Wow! What a great thread! I’ve been reading through this all morning. The comments of others, and your answers, have brought up questions that I have, but had no reliable resource for answers! So, allow me to start with this: I own Magneplanars. I keep reading that tube amplifiers are a poor choice for these speakers. I like tubes though, and I have a tube preamp, and a hybrid power amp. The amp is a CJ EV2000, which uses 5751 tubes with a mosfet output to make 200 w/ch. I like the sound of my system, but it could be better. It seems to me that I don’t really need so much power, and I don’t need so much gain from a preamp. I rarely listen to music above 85 dB in my 21’x14’ living room. I’m considering buying a Schiit Saga passive/tube buffer “preamp” to replace my current preamp, and buying a quality tube amplifier. It is so difficult to compare things these days due to the fact that audio shops have all but disappeared. What are your thoughts about my situation in terms of “how much power” is appropriate, and “how will a quality tube amp drive my speakers”? Thank you for your insight! |
Speaking of Maggies... I would like use a quality, lower powered tube amplifier to drive mine. What is your idea of an appropriate amount of “tube” power for them? I sit about 9 1/2 feet from the speakers in a 14’ x 21’ x 8’ room, and typically listen at 80-85 dB (measured with a RS meter; C weighting/slow response). They’re rated for 86 dB/ 2.83v/ 500 hz. My preamp volume control is almost always around to 9:00. I really appreciate the idea of simple circuit design for both the amplifier and the preamp. I just feel like I’m not using the power in my amp (200w/ch), and also that I’m not using the gain in my preamp (12 dB). Power is expensive, and I’d rather put the money into the quality of the amp if I don’t “need” the hundreds of watts. |
@bdp24
Thank you for your reply. Roger commented on your reply, but my question remains somewhat unanswered. Your advice, which is common (though not universal), is why I’ve never tried a 25-50 w/ch “quality” tube amp. I’d love to be able to try some amps at home, but the few dealers within reasonable distance don’t have much to choose from. One guy carries Line Magnetic, but I’m not interested in buying one of those, and don’t want to try something I’m not planning to buy, just to see if it has enough power. I’ve had five different pair of Maggies in the past 32 years, among other types of speakers. I always end up going back to them after trying something different. I don’t listen very loudly, and I don’t feel like I’m using anywhere near 200 watts per speaker, so I asked a tube amp designer what he thought would be an appropriate power output for my speakers. I have a Dynaco st 70 in my weight room system, but it isn’t a “high end” amp, so I’ve never used it in the main system, as I don’t think it would represent what a really good amp could do. I had a VAC 100 w/ch amp in the past. It was plenty powerful, but ended up losing out to a Krell KSA 250 (purely on sound quality) when I was able to do a side by side comparison. I also had CJ Premier 5’s, but they’re very powerful, so not what we’re talking about here, and ultimately proved problematic, so I replaced them with the hotrodded CJ Evolution 2000 tube input/mosfet output amp I have now. I do know that in the late 80’s/early 90’s, iirc, Magnepan had a 1960’s tube integrated playing into their speakers in their lobby... I think it was a Scott, @ 20 w/ch. I’m sure it was played at a very low level. Roger’s RM 10 looks interesting to me, as does the Decware Torii Mk IV. From an electrical stand point, would these drive MG 1.7i speakers playing music at 80-85 dB ? That’s what I’d like to know before I buy something without the benefit of hearing it first. |
@bdp24 That's actually a good suggestion, and easy for me to do, and I have no good reason why I haven’t. I had a Forte model 4a for awhile as well (50 w class A), but never tried that on Maggies either. I have different systems in different areas of the house, and typically don’t mix them (?). I did try a passive preamp in the main system recently and did Not like how it made the system sound. Maybe my preamp isn’t too bad after all... I will try the Dynaco with the Maggies this weekend. Thank you for taking an interest in my quest for sonic nirvana! Lol |
@ramtubes.
