@ OP. How do you feel about Spectral Audio designing amps with extreme bandwidth? Are there benefits for solid state amps?
Does anyone care to ask an amplifier designer a technical question? My door is open.
I closed the cable and fuse thread because the trolls were making a mess of things. I hope they dont find me here.
I design Tube and Solid State power amps and preamps for Music Reference. I have a degree in Electrical Engineering, have trained my ears keenly to hear frequency response differences, distortion and pretty good at guessing SPL. Ive spent 40 years doing that as a tech, store owner, and designer.
.
Perhaps someone would like to ask a question about how one designs a successfull amplifier? What determines damping factor and what damping factor does besides damping the woofer. There is an entirely different, I feel better way to look at damping and call it Regulation , which is 1/damping.
I like to tell true stories of my experience with others in this industry.
I have started a school which you can visit at http://berkeleyhifischool.com/ There you can see some of my presentations.
On YouTube go to the Music Reference channel to see how to design and build your own tube linestage. The series has over 200,000 views. You have to hit the video tab to see all.
I am not here to advertise for MR. Soon I will be making and posting more videos on YouTube. I don’t make any money off the videos, I just want to share knowledge and I hope others will share knowledge. Asking a good question is actually a display of your knowledge because you know enough to formulate a decent question.
Starting in January I plan to make these videos and post them on the HiFi school site and hosted on a new YouTube channel belonging to the school.
I design Tube and Solid State power amps and preamps for Music Reference. I have a degree in Electrical Engineering, have trained my ears keenly to hear frequency response differences, distortion and pretty good at guessing SPL. Ive spent 40 years doing that as a tech, store owner, and designer.
.
Perhaps someone would like to ask a question about how one designs a successfull amplifier? What determines damping factor and what damping factor does besides damping the woofer. There is an entirely different, I feel better way to look at damping and call it Regulation , which is 1/damping.
I like to tell true stories of my experience with others in this industry.
I have started a school which you can visit at http://berkeleyhifischool.com/ There you can see some of my presentations.
On YouTube go to the Music Reference channel to see how to design and build your own tube linestage. The series has over 200,000 views. You have to hit the video tab to see all.
I am not here to advertise for MR. Soon I will be making and posting more videos on YouTube. I don’t make any money off the videos, I just want to share knowledge and I hope others will share knowledge. Asking a good question is actually a display of your knowledge because you know enough to formulate a decent question.
Starting in January I plan to make these videos and post them on the HiFi school site and hosted on a new YouTube channel belonging to the school.
845 responses Add your response
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.Dr Herbert Melcher showed that there are tipping points in the brain. Normally music is processed by the limbic system. But when things audio go amiss, the processing is unconsciously transferred to the cerebral cortex. At that point the music 'subjectively' loses its 'soul'. For this reason, its really important to know how the ear/brain system perceives sound, so as not to violate its perceptual rules (if you want the gear to be emotionally involving). Once you know that, it becomes and engineering task that is fairly mundane. He made excellent equipment and I can see from JAs measurements he did a good job on the three major characteristics of a good amplifier, one that would drive a wide variety of speakers well. On this I am in complete agreement with Charley. Im not sure why I need to listen to his amps, I am confident they sound find. Charley and I are on the same page with what is important.Charles made **zero feedback** amps and IMO his are some of the best solid state amps made. What I like about his approach is that he solved the issue of an amp that acts as a voltage source while also lacking the usual coloration of brightness caused by the distortion of added feedback. The industry needs this sort of diversity and he is missed. |
I feel one of the great benefits of tube products is the limited bandwidth eliminates susceptibility to much of the higher frequency ac noise. Comments?You can have plenty of bandwidth and not have noise problems. Noise is best handled by proper power supply design and good grounding technique. I find also that fully balanced differential circuits are handy for noise rejection as well. This means that you can have a wide bandwidth tube amplifier and have it be very quiet, even though it may not be shielded by a chassis. |
