Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
VTL is pretty sure it is a problem with the tubes in the output stage. I am buying a pair of tubes from them that they will screen for noise. -- duke43j duke43j's Profile: http://forums.slimdevices.com/member.php?userid=15911 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
duke43j;426351 Wrote: Does anybody have experience using one in their system? I've been using a PS Audio 4.6 in passive mode for about 20 years. I'm happy with it. Soon I'll move to using a single input stereo volume control with balanced input and output cables. The issue of volume controls sounds better at high settings applies to active preamps too. Passive = higher setting = better, other things being equal. You cited impedences as a concern. That is a practical issue to deal with. Trace routing and grounding in the passive preamp can matter too. Quality of the volume pot. matters. Beyond that, there are all the fairy land audiophiles issues. Bill -- Listener Listener's Profile: http://forums.slimdevices.com/member.php?userid=2508 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
Hi Listener. Do you know what the input impedance and gain of your amp is? Also, the output impedance of your preamp? Did you have trouble finding cables that would work OK. It seems that this is more an art than a science, but I would like to find out the parameters I need to stay within to be assured I will be OK with a passive. Hi Phil. Boy, you are really getting into this. I don't have a schematic with my manual. Also nothing on their website. Sorry about that. -- duke43j duke43j's Profile: http://forums.slimdevices.com/member.php?userid=15911 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
duke43j;427475 Wrote: Hi Phil. Boy, you are really getting into this. I don't have a schematic with my manual. Also nothing on their website. Sorry about that. I looked too - nothing on the web. Still, with only 4 valves it can't be that complex. I used to repair valve gear (30 years ago) - it was my first proper job! I suppose trying to diagnose an issue like the one you appear to have is a mental challenge for me :-) Armed with a signal generator, basic scope and multimeter, most valve amp faults can be pinned down in about 30 mins. In most valve pre-amps the only expensive components are the mains transformer(s), the valves and the pots switches. Aside from these, a repair is usually going to be less than $20 in parts. One last question: has your pre-amp ALWAYS been like this since you have owned it? Regards Phil -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... SB3 (wired) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Townsend Supertweeters, Blue Jeans Digital,Kimber Speaker Chord Interconnect cables Outdoors: Boom Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
2) the hiss reduces with new valves then quite rapidly comes back (2 months?) Yes 3) the output impedance of the 2.5 is 200 ohms, the input impedance of VTL's own power amps is 100k Yes 4) hissing noise is not due to impedance problems IME - and according to the specs you shouldn't have a problem anyway if everything is working properly I don't know how to explain why it's OK in his system, but not in mine. 5) I suspect that you have a faulty resistor or capacitor in the pre-amp - or possibly a fault in the valve heater circuits. New valves cause a change in bias conditions but over time the underlying fault causes the new valves to deteriorate. I've seen this in valve guitar pre-amps. The problem is in both channels. It is unlikely the same fault would be in both channels. 6) It is possible a fault is damaging the valves - do you have an old set? - swap them out with the current set and see if the old ones immediately hiss. Not sure I understand you here. New tubes are OK for a while. Old ones hiss. 7) How does the hissing change with the volume and mute controls on the pre-amp? is the hissing identical on left and right channels? Volume control has no effect, so the noise is coming from after the volume control. Mute kills the noise. Both channels are identical. 8) You commented that the top end sounds rolled-off... but the specs say the preamp goes to 60kHz -3dB... that seems odd. I'm dubious of specs written like that. Three dB down from 20 to 20 KHz is not very good for a preamp. I really don't care what the unit does above 20 KHz. Besides, the tonality is not a problem. It is just not as extended as the DAC = amp configuration. I suspect it was designed that way to give the unit a warmer sound. I'm hesitant to send the unit back to VTL because: a) I suspect they would say I just need new tubes b) While it was being repaired, the amp speakers would be connected to the TV (I am outvoted on this). I wouldn't be able to listen to music. I'd have withdrawal symptoms. DTs, etc. Based on what you say, I believe I will contact VTL to see what they say. Thanks for the suggestions. I rather hope it is broken. It would save me the expense of upgrading. -- duke43j duke43j's Profile: http://forums.slimdevices.com/member.php?userid=15911 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
