Agreed, in that case it is. I was looking at the bigger picture. I'm not sure where that falls into the equation but according to ears I trust they say best is
.....autoformer at 1:1 or less
.....then autoformer with a small amount of voltage gain
.....then true transformer at 1:1 or less
It is wild conjecture on my part but logically following that sequence a step up followed by a pot would seem to be the next lower desired configuration.
I'll probably never try it but it would be an interesting experiment.
. |
Al is correct, not a TVC but a slightly different animal. Considering I have spent a lot of time with Jack Elliano the last few weekends (we are Las Vegans) I can say the guy knows his stuff and his SET amps sound great (with which he uses a PVA with 1:8 ratio). However, I think in this case Al and I are in agreement. I've fiddled around with this and a 1:1 or 1:2 ratio would be best. My main problem right now is I can't get the volume control past 9 o'clock, which supports the case for a lower ratio IMO.
Question: Jack tells me the transformers are wound for 100 ohm impedance, meaning the source must have an output impedance of 100 ohms or less. Any of this make sense? |
For comparison, the S&B 102 has a Zin 0f 10.4k and Zout of 1.4k @ 1kHz at it's worst case of zero attenuation. Zin halves for within each of the next few -3dB steps and Zout doubles. My setup never approaches the end of the dial.
http://www.stevens-billington.co.uk/page102.htm |
Why does the I/C from the source to passive pre have to be as short as possible while from the passive pre to power amp can be longer? |
Cdc: Why does the I/C from the source to passive pre have to be as short as possible while from the passive pre to power amp can be longer? Actually, the reverse is true. The high output impedance of a passive preamp will form an RC low pass filter in conjunction with the capacitance of the cable that is connected to its output. The longer that cable is, and the higher the capacitance per unit length of the cable, the more likely it is that significant upper treble rolloff will occur. The relatively low input impedance of a passive preamp will produce a minor increase in the amount of current flowing through the cable between source and preamp, thereby perhaps increasing some subtle cable effects if the cable is long, but those effects will be minor in comparison to the effects of excessive capacitance in the cable connecting passive to power amp. Clio09:Question: Jack tells me the transformers are wound for 100 ohm impedance, meaning the source must have an output impedance of 100 ohms or less. Any of this make sense? Transformer impedance ratings, as distinguished from the reflected impedances corresponding to the connected source and load impedances and the turns ratio, have always been something of a mystery to me. Perhaps someone else will comment more knowledgeably. But I believe that the rated impedance of the transformer itself corresponds to how lossy the tranformer is in terms of flux leakage and dc resistance, and represents the amount of current limiting that would occur in the primary with the secondary short circuited (and a voltage source with near-zero output impedance connected to the primary). The higher the output impedance of the source component, the greater the losses that would result from that transformer impedance. Best regards, -- Al |
Almarg: The higher the output impedance of the source component, the greater the losses that would result from that transformer impedance. While I only quoted part of your response Al, Jack did mention DC resistance and sound degradation, particularly in the bass the higher the output impedance of the source. The PVA is really designed for opamp driven sources and when I asked if I could use my 600 ohm Zout Otari tape deck with the PVA I was told that I would get some bass distortion and potentially other losses due to the mismatch. With my Kenwood KT-8300 tuner and digital set-up the sound is fine. |
It has been a long time since I read Stereophile, but Sam's Corner in the February issue has a write up of the old Halcyon PVA and the Lightspeed Attenuator that I own. The article prompted me to put the Lightspeed back in my system for a whirl. I'm not regretting it. This opto coupler designed passive is truly remarkable. As usual careful system matching applies. I believe minimum amp Zin is 50k ohms and high sensitivity is best. Here is some additional information for anyone interested: Lightspeed AttenuatorSingle input/single output only. I have a version with dual attenuators. One of the designers comments is that this type of design removes the sonic effect of the switch from the equation. |
just ordered one from george. |
I want to try the lightspeed Attenuator as well. Pubul57, how much does it go for? |
$450 shipped from Australia; it takes two weeks or so before shipping. I get the feeling the Stereophile review is making him busy. It will be interesting to compare with the Goldpoint and then I'll sell one or the other. Either way, these passives are a really "inexpensive" way into some pretty darn good sound. I don't know if I will like them better than my Joule or Atma-sphere preamp, it just may be different, but worth having in the mix. |
I think you will like it. Definitely makes you think about what it takes these days to get high quality sound. As an example, the combined cost of my Lightspeed and RM-10 MkII is $1450. That's a lot of sound per dollar in my opinion. |
Anthony, if the Lightspeed is as good as it seems, I think it and the RM10 would put ALOT of $10-20K pre/amp combos to shame - IF 35 watts is enouuh power. Looking at the diminutive RM10 (size of a hardcover book) reminds me of that old Steinway piano ad about how they laughed as the fella sat at the piano, till he started to play. Can't wait to give the Lightspeed a try, but the Goldpoint ain't chopped liver either. |
What frequencies can "meat on the bone" be found? And are those flesh tones in the source signal, or added later? Or are active tube stages just keeping something from being lost that simply gets sucked up by essentially straight wire connection. Maybe we have a long addiction to distortion, and what it is gone something just seems to be missing. |
I remember a conversation I had with Kevin Carter when he was building me a TVC, my first passive. I had made some comment to the effect that passives have the reputation of leaning out the sound. It took him less than a second or two (meaning he didn't even have to think about it) to reply that its active preamps that add something to the sound.
