I'm just trying to illuminate the common mistake of choosing/disregarding a device on the basis of individual (and often misleading) metrics. Putting so much importance into a single specification can have the affect of driving the entire amplifier topology, which will inevitably produce compromises in other areas of performance. Just ask Wells Fargo how narrow metrics affect decision making...
People have done some work in that area, but I don't think exactly what is needed here. If interested in some of what has been done: https://www.researchgate.net/profil..._amplifier/links/53e9120d0cf2dc24b3c7ea94.pdf and: https://www.researchgate.net/public...ed_on_SiGe_heterojunction_bipolar_transistors
jacco,
When Ostripper was going strong on the Slewmaster thread there were those who wanted to take his perfectly designed circuits and add a vacuum tube input section and actually did that. I personally don't see why anyone today would really want to do that but there are enough audio types that just seem so enamored with tubes that it is just inevitable it seems that someone is going to add a tube section. I've had my Mac's and I don't think I could ever go down that road again, not to say I didn't like them, just that I don't want to deal with tubes any more than I really want to use my Revox tape machine sitting on a shelf. But I do understand that a simple single tube added to an audio product does seem to have a certain draw whether that is nostalgic for some older audiophiles or something unusual for the Gen-X crowd who never had anything with tubes in it.
When Ostripper was going strong on the Slewmaster thread there were those who wanted to take his perfectly designed circuits and add a vacuum tube input section and actually did that. I personally don't see why anyone today would really want to do that but there are enough audio types that just seem so enamored with tubes that it is just inevitable it seems that someone is going to add a tube section. I've had my Mac's and I don't think I could ever go down that road again, not to say I didn't like them, just that I don't want to deal with tubes any more than I really want to use my Revox tape machine sitting on a shelf. But I do understand that a simple single tube added to an audio product does seem to have a certain draw whether that is nostalgic for some older audiophiles or something unusual for the Gen-X crowd who never had anything with tubes in it.
Interesting they still only get .3nV at 4.2K. I don't know the parameters of the SiGe devices they use, GaAs also works at 4.2K. I don't think cryo operation is practical here besides SiGe has bad 1/f noise.
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KHM,
Glowing tubes are still cool as all get out. 🙂
At some point or another, I hope to build a tube-based headphone amp. Seems fun and a good application. (Matching components with application, hmmmmmmm... no lessons to be learned there)
Glowing tubes are still cool as all get out. 🙂
At some point or another, I hope to build a tube-based headphone amp. Seems fun and a good application. (Matching components with application, hmmmmmmm... no lessons to be learned there)
Check with the gents in the digital department, I'm sure they have some logic gates with impressive slew rate, just re-label a few of them 😉
Rayma,
I had a Heathkit digital clock I built when I was like 16 years old that lasted for 40 years before the digits finally died out. If I'd know I could have replaced them at the time I would have kept it, it kept great time. I guess I look at some of the boards offered here on diy as a continuation of the Heathkit kind of building a great piece where all you have to know is how to solder a circuit together and sort out some parts. I did learn a lot building that clock so long ago.
I had a Heathkit digital clock I built when I was like 16 years old that lasted for 40 years before the digits finally died out. If I'd know I could have replaced them at the time I would have kept it, it kept great time. I guess I look at some of the boards offered here on diy as a continuation of the Heathkit kind of building a great piece where all you have to know is how to solder a circuit together and sort out some parts. I did learn a lot building that clock so long ago.
I started in my early teens with Knight and Heathkits, and then Dynakits. My very first kit was a point-to-point
12W mono tube integrated amp. It worked. https://www.youtube.com/watch?v=1w-zZ5Vc05w
The Nixie tubes seem to be a minor fad now. Nixie Clock | eBay
Dig the Russian-built Nixie tube wrist watch. http://www.ebay.com/itm/Nixie-tube-clock-Wrist-Watch-with-am-pm-option-/262600750460
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(I'm positive I watched too many John Wayne movies, and too often)
Current market value(?) of a Toshiba dual JFET is $15-$20, even single ones have reached silly price levels.
Tubes are voltage driven devices, as are FETs. A dually as e.g. the 12ax7 can be had for less and work just as well as differential input stage, with a life expectancy of many hours.
The Rusky dual triode equivalent cost me a dollar each, even got plenty spares.
For a dollar extra, I have them sticking out the top of the amp case, in pretty little red riding hood overcoat & knickers.
http://www.diyaudio.com/forums/atta...d1210075638-kleinschmidt-10a-red-russian2.jpg
http://www.diyaudio.com/forums/atta...60-kleinschmidt-10a-little-red-ridinghood.jpg
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That tube looks much cooler without the cover installed.