duke43j;426822 Wrote: Shortly after I bought the VTL I took it back to the dealer to try it in his system. The noise wasn't nearly as pronounced through his McIntosh amp and BW 800 speakers. I had to put my ear right up to the speaker before I heard any noise. From that demo I concluded that my preamp wasn't broken, but my system was somehow more sensitive to the noise (possibly a low input impedance of his amp vs. my 100 KOhm amp??). In looking for another preamp I've been shying away from tubes because of the noise problem I'm currently having. Going to a dedicated stereo system is not practical in my house. But I like the idea of trying an upgraded VTL preamp. It would tell me if I need to just get a better quality tube preamp, or move to solid state. From the comments you've given me it sounds like passive preamps are not for me. You mentioned the Ayre preamps. Can you describe their tonality (i.e. compared with your VTL or with other solid state preamps)? The Ayre K-xr is out of my league, but the K-5xe has a surround bypass and is within my price range. It really sounds like something is wrong with the pre-amp. How long ago did you check it at the dealer? An amplifier can deal with under or over voltage better then a pre-amp, do you know for sure that you have proper voltage and current at the outlet you are using? The VTL is a quality tube pre-amp and should work with just about any amp/speaker combination out there. Which is why I feel its something in your home or the pre-amp itself. Also do we know if the amp is OK? Did you take your pre-amp and AMP back to the dealer and listen to them on a pair of the dealers speakers. Can you isolate the pre-amp on another phase or with an isolation transformer to rule out any ground loops? Not being onsite seeing and hearing it, I am trying to think of anything it might be. Phil also raises some points that need to be verified/eliminated. Onto the Ayre K-5xe, it is an excellent SS pre-amp. It is very nature or neutral as in like its almost not even there in the system. Ayre sounds great with Thiel or Vandersteen speakers. Now the KX-R is the true meaning of a SS pre-amp that doesn't add, color, subtract, or do anything to the signal, the music just lives. I am seriously thinking about ordering one but have my eye on the new Vandersteen Model 7s. So if the K-5xe is in your price range that would be an option and have no concerns about buying a used one. But again, I think it at least pays to have the VTL checked/serviced and verify that the amp is not part of the problem. -- iPhone *iPhone* Media Room: Transporter, VTL TL-6.5 Signature Pre-Amp, Ayre MX-R Mono's, Vandersteen Quatro, VeraStarr 6.4SE 6-channel Amp, VCC-5 Reference Center, four VSM-1 Signatures, Runco RS 900 CineWide AutoScope 2.35:1 Living Room: Duet, ADCOM GTP-870HD, Cinepro 3K6SE III Gold, Vandersteen Model 3A Signature, Two 2Wq subs, VCC-2, Two VSM-1 Kitchen: Squeezebox BOOM Bedroom: SB3, GFR-700HD, Thiel 2.3, Second Boom Home Office: SB3, NAD C370, two VSM-1 Home Gym: SB3, Parasound Vamp v.3, Thiel PowerPoint 1.2 House Portable: SB3, Audioengine A5 Thunderbird: Duet, Mac Mini Expedition: SB3, ToughBook iPhone's Profile: http://forums.slimdevices.com/member.php?userid=13622 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
Hi iPhone. My VTL 2.5 preamp has quite a bit of noise through my speakers. The noise is quite audible from 9 ft away during quiet passages (not noticeable during moderate or loud passages). New tubes solve the problem for a month or two, but they eventually get noisy also. The preamp is also connected to my surround processor, so it is turned on quite a bit of the time. I like its smooth sound, but it does roll off a bit on the high end. When I connected my Benchmark DAC directly to my amp the noise went away (which I expected), but also the highs were more extended and the bass was quicker. Always looking for a way to improve things, I started looking into preamps when I discovered the idea of passive preamps. As I've said above, they sound good on paper (no active components to introduce noise or distortion), but the casual comments I've read on the web lead me to believe they are tricky to integrate into a system. I really don't want to make it a career to continuously fiddle with the system to get it to sound right. On the other hand, if I only need to be careful about using an amp with a high input impedance (mine is 100K), I'd still be interested in them. -- duke43j duke43j's Profile: http://forums.slimdevices.com/member.php?userid=15911 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
duke43j;426731 Wrote: Hi iPhone. My VTL 2.5 preamp has quite a bit of noise through my speakers. The noise is quite audible from 9 ft away during quiet passages (not noticeable during moderate or loud passages). New tubes solve the problem for a month or two, but they eventually get noisy also. The preamp is also connected to my surround processor, so it is turned on quite a bit of the time. I like its smooth sound, but it does roll off a bit on the high end. When I connected my Benchmark DAC directly to my amp the noise went away (which I expected), but also the highs were more extended and the bass was quicker. Always looking for a way to improve things, I started looking into preamps when I discovered the idea of passive preamps. As I've said above, they sound good on paper (no active components to introduce noise or distortion), but the casual comments I've read on the web lead me to believe they are tricky to integrate into a system. I really don't want to make it a career to continuously fiddle