I'm leaning towards the opinion these days that a lot is in the engineering and mixing and that active preamps are more like tone controls. I was hanging out with some audio engineers this past weekend and one guy liked having his speakers against the wall to improve the bass response. I commented that to me that would hinder depth of sound stage and that is why I prefer having my speakers out in the room. His comment was that much of the depth in the sound stage comes from how the recording was done, not where the speakers are placed. I'm not sure I buy that one yet, but considering the number of fine speakers out there that are corner/wall placed, maybe there is something to it.
I agree with the argument that its the lack of distortion that creates the notion that something is missing in the sound. A tube amp should provide all the distortion one needs. |
I agree and I guess it comes down to how we answer the question, what is the best preamplifier? The one does nothing )very little) to the signal or the one that sounds best to us for whatever reason. In discussing this with Ken Stevens of CAT, he felt a preamp should have the tone color of water - none; that is the job of the preamp, if you want tone color, find it somewhere else in the system or you end up with band aids to complement the various colorations within the system, but the preamp should be as neutral as possible, that's why I think the passive approach is a step in the right direction, if it works nice with your equipment. The Goldpoint is such a piece, and frankly, I don't sense any rolloff or lack of dynamics compared with my Joule and Atma-sphere pres, but it does not sound like them either. |
I am using a Diy Passive at the moment as I am comparing different designs of Power Cables on my CD Player. Although I enjoy listening with my active, it is warm and colored. It is however, refreshing to have the clarity,transparency and detail of the passive at present. It is a much more elegant sound.
Cambridge Audio CD Player Output 2 Volts
.5 meter Virtue Audio Nirvana IC to Passive
Passive is wired with OCC-OFC Silver Wire and signal goes straight to a Dact-type 10K Attenuator.
Same 1 meter Nirvana IC from passive to an Audio Research VT50 input 100K.
Speakers are modified monitors and Powered Sub.
Active preamp is a heavily modified Audio Research SP 14. |
I know this whole issue is a matter of taste, and will never be resolved, but I will say this for the passive argument. I had this long discussion with Roger Modjeski of Music Reference and RAM Labs - that is, a fella known as one our our great designers of equipment and a tube lover. I asked him, point blank, when I was considering buying his $135 Pot-in-a-Box if it were not possbile for any active preamp to be better, he said no. Now I know there are many of us that love our actives, I do, but he is one pretty qualified person to talk about preamps since he can design whatever he wants, and he does love tubes, but in his view a passive does what a preamp should do IF it is in a good source to amp environment. It at least made me feel that a passive isn't just a cheap solution to volume control, but for some might be as good as it gets for a preampifier (in the right system). |
Rrog, well its true I thought the thread outlived its usefulness I am glad it didn't stop there otherwise I wouldn't have learned about the Lightspeed which in my opinion is extremely unique in its design. Thus the thread has produced what I orinally was seeking to begin with, something new and innovative. |
Clio09,
I think there is something to the perceived soundstage depth argument postulated by your sound engineer friend. Much like finding the "correct" volume for any given recording, I often find myself shifting my chair slightly forward or back (maybe 3-4" either way) to find the correct listening perspective for any particular recording where center images snap into focus, and the soundstage expands nicely in all three axes. Given the wide array of monitoring positions and speaker locations used by mixing engineers while twiddling the pan pots, it would seem logical that reproducing any perspective of depth and width would vary based upon these unknowable factors (not that stereo isn't a complete contrivance anyway). While I don't agree with shoving speakers against a wall unless they're designed for it, the discussion is an interesting one. |
PhD, for some reason, George sold it to me for $415, but you do have to buy a 12DVC 400mA AC/DC adapter, which seem to only be available in Canada, ended costing $30 for the unit plus shipping. |
Mine cost a little extra because I had George wire it with 2 volume controls. He referred me to Allied Electronics for a Stancor regulated (very important) power supply. Mine is also wired with the center pin negative on the PS since that is the way the Stancor is wired. I've always been curious as to the battery PS, but this time I think I'll leave well enough alone. http://www.alliedelec.com/search/productdetail.aspx?SKU=9289895 |
Given the wide array of monitoring positions and speaker locations used by mixing engineers while twiddling the pan pots, it would seem logical that reproducing any perspective of depth and width would vary based upon these unknowable factors. I'm starting to understand some of this through my friends here, as well as the effect of miking. I'm going to change my speakers out in the near future so I can listen to my Tonian Labs TL-D1's for a bit. At that time I will try the near wall, or even corner placement. |
Thanks Almarg. This was from Sam Tellig's column on the Halcyon passive pre.
He recommended .5m max from the source to pre and 1m max from pre to power amp. Then again I don't understand why you would store e and electronic component in a wine cellar either. |
