John Curl's Blowtorch preamplifier

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john curl said:
Bourns is a good, low cost, alternative.

I like Bourns sound quality, but we had tracking problems with early pots.
Audible Illusions used a modified Bourns pot for many years in their tube preamp.


Thanks John.
My suggestions are of course for low cost, in compare to Blowtorch.
There are many less good potentiometers to find in amplifiers
than the Bourns conductive plastic, CP, models.


About tracking 🙂
Almost all dual log potentiometers for stereo audio use,
have some tracking deviations, unlinerity, maybe like 0.5-1.0% for a good quality.
Here is where a stepped attenuator, with say 10 fixed resistor dividers can be a bit better. Will allow you to fine trim to accuracy.


But how important is Volume Attenuator matching between left right?
I would say it is not very important, at all.

Considering the mismatch that can take place in
... X-over and Speaker driver components.
+ Room sound reflextions
+ Our human hearing imperfections!
*************

😀 There is no man around,
that have the same audio freqency hearing curve
for his left and his right ear.
I would say :;

(of course humans get used to these his own ear imperfections
& final preception may filter & mask this mismatch effect very well)


Lineup
 
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Indeed.

I try to share some of my experiences by letting people know what I have found be very good components and practices. Maybe some will try these, and see if they like them, too.

I am also learning from people posting here. There are some very good designers here with long experience. There are also some people that ask hard questions which makes me think twice.

I am not sure Jan is totally correct in his statement. As I see it the BT uses mostly very good parts and has a very good amplifier and PS design.

You say the parts are expensive, but say that they are worth every penny. I think we have a major difference in thinking here.

Regarding TKD pots, I have not said that I reached the conclusion below. I think you have mixed me up with someone else.....

I prefer stepped attenuators with either relays or a rotary switch.




Sigurd

syn08 said:


So, you always measure your stuff and then search deeper than this. You are comparing measurement results with subjective tests and try to understand why preamps sound different.

This is impressive stuff. Could you share some of your experience regarding this approach? A case study would do great.

Just curious, how have you reached the conclusion that the TKD pots are the best? There must be something that persuaded you to invest that kind of money. Was it the specification, some subjective listening results, some measurements? Word of mouth recommendation, price, reputation?

The BT (or whatever other brand) costing 15k tells me absolutely nothing. As Jan already mentioned, there is no obvious relationship between the cost and the performance. To me, it is 15k because it uses expensive TKD pots(?), an amazingly expensive case, etc... The next step, from these expensive parts to the BT ultimate quality is not clear to me. How a BT with Alps pots would measure and sound, we don't know and it is unlikely we'll ever do.
 
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Sigurd Ruschkow said:
[snip]I am not sure Jan is totally correct in his statement. As I see it the BT uses mostly very good parts and has a very good amplifier and PS design.

You say the parts are expensive, but say that they are worth every penny. I think we have a major difference in thinking here.[snip]Sigurd


Not really. I didn't say that the parts are not worth their money. Although, I believe that in tests that focus on the sound, excluding all other factors, many of those parts would not sound different from less expensive ones.

My reasoning was more that a major part of the price point of very expensive hi-end stuff is caused by the very limited production run. Therefore, it logically follows that price is no indicator for quality, and as collorary that it is in theory possible that widely differently priced amps could be identical inside and out and sound identical.

Jan Didden
 
Re: Re: Pass Labs

analog_sa said:
Better? Of course, all the annoying clicking noises are gone. Not to mention they're even cheaper than relays.

As much as i like Pass preamps, they are hardly pushing the boundaries of transparency.

Actually the circuits are quite unique and have a patent pending. They are in
fact more expensive than relays.
 
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PHEONIX said:


Hello Sigurd

What reistor to you use in switched attenuator that you like, and how many position is the switch.

Regards
Arthur
I'm not Sigurd, but I've tried both 1 dB steps and 1.5 dB steps. I find 1 dB just right, passives can be bought with 0.1 dB steps, you might convince me that 0.5dB is needed but past that I believe we've traded too much money for little return.
 
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Sigurd Ruschkow said:

You say the parts are expensive, but say that they are worth every penny. I think we have a major difference in thinking here.

May I suggest some sublime cables to match your sublime TKD pot or switched sublime foil resistors preamp?

http://www.kosmic.us/equip-cables-acrolink-mexcel.html

I agree, "we have a major difference in thinking here."
 
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syn08 said:


May I suggest some sublime cables to match your sublime TKD pot or switched sublime foil resistors preamp?

http://www.kosmic.us/equip-cables-acrolink-mexcel.html

I agree, "we have a major difference in thinking here."

