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.
Roger nice job handling Teo. IMO he embodies everything that is wrong in high end audio these days.
Some Ignorance is so manifold that it is used to commit to attacks so libelous and underhanded... that the person initiating is practically kicked off a given forum. So obvious to all, that there aren’t even words for it.
And then that illiteracy and ignorance is paraded about as somehow being informed. That we can all be that dense. Jebus. What a horrific world that would be.
So far gone that it can’t even be explained to a given person how far off base and wrongheaded a given comment might be.
Ralph (Atmasphere), thanks for your characteristically very constructive and informative post above. A very minor correction, though, for the record. I’m sure you misspoke when you referred to pi-squared. The 6.28 factor you referred to is of course correct, but that is 2 x pi, not pi-squared.
Roger, this is a GREAT thread, thank you. I agree that all of the nasty comments and bickering should be kept out of this thread ( as well as all threads ). This thread is about learning, as I see it, and I am learning a great deal ( maybe understanding 1 % of it ) And yes, this thread has me thinking about trying tubes again in a power amp. : Going back to damping. In my early years, I owned several ss power amps, a few high powered. Two in particular, were an original Ampzilla, and a factory built Dynaco 400. Having many speakers at the time ( DQ10, AR 3, Klipsch Lascala, just to name a few ), the Dynaco had a bloated, slow, ill defined bass in comparison to the Ampzilla. Both were rated at 200 wpc into 8 ohms ( as I mentioned, these characteristic were also in all of the tube amps I had at the time ). Can you explain if these characteristics between the Amnpzilla and Dyna had anything to do with damping ? Thank you in advance. Enjoy ! MrD.
I know some people like to put chokes between output and drivers B+. It adds better isolation on high frequencies between power supplies. But what do you think does it have any real effect?
What do you think about separate power supplies between left and right channels for 300B SET amplifier? Does it do a significant difference?
I’m sure you misspoke when you referred to pi-squared. The 6.28 factor
you referred to is of course correct, but that is 2 x pi, not pi-squared
Yup- thanks for that. My medication is a bit too powerful today...
It adds better isolation on high frequencies between power supplies.But what do you think does it have any real effect?
What
do you think about separate power supplies between left and right
channels for 300B SET amplifier? Does it do a significant difference?
A choke is helpful as it can be used to help filter out the 60Hz sawtooth waveform that is part of the rectification process. They can be quite helpful in that regard, as to do it with resistors and filter caps essentially requires more filter caps and also means a bigger voltage drop in the power supply, where voltage might be at a premium. IOW you can have a fairly low voltage drop across the choke due to a low DC resistance, yet still filter out noise in the supply.
Separate supplies is not a bad idea at all, although in a class A1 SET you shouldn't have a lot of noise in the supply. If you have separate supplies though, you could also have separate chassis for left and right. This would give you the ability to run shorter speaker cables, which is really helpful when working with amps with a higher output impedance such as an SET.
The trick is that when things stereo share a common power supply its possible for them to talk to each other (the term is 'crosstalk') and essentially interact unless great care is taken to deal with the power connections and ground connections correctly. Otherwise you can increase IM distortion and IM needs to always be kept as low as possible.
What is the role and importance of significantly upgraded power cords in component design? It seems to me that the PC is a fundamental part of the electronic device and that the manufacturer should optimize the cord for the device in building it. What are your thoughts on the matter as someone who actually builds electronics?
@noromance, I respect Roger’s directive to keep this thread focused on amplifier design, and questions about that topic alone. I brought up Harvey Rosenberg and the Decca only in response to tomic601’s (who has a close relationship with Roger, if I'm not mistaken) mention of mentoring. I’m happy to share what Harvey had to say to me about the Decca, so I’ll start another thread dedicated to that subject. Let me find my notes and collect my thoughts, and I’ll lay it on ya! I know you have a Decca or London, and are therefore very interested in what Harvey had to say about them.
@cardiffkook, I’m sure Roger will get to your question, but in the meantime you should know that he does NOT share your feeling that "the PC is a fundamental part of the electronic device", and does not "optimize the cord for the device in building it." He infact includes NO cord with his power amps! Further, he says his reason for doing so is that everyone has a spare computer power cord laying around ;-) . Anyone wanting a 'better" pc can get a 3’ long 10g Signal Cable one for $59.
