Yes that part is a fluke but it's an out for folks who just want to order some cheap parts from a major distributor and not risk fakes, etc. Plenty of projects posted here where they did just fine.
It is a shame that good complementary jfets are hard to find. They will not be completely unavailable in future, but they certainly will not be as cheap or as easily found as in the past. For many line level applications, the extremely low 1/f noise of the Toshiba parts is not really necessary. Just phono inputs or analog tape reproduce inputs come to mind, or of course, microphone inputs.
I had designed without complementary input devices, until complementary devices became available, but I would not like to revert to non-complementary jfet designs, if at all possible.
I had designed without complementary input devices, until complementary devices became available, but I would not like to revert to non-complementary jfet designs, if at all possible.
Not necessarily. A 'conventional' valve amp with decent amounts of feedback could have lower group delay than a 'zero feedback' SE. Although there may be many caps and transformers, the dominant one will be modified by feedback and the rest won't have much effect until subsonic frequencies. Could still end up worse than SS, but below the threshold so OK.RNMarsh said:
Don't forget that something has to set the LF rolloff to a sensible figure, so that subsonics you can't hear don't create distortion and IM with things you can hear.
I have listened to one of these, you actually could hear the London subway on some old Mercuries (<10Hz components for sure). Amazing
LP? Thats the reference now?
Guess I am not a normal person.... have a large living room. Now use 4 -15 inch cerwin vega bass drivers and adding a pair of TC Sounds Ultra 5400 18 inch drivers for subs sitting in the garage waiting for time to get it done. Not much compression and lots of dynamic range.
Guess I am not a normal person.... have a large living room. Now use 4 -15 inch cerwin vega bass drivers and adding a pair of TC Sounds Ultra 5400 18 inch drivers for subs sitting in the garage waiting for time to get it done. Not much compression and lots of dynamic range.
Did you miss the words "system"? A single component does not make a system. Look at just the low end roll off of the source (say LP cartridge), the MC pre-preamp, RIAA preamp, line amp, power amp and electronic crossover , if using one. Measure the System from it's input to it's output. It wont look so nice nor measure so well, then. But, that is what you are listening too - a system of interconnected components with thier total sum affects.
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My current living room is not small, but I am satisfied by couple of 12" woofers in concrete boxes, and one concrete horn subwoofer under the floor that uses also a pair of 12" drivers. The reference is DVD and blue ray movies. Running horses and earthquakes feels quite real. What else to wish? However I can put few 18" drivers under the floor, but what about walls and ceiling, what are their resonant frequencies? Do I need to follow realism of destruction of houses in the movies I watch?
In any case, I find that servos work, are reliable, can sound good enough to give me A ratings in the audio press, take very little space, and can be quite inexpensive, compared to an AUDIO GRADE film cap like the ones that Dick Marsh designed for Rel. IF I had to use a 1uF coupling cap, I would recommend RTX 1uf, 100V @ $18.25 ea, or the TFT 1uf, 100V @ $218.50 ea, and might even try the PCU 1uf, 200V @ $170.50 ea.
For Parasound, maybe I could get away with PPFX 1uf,200V @ $16.50 ea.
I hope that Richard Marsh will suggest which of my choices would be best, or offer another alternative. What do you recommend, Dick?
For Parasound, maybe I could get away with PPFX 1uf,200V @ $16.50 ea.
I hope that Richard Marsh will suggest which of my choices would be best, or offer another alternative. What do you recommend, Dick?
What do you heavies think about this servo? And how does a short across the R9-C10-C12 network work?
My current living room is not small, but I am satisfied by couple of 12" woofers in concrete boxes, and one concrete horn subwoofer under the floor that uses also a pair of 12" drivers. The reference is DVD and blue ray movies. Running horses and earthquakes feels quite real. What else to wish? However I can put few 18" drivers under the floor, but what about walls and ceiling, what are their resonant frequencies? Do I need to follow realism of destruction of houses in the movies I watch?
Nice to know others are here which go the extra mile to have full blown system without compressed dynamics. We have all this dynamic range available now but many never hear it because the typical speaker system is anemic in this regard. My ceiling is about 20 feet up... sloping to 13 feet. Over 30 feet long room so it takes some serious power output to blow this roof off. But I'm trying.
Jeeeezus are they charging that much for the best caps on the planet? Wish the patent hadnt expired so I could get royalties. A film cap to get a patent for improved performance (higher self resonance) in decades. No cap sold for audio use is patented/unique, as far as I know..... just rehash of what has been done before so the cost should be low for them. The REL cap to be made under the patent required buying a customised (new) cap winding machine.... but that cost has long been paid off. Now it is just low volume causing the price to be high.... btw - the styrene from REL is the best quality available.
I wouldnt pay that much and would find some way around using them, if I could.... But the best would be an annealed styrene film and foil and a Teflon film and foil (tin foil) with copper leads with gold plating and made under the patent (stock REL are not the same as the MultiCap but use same materials).
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I think I could lose a few pounds. Well, make that a solid twenty.
Five caps instead of one or two. Stability issues if the servo has too much gain.
A differential integrator that probably is not needed, as the simulated power amp is single-ended. But one is equipped for a bridge-tied load I suppose.
The second stage is a d.c.-offset-free three-pole lowpass. It has some advantages (no offset voltage or current, no opamp input common-mode swing) and some disadvantages (sensitive to loading, as the output impedance is not low, as it would be from a conventional active filter's opamp output). Kendall Castor-Perry showed some filters based on the topology fairly recently (sorry don't have the ref.) although it is quite old --- I recall puzzling over it in an Ideas For Design many years ago, and having the same reaction as you to what looked like a "short".
Brad
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