Wow, thanks for the link! I just ordered enough to wire my whole system, and my mother in-law's. I plan to be in sonic heaven soon.

What could possibly go wrong? :cannotbe:

On a serious note, I'm curious as to how much business a site like this does.🙁
 
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MikeBettinger said:

On a serious note, I'm curious as to how much business a site like this does.

Here's another link: http://www.lotusgroupusa.com/Mexcel.htm Check the price list - the Sublime is reached for the 2.0 meter 7N-S20000 speaker's cable, at the bargain price (and certainly "worth every penny") of $11,000 (eleven thousands US dollars).

There is also a $3,200 (thirty-two hundred US dollars) power cable, probably blessed by Tibetan monks. Can you even imagine the sound of a BT preamp using such a power cable?

And here's the japanese manufacturer's website: http://www.acrolink.jp/english/

Quote:

Ultra high purity, 6N (99.99997%) copper; advanced refining process still leaves the great variations in composition of impurities and crystalline structure according to employed method. All 6N copper materials are different, and in reality, most of so colled 6N,7N materials are not measured comprehensively. As shown in disclosed analysis table, ACROLINK is the sole producer of stabilized ultra pure copper. It is essential to maintain high purity, when necessary to achieve extended frequency response because composition of impurity inhibits capability due from impedance variance.

A unique stress-free process is applied after formation of actual cable core structure for maximum effect, in special environment maintaining original purity to restore crystalline disorder caused by extrusion process

Insulation material High performance Ecological Polyethylene has excellent sound quality and low dielectric constant factor. New polymer polyolefin, presently the best material available, has been chosen as insulator for extremely low dielectric constant factor which is 1/3 of polypropylene and 1/4 of PVC.

Resonance absorption is one of big factors to decide final sound quality. ACROLINK always paid extra attention and built up tremendous know-how. Every product is carefully composed with selected materials in order to achieve perfectly balanced and effective absorption.
 
Cables are not parts. They are accessories. Last BT 5 pieces batch was sold for $11000 each. Guess who is making money. John Curl or the cable guru? So even if they only sell a handful of such cables worldwide, there is fat profit.
 
I have listened to many super expensive cables due to my doing enough repair and installation service for some very rich audiophiles and a luxury high - end importer.
Such accessories are colored in my experience. The thing with high end components is that the most of them are being developed with such accessories present. Also elaborate racks etc. They are made to sanitize some certain school systems. With others they work dissonant. They are audible enough so to break or make certain aesthetic criteria that the customers are after in the final sound, they don't care if transparent or correct to the recording, just to like it. All those systems have a certain tone, they translate.
 
I believe he is correct. As of this writing, I believe no-one has overcome the laws of physics with regards to transmitting a wideband 'signal' (motional electrical function) down a 'waveguide' (And yes, the word applies) without the signal interacting with the materials involved. Besides, the signal itself has a 'perfect' conduit for only one specific 'frequency', on all others it is 'electrical dissonance'. Only at ultra high frequencies does the cable become the simplistic lumped parameter that it can be. There is only one transmission method (and cable) I am aware of that meets the criteria that a horrendously wide band signal (that starts at near DC and proceeds through the skin effect region) such as an audio signal needs to see, in order to be transmitted more correctly. Ie, with the least amount of harm and interference. Many here know this, but fail to remember why it is important to consider that: Audio signals are far more bandwidth intensive than any other signal other than a digital one. This is due to the fact of how the signal rides in the cable at near DC..and then proceeding upward, through octaves (or doubling of frequencies) and then through each, calculating the changes in impedance considerations due to pathway and signal interactives. It seems simple, but it gets quite complex.

The complexity of the situation and the resultant sonic 'mash' causes folks to try just about anything in the world of cable design-to try and fix it. So far, no cable does it all, for all frequencies. Save one. 😉

Getting back to the potentiometer.

The same considerations exist elsewhere. Hhmmm. So..on a power amplifier (simple amp, NPN-PNP-BJT, one pair per channel)......I tried about 470k from emitter to ground. I'm still listening.

Remember..the ear is a 'transient - over time' type device. Avec Harmonics as a consideration. Which is why one might never quantify, in measurements, the addition of the 470k resistor. But it can be heard.


A very light exaggeration, but still it holds much truth:

To the measurement system, the peak transients equal about 0.1% of the signal.

To the ear, they equal 100% of the signal. Measure and quantify what the ear hears.
 
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