@jdjohn Any thoughts on kits like this modeled after the Dynaco ST-70? http://www.tubes4hifi.com/bob.htm#ST70 This isn't a mod or upgrade for stock ST70s, but a kit for building a brand-new amp. Some of the design changes are listed under 'ST70 amplifier features' if you scroll down the page a bit.
Looks good. I like to see the 3 tube driver board. Do they have a schematic?
The original single 7199 tube driver was flawed by tube to tube variations. Some good 7199 would bias up in a region that actually produced a lot of distortion and reduced power. There are many 3 tube drivers. I would like to know more about theirs.
We get requests from folks who want their old RM-9s refurbished. One of the common side requests we get is to put in an IEC inlet in place of the captive power cord, which from Roger’s perspective is more than adequate for the job, of reasonable length, and quite flexible. We try to talk folks out of this as there is just not enough room between the transformer cover and the edge of the frame to add an IEC inlet. In addition, the RM-9 frame makes this task rather difficult as you have to cut into the wood and there is risk of damage if not done properly. So for those who insist we advise them we will chop the stock cord about 6" from the top plate strain relief, attach a male IEC, and finish it off with shrink wrap and the customer gets to choose the power cord of their choice. Now the signal comes from the Romex in the wall, through the designer power cord, then that last 6" through the original stock power cord into the power supply.
However, some may not be aware that Roger does acknowledge a power cord can make a difference in the system. In this case, a power cord that addresses hum caused by having
DC on the line, which can be a hard problem to fix. So he designed a power cord
rated at 5 amps that removes DC and will quiet troubled transformers.
Question about the effects of different impedance settings and phono cartridges.
I’m a newbie with high end turntables (just replaced my old turntable with a much better one). My phono stage is convenient in that it allows easy access to changing the impedance levels from the front panel. I actually enjoy playing with the impedance settings to alter the sound to taste depending on what I want.
Mine is an MC cartridge and I find an impedance setting of 100 Ohm to be just about right in terms of sounding tonally accurate (like my digital source).
I won’t be telling anyone here what they don’t know when I mention that as I set it to higher impedances, the sound gets brighter and more taught (to more "pinched" and less relaxed/natural sounding towards the high end of the impedance settings). And the sound becomes darker (more rolled off in the highs), richer, more spacious and the bass seems to bloom a bit more in size and lose some tightness. I actually often enjoy just dipping down the impedance from the 100 Ohm setting to the 33 Ohm setting, to enjoy the slightly richer sound sometimes.
So my question is: What exactly is happening to cause the type of sonic changes on hears when changing impedance settings for a cartridge?
My know-nothing layman’s hunch is that it’s similar to how speaker impedance interacts with certain tube amps, where some combinations contour the frequency response...and (sorry for the word) damping factor? (The changes in the bass in lower impedances do give me that "lower damping factor in the bass" vibe).
and I might add that the 5A rated power cord is reasonably priced on the RAM tubes website.
@ eric - no mentoring relationship w RM other than this thread which I am greatly enjoying....and learning...the Analog circuits book arrived today and I am diving into it with a glass of Malbec and some Peter Gabriel on the box ( shock the monkey ? ) I think my trajectory will include burning amp 2019 IF they will have me. Just about to order the scope, R Vandersteen who I do consider a mentor recommended a used Tektronix TDS 220... but Amazon has a new w warranty Tektronix for not much more than the hawks at ebay want used..
@tomic601, Oops, I had you confused with clio09! He DOES have a professional relationship with Roger. I’ll put the Decca info up in a thread, for all to see, hopefully tomorrow---Eric.
Roger this is related to a question you raised in past post on subs and remote controls.
ramtubes - The amp is any old SS 100+ watt amplifier. Currently a nothing special Denon. The woofer level control is on the crossover.
This solves a lot of problems with powered subs. Unless they have a remote (do they now?) it is difficult to adjust the level for different CDs,
Firstly I Agree, especially if someones subs are setup in typical fashion across the room with the main speakers.
