John Curl's Blowtorch preamplifier

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#15,603
Peter Daniel said:
Yes, but remote operation can be still implemented with Shallco switches and stepper motors, not only for volume but also source selecting and phase switching.
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Yep, been doing that in a commercially available product now for 13 years.
The prototype is 14 years old. That's using a 45 position Shallco.

http://stereophile.com/solidpreamps/609/

Still in production. Still one of the best sounding preamps out there. Only relays in there are to short the outputs for the mute function. None in the signal path...
 
#15,604
Bobken said:
Sonically, I still prefer my own manual Shallco/naked Vishay attenuator over the commercial design mention above, but the design brief for that attenuator was for 64 discrete steps of precisely 1dB each, which is a bit difficult with Shallcos or Blore Edwards switches. AFAIK Shallco's maximum (single-switch) capability is 47 positions,
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Actually their largest switch has 60 positions. We use that with stepper motors and 1 dB steps. Not quite to your design brief of 64 steps, but close enough....

http://stereophile.com/images/archivesart/1108ayre.2.jpg
 
#15,609

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#15,611
john curl said:
The EAR knows, Jan, why fight it?
[snip]
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Ahh! But here we part. The ear knows nothing, just as a mike knows nothing. The BRAIN get the ear's input and integrates, manipulates and deceives and then tells us, innocently: this is what you hear...

john curl said:
[snip]or the record, I have been professionally using miniature signal relays for the last 40 years.
Yes, 40 years ago Teledyne made a DPDT 1A relay in a TO-5 size transistor can.
I used them in projects for Ampex Research.
I also used them more than 26 years ago in the JC-80, using hermetically sealed units.
AND I use them in the latest JC-2 preamp, by the dozen.
NOW, where am I making a mistake? Have I overlooked something?

Please Jan, read Ragnar Holm's book cover to cover, then come back and we will discuss the merits and demerits of relay contacts in a useful way. I hope for more enlightenment.
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Actually I agree with you here, I don't believe that good small signal relays would damage the sound. It's a matter of selecting a good relay and of course how to embed it in the circuit. I know you know how to do that right.

Jan Didden
 
#15,612
Silver Shallco switches are still better. That is my opinion, based on experience. You, Jan, may think that this is my imagination, and I will leave you to you opinion.
And it is not just MY opinion.
Charles Hansen and I spoke yesterday by phone. The first time in months. We are competitors, you know, but we respect each other. Just like race car teams in F1 racing.
When we discussed your reaction to switches vs relays, Charles noted that it is amazing how MUCH difference there is between relays and a silver Shallco switch. You see, we become amazingly attuned to small differences, due to our experience. Perhaps, like an experienced wine blender or taster.
For example, my 944 uses a different transmission construction than a 911. I don't know the difference, myself, as I have only driven a 911 once in my life. However, an experienced 911 driver might note it easily.
To glibly deny our experience, wastes my time, and yours. It would be like arguing with Erno Borbely about the differences between toroid and R-core transformers. (Charles and I also like R-core transformers) when you were interviewing him. (You didn't, thank goodness).
Still, I need constructive criticism to keep myself in check, and I appreciate anything that helps to grow and refine the understanding of what makes audio design more productive.
Let us learn together.
 
#15,614
janneman said:
It's a matter of selecting a good relay and of course how to embed it in the circuit.
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I've listened to dozens of relays and still haven't found a single one that I would use in one of my products.

I wish I could -- a good small signal relay is only a couple of dollars, has only a few tens of milliohms of on resistance, and only a few pF of off capacitance. There's certainly no FET switches with spec's that good. But all the relays I've listened to degrade the sound to an unacceptable degree.

Bobken says that he found one that was acceptable -- not great, but acceptable. I'd sure like to know what it is, because I haven't found one that was even acceptable.
 
#15,618
john curl said:
The 'worst' and most disappointing sound track that I ever heard was the DIGITIZED 'Dolby Digital' version of STARWARS part IV. Walking out of the listening theater, I muttered: "If this is the future of audio, I quit!"
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John

My kids are listening to music from their laptops and Sony mobile phones.

So the future isn’t bright, I don’t think you have to wear shades.

Stinius
 
#15,619
Charles Hansen said:


I've listened to dozens of relays and still haven't found a single one that I would use in one of my products.

I wish I could -- a good small signal relay is only a couple of dollars, has only a few tens of milliohms of on resistance, and only a few pF of off capacitance. There's certainly no FET switches with spec's that good. But all the relays I've listened to degrade the sound to an unacceptable degree.

Bobken says that he found one that was acceptable -- not great, but acceptable. I'd sure like to know what it is, because I haven't found one that was even acceptable.
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You must have much better ears than Nelson Pass and people who rave about his products (which quite liberally use relays).
Or people at say Madrigal/Levinson, Burmester, Krell or Halcro ?
In fact Bruce Candy defends use of mechanical relays in his preamps by saying they have zero distortion.

Hmmm...
 
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