John Curl's Blowtorch preamplifier

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#7,961
janneman said:
I find it odd that, while audio is ALL about perception, nobody is interested to know how we perceive. What's the point fiddling with equipment if you don't even know how you handle the result?
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Back when I always trusted my ears implicitly I had no need to know, I just fiddled.
Now I know a little more I still fiddle, I guess I just like fiddling. There could be no point, but I can't stop, maybe therapy is needed, but that can be even more expensive, and you end up with nothing 😀
 
#7,962
A component or subsystem that is responsible for adjusting the volume is so vital, IMO, that 800 USD is a good price!

A stepped attenuator made with a Shallco and then filled with high end resistors will be in the same price range.

Ayre's remote controlled stepped Shallco atttenuator with a belt drive used in their latest preamp is no cheap choice either.
Nor is Lyra's version.


This is far far far from snakeoil business!


Sigurd



syn08 said:
Let me understand this correctly: $800 for a pot? Have you people hit the jackpot?

Somebody was asking for an example of snake oil merchands...
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#7,963
This is kinda sad!
Why not use the good parts of the BT (electronics and PCB layout and wires) and get rid of the too costly case and pot and exchange the case with a more normal case (which needs to have some research put into it) and a remote controlled stepped attenuator and call it BT MkII?

One could even just use manual Shallco with bulk metal foil resistors if remote controll is too much work.



Sigurd

john curl said:
Now, some can understand why the Blowtorch cost so much. We didn't compromise and used these TKD pots. They got so expensive, later, that this made us not want to make any more units, as well as the extra cost of the cases over time. This is why the CTC is not made anymore.
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#7,964
Sumph Music SPL

Regarding SPL from s full symphony orchestra, the max SPL can vary a lot. String music is often low but brass music can be so high that one needs to protect one's ears.

I was at a concert a week ago where the Swedish Royal Philamonic Orchestra played film music by John Williams. Music from Star Wars, Jaws, Harry Potter, ET, Indiana Jones, Jurassic Park etc etc,
and his music often uses brass a lot. I think it was 14 brass players playing at this concert, and I can tell you that it was sometimes so loud that my kids had to protect their ears, and I found it too loud, and I do like it very very loud.

This was from 1st balcony and in a huge modern church, and the acoustics is not as good as the concert house where the orchestra usually plays.


Sigurd

bear said:



Now, as far as "symphonic levels" are concerned?
You're gonna be surprised.
I've measured a symphony orchestra, with full choral singers in the Troy Savings Bank Music Hall (google it), an 1890's construction fwiw, and the max levels at the front of the first balcony were <100dB.!!


_-_-bear
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#7,965
Sigurd Ruschkow said:
A component or subsystem that is responsible for adjusting the volume is so vital, IMO, that 800 USD is a good price!

A stepped attenuator made with a Shallco and then filled with high end resistors will be in the same price range.

Ayre's remote controlled stepped Shallco atttenuator with a belt drive used in their latest preamp is no cheap choice either.
Nor is Lyra's version.


This is far far far from snakeoil business!


Sigurd
Click to expand...
Hello Sigurd

Dont assume that the Lyra uses expensive high end resistors in their stepped attenuator in the latest line stage.

Have you heard either the Blow torch preamp or the Lyra Connosieur 4L-2L SE preamp .

Regards
Arthur
 
#7,966
Damien,

I pay 3X-4X more for a the smaller in size bulk metal foil pots from Texas components. I use them for trimming purposes inside amplifiers.

From where do you buy them for only 12 USD?




Sigurd

1audio said:
Quick, cheap and essentially as good as you can get for a pot Trimmer . Adjustment is a little tedious but in reality most people don't adjust for every cut. And for a modest investment ($12 ea) you can have a baseline to compare to.
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#7,967
Hi Arthur,

I have unfortunately not had the oppurtunity to hear either the Lyra amps nor the BT. They are not available here in Sweden and I do not travel much anymore (except for vacations with the family).

I am under the impression that Jonathan Carr has used bulk metal foil resistors in the 4-2L SE. When he was on the forum a few years back, he sometimes mentioned the bulk metal foil resistors as being some of the best, if not the best there is.

Do you maybe know more about the resistors Jonathan used for his Shallco rotary switch?

BTW,
anyone know what Jonathan Carr is doing these days (no new amps for ages)?


Sigurd

PHEONIX said:

Hello Sigurd

Dont assume that the Lyra uses expensive high end resistors in their stepped attenuator in the latest line stage.

Have you heard either the Blow torch preamp or the Lyra Connosieur 4L-2L SE preamp .

Regards
Arthur
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#7,970
Hi there!

We don`t have the motorized version of the CP2500.
This is because Thel and the german importer have made a production tool to couple the motor unit (clutch) to the shaft of the pot. I don`t have any access to this.

I, personally, like stepped ones most. Not that much steps. I`m happy with 6 or 12 steps. Usually I use a UK made make-before-break switch, pure silver contacts, wired as series or shunt attenuator (depends on purpose).

Ralf
(Audioprojekte.de)
 
#7,971
hi,
thanks KSTR, KBK and non-sparking very interesting.

i think that the motorised TKD 10K 2CP-2500 from Thel looks favorite still, price is just about affordable.

With regard to the bypass resistors on the pot, no mention of values any thoughts on this? i have no clue to this myself as i do not see the logic, experiment with the values would be the best way i suppose but where to start and with what?
 
#7,972
Thanks for the info! I did not know that they were so differently priced than the smaller 1260 types that I use.

For my current balanced line amp I need 12 pots and 12 * 50 USD = 600 USD worth of pots for setting operating points,
so 12 USD is a bargain! but they will not fit on the current layout, so I will use the larger pots in the future.



Sigurd

1audio said:
Mouser lists the rectangular version for $12 ea. They have always been much cheaper. I'm not sure why. The performance is the same (except tempco options are different).
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#7,973
fredex said:


Back when I always trusted my ears implicitly I had no need to know, I just fiddled.
Now I know a little more I still fiddle, I guess I just like fiddling. There could be no point, but I can't stop, maybe therapy is needed, but that can be even more expensive, and you end up with nothing 😀
Click to expand...


Therapy?? Example: If you want to know why your tube amp starts distorting when you lower the grid bias, would you go in therapy?? I just would get a book about tube amps.

If you are intrigued why one person reports large improvements by putting in an output coil in his power amp, and another reports large improvements by removing the output coil from his power amp, would you go in therapy? I just would get a book about perception. And review my book about power amps, just in case I missed something 😉

Jan Didden
 
#7,974
No idea what the parallel resistor is for.

I`ve attached a simplified diagram of such a pot. Where positions a to h are sample positions of the wiper. Resistors R1 to R7 are the main track, and R8 to R13 symbolize the LASER trimmed parallel resistors (to achieve a good degree of precision).

If you take a closer look at the diagram, you will notice that the pot is not suitable for shunt or H-shunt (sym.).applications.


An externally hosted image should be here but it was not working when we last tested it.
 
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