My solution I am using for the last two years, two Dynaudio BM12s studio subs in Room B with my Wayne Picquet restored Quad 57's. They (BM12s) are one example of a solution with a credit card sized remote control that handles db and crossover levels, phase, and allows you to save 4 settings. Classical is typically a higher DB setting then compressed popular music. The BM12s are handling 60 hz and down and the RM10 has full control of the 57's. The subs come with their own Class A/B amps and on the boxes are heat sinks. Mine are now positioned on either side of the listening couch. This allows for the db levels to be set the lowest, phase 180. The sub amps heat sinks don't even get warm. Very little vibration from the boxes.
************
We last conversed about a year ago when I inquired about slope cards for an RM3 that I own. I was thinking about a project to bi-amp my Matrix 800's at the time.
btw - A nice surprise coming back here for winter conversations to find you have the most popular thread on Audiogon. 8^)
@ct0517 - nice set up. I sometimes use my RM-10 with my ESL 57s in biamp set up. The Class AB amp I use for the bottom is a Luxman M-02. I use the Beveridge RM-3 (no remote) to crossover at 100 Hz, 4th order crossovers for both high and low pass. Rather than two woofers I use four in an asymmetrical array. I am curious how you settled on the 60 Hz cutoff and what other levels you may have experimented with.
I favour amplifiers that are either Class A or at least have very rugged power supply capacity (I use several Classe DR3 VHC, a Belles A, a Rowland 5). What are the symptoms of the supply caps being on the way out and at what general age do they become seriously at risk? The Classe amps, for instance, are hitting 30 years old now.
Got into these way back to be able to drive 1 ohm speakers but stuck with them after speaker changes as I love the sound.
What is the role and importance of significantly upgraded power cords in
component design? It seems to me that the PC is a fundamental part of
the electronic device and that the manufacturer should optimize the cord
for the device in building it. What are your thoughts on the matter as
someone who actually builds electronics?
There is a voltage drop across any power cord that can influence the output power of the amplifier. What is less well understood is that it can affect distortion too. Much depends on the amplifier design of course, but these effects are measurable and no surprise in some cases that they can be heard too.
Question about the effects of different impedance settings and phono cartridges.
The loading is there for the preamp, not the cartridge! I know this sounds counterintuitive but here's how it works: The cartridge has an inductance and the tone arm cable has a capacitance (along with the input capacitance at the preamp). Together they form a tuned circuit. With a Low Output Moving Coil cartridge, this resonance can be at several MHz. If the preamp is unhappy about Radio Frequency Interference (RFI) at its input, it will affect the sound- the additional distortion will likely make it bright. The loading resistor detunes the resonant circuit and thus prevents the RFI. Problem solved? The downside is usually two things: 1st, by loading the cartridge in this manner you are causing it to do more work. The energy has to come from somewhere and that means the cantilever will be more stiff- less able to track higher frequencies! The second problem is that (generally speaking) a preamp that requires loading to sound right probably also has stability issues, usually because the designer hasn't sorted out the facts in the 2nd paragraph below your quote. This instability often results in excess ticks and pops that **actually would not be audible were the preamp actually stable**!
Im sorry, but you asked. I'm sorry to be so negative about ARC, but I was a dealer for them from 1975 to 1980. If you have not heard about the "pink papers" thats a story in itself. ARC treats dealers with a heavy hammer, large opening order and threats if you do not follow the party line. Bill called us up one day because he heard we were doing A/B comparisons for our customers. He said "stop immediately or I will pull the line"
Of course I respect your technical experience and ARC anecdotes, but let me just weigh in on ARC. Perhaps I have been crazy lucky, but I have owned ARC gear for quite awhile and my anecdotal experiences are quite different than yours.
In particular, as far as linestages go, I've owned the Ref 3, Ref 5, Ref 5SE and now currently, the Ref 6. As far as amps go, I've owned the VS110, the VS 115, the Ref 150 and now the Ref 150SE. My CDP is the Ref CD-8 and my phone pre is the PH-8.
To date, I have had only one problem; namely: blown bias resisters in my older amps. Other than that, no other problems whatsoever. In the case of my Ref 150SE, I am running KT-150s. So far, … fingers crossed, ... no problems with arc'ing or blown bias resisters.
