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In Reply to: RE: VINTAGE PHONO STAGE - RIAA posted by Poinzy on October 17, 2015 at 17:12:23
I don't think you killed the conversation. While I believe that there are luminaries like Peter J. Walker of QUAD, who can design a circuit and know how it will sound without listening, I think there are precious few others who can do this. I have never heard anyone in the Asylum claim that skill. So the only what the original poster is going to get an answer is if someone recognizes the circuits and has heard them.
Sometimes (if you lucky) Peter Qvortrup of Audionote fame will post. He is the only one I can think of that could possibly answer the question on sight (and experience) alone.
Dave
Follow Ups:
Sonics aside, does one design seem better from an engineering point of view? As an efficient/effective use of components for a RIAA network? Or comparatively speaking, how these first generation solidstate phono stages differ from contemporary high-end circuits.
Thanks again
It's not 100% certain because images are blurry but the leftmost circuit appears to utilize PEC modules for the equalization components. If so this could have a possible negative impact on the sound because PECs almost always contain high dielectric constant ceramic caps. The sound of this type of cap is viscerally despised by many experienced listeners.
what is a PEC module & how would I know if there is one of these despicable devices in my amplifier? Still learning...
ljb
PEC = Packaged Electronic Circuit. An early implementation of circuit integration/miniaturization. Usually contains ceramic caps and/or carbon film resistors on a ceramic substrate. PECs were specialized designs to accomplish a specific function so there were scores of them produced, all different. Typically used where cost or space savings was important...like AA5 AM radio. The one in the attached pic is the low filter module for a Mac MX110 that uses other PECs for hi filter and tone controls. This one ~ 1"x3/4"x3/32"and contains 3 caps and 4 resistors. Usually assoc with tube equipment but also in early SS products. Visually IDed by appearance. The spawn of satan from an audiophile perspective. Others may disagree.
Edit: Before the Internet correctness police strike, I've also seen PEC = Printed Electronic Circuit.
Edits: 10/21/15
Thanks! It would appear the amplifier section of my Sansui 1000a has 3 of these travesties - 1 for the tone control section and 1 each for the hi/low pass filters, respectively. I assume, if space can be found, that these can be replaced with discrete components?
ljb
Yes, if you have the space and the correct circuit you can replace the PECs with discrete components. I did just that with one of my MX110s for lo and hi filter PECs. Did this mostly because a couple of PEC resistors had drifted way off value and not for cap sonics. The drifted resistors set the operating point of one of the 12AX7 buffer amps. I designed a couple of PCBs just a little larger than the PECs to neatly contain everything.
In a perfect world I'd replace the tone control PECs too but it's so tight in there, the sonic improvement wouldn't be worth the considerable effort.
An observation is that many owners of restored vintage equipment rave about the vast improvement in sound they experienced when the obvious ceramic coupling caps were replaced with the current cap flavor of the day. Little do these enthusiastic cap promoters know of the ceramic caps still lurking in the infrequently replaced PECs. Power of suggestion?
For any given schematic, there can be pretty significant differences caused by the quality and matching of both the active and passive devices. Neither schematic included the power supply either!
Yes, A has a few PEC's inside.
I didn't want to divulge the brand/model of each so preconceived notions would not influence analysis of the schematics. Since that was unfruitful here are links to the full service manuals...
A:
http://www.fisherconsoles.com/non%20console%20manuals/fisher%20tx50%20beg%2010001%20sm.pdf
B:
http://elektrotanya.com/scott_260_sm.pdf/download.html
Maybe those who have heard both can attest to the sonic merits of either in correlation to their circuit topologies.
Thanks
...you really can't assess sonic attributes based on circuit topology alone. What you'll hear is the amalgam of circuit topology, physical components, physical layout/construction technique and to a lesser degree, overall packaging and external influences such as power supply topology. There are many ways to skin a cat.
The fact that one circuit is implemented with PECs is a major strike against it regardless of the merits of the basic circuit.
Understood, but in a more literal sense, how do early solidstate Fisher and Scott units compare?
Much has been written on both manufacturers' tubed integrateds yet there seems to be significantly less information on their brief period of US made transistor products.
So, if anyone has heard the units depicted in the links (or other models from those series) I would be curious to see what the general consensus is.
Thank you
I have an early solid-state Scott receiver but I have never played it. I obtained it strictly for the knobs that matched my earlier Scott tube gear. I know there are certain pieces that have their fans. The Marantz 7t has its fans. However, I have always considered the early solid state Fisher and Scott units to be more trouble than they are worth. My Scott receiver was free. I'd love to be proven wrong, since you can find them cheap, but that is my current view.
Dave
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