are they, the fresher they are.
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Old 1st March 2012, 05:57 PM   #20994
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Quote:
Originally Posted by john curl View Post
Well, thank you very much, SY, yes, I have to 'eat' and we found that it just was not worth it to make CTC Blowtorch preamps after the initial run. No profit in it.
Eating is good. And profit is good too, albeit elusive.

This reminds me of would-be businesspersons, usually chafing in their day job, who look under the hood of some existing product, do a quick estimate of the Bill of Materials cost, and reckon that the machine is overpriced horrendously. One young man (well he's a lot older and presumably wiser now) decided he could make a product to compete with the Valhalla Scientific power meter, and sell it profitably for about double his parts cost!

Aside from living at home, eating and sleeping rent-free, and having a free workspace (the garage), he was hopelessly unaware of the intricacies and requirements of running a manufacturing business.

And another friend, who ought to know better, but again has never manufactured anything, also somehow believes that he can sell a piece of test equipment for not a lot more than a similar markup on parts. Despite being in his eighth decade and a one-man band, he expects as many as 40 or more customers to pay a substantial sum for an instrument that will somehow require no support from him (well, there won't be anyone else!). I asked him why he was doing this, and his answer was: To make money!


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Old 1st March 2012, 06:16 PM   #20995
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Sy,

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So are you saying that there's merit in a $350k component with dreadful performance?
Funnily enough, the US is AFAIK the only country that has actually trade enforceable standards regarding amplifier advertising/measurements. If you feel that there is something going on that violates these maybe you should, instead of airing your complaints here take them to the correct authorities.

Do I personally see merit in a 350K Amplifier (regardless of what it measures like)? Nope. But some people do and they are welcome to their 350K Amplifiers.

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I don't follow your plastics chemistry analogy. In that field, data and performance are the drivers. You can't market a $1000/kilo plastic with lousy measured mechanical performance by claiming it made your toothbrush feel better.
No, that you cannot. But you can engage in many ways that are likely worse, from an ethics viewpoint. Surely you know about the goings on than me, seeing you directly work in this sector, I only get involved very peripherally in the context of ERP System Implementations, where testing for plastics is now a ridiculously big issue.

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Old 1st March 2012, 06:29 PM   #20996
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I know a man who works for laboratory nearby that designs silicon-organic plastics. They could be sued and suffer significantly for crash of European air-liner, if his boss did not have a paper where he clearly recommended that particular plastic for hockey sticks.
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Old 1st March 2012, 06:42 PM   #20997
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If you feel that there is something going on that violates these maybe you should, instead of airing your complaints here take them to the correct authorities.
I have no idea what they do and don't advertise, nor have I mentioned that. Nor have I "complained" about it- this all seems to be made up from thin air.

I suspect that the "authorities" don't give much of a flying intercourse about overpriced poorly-performing fashion baubles. Nor should they. If someone is stupid enough to buy it, that's their worry, not mine.

Quote:
But you can engage in many ways that are likely worse, from an ethics viewpoint. Surely you know about the goings on than me, seeing you directly work in this sector
Yes, I do. By and large, most industry behavior is reasonably ethical. Materials advertised to have a tensile strength of "x" usually have a tensile strength of "x." No one tries to sell $1000/kilo plastics with vague claims of them making products feel better. Attempts to market materials fraudulently are quite rare- I've seen that happen maybe twice in the 30 years I've worked in the plastics industry. But high end audio is a fashion industry, so I think you'd do better analogizing to (say) the jewelry business or perfumery. Or even the wine business, where I saw dozens of examples of outright fraud in the decade or so I spent doing that.
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Old 1st March 2012, 06:47 PM   #20998
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I saw dozens of examples of outright fraud in the decade or so I spent doing that.
What?
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Old 1st March 2012, 06:54 PM   #20999
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At the risk of going off-topic (loud chorus of laughter) I have to mention a plastics story.

I have two on-loan turntables, both Heybrook TT2, which if I understand correctly were promoted as something of a poor-person's Linn. One is fitted with an SME V arm and a Grado moving iron cartridge of some vintage.

To begin with, for both turntables they were dead-on-arrival, much to the surprise and consternation of the loaning party. So I have had to replace components in both power supplies (crystal-oscillator-derived signals and a discrete high voltage amplifier for the synchronous motor). Two different crystals are switched via the top rotary switch, a terrible idea, and as well the dry-contact character means the switch gets intermittent, with the thing just quitting in the middle of a play sometimes. But you roll with the punches.

Also, with both 'tables, just sitting there or with use, doesn't seem to matter, the hinges for the dustcover eventually break out of their slots. So they have to be removed and the cover, if used, placed over the machine and positioned carefully. OK, inconvenient but again one r's with the p's.

So one day I noticed that a large accumulation of dust on the cover might do with some wiping-off, and got a dustcloth. I did this, perhaps a bit unwisely, while a record was being played.

The static charge thus induced lifted the SME arm right off the record, to stick to the cover. Electrostatic force 1, graviational force 0, for that round.

It did lead me to speculate about how many times residual electric fields might be spoiling the assumptions of carefully adjusted tracking force.

As one might suppose, I play records with the cover removed now, factoring in the greater need to wash the records from time to time.


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Old 1st March 2012, 07:06 PM   #21000
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Saddest of all, it's easy to add antistat into plastics during manufacturing and avoid the whole issue.
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