Notably, JA reported that "Fig.1 indicates that the Ref150 has a wide bandwidth, particularly into loads higher than the nominal tap value, which correlates with a well-defined 10kHz squarewave (fig.2). While this graph reveals a small but critically damped overshoot on the leading edges of the waveform, presumably due to an ultrasonic transformer resonance, no ringing is visible." By comparison, the Ref 75 did not test as well. And you noted the same in your prior post.
I can't speak to whether the circuits in my ARC gear are elegantly simplistic or labyrinthically complex . I am not a EE. But so far, my gear is holding up pretty well.
As far as SQ is concerned, … no comment. I have not had an opportunity to A/B ARC gear against any other brands. But to my untrained ears, my gear seems to sound OK.
Perhaps your views about ARC might change if you road tested some of their current models. I understand that ARC opted to simplify the circuits in its latest offering, the Ref 160 mono blocks. Haven't heard them, but it doesn't matter. I am not going to drop $30K on mono blocks.
Btw, I owe you two quads of KT-150s for matching. The 3rd party vendor from whom I purchase the tubes didn't match the tubes to ARC spec.
VAC seems to be doing some good work these days. I have worked on one of
their big preamps, it was nice but picked up hum from a power amp 2
feet away. We were surprised.
Clio09 I am curious how you settled on the 60 Hz cutoff and what other levels you may have experimented with.
Clio09 atter much experimentation I found the 57's positioned the way they are in my space to be the most room filling and linear top to bottom - down to about 50-55 hz. Still, to get the bottom octave and bass impact (it's a large room) I needed to add subs. I used to have a big HSU set up in nearfield next to me. It was fine as long as you were sitting in one spot. But if one uses the room - walks around, and sits in different spots around the room; multiple subs are the answer to eliminate the bass nodes. Adding the two 12" Dynaudio subs improved on the single large HSU. Keeping the HSU as a slave would have been interesting, but my son took it. 8^0 The lowest crossover point on the Dynaudio BM12s is 60 hz. So that is where they are set. I have tried higher settings in the past with other subs and felt it interfered with the 57's bass too much.
I just want to say thank you Roger. With respect to tube amp output impedance
selection, I had never heard that you should “Always use the lowest tap that
gives you enough volume without distortion (clipping)”. I have a pair of Kef LS50s in an acoustically
treated room (16’ x 11’ x 10’) that I’m driving with a pair of ASL DT200
hurricane mono-blocks (100 watts per channel).
I’m not worried about clipping. I immediately tried your suggestion by switching
the LS50s from the 8 ohm tap to the 4 ohm tap.
And, just like you said, the bass tightened up, so much so that it
shifted the tonal balance of the system up.
This caused the system to actually sound a little strident. Well, I had used a parametric equalizer to
boost frequencies around 10KHz a few decibels to offset the acoustically
treated room, I thought. I removed the
boost and Voila’, things are noticeably better all the way around.
I have another set of tube mono-blocks that use
4 EL34s each. I think that these are
more sonically pure than the Hurricanes but they don’t seem to be able to
control the bass on the LS50s to an acceptable level. I can’t wait to try the 4 ohm tap on
those. Thanks again for sharing this
knowledge with us.
I said I was done in this thread and once again, I lied. I swear this question is in good faith and not meant to challenge or make a point. While looking over at Tungsol's website I saw this;
Engineers and musicians have long debated the question of tube sound versus transistor sound. Conventional methods of frequency response, distortion, and noise measurement have always assumed linear (clean) operation of the test amplifier and have shown that no significant difference exists. In actual operation most amplifiers are often severely overloaded with signal transients. Under this condition there is a major difference in the harmonic distortion of tube and transistor circuits.
RM or RK, there has been this overriding premise (by RM) that most of us have more power and overhead in our amps than we really need. What is your response to the premise above (and everything else in the link provided)? I can find the link if you like, but in one of Charley Hansen's last interviews with Stereophile he stated that after thinking throughout most of his engineering career that tube-o-philes' preferences were largely imagined, he had come around to the thinking that it is in fact extremely difficult to engineer a solid state amp that captures the same magic that a tube amp can have (and in the meantime Charley acknowledged that he had come around to believing that there is in fact a certain tube magic) and that he thought his latest amp design had captured that magic. I only bring up Charley's arguably unrelated "epiphany" because it may or may not be related to the premise of Tungsol that most amps are severely overloaded in actual operation. So what do you say about this? I happen to have 150 watts of glorious tube power (actually more) with my ARC 150SE matched to very efficient and easy to drive loudspeakers-DeVore O/93's-and I have no problems with audible hum and I am very happy with how my system sounds.