@krelldreams 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. I appreciate your balanced view on two designers, with very different viewpoints, airing their design thoughts in public. Im fine with it and I hope readers understand that sometimes a statement is so shocking to me that I get a little worked up about it. I have experienced and previously stated where cartridge loading makes large difference. I love to do things on the fly with minimum time between evaluations. Therefore I built a 6 position load box for my Denon 103 from 10 to 200 ohms, including no load. I can just dial through and listen. The Denon is a cartridge that needs loading otherwise it is bright and harsh. Around 100 ohms it sounds good to me. Below that it gets kinda dead sounding. On the other hand we did the same with the Lyra and no load sounded the best. We had a switch of 12 loads from 3 ohms to no load. From 10 ohms up we heard no difference. The audience was 40 people who generally agreed and were surprised at what they heard. I fully agree and have stated before that each of us have a system that is "his sound". It can be fun to visit and listen to others sound. Now what does one do when (and this is a horribly delicate situation which I have encountered too many times) one visits a friend and while the owner thinks things are fine the system is actually broken. When I found the bad 6SN7 in the Oppo the owner said it had probably been like that for a month. When we find a speaker out of phase it might have been that way for half a year. When I hear a distorted amplifier and I put it on the bench and find it way out of spec what has the listener been doing? I visited another audiophile who had $100,000 of good gear in a cubic room about 14x14x14 feet with all hard surfaces and no treatment at all. The room was so live I couldn't even carry on a conversation. I politely said.. "Hey its nice outside can we go sit in the sun and chat" When we came back in to listen he asked me what I though of his system. I told him, Sorry I cant hear the system I can only hear the room. Once again he though because he had good equipment that it had to sound good. Of course we should trust our ears but where is our reference? How many high end systems are being listened to with something out of wack. I am likely one of a very few designers that actually will repair others equipment. I do this because I like to see others work, how they make things, how their things perform. I have tested over 400 amps and preamps and can tell you all about what is going on in them. |
@ptss
@ OP. How do you feel about Spectral Audio designing amps with extreme bandwidth? Are there benefits for solid state amps?
When I went to Vegas in 1978 Spectral was playing B&W video through their line stage. The volume control thus because the contrast control which they encouraged everyone to play with. The picture was ok so it was at least a few MHz of bandwidth. I guess they liked bandwith. Their designs were, in my opinion, excellent. I dont see how it makes a difference to go that far and it is an invitation for RFI to be passed on to the power amp. After a certain point slew rate and bandwidth are just for bragging rights. In output transformer tube amps wide bandwidth, maintaining stability and getting the big 3 parameters reasonable, is the greatest challenge |
I am likely one of a very few designers that actually will repair others equipment. I do this because I like to see others work, how they make things, how their things perform. I have tested over 400 amps and preamps and can tell you all about what is going on in them. Well there's another thing we share. I put myself through college doing consumer electronics repair. I got the job right out of high school in 1974. I enjoy seeing how things are built and how problems were solved. We don't see much gear shipped to us, but we do a lot of local repairs on competitors equipment, as well as guitar amps, semi-pro and pro audio. |
Hi to all. Perhaps I was not clear in my original posting that this is a thread to ask the OP a question and have it answered by the OP. It was not an open invitation for other designers to answer questions or give their opinions on my answers. The whole point is to give the public some insight on how I design things and how I evaluate my own and other equipment. If you notice John Atkinson and I have similar views on what an amplifier ought to do. If other designers want to have such a thread all the better. I would not care to comment on their thread because those are their answers, their views. In the end I hope to educate. As far as selling anything I am happy to share the workings of my A/B test set up for no charge or build one for someone if they want to get into A/B testing. I am most happy to discuss interactions in equipment, how I go about designing, how I listen. Far down the list is the sound of particular tubes or brands of the same tube. I will talk about what different tubes can and cannot do well. I can talk about how some circuits are more sensitive to tube rolling and some are much less so. Now can we please proceed with this in mind. |