I had some old Mac amps that used 12ax7 12au7 and I think 6BG6 output tubes. They weren't pretty but they were what was once used in all the Disneyland rides for the sound systems with Altec and JBL speakers.
I had some old Mac amps that used 12ax7 12au7 and I think 6BG6 output tubes. They weren't pretty but they were what was once used in all the Disneyland rides for the sound systems with Altec and JBL speakers.
Just go single ended JFET input singleton topology. You get everything you need - low noise, hi-Z in and predominantly 2nd and 3rd H's.
No warm tube glow?
Stick a few red LEDs under the bonnet with appropriate holes in the chassis.
Turn the lights down, pour a glass of cab, put some Person Houston on the TT and you're golden
😉
No warm tube glow?
Stick a few red LEDs under the bonnet with appropriate holes in the chassis.
Turn the lights down, pour a glass of cab, put some Person Houston on the TT and you're golden
😉
NOT THE SAME! 😀
(If I'm going for peaking, I want ALL my peaking...) Most of us do this stuff for fun, right?
Why Mr. Soibelman, a nostalgic audiophile/freak*, you ?
(* multiple-answer interactive post, individual freedom of word choice by the reader)
Respectfully, I have to disagree with johnc124's contention that we audio designers don't know what we are selecting. It would be wonderful if the spec sheets could give us all that we need to find a good sounding IC, but at least in my experience, it isn't always true.
Serious audio designers actually listen to the IC's that they might use in their audio product. There ARE competitive designs and it is possible to find several that will meet certain minimum conditions needed for a specific audio stage.
For example, I needed a front end IC for the Parasound JC-3 phono amp that could be stable with a gain of 3, 1nV/rt-Hz input noise, and a slew rate around 20V/us or more. I shopped around and found 3 contenders: The classic AD797, the LME49990, and a TI part (can't remember the exact #, but it had a different output stage than the other two).
All three met the conditions and essentially measured just fine in my circuit. However when I swapped in each part, I found that they did NOT sound the same. Now, two parts, the LME and the AD sounded good, but different! However, the TI part sounded lousy. Why? I don't know, but I selected the LME part, because it was the cheapest of the two winning contenders.
I get an 'A' rating on this phono stage in both Stereophile and TAS without advertising, for the past several years. I am sure that if I did NOT select the input IC the way that I did, I could have easily designed a 'dud' on the audio market, getting a 'B' rating or even no rating at all, making it a failed product that would soon be discontinued. I HAVE made 'dud's' before with Parasound that met the same fate, and for the SAME reason: I did not listen to the product, only measured it, before release. I hope to not make that mistake again.
It appears that we still do not know what our ears can notice, sometimes, and just reading the spec sheet will not get us everything that we need.
Serious audio designers actually listen to the IC's that they might use in their audio product. There ARE competitive designs and it is possible to find several that will meet certain minimum conditions needed for a specific audio stage.
For example, I needed a front end IC for the Parasound JC-3 phono amp that could be stable with a gain of 3, 1nV/rt-Hz input noise, and a slew rate around 20V/us or more. I shopped around and found 3 contenders: The classic AD797, the LME49990, and a TI part (can't remember the exact #, but it had a different output stage than the other two).
All three met the conditions and essentially measured just fine in my circuit. However when I swapped in each part, I found that they did NOT sound the same. Now, two parts, the LME and the AD sounded good, but different! However, the TI part sounded lousy. Why? I don't know, but I selected the LME part, because it was the cheapest of the two winning contenders.
I get an 'A' rating on this phono stage in both Stereophile and TAS without advertising, for the past several years. I am sure that if I did NOT select the input IC the way that I did, I could have easily designed a 'dud' on the audio market, getting a 'B' rating or even no rating at all, making it a failed product that would soon be discontinued. I HAVE made 'dud's' before with Parasound that met the same fate, and for the SAME reason: I did not listen to the product, only measured it, before release. I hope to not make that mistake again.
It appears that we still do not know what our ears can notice, sometimes, and just reading the spec sheet will not get us everything that we need.
My contention is certainly NOT that audio designers don't know what they are selecting. My contention is when benefit or blame is assigned to individual performance parameters. In response to your example of selecting between 3 op amps and using a listening test to decide, great! I think that's completely valid.
My concern is if you drew a conclusion from this one experiment, and applied it to op amps as a whole. For example, if you decided that slew rate (or some other parameter) was the sole differentiating factor between the 3 op amps you evaluated, and from then on you would only consider op amps with a slew rate above a certain threshold. These design opinions have a habit of spreading through the audio industry. And next thing you know op amp manufacturers are bending over backwards to improve a parameter which may not have had any bearing at all on sound quality (trust me, this happens).
Love my Halo a23 amplifier, keep building great sounding products.
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