I’m not ready to abandon passives from one less than favorable experience. The passive I have is a Luminous Audio Axiom... one input, one output, and volume pot. I listen to vinyl 95% of the time, so I was feeding it from the output of a phono preamp. To my surprise, the output with the pot at about the 10:00 position was approximately the same level as my tubed linestage at 9:00. The sound was bright.. too bright, and the deeper bass sounded more prodigious, but a layer of midbass was missing, and female vocals, which had sounded natural minutes before (through the preamp) were almost painful to my ears. It was like someone made the old eq smiley face curve on my system. The cables I’m using are old Tara labs solid core... 1/2 m from the ‘table to the phono pre, and 1 m from the phono pre to the amplifier. The amp sensitivity is rated at 900 mv, the cartridge has an output of 2.5 mv, and the phono stage is 42 dB/47k. I was going to question you about preamps, but didn’t want to stray too far from the thread topic. However, as I have found, others may be interested in your answers. I read forum threads that interest me frequently, but rarely write in. This one caught my attention more than usual because it was started by someone who actually builds this stuff... and is known to do it successfully. No offense to anyone else! I read all opinions and add them to my mental database. One thing I’ve learned is, what appears to make sense on paper is not always the case in practice. Thank you for your time. Truly |
It doesn’t make sense to me that some people get so angry/defensive/personal/nasty when discussing audio equipment! It’s fascinating in a way, but doesn’t do much to educate anyone, and most certainly impedes oneself from getting an education. I listen to music because it makes me feel good. I don’t want a discussion about the equipment needed to play music to piss me off! I believe we can agree to disagree on matters of opinion. This thread has much in the way of fact, but also with opinions masquerading as facts sprinkled in. Back on topic... What differentiates a passive “preamp” from a “tube buffer” with level and switching control? I really like the idea of a simple level control with switching capability, but as I stated earlier, my first try at using a passive, albeit a very inexpensive example, was less than stellar. Specifically, I’m looking at a Schiit Saga to try as a replacement for my tubed preamplifier. I’m weighing options for use with a tube amplifier, but I’d also like to understand what a tube buffer does differently than a tube preamp. Also, would the gain of a preamp “help” a lower powered amp sound more muscular, or is that more “made up” information?
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@ramtubes. Thank you for your reply to my questions.
You asked: “If you have a good preamp, why change?”. I’ll list a few things that have me looking elsewhere.
1.) I bought this preamp new, and after about two years it developed an issue. Every few times I switched sources, the left channel would fail to output sound. After cycling the selector the sound would return to normal. I called the manufacturer for advice. They told me to spray the switch with contact cleaner, which I thought shouldn’t be necessary for a two year old unit, but I did as they suggested. While it was open, I noticed that there was a screw missing from the vertical board that the selector switch was attached to. When I rotated the switch, the board moved around. I installed a screw in the corner of the board where it had been missing, and it no longer moved when I rotated the switch knob. That seems to have solved the problem, but made me wonder what else could have been overlooked.
2.) I recently bought an inexpensive, but well-reviewed phono preamp for another system. I decided to see how this stand alone phono pre compared to the built-in phono stage of my main preamp. The inexpensive phono preamp, through the tube linestage of my main preamp, sounded noticeably better. I asked the manufacturer, as diplomatically as possible, why this might be. They told me that the tube line section of the preamp is much better than the built in ss phono stage. Why include a phono stage that you know is inferior to the rest of the unit?
3.) I’ve read that the 12au7 is not the best tube to use in a preamp circuit. My preamp uses all 12au7 tubes (4 of them), and I’d like to try something that is designed around a different tube type.
4.) This preamp is made by one of the manufacturers whose amplifiers left you “not impressed”.
I like the way my system sounds, but for the reasons listed above, I’m feeling like replacing this preamp could allow the whole system to sound better... especially after the surprising phono preamp experiment. A system can only be as good as its weakest link, right? |
@bdp24 .. I had an older CJ preamp, a PV-8, which sounded as you describe. I replaced that with this one, a Rogue Perseus Magnum. It improved on the sound I was getting from the PV-8 in some areas, but I also felt like there was something missing when playing LPs. I didn’t realize it at the time, but discovered that the Rogue uses a ss phono stage, rather than tube... the tubes were only in the linestage. I don’t know if that was the difference in the sound, or some other area of its performance. The Rogue sounded a bit clearer and had better sounding bass, but after I got used to that improvement, I sensed that the LP playback was a bit veiled. When I tried the inexpensive phono preamp, a schiit mani, there was an obvious improvement in every parameter... like the cleaning of a window to the sound. I want more of that ;) |
@bdp24. All understood. Thanks. I guess the trick is to figure out what’s causing it, why it’s happening, and how to fix it. That’s what I’m hoping to learn more about.
I believe that my speakers, my amplifier, and my vinyl playback system are better able to communicate the music to me than my preamplifier is. I wouldn’t say it’s a “bad” preamp. I just have a sense that it’s not as “good” as the rest of the chain, and is therefore frosting my window, so to speak.