with the system to get it to sound right. On the other hand, if I only need to be careful about using an amp with a high input impedance (mine is 100K), I'd still be interested in them. I am kind of thinking what Phil is that your VTL Pre-amp has a major problem that needs repaired. I would also see if the dealer will let you borrow a higher model VTL that has Balanced XLR connectors. That alone should be a huge improvement. Really two routes to go here in my mind from what I think your driving at. Either go dedicated stereo music listening only and use the SB3 as the volume device with fixed attenuators (or upgrade to a Transporter) or move up the line as far as active pre-amps go. The VTL 6.5 has Balanced XLRs and Home Theater Bypass and there are other good pre-amps with XLRs and Bypass as well (but I'm a tube pre-amp guy). The Ayre Pre-amps would really sound great with what you currently have. I have used passives in the past and tried them recently, some good some bad. The biggest thing I have seen is that it takes big bucks to do one right that has multiple sources. Which always leads me back to the KISS principle, Squeezebox Source (SB3 or Transporter), high quality fixed attenuators, amp, and lastly speakers. When I really want to go native, I run the Transporter straight into the Ayre Mono-Blocks and it is truly amazing how the Vandersteens sound with only Source, Amp, and themselves. If I didn't watch a movie almost daily, I would probably leave it that way. -- iPhone *iPhone* Media Room: Transporter, VTL TL-6.5 Signature Pre-Amp, Ayre MX-R Mono's, Vandersteen Quatro, VeraStarr 6.4SE 6-channel Amp, VCC-5 Reference Center, four VSM-1 Signatures, Runco RS 900 CineWide AutoScope 2.35:1 Living Room: Duet, ADCOM GTP-870HD, Cinepro 3K6SE III Gold, Vandersteen Model 3A Signature, Two 2Wq subs, VCC-2, Two VSM-1 Kitchen: Squeezebox BOOM Bedroom: SB3, GFR-700HD, Thiel 2.3, Second Boom Home Office: SB3, NAD C370, two VSM-1 Home Gym: SB3, Parasound Vamp v.3, Thiel PowerPoint 1.2 House Portable: SB3, Audioengine A5 Thunderbird: Duet, Mac Mini Expedition: SB3, ToughBook iPhone's Profile: http://forums.slimdevices.com/member.php?userid=13622 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
Shortly after I bought the VTL I took it back to the dealer to try it in his system. The noise wasn't nearly as pronounced through his McIntosh amp and BW 800 speakers. I had to put my ear right up to the speaker before I heard any noise. From that demo I concluded that my preamp wasn't broken, but my system was somehow more sensitive to the noise (possibly a low input impedance of his amp vs. my 100 KOhm amp??). In looking for another preamp I've been shying away from tubes because of the noise problem I'm currently having. Going to a dedicated stereo system is not practical in my house. But I like the idea of trying an upgraded VTL preamp. It would tell me if I need to just get a better quality tube preamp, or move to solid state. From the comments you've given me it sounds like passive preamps are not for me. You mentioned the Ayre preamps. Can you describe their tonality (i.e. compared with your VTL or with other solid state preamps)? The Ayre K-xr is out of my league, but the K-5xe has a surround bypass and is within my price range. -- duke43j duke43j's Profile: http://forums.slimdevices.com/member.php?userid=15911 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
A couple of thoughts: 1) You shouldn't get audible hiss from 9ft away at normal listening levels from ANY amp 2) the hiss reduces with new valves then quite rapidly comes back (2 months?) 3) the output impedance of the 2.5 is 200 ohms, the input impedance of VTL's own power amps is 100k 4) hissing noise is not due to impedance problems IME - and according to the specs you shouldn't have a problem anyway if everything is working properly 5) I suspect that you have a faulty resistor or capacitor in the pre-amp - or possibly a fault in the valve heater circuits. New valves cause a change in bias conditions but over time the underlying fault causes the new valves to deteriorate. I've seen this in valve guitar pre-amps. 6) It is possible a fault is damaging the valves - do you have an old set? - swap them out with the current set and see if the old ones immediately hiss. H 7) How does the hissing change with the volume and mute controls on the pre-amp? is the hissing identical on left and right channels? 8) You commented that the top end sounds rolled-off... but the specs say the preamp goes to 60kHz -3dB... that seems odd. Finally, try this. I believe your preamp has two 12AU7 and 2 12AT7 valves - try swapping the valves of the same type with each other. It's very rare for more than one valve to develop an identical fault at once in a pre-amp. If the hiss stays the same I'd strongly suspect a faulty resistor. It's hard to diagnose/suggest further without a circuit diagram. I urge you to get the pre-amp serviced professionally. -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... SB3 (wired) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Townsend Supertweeters, Blue Jeans Digital,Kimber Speaker Chord Interconnect cables Outdoors: Boom Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