Well, it turns out that it was my friend Ralph (we have never met, I simply call him my friend) who misspelled Charley's name. It is in no way an excuse for bad specs- and in fact our amps have some pretty good specs (if proper measurement technique is used, which means **don’t ground a speaker terminal during testing**, which is the mistake that almost everyone except Charles Hanson made/makes). I suspect you didn’t read the paper at the link very carefully, since you claimed that you read it, yet still with the remonstrations!Sorry. Now back to my sorely missed idol, the great Charles Hansen. He gave an interview to S'Phile back in October 2016 (or at least, published in that issue) and said this; My point being that here we have this great engineer who thought he had engineered a product that tested well and sounded great and then he had an epiphany of sorts that something better was indeed out there and attainable. I continue to believe that old maxim that we're all tired of reciting let alone hearing; not all things that matter are amenable to testing. In a separate post your "intake guy" Clio-something really gave me the business about being a troll and not having anything technical to add. He's kind of right and kind of wrong IMHO. I may not have technical expertise but I will never believe that JA's measurements trump listening impressions. Roger-the Roger that I have metaphysically shaken hands with-enthusiastically too-you have endorsed JA's measurement techniques again and again and yet the fact of the matter is that JA has never given any tubed amp an enthusiastic endorsement from the standpoint of measurements. If your amp is an exception, than fine, that would be one instance of my "never" being incorrect. He may have given that monster hybrid integrated by Musical Fidelity-a known S'Phile darling-a thumbs up from a measurement perspective as well. So that would be two exceptions. Btw, go back to the full link of Charley Hansen's interview and see what he said about finding a power cord laying against the carpet at a show and finding that one wood block cured his perceived dissonance. What do you have to say about that? That it was in his mind? |
In a separate post your "intake guy" Clio-something really gave me the business about being a troll and not having anything technical to add. Actually, I said you bring zero value. The statement wasn't referring to just technical value. Perhaps you got confused with the other part of the paragraph where I said you lack the knowledge or credibility to refute anything Roger says. I was in fact referring to your lack of technical knowledge in that instance, but of course you already copped to that previously. |
@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? |
@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. |
I have for years heard accusations from audiophiles about TAS and now Stereophile requiring advertising from any company wanting one of their products reviewed. I have never seen any proof of that, and have to point of that though I have never seen an ad from Music Reference in Stereophile, a review of the RM-200 by Michael Fremer has twice appeared in the mag; once of the original version, a second of the Mk.2. That the Arma-Sphere M60 and/or MP-3 have not been reviewed is ridiculous. They review all kinds of over-priced status symbols, why not some high-value mid-priced pieces (the stuff most of us are interested in owning)? |
@fsonicsmith not all things that matter are amenable to testing. Indeed we cant test for everything. However we can test for the big three and include that information in our listening. For instance if one amplifier produces a lot more bass from a speaker which amp is right. If the person prefers more bass then he buys that one. However usually when there is more bass the bass is not as good. Its uneven, boomy, the extreme being the "one note" bass. Now if we measure the amp with more bass and find it has poor damping we can say to the first order that is due to the poor damping. What gets interesting is when we have two very good measuring amps that sound fairly alike and one is tube and one is SS then we have to start wondering as Charlie did, What is it tubes do differently? I hope someday I make a better amp than what i have made so far. An RM-9 is hard to beat. So are all the Marantz tube amps. Perhaps I have equaled the Marantz 8B, Saul's favorite. Perhaps I have better bass because now we have much larger filter caps than he had. Other than that not much has changed. BTW Saul told me that around the shop they firmly preferred a pair of Mono 8s to the famous Model 9. |