I said I was done in this thread and once again, I lied. I swear this question is in good faith and not meant to challenge or make a point. While looking over at Tungsol's website I saw this;
Engineers and musicians have long debated the question of tube sound versus transistor sound. Conventional methods of frequency response, distortion, and noise measurement have always assumed linear (clean) operation of the test amplifier and have shown that no significant difference exists. In actual operation most amplifiers are often severely overloaded with signal transients. Under this condition there is a major difference in the harmonic distortion of tube and transistor circuits.
Please be aware that this paper was not written by any Tungsol engineers who are long gone as well as their factory and any tribal knowledge.
This is the work of New Sensor who has taken over the name, probably with no resistance, and making the tubes in Russia. Im not saying these are bad tubes but they are not Tung Sol of America. The KT series apperars to be good and I have tested the 120s and 150s. The data sheet for the 150 is in Tungsol style but not of Tung Sol quality. No plate curves, Gm seem too high. Not informative as in the good old days. I have offered to help them.
Also keep in mind that New Sensor sells to the guitar amp market by 100 to 1. Nothing wrong with that. Thanks to the guitar guys for keeping the demand for tubes going. We audio users are a drop in the bucket.
This has been a great and informative thread. Thank you for sharing your time, knowledge, and insight. I've learned a lot.
A question for you: any further thoughts on ARC's M300 monoblocks? They're a fairly...unique design and perhaps the best evidence of your view that WZJ's ARC designs were often over-complicated. That said, I enjoy them, and they've only blown up a couple times over the years. Any further comment?
(As to your point about the reliability of ARC products, I also have a pair of Ref 600s and pray every time I switch them on that they don't go up in flames.)
One other question: for those of us with super-inefficient speakers like Magnepans, what should we be looking for in an amplifier?
We can see that current ARC amps are no where close to what Bill achieved. One problem with complexity is fixing it. How bad did yours "blow up" 2 times?
If you can handle the the praying for no smoke and afford the rather short tube life then carry on. For those who cant I would go SS.
There comes a point when tube amps just get too big. The alternative is get a high power tube amp with transmitting tubes. One pair of moderate sized transmitting tubes, like 833s, can produce 300-1000 watts. Having a lot of smaller tubes in parallel is not so practical. One pair of 833s is about the same cost as one pair of KT 150s. or other KTs. And they look really cool. Id make you a pair if you wanted. Thats the big tube WAVAC Uses SE but I would go push pull.
@prof
So my question is: What exactly is happening to cause the type of sonic changes on hears when changing impedance settings for a cartridge?
My know-nothing layman’s hunch is that it’s similar to how speaker impedance interacts with certain tube amps, where some combinations contour the frequency response...and (sorry for the word) damping factor? (The changes in the bass in lower impedances do give me that "lower damping factor in the bass" vibe).
Good question. Cartridges are very different in how they respond to loading. My Denon 103 is a 14 ohm cartridge (as I recall) and likes 100 -200ohms load. More load drops signal level, dont ever go that far, and makes the sound rather dead. No load is rather bright.
On the other hand the Lyra cartridges are so low in impedance that they dont respond to loading so we, in the SF audio society did some tests and found the Lyra best unloaded.
There is not any relation to speakers and amps that I would care to make. A cartridge is a source, the load is a resistor. Not much else going on.
@bifwynne
Btw, I owe you two quads of KT-150s for matching. The 3rd party vendor from whom I purchase the tubes didn't match the tubes to ARC spec.
Btw, I owe you two quads of KT-150s for matching. The 3rd party vendor from whom I purchase the tubes didn't match the tubes to ARC spec.
We have been awaiting your tubes. Time has passed and we have to get back on the same page as to the specs for current and G2 volts. Better not to wait on these things. Strike while the iron is hot as they say.