duke43j;426351 Wrote: I've been looking into passive preamps on the web. They sound interesting because they should ideally have no noise or distortion. The biggest issue is the input and output impedance, and how well it matches up with the source and power amp. Based on some of the articles, it seems they can be fussy. Some people are saying that they only sound good over a limited range of volume settings. Others are saying you need ultra-low capacitance cables. Does anybody have experience using one in their system? Having built a few passives using very high quality parts, I would agree with everything you've written. Also, modern active devices have no noise and no distortion - well, they are so low as to be meaningless/undetectable. Passives can create a sat upon sound, lacking in life. Cables are extra important since they form a very obvious part of an LRC circuit in passives. YMMV. -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... SB3 (wired) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Townsend Supertweeters, Blue Jeans Digital,Kimber Speaker Chord Interconnect cables Outdoors: Boom Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
Thanks Phil. That was pretty much the impression I was getting from reading through dozens of web pages. But the idea of a passive preamp sounded so good I was hoping that they were just nit picking. I got the idea of a passive pre when I connected my DAC directly to my power amp. The biggest difference was a slight change in tonality and significant reduction in noise compared with my tubed preamp. I was hoping to trade my tubed preamp in for a passive and maybe have money left over. But I certainly don't want to be constantly tinkering with cables and such just to save a few dollars when I have a perfectly good (albeit a bit noisy) preamp already. Thanks for the input. -- duke43j duke43j's Profile: http://forums.slimdevices.com/member.php?userid=15911 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
I have been using a Creek OBH-12 remote passive attenuator for over 10 years. This discontinued component has to be 1 of the cheaper passives at under $300 new. Before owning this I owned, auditioned, demoed, and borrowed many preamps. They all imposed themselves, in some fashion, on the resultant presentation. Besides the cautions you have already mentioned, the most important point to keep in mind is gain staging. I have had the lifeless sound described previously and it is rectified by having an amp with sufficient gain. While sheer power will drive your speakers to an acceptable level, unless the gain is adequate its akin to boosting a low level signal until one can hear the underlying noise, not taking advantage of the signal to noise ratio inherent in the component. Said another way, its like going 30mph in 5th gear. For 2 channel, I would never go back to an active preamp. -- konut konut's Profile: http://forums.slimdevices.com/member.php?userid=1596 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
I have tried a variety of passive and active preamps (too dang many really), and if you can get it right, the passive approach provides the best result in my experience. Assuming you've already achieved a good match between speakers and power amp: Make sure the power amp has an input impedance that is -at least- ten times greater than the output impedance of the passive preamp (at all level settings), and use the absolute shortest possible interconnect cables between the passive and the power amp. Works and sounds outstanding with the Squeezebox Classic. :) -- NewBuyer NewBuyer's Profile: http://forums.slimdevices.com/member.php?userid=7862 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Anybody have experience with passive preamps?
duke43j;426351 Wrote: I've been looking into passive preamps on the web. They sound interesting because they should ideally have no noise or distortion. The biggest issue is the input and output impedance, and how well it matches up with the source and power amp. Based on some of the articles, it seems they can be fussy. Some people are saying that they only sound good over a limited range of volume settings. Others are saying you need ultra-low capacitance cables. Does anybody have experience using one in their system? There are some very nice passive preamps (really a misnomer) available. The biggest issue in my opinion is what and why you would be using one. You haven't told us what you have in mind, what you would use it with, and why? I love my tube pre-amp and have had some very expensive passives in my system. The best in my opinion is to just not have any if one doesn't need to switch componets, just a Transporter and an amp. About as passive as it gets! -- iPhone *iPhone* Media Room: Transporter, VTL TL-6.5 Signature Pre-Amp, Ayre MX-R Mono's, Vandersteen Quatro, VeraStarr 6.4SE 6-channel Amp, VCC-5 Reference Center, four VSM-1 Signatures, Runco RS 900 CineWide AutoScope 2.35:1 Living Room: Duet, ADCOM GTP-870HD, Cinepro 3K6SE III Gold, Vandersteen Model 3A Signature, Two 2Wq subs, VCC-2, Two VSM-1 Kitchen: Squeezebox BOOM Bedroom: SB3, GFR-700HD, Thiel 2.3, Second Boom Home Office: SB3, NAD C370, two VSM-1 Home Gym: SB3, Parasound Vamp v.3, Thiel PowerPoint 1.2 House Portable: SB3, Audioengine A5 Thunderbird: Duet, Mac Mini Expedition: SB3, ToughBook iPhone's Profile: http://forums.slimdevices.com/member.php?userid=13622 View this thread: http://forums.slimdevices.com/showthread.php?t=63739 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