@krelldreams 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? The advantage lies in fewer tubes to fool with, a little less heater draw so the power transformer will run cooler and you get away from the tight matching of 4 tubes. The path is the same. The idle current will be the same. Might have to shift the bias a little. I know the 120s work. We have had several people do it. If I get a chance I will give the 150s a try in an RM-9. Might look cool having 4 x 150s in the front row. |
@bdp24 I have for years heard accusations from audiophiles about TAS and now Stereophile requiring advertising from any company wanting one of their products reviewed. I have never seen any proof of that, and have to point of that though I have never seen an ad from Music Reference in Stereophile, a review of the RM-200 by Michael Fremer has twice appeared in the mag; once of the original version, a second of the Mk.2. That the Arma-Sphere M60 and/or MP-3 have not been reviewed is ridiculous. They review all kinds of over-priced status symbols, why not some high-value mid-priced pieces (the stuff most of us are interested in owning)? True, I have never advertised in Stereophile. I run a different ship than most. I was offered to share the front cover for the Fremer review but declined. I want my amps to sell on their merit not advertising. The people who know will find me, its never been a problem. I find Stereophile and JA the most unbiased folks in the industry. TAS is and always has been a joke technically. Harry made the best of it as the self acclaimed "Audio Pusher". I read a few issues over the summer and saw that their current model is the "two page review" Every review was two facing pages. How boring. Where do the reviewers find all those words? TAS will never measure anything and what am I supposed to learn from all those words. Stereophile also reviewed the RM-5 and RM-9 in the 80s. Im quite sad where things have gone in this industry I have devoted my life to. Need I say more? |
Ramtubes 12-6-2018 That’s interesting to hear, Roger. Although to be precise I’m pretty certain that the 8 and 8B were both single-chassis stereo amps. I’ve never heard an 8 or 8B but during the 1990s I owned a pair of Model 9 monoblocks and a pair of Model 2 monoblocks. And I greatly preferred the sound of the 2s to the 9s, although in fairness I can’t exclude the possibility that condition may have been a factor in that. The 2 was similar in some respects to the 8 and 8B, which came later of course. Although in addition to being monoblocks the 2 employed tube rectification, while the 8 and 8B used solid state rectification, and the 2 used 12AX7 input tubes while the others used 6BH6s. I’ve commented here in the past that at least when used in conjunction with speakers having benign impedance characteristics and not requiring more than the 18 or 20 watts or so that the 2s were capable of in triode mode, in that mode the 2s were one of the best sounding amps I’ve ever heard. Regards, -- Al |
@almarg That’s interesting to hear, Roger. Although to be precise I’m pretty certain that the 8 and 8B were both single-chassis stereo amps. I never got my hands on a 2 but I studied the 5 (half of an 8) in great detail and I saw how they did the tertiary feedback winding. I had to do a lot of experimenting to make that work out but its a trick I have rarely seen in other amplifiers. The separate feedback winding makes the amp more stable into reactive loads. Perhaps few know that we made all the transformers for the RM-9. I cut my teeth on the design of that output transformer. The 9 was quite a departure from the 8, far more complex, perhaps better specs, but when you take specs too seriously (as in too much feedback) things can go downhill. |
@ramtubes, oh yeah Roger, now I remember Dick Olsher's review of the RM-9 Mk.2. I found Olsher to be a reviewer from the Gordon Holt school (a school I approve of ;-), and he loved the amp. I believe his closing line was something like "Who needs an MC75 (the classic Mac amp) when we have the RM-9 Mk.2?" I also remember The RM-5 and the Audible Illusions Modulus 2 were considered THE bargain tube pre-amps to choose between. I found the AI Mod's 30dB of line stage gain unfortunate and ill-advised, as well as it's dual-mono volume controls. The Modulus is still in production (in updated form, of course), so Roger, any thoughts of offering a contemporary RM-5 type pre? |
This is kind of an obtuse question, but why do some amplifier manufactures say to use a preamp between their amplifiers and the streamer when you are only using a streamer and power amp, no vinyl and no other sources. I understand the need for a volume control and to have the impedance's low for the streamer/DAC and high for the power amp. My streamer/Dac is <100 ohms and the power amp is 47K. There is an implication that the preamp does other things that affect the SQ. Any idea what those are? An Allegri+ addresses the impedance problem and give a volume control and is extraordinarily transparent on my Ribbon Speakers. My amp and steamer is very high end. Is there more? |