The difference between Bill Johnson amps and the current products is night and day. I appreciate the simplicity but not so much the performance specs. However specs arent everything. We are finding out some very interesting things on some listening tests. Very hard to get a really good handle on an amp without an A/B and a reference.
Nice circuit, simple. The 16 ohm tap is a bit silly and taking the feedback off it can have both good and bad effects. Otherwise, classic Marantz, Heath, Eico, etc.
@cardiff
Here is one nobody seems to have asked yet...
What is the role and importance of significantly upgraded power cords in component design? It seems to me that the PC is a fundamental part of the electronic device and that the manufacturer should optimize the cord for the device in building it. What are your thoughts on the matter as someone who actually builds electronics?
I put the proper cord on my RM-9 but now people want me to put an IEC on there so they can use theirs. I did opimize but thats not good enough for the PC and fuse people. May I also offer that a captive cord has one less pair of connections. When you pull current on a IEC it gets hot, is that good?
Before audiophiles got into power cords most manufacturers went to IEC connectors for no other reason that it makes the amp easier to handle and pack up, not so people could go fooling around with wire.
@atmasphere
A choke is helpful as it can be used to help filter out the 60Hz sawtooth waveform that is part of the rectification process.
Ralph, Im sure you meant to say 120 Hz ripple, not 60 Hz unless you are using half wave power supplies.
Chokes are indeed great things and not found in many amplifiers these days because its just too much trouble for some designers to have them made. I put two in the RM-9 MK II as Ultralinear amps benefit from them greatly. The G2 on an ultralinear has the same ripple as the plate. Where a pentode amp can have additional filtering for the G2.
@teo
Some Ignorance is so manifold that it is used to commit to attacks so libelous and underhanded... that the person initiating is practically kicked off a given forum. So obvious to all, that there aren’t even words for it.And then that illiteracy and ignorance is paraded about as somehow being informed. That we can all be that dense. Jebus. What a horrific world that would be. So far gone that it can’t even be explained to a given person how far off base and wrongheaded a given comment might be.
I think im being called out but so poetically I can hardly be certain. I think Teo has a better future as Poet and Philosopher.
@mrdecibel Roger, this is a GREAT thread, thank you. I agree that all of the nasty comments and bickering should be kept out of this thread ( as well as all threads ). This thread is about learning, as I see it, and I am learning a great deal ( maybe understanding 1 % of it ) And yes, this thread has me thinking about trying tubes again in a power amp. : Going back to damping. In my early years, I owned several ss power amps, a few high powered. Two in particular, were an original Ampzilla, and a factory built Dynaco 400. Having many speakers at the time ( DQ10, AR 3, Klipsch Lascala, just to name a few ), the Dynaco had a bloated, slow, ill defined bass in comparison to the Ampzilla. Both were rated at 200 wpc into 8 ohms ( as I mentioned, these characteristic were also in all of the tube amps I had at the time ). Can you explain if these characteristics between the Amnpzilla and Dyna had anything to do with damping ? Thank you in advance. Enjoy ! MrD
.
Thanks, the nasty comments and bickering are charateristics of the people who make the comments. I ignore most of them. When I look at the threads they get on I can hardly imagine what sort of person they are. I am happy to have little of them here. I guess every forum has its trolls.
At to your sonic observations. Ampzilla was and is a great amp. I think Jim B designed the Dynaco also, but I am unsure. If you find a schematic I can likely tell. People should know that some designers art is easy to spot, just as an artist’s paintings or sculptures. Bongo Jim, as we called him, was a really great amp designer, great pianist and all round fun guy. I have a picture of him Bacsom King, Mike and Laura Elliott at a BBQ at my home in Santa Barbara many years ago. Ill try to find and post it.
Sounds like you have had some bass issues. Both SS amps should have good damping, I know Zilla did. Tube amps with poor damping = bloated bass and other problems. Would love for you to hear the listening test we have going on right now with two identical amps except that one has been modified to have 4x damping and 1/4 x distortion. The bass difference, clairty and air on the QUAD 57 are quite apparent. We are doing some serious listening with a very tight setup.