I initially joined this conversation to discuss options for using a simpler circuit vacuum tube amplifier in my system, but as I thought more about it, and followed the thread, it occurred to me that my preamplifier may need to be improved before I venture into replacing the amp.
It’s helpful to read the opinions and experiences of others, and it’s very valuable to have the perspective of successful component designers (Roger, Ralph, etc.). I appreciate all the contributions (except those added by the trolls... occasionally entertaining, but useless here).
I realize Roger is focused on the power amplifier, but he has created well-regarded preamplifiers as well. Ralph currently offers both. They have figured out the “What, Why, & How”. |
@bdp24.
I’m thinking that may be exactly the avenue I’d like to explore further. I’m looking at phono preamp options as we speak. I have a very simple passive device, which I did try, but didn’t care for. I am very willing to try other passives though, since the one I have was purchased to provide level control for our kitchen system, where I was using a 1960s HH Scott tube power amp.
The unit is a Luminous Audio Axiom. When I ordered it they asked what amp it would be used with so they could make one to work specifically with That amp. It is entirely possible that it is a mismatch with my primary amplifier.
Roger asked for specs... the only spec I know of is “1.2k” hand written on the bottom of the case. This was only a test anyway since I’d need more than the single input this one provides. I was not aware that Music Reference made passive devices (?).
I am considering both tubed and solid state phono preamps. Any design parameters that I should be paying attention to? Any designs to avoid? I currently only need one for a high-output MC cartridge (MM gain and loading), but I plan on trying other cartridges in time as well. I’m not opposed to getting a step up device if a cartridge I get in the future needs one.
Thanks again for the advice!
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@clio09. I believe bdp24 was suggesting I consider having Roger build me a passive (for switching and level control), not a phono preamp. In addition to an input for phono, I’d like to have at least two other inputs, and preferably two outputs as well.
I searched RM4+ and found only RM4, which appears to be a MC phono preamp only (?). If there is such a thing as a phono preamp which adds a couple of aux inputs for other sources, and a level control, I’m all ears. I’m not familiar with the “pot in the box”. Would you provide some more details as to its design?
Also, in your opinion, from a designer’s standpoint, what are some some things to look for, and to avoid in choosing a quality phono preamp? Thank you.
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@ramtubes.
I will measure the Axiom with a meter. Actually, after considering your comments regarding my experience with the passive, I reinstalled it in my system. This time I reduced the gain of my phono preamp, and I’m giving it another go ‘round. I’m using a variety of albums by a variety of artists in a variety of genres. I made my judgement in haste the first time, because the first LP I played sounded bright. I know better than to make a judgement so quickly without giving the component in question some time. I’m glad you questioned my impressions! This passive was never intended to take up residence in my main system, but I’m beginning to think a higher quality passive unit may indeed be a good fit. As to the phono preamp, I would actually prefer to used a tubed unit if possible. I appreciate you taking the time to discuss the details of these things. Clio gave me a contact email for getting information about products, which is outside the scope of this thread. I will continue to evaluate this passive in my system for awhile to get a handle on its strengths and weaknesses. It is sounding quite nice. Maybe it was revealing a bright recording that the preamp was taming..? Anyway, I’ll keep at it. Thank you again |
I wanted to weigh in on the power cord debate. I purchased a few of them several years ago. I did it because so many people were raving about how great they are, including one friend of mine in particular. When I replaced my stock cables, I did so without doing an intensive A/B comparison. I just took the stock ones out and put the “good” ones in. Sounded great... but it sounded great before. Not much to say other than that. If I have to work really hard to detect a difference, it’s not worth it. I honestly don’t have very expensive cables, considering the cost of my gear. I use Anti-cables for my speakers, and a mix of moderately priced Tara Labs and Audioquest for interconnects. My friend uses VERY expensive cables, and has components and speakers that are more expensive than mine, but we both agree that my system sounds better. I wouldn’t argue with someone who tells me their cables make a huge difference. To them maybe they do. But to me, so far, they haven’t. I have no problem hearing differences in different pressings of the same LP. I hear differences between amps, preamps, LP playback systems, speaker positioning, etc. But cables, not so much. It’s also odd that people who love cables get so angry and defensive when other people don’t get excited about them. Hey, if you dig ‘em, get ‘em, and be happy with what sounds good to you. You don’t have to get so mad. |
@ramtubes. I’d like to personally thank you for taking the time to sift through all these messages and provide your input on many of them. There’s a lot of valuable information here. I’d like to thank @atmasphere as well! Differing viewpoints gives us all a variety of things to consider. One should never stop seeking knowledge. |
What causes a designer to choose a certain tube type for an audio circuit? Is the circuit designed around a specific tube, or is the best tube type found for the circuit that’s been/being designed? I know there are different electrical properties (I’m not an EE, so that is my untrained understanding), but does one choose the tube primarily for its electrical ability, sound, reliability, or some combination?