@bdp24 - dual controls are not too fiddly if they are 1db or less stepped @apogee14151617 - all components active and passive alter the sound. There is no electrical reason to have a preamp if the source has output level control or the amp has input level control. I use a passive 1db stepped resistor of my own design. It has a sound, but everything does. |
why do some amplifier manufactures say to use a preamp between their amplifiers and the streamer when you are only using a streamer and power amp, no vinyl and no other sources. I understand the need for a volume control and to have the impedance's low for the streamer/DAC and high for the power amp. My streamer/Dac is <100 ohms and the power amp is 47K. There is an implication that the preamp does other things that affect the SQ.The answer is highly system dependent of course, but one reason is that a preamp is or should be designed to minimize artifacts occurring from the interconnect cable between the preamp and amp. Sometimes digital sources are not very good at this. A second reason is that a preamp can provide a fairly high impedance load for the source, meaning that the latter does not have to work as hard to make its signal. This could result in lower distortion- and no place better in the system to get things right! |
minimize artifacts occurring from the interconnect cable between the preamp and amp.Source output 22R, amp inputs 23k5 or 100K. Adding a preamp with attendant switching, circuitry, noise and additional cables is little more than a subtle tone control. It maybe different, but it may not be better. |
Source output 22R, amp inputs 23k5 or 100K. Adding a preamp with attendant switching, circuitry, noise and additional cables is little more than a subtle tone control. It maybe different, but it may not be better.Some volume controls in DACs are actually far more than subtle in their operation. Stripping bits isn't the best way to control volume. For that reason the buffered volume control that can be in an active line section could be more neutral. One thing is certain: when it comes to preamps, passive volume controls or running direct, because there are so many different products and approaches to this problem no generalization about the matter could be seen as true. |
@bdp24 I also remember The RM-5 and the Audible Illusions Modulus 2 were considered THE bargain tube pre-amps to choose between. I found the AI Mod's 30dB of line stage gain unfortunate and ill-advised, as well as it's dual-mono volume controls. The Modulus is still in production (in updated form, of course), so Roger, any thoughts of offering a contemporary RM-5 type pre? Thanks for the memories... who sung that? The Modulus and RM-5 present a great example of dueling designers. Art did not put feedback around the line tube as I did. I also made it variable with dip switches for many gain settings from 0 to 30 dB which is the full gain of the tube. He later put a cathode bypass disconnect to lower the gain but that is a Very bad idea as it raises the output impedance to about 10K. The feedback in my line stage lowered the output impedance to about 1K. Im surprised people didnt hear the difference more easily. Again, that would have showed up in an A/B which is just not done is it? Where I did volume and balance Arthur liked his dual controls. Other than that the preamps were pretty except for the power supply. His blew up, mind didnt. Problem was, Arthur was not an engineer and the preamp was the work of many people. I think he bought the company from Bruce Moore. Hope Im not bragging on mine too much, just the facts Madam. He claims in the TAS book to have sold 25,000 units. His tech, Meserve. was my tech in the 1980s and said theres no way. We sold 960 over the 15 years we made it. All sonically and ciruits wise the same.. Only thing that changed was the jacks as better ones came alone. If you can find a MKIV that was the nicest as we put on a phono tube off switch, heavier metal, nicer jacks. We only made 50 so good luck. The MKIII is more available and just as good except for those two things. |
OP do you believe in the burn in process of an amp that over time the sound will settle and finally focus on a cohesive musical experience or is it to your opinion all in our brain that is adjusting to the sound of the component? When I mention burn in process its regard to periods of 300hrs and more (eg Naim or Simaudio Moon amps). |
@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! |
| Post removed |
krelldreamsIf your Alps pot’s passive pre, input to output measures 1.21kohm then you have a 5kohm Alps pot. Your source may well be doing it hard into this 5k load, and making things "leaner". Passives should be at least 10kohm to suit "most" situations. Or higher (>10kohm) if the amp is also >50kohm or more. Cheers George |
Passives should be at least 10kohm to suit "most" situationsIt depends on the source output impedance what the passive resistance should be. If the output impedance is < 500Ω, a 5k pot is fine. Pots have a different sound than stepped resistor controls. IMO, P&G pots were more musical than Alps when I used passive level controls in the studio. Additionally pots, especially log, track nowhere near as well as stepped resistors. Clio wrote about a phono preamp with passive level control and aux inputs. What a great idea!Whether it is a great idea depends on the topology and to what it is connected. |
