John Curl's Blowtorch preamplifier

[john curl]

Well, a slightly larger resistor helps to approximate this ideal.

 

[albin]

new stuff is wrong

Philosophical,Isn't this the only way forword
x posts I don't won't to offend but it's allways like this

regards
me

 

[john curl]

Think it through with a real resistor that you can buy, (or afford). Include thermal capacitance.

 

[pooge]

I'm referring to the post were Peter Daniel said:


Yes, Placette is very well regarded and I've been using it for a while myself. However, after initial excitement, I was starting noticing defficiencies, mainly the coloration.

And:

But in the end, TVC is not perfect either. I have a chance listening without any attenuator now as the amp has just the right gain for normal levels and it's very revealing experience.

So what exactly is your point?? You seem to be talking down TVCs while relying on a post that says they are the best volume control he's heard. Nothing is perfect, or we wouldn't be having this discussion.

 

[albin]

I think the time difference screws things up

Well, a slightly larger resistor helps to approximate this ideal.

I'm a bit in my cups now,burning amp might be good but the distances are extreme.
i'll get my coat
regards
Max

 

[GK]

I'm staying out of the resistor discussion. When a tech at Mass. General says upgrading a doppler ultrasound with naked Vishay resistors gets the surgeons to claim a "huge" improvement in circulatory diagnostics maybe I might listen.

Oh c'mon, I'm sure that happens all the time.

 

[john curl]

In many cases, the SIZE or length of the resistor is not very important. Usually, you need a certain distance between point A and point B for a feedback resistor. All else being equal, a larger resistor probably is better.

 

[albin]

if you work in 2 dimensions

What about 3
orthoganality & all that

 

[audiowolf]

While we are on the topic of resistors...here is a new line of 4,000 volt rated parts....I would guess that most of us would never need these, but in a time when most everything is going to 3 or 4 volt supplies and low standby currents [ class B yukky op-amp stuff, ] it's interesting to see parts being developed for really high voltage. the extreme other-end of the voltage range

http://www.ecnmag.com/product-Resistors-Present-High-Dielectric-Withstanding-Voltage.aspx?menuid=338

 

[stinius]

In many cases, the SIZE or length of the resistor is not very important. Usually, you need a certain distance between point A and point B for a feedback resistor. All else being equal, a larger resistor probably is better.

I’m not sure how you came up with this theory, and it seems a bit vague.
My answer would be NO, but please explain the theory maybe you are right.

Cheers
Stinius

 

[bear]

I'm staying out of the resistor discussion. When a tech at Mass. General says upgrading a doppler ultrasound with naked Vishay resistors gets the surgeons to claim a "huge" improvement in circulatory diagnostics maybe I might listen.

Scott,

I just spent an AM in the factory & lab of a fellow who has multiple patents on transducers used for ultrasound imaging of arteries and the like... the upshot of our discussion on his work went something along the lines that he gets/got the superior performance he gets because he shaves every fraction of a dB of performance that he can in every area that is possible. It adds up. Cascading tolerances and all that rot?

To me that is akin to all of these discussions, resistors included.

Perhaps 10 seconds into the future when these differences or non-differences (in resistors or what have you) are parameterized and can be measured, as some other formerly unmeasurables are now, this sort of question will be looked back upon as somewhat silly.

Of course some think that this will never happen because "it doesn't exist." Which is fine too...

_-_-bear

 

[Steve Dunlap]

So what exactly is your point?? You seem to be talking down TVCs while relying on a post that says they are the best volume control he's heard. Nothing is perfect, or we wouldn't be having this discussion.

I'm not talking down, just trying to point out that there are drawbacks (or compromises) to every thing you must add to the signal path. I feel there are less expensive and proven solutions for everything that TVCs are claimed to do so well.

With cost no limiting factor these days, why isn't John and everyone else using TVCs?

 

[albin]

When electrons tussle with each other

I'ts always at the speed of light,all the time,electrons never stop.matter is empty except for electronic interactivity
idiot
I am
regards
Max

 

[CG]

A long time ago, Roederstein actually published distortion graphs of their Resista brand resistors in their catalog. What I do remember is that the 1/2 watt version had clearly lower THD (yep) than the 1/4 watt variety.

So far, I haven't located the catalog but I am still looking...

 

[scott wurcer]

0 to 80V in 10uS. Then -80V in the next 10us. It is SUPER RESISTOR! Unfazed by extreme voltage swings, able to stay at EXACTLY the same resistor value, no matter what! No excess noise!

John please tell me where in the Blowtorch there are 160V p-p signals. How does excess noise figure on the 10us time scale, it's not particularly temperature dependent either? We have had thin film resistors for 30yrs with almost unmeasurable excess noise, this is just blowing smoke.

 

[Joshua_G]

The thread becomes very interesting.
It seems to me that some core issues are being addressed.
However, I have nothing to contribute at this time – that is – I'm listening with me ears wide open (but mouth shut).

 

[scott wurcer]

Scott,

I just spent an AM in the factory & lab of a fellow who has multiple patents on transducers used for ultrasound imaging of arteries and the like... the upshot of our discussion on his work went something along the lines that he gets/got the superior performance he gets because he shaves every fraction of a dB of performance that he can in every area that is possible. It adds up. Cascading tolerances and all that rot?

_-_-bear

That's the point bear he measures it. I've known dozens of these guys outside of audio, good solid engineering often self taught. It's ONLY in audio that this stuff turns up.

 

[john curl]

The Parasound JC-1 does exactly what I described.

 

[analog_sa]

With cost no limiting factor these days, why isn't John and everyone else using TVCs?

Because they are coloured and limited in resolution? TVCs make sense only in passive preamps as they solve some of the passives deficiencies. Once you choose to go active they suddenly become a limiting factor.

 

[PMA]

I thought we were discussing volume control resistors. In my high voltage dividers, voltage stresses over components are much higher than this described in JC-1. Does it mean I should use resistors from a HV divider to a volume control?