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Haha... Nimble Tube-Roller Society! That exchange must have been just before I started buying stereophile (1986). I agree that having the freedom to choose different power tubes for the same amplifier is liberating from an owners standpoint (well, at least THIS owner!). It is also a very good point that buying something designed around a “single source” part is risky. I had an H.H. Scott LK-150 power amp (built in 1961) that I’ve used 6550, KT88, and now KT120 power tubes in. My son is using the amp now. That’s still a great amp (in my opinion). My point is that even though those tubes are from the same “family”, it was great to be able to try different flavors in the same amp. Regarding preamp tubes; I’ve had preamps that were built around different tube types, and they all had their strengths and weaknesses. I didn’t really attribute those differences to tube A vs tube B. But I knew not what made them sound the way they did. That’s why I wanted to take this opportunity to ask someone who has to make a decision about which to use. As you said, how can one compare between tubes used in completely different units? |
@ramtubes.
You mentioned, that in the RM 9, two KT120 or KT150 output tubes could be substituted for four EL34s in each channel. Is there an advantage to using fewer higher output tubes as opposed to using double the number of lower output power tubes, or vice versa? In other words, is the former following a “simpler” path than the latter?
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What prompted my question regarding tube types was the discussion in this thread about 6sn7/12au7/6sl7/5751/12ax7 tube type use for preamps and amp inputs. But there is also the question of power output tube choices - el34/6550/kt88/kt120/kt150, etc. It appears that some designers use the same tube types in their products, however there are instances where designers switch types year to year, or even have concurrent products performing the same function (amp or preamp) but using different tubes. Consumers and reviewers, also, sometimes prefer only 6sn7 or 12au7 based preamps, or kt120 or el34 amps, for example. I was hoping to get the viewpoint of someone who makes this choice.
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I’d like to add this: I appreciate the fact that there are two professionals contributing here, despite the fact that there is tension that’s been created by disagreement. I’m trying to read through the commentary to the points being made, the examples being given, and the facts. The reality is, there are many ways to arrive at the same destination. I’ve listened to, and owned A LOT of gear in my life, though none, so far, by either of these designers. Some products allow the music to communicate to you, some don’t, and a combination of components may speak to me, but not to you. I know this isn’t a technical question, but I felt compelled to write it nevertheless. |
@atmasphere.
Great comment (on hearing)! I believe our hearing mechanism is somewhat of a “moving target”, so to speak. I’ve wondered why sometimes music through my system sounds great to me, and other times, not as good. Even when playing the same recordings at the same volume. The disparity is occasionally such that I think something is “broken”. Fortunately it sounds good much more frequently than it does not.
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@ramtubes.
I measured the impedance of my passive across the input to the output as you requested. It measures 1.21kohm, which is as written on the bottom of the case. I opened the case and found an Alps volume pot, two resistors, and wiring. I played lots of music through it, using my phono preamp as the source, and I periodically placed my preamp back in the system for comparison. My verdict, with this passive unit, in my system is as follows: The system with the passive has clear high and mid frequencies, good space, and sounds spacious... but it is a bit brighter, a bit leaner, and is less pleasant to listen to than with the preamp. I’d call the sound with the preamp “smoother” and “warmer”. The vocals through the preamp were slightly veiled compared to the passive though, which annoyed me. So.. after this exercise, I believe that either a better quality passive, or a more transparent preamp, is what I’d want. What design elements could improve the sound of a passive device? Clio wrote about a phono preamp with passive level control and aux inputs. What a great idea!