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. |
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.See http://ielogical.com/assets/Audio/PassiveLC1.png here http://ielogical.com/Audio/#LastHurrah. It is possible to use a single resistor value to give perfect passive tracking for any amp impedance. Only caveat is ensure source has low output impedance, say less than 500R and power amp has reasonably high input, say 20k+ |
Mr. Modjeski seems to endorse passivesYes his amps are loved by passives and with my customers that use them. My power amp is a CJ Evolution 2000 its input impedance is 100k ohms, and input sensitivity is 900 mV to full output. It should also love passives, with that 0.9v input sensitivity. And that 100k input impedance you could of had a 20k Alps passive, not just 5k, A 20k Alps pot would have been fine for just about any source then, which by the way you have not told what you have as the source.?? because if it has high’ish output impedance it won’t be comfortable with that 5kohm Alps pot as it will load down it's output and also create a voltage divider. Cheers George |
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. |
@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 |
krelldreamsWhat would your phono stage be, hopefully I can find it’s output impedance and if it has capacitor coupling and if that’s big enough, to work into a 5kohm Alps pot., if not it will roll off the bass prematurely, "creating a leaner sound" As far as the DacMaigic goes (at<50ohm output impedance) there’s no problem for it to see, your 5kohm Alps pot. But it has an output coupling cap also and with the 5kohm Alps pot that coupling cap has to be at least 5uf in size to be -3db at 10hz if smaller than this it could prematurely roll off the bass also, "creating a leaner sound". Cheers George |
What would your phono stage be, hopefully I can find it’s output impedance .... George, I was wondering the same thing, so I took a look at Krelldreams’ posts earlier in the thread and it appears he is presently using a Schiit Mani phono stage (op-amp based, 75 ohm nominal output impedance, $129), but is looking into alternatives. While I understand that the Mani has received a lot of praise, and is certainly considered to be an excellent value at its very low price point, I can’t help but wonder if his finding that... 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. ... is simply due to the output of the passive preamp accurately reflecting what the Mani is providing to it. So it seems to me that it may be wise for Krelldreams to defer addressing the preamp question until an upgraded phono stage has been purchased and is in use. Best regards, -- Al |
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... |
almargThink I found it. Output impedance of the Mani at 75ohms is fine, but if you have a look (linked) there does look to be 2 x Wima output coupling caps on the Mani 's board, I say by the look of them maybe 0.47uf. These into a 5kohm load of the the passive Alps would give a -3db already at 67hz, and could very well be the leaner sound being heard. https://ibb.co/WsFNvhk Could even be the same with the DacMagic. Cheers George |
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. |
@ramtubes, Here's a question for you Roger regarding a matter that was being discussed amongst Maggie owners on The Planar Speaker Asylum forum yesterday. One poster said of hearing from tube amps something I too hear, and that is of a sound stage that begins in front of the loudspeakers. I heard that for the first time when Bill Johnson played an LP of Holst's The Planets (in 1973 at Audio Arts in Livermore, after he finished setting up his complete system in the shops really good room), a recording made in a large hall. The front of the orchestra was clearly located between myself and the front plane of the Magneplanar Tympani T-I's, and the rear of the orchestra was waaay back behind the speakers, sounding as if it was actually further away than was the wall behind the Maggies. I could hear the delicate triangle in the rhythm section, elevated on risers, playing in the quieter sections of the piece. It was thrilling! Prior to that experience, at Sound Systems in Palo Alto I had heard a pair of the original Infinity Servo-Static ESL's, powered by the then-new line of SAE electronics. Through that system I did NOT hear the image "thrown" forward of the speakers. I have subsequently heard the forward image (and great depth) from other systems (including my own), but only when the electronics are tubed. So my question is, why is it tubes are able to do that? Is it a matter of tubes being lowest in distortion at lower-signal levels (where imaging resides?), and transistors in their curves highest? |