Regarding the A/B testing, while we began last weekend Roger spent the better part of the week optimizing the set up, no easy task said he. He has now been inviting folks over to listen and I took another stab at it today. This time I brought some go to CDs that I like to use, simple music for the most part, trios and duos, but there are certain things I’ll be listening for. In some cases it’s not even the music, Edgar Meyer’s and Yo Yo Ma’s breathing, Keith Jarrett’s chirping and Gary Peacock’s fretting, The footsteps in Todd Garfinkle’s Jun, the resin on the bow, stuff like that. In other cases it’s the bass, piano, strings, cymbals and high hats.
My session lasted an hour or so and in addition to some unique experiences there were some consistencies across all the music. I originally commented in my notes that the bass produced by the un-modded amp sounded fat but pleasing. However, after more listening, and especially as the bass notes went lower, it was clearly bloated. Not to mention that while the individual bass notes during the solo on Keith Jarret’s version of When I Fall in Love on the modded amp were clearly defined, they were at times smeared on the un-modded amp. In addition, the cymbals and the high hats were slightly muted on the un-modded amp and I could hear a bit of hash as well.
A couple lessons I received in the process. If I didn’t get it before, and I thought I did, I now know for certain the effects a low output impedance amplifier has on a speaker and the resulting sound. In addition, while I can easily hear the effects of an amplifier that clips or has higher amounts of distortion, I think for the first time I could clearly hear the effects of low amounts of IMD as I A/B'ed the amps. Now Roger has invited a few folks from the SFAS to be part of the next group who will participate in the listening test. It will be interesting to hear others impressions and compare notes.
"The difference between Bill Johnson amps and the current products is night and day. I appreciate the simplicity but not so much the performance specs. However specs arent everything. We are finding out some very interesting things on some listening tests. Very hard to get a really good handle on an amp without an A/B and a reference."
Not sure what you feel is deficient with the ARC Ref 150SE specs. If you care to elaborate, please do.
Also, have you ever bench tested the Ref 150 SE or Ref 6 linestage? Further, have you ever A/B'd any current ARC models against other brands that you think highly about?
My speakers are pretty sensitive. Rated at 92db. I can play music (rock or classical) at ear-splitting levels without any apparent sonic congestion. Of course, I can't speak to distortion because I don't have the means or ability to measure those specs.
That said, maybe it really does not matter what I think. There are a million threads where folks tout the attributes of their gear and so I guess everyone has their own favorites.
In any case, I would like to know your reactions if you bench tested or critically listened to any *current" ARC gear.
Keep an eye peeled for my KT-150s. I am also sending some old ARC winged C 6550s that I used on some older ARC amps (roughly 2000 hours on the tubes). I would like to know if they have juice left in them. Also, the 6550s might give you a clue about the tubes specs ARC used to match their tubes for purposes of matching my KT-150s. The KT-150s are da*n expensive tubes.
@bdp24 - Eric this has truly been an eye opener. Roger can now do A/Bing on any number of amps. Fritz Heilor lives in the area recently donated a pair of speakers to us to use in a biamping experiment (Roger is impressed with his designs), so besides the Quads we have some box speakers available to us as well. The more the merrier I say. However, this listening stuff is really hard. After an hour or so I really needed a break. While some of the differences were not subtle, in may cases you really had to focus to hear the differences, and at least to my ears, there were cases where there was no difference at all.
I put the proper cord on my RM-9 but now people want me to put an IEC on there so they can use theirs. I did opimize but thats not good enough for the PC and fuse people. May I also offer that a captive cord has one less pair of connections
That is what I suspected you would say. I have tested expensive upgraded power cords in my system and never noticed any improvement or difference. I notice large differences between amps, preamps, cartridges, cartridge loading and even in minor changes of speaker toe in. But in my system, I have yet to hear any difference between pc's. I am not saying there are no differences, just that I haven’t heard any so far in my system, compared to the cord included by the manufacturer.
We need to stay away from the power cord debate here, imo. However, I have stated in other cable threads the subtle, to dramatic differences pcs make, to these ears. Cannot explain why, and I do not really care. But in my listening room, with my equipment and system, and with every one of my familiar recordings, I hear it immediately. I am talking about IEC cords, and those I have replaced with hotwiring. Sorry Roger, I will try and stay on point. Enjoy ! MrD.
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