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Thanks George. I like the idea of a passive control device, and I’m trying to learn about the system matching aspect so I can try an appropriate unit. I did appreciate the clarity, but was distracted by what I’ll call an overly etched, and leaner presentation. I can accept the fact that there may be more going on here than the “passive vs active” thing. The only passive I have was ordered for a very different application... level control for a CD player into a vintage tube amp for a second system. To be honest, it sounded pretty good despite the fact that it was MUCH less expensive than my preamp (1/10 the cost). Mr. Modjeski seems to endorse passives, and I’d like to at least explore this avenue with the right unit (for my system). My power amp is a CJ Evolution 2000 which was upgraded/updated by Bill Thalmann of Music Technology (formerly of CJ). Its input impedance is 100k ohms, and input sensitivity is 900 mV to full output. I’d like some flexibility with whatever I choose as a source switch/level control in case I decide to use a different power amp. |
Sorry, I had mentioned my sources in a previous post, but this thread has many, many posts by many people! I primarily listen to LPs, but I do have a DAC (Cambridge DacMagic Plus), and an Audioquest Beetle to stream Spotify over Bluetooth. I initially entered this thread to ask Roger his opinion about using a tube amp with my Maggies, but realized, after considering my system, that my preamp is likely the weak link. That realization lead me to learn more about improving the switching and level control functions... whether by a traditional preamp, or by using the combination of a passive device with a dedicated phono preamp. I had a passive in a different system, so I tried it in the main system to check it out.
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@ieales.
Thanks for the link.. I’ll check it out. My comment regarding the phono preamp with aux inputs and level control was made selfishly because I am very much interested in outstanding LP playback, and only listen to my digital sources casually (for background music, or if I’m not in the mood to flip records). Therefore a high quality phono preamp with a couple auxiliary inputs and a volume control is very attractive to ME |
Gentlemen, thank you for your advice. I actually never intended for either the Axiom passive, or the little Mani to take up residence in my main system, however I decided to try them, which lead to my interest in replacing my preamplifier. What started this for me was the purchase of the Mani for another system in the house, where I would like to set up an old Sonographe turntable, which lacks a phono input. Upon receiving the Mani, I thought I’d see how it compared to the phono stage built in my Rogue preamp. To my surprise it sounded better in every way. That prompted me to not only look for a better phono preamp, but also had me questioning the rest of the preamp! A call to Rogue revealed that they hold the tubed line stage in higher regard than the included, solid state phono stage. So now I am actively looking to address both (line and phono). Since LPs are my primary source, I thought maybe it would make sense to get as transparent a source-selector/level control as possible, while putting a larger part of the budget toward the phono preamp. This is veering a little off the topic of the thread, but I wanted to explain my presence here. I hope it’s not too far off... |
What I’m hearing is a thinning of the midbass range. The lower bass is coming through. There is also the etched character I hear in the higher frequency range. These are slight, but obvious changes in the sound which, together, render the music “less” pleasing to listen to. Still a good listen, but not as good, overall, as through the preamp. Maybe the Mani on its own is a bit lean and a little bright, and the tube preamp is adding some bloom and rounding off the rough treble edge..? Complimentary distortions? I used to be able to find complimentary components via trial and error, and a lot of listening. That method has been made impractical due to the sparsity of brick and mortar shops to deal with. Thus I’ve been following this discussion to learn what electrical/design properties can cause some of the differences in what we hear from our component systems. I have painstakingly tweaked the positioning of my speakers, the set up of my turntable and cartridge, the paths of my cables, seating location, room treatments, etc. Everything I can do myself to take advantage of what I already own. I believe my turntable, speakers, and power amp are of very good quality, and I’d been mostly happy with the preamp choice... until I inserted that “almost free” Mani, and it noticeably improved the sound of my LPs! I will absolutely seek out a higher quality phono stage, but I want that quality to be allowed to pass mostly undiminished to the amplifier.
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@ramtubes.
It is very likely that what I’m hearing with this preamp vs passive thing is a less than perfect passive, against preamp distortions which “smooth” the sound. I’d like to know more about your suggested solution to this issue, but contact outside of this discussion is probably best.
I do have technical questions regarding cabling and AC outlet use though! I’m not excited about super expensive cables (I’ve tried many with very little in the way of difference), but there are electrical differences (capacitance, inductance) in wire. Also, there are different metals and connectors used. What should one look for in terms of material (copper, silver, etc), and electrical properties (capacitance, etc) when choosing wire?
Regarding AC outlet use, how does one best work out the unavoidable need to plug various components into a two outlet wall plate? I had an electrician run a dedicated 30A, 10AWG line to the duplex behind my system location to isolate the stereo components, and to provide enough amperage for the amplifier’s initial turn on draw (it was tripping the 20A breaker). I have seven components that need power. I plug my power amp into one of the outlets, and a “high end” six outlet power bar to the other outlet. Is there something special, and necessary about power strips for stereo components? If so, what does one look for when choosing between them?
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