John Curl's Blowtorch preamplifier part II - Page 305 - diyAudio
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Old 25th November 2009, 04:13 PM   #3041
iko is offline iko  Canada
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Reminds me of some of the BMWs, which have the little sticker about high octane gas requirement. The car's been obviously engineered to run better on high octane gas. Perhaps all you were missing John, is the little sticker that mentions cable requirements. One can hardly make the argument that said BMWs are subject to bad engineering because they require good gasoline.
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Old 25th November 2009, 04:24 PM   #3042
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Ikoflexer, we OFFERED to build in a low Z buffer, IF it was requested. This was in our specifications. Every BLOWTORCH was made to custom specifications. You could have: phono, balanced input, different impedance TKD pots, and an OUTPUT BUFFER. These usually cost extra, but they were offered to discerning clients, to meet their specific needs. Balanced output was usually offered without charge, but I have an example here that does not have balanced output, as the client thought it unnecessary at the time.
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Old 25th November 2009, 05:23 PM   #3043
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Repent, Sinners.
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Old 25th November 2009, 05:33 PM   #3044
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Originally Posted by scott wurcer View Post
This is one tradeoff I have no problem with. The best pulse generator we ever had was open loop current out with the 50 Ohm termination only at the other end. And yes, cables made a difference.
Yes. HP 8001 anyone? It made a difference in fractional uS risetimes and high frequency transients. About 4 orders of magnitude above audio frequencies?

Anyway, 1k was never a standard. 1k, and sometimes even up to 5k, Zout came from the technical limitations of vintage (tube) preamps and/or its designers. Nowadays, it is really trivial to get a few orders of magnitude lower Zout and that way, orders of magnitude less influence from load pecularities. Tradeoff? What tradeoff?

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Old 25th November 2009, 05:39 PM   #3045
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John, I wasn't criticizing your choices, in fact I find them perfectly sensible. You achieved the results you wanted.

These people are shouting from the hill top that your preamp is obsolete, meaning there are much better choices lately. Hey, the Honda S2000 is an engineering masterpiece, but I'll go out on a Sunday anyday in this obsolete one

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Old 25th November 2009, 05:54 PM   #3046
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[snip]These people are shouting from the hill top that your preamp is obsolete, [snip]
Really? The only thing I noted was a discussion on preamp Zout.

Also, John stated that the reason for the high Zout on the BT was that it was requested by the customer. So, why not give him what he pays for? John is perfectly able to make a Zout as low as he wants, within reason.

But in engineering terms, high Zout is not a good thing because you surrender the performance of your preamp to whatever is hung off of it.

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Old 25th November 2009, 06:01 PM   #3047
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Originally Posted by ikoflexer View Post
Reminds me of some of the BMWs, which have the little sticker about high octane gas requirement. The car's been obviously engineered to run better on high octane gas.[snip].
'Obviously' this is extremely naive.

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[snip]One can hardly make the argument that said BMWs are subject to bad engineering because they require good gasoline.
In fact one can. It's more difficult to engineer a car to run well on low octane than high octane fuel.

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Old 25th November 2009, 06:03 PM   #3048
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Originally Posted by janneman View Post
Really? The only thing I noted was a discussion on preamp Zout.

Also, John stated that the reason for the high Zout on the BT was that it was requested by the customer. So, why not give him what he pays for? John is perfectly able to make a Zout as low as he wants, within reason.

But in engineering terms, high Zout is not a good thing because you surrender the performance of your preamp to whatever is hung off of it.

Don't read what isn't there

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Old 25th November 2009, 06:11 PM   #3049
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'Obviously' this is extremely naive.
In fact one can. It's more difficult to engineer a car to run well on low octane than high octane fuel.
jd

It's not like they haven't done it, as in the R1200GS bike, which features automatic knock control. But as an engineer you know yourself the difference between not having the problem in the first place, and having the problem AND adding extra design and manufacturing to provide a solution.

Sometimes you can have a simpler design (and manufacture) IF you allow for less options, as in "stick to cables with X and Y parameters" or "stick to high octane gas." I do see it as a trade off. Plus, he says the offer for the extra circuitry was available. I find that reasonable.
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Old 25th November 2009, 06:17 PM   #3050
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Originally Posted by ikoflexer View Post
It's not like they haven't done it, as in the R1200GS bike, which features automatic knock control. But as an engineer you know yourself the difference between not having the problem in the first place, and having the problem AND adding extra design and manufacturing to provide a solution.

Sometimes you can have a simpler design (and manufacture) IF you allow for less options, as in "stick to cables with X and Y parameters" or "stick to high octane gas." I do see it as a trade off. Plus, he says the offer for the extra circuitry was available. I find that reasonable.
Sorry, but ignoring the problem and leaving it up to the customer to fix it (i.e. find cable xyz) is bad engineering in my book. But I agree, if that is what the customer wants, hey, it's his money.
But anyway, I prefer to stick to engineering. Anything else like you mentioned above comes dangerously close to marketing strategy

BTW Nice car. Shelby?

jd
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