Constant Power

[Atmasphere]

Yes, but it's not just supposed to sound loud, it's supposed to sound harsh and fatigueing, right? That's the part of my listening experience that parts with your theory. I play the system, I ease it up a bit at a time, enjoying the music, I listen, I get called away for a moment and mute the system, I come back in and unmute, and find I was playing the music very loud without realizing it. I was playing it too loud but it didn't seem too loud. This is the opposite of the experience you're describing. And if I can inadvertently find myself playing my system much louder than necessary, without experiencing any harshness, fatigue, irritation, why should I care what the decible level is?

I'm not saying you're wrong; the human ear is more sensitive to odd-order harmonics? OK. Enough odd-order harmonics will make audio seem louder, harsher and brighter? I believe you. Negative feedback can increase these harmonics to that irritating level? OK, but I've got a relatively inexpensive pair of powered speakers here that have completely avoided the problem. And I've had a handful SS (and tube) headphone systems in this house (some expensive, some that were pretty cheap) that completely avoided the probelm. So I'm afraid I'll have to conclude that it's not that much of a problem, certainly not one that is begging for a high-priced solution. YMMV.

Tim

If you measure the sound pressure level then you will know for sure. Until then its just speculation.

I find this somewhat amusing because often I get accused of being on the subjective side of a lot of discussions (although that really isn't true). There is a big difference between measuring things, and then actually going for the things that the ear actually cares about. I prefer to do the latter if I can. In this case I am suggesting take a measurement and you are saying listening is OK. That just seems really funny to me- usually you are on the other side of such a conversation, right?

 

[KeithR]

Yes, but it's not just supposed to sound loud, it's supposed to sound harsh and fatigueing, right? That's the part of my listening experience that parts with your theory. I play the system, I ease it up a bit at a time, enjoying the music, I listen, I get called away for a moment and mute the system, I come back in and unmute, and find I was playing the music very loud without realizing it. I was playing it too loud but it didn't seem too loud. This is the opposite of the experience you're describing. And if I can inadvertently find myself playing my system much louder than necessary, without experiencing any harshness, fatigue, irritation, why should I care what the decible level is?

I'm not saying you're wrong; the human ear is more sensitive to odd-order harmonics? OK. Enough odd-order harmonics will make audio seem louder, harsher and brighter? I believe you. Negative feedback can increase these harmonics to that irritating level? OK, but I've got a relatively inexpensive pair of powered speakers here that have completely avoided the problem. And I've had a handful SS (and tube) headphone systems in this house (some expensive, some that were pretty cheap) that completely avoided the probelm. So I'm afraid I'll have to conclude that it's not that much of a problem, certainly not one that is begging for a high-priced solution. YMMV.

Tim

Until you try an amp without negative feedback, it seems impossible for you to judge its effect.

 

[Phelonious Ponk]

Until you try an amp without negative feedback, it seems impossible for you to judge its effect.

We're not talking about the effect of amps without negative feedback. We're talking about how negative feedback affects amps. It is alleged here to make them bright, harsh, difficult to listen to at high volumes and/or over long periods of time. I don't ever need to hear a no negative feedback amp to make that judgement. The alleged negative effects, as described here, do not exist in my current speaker and headphone systems and did not exist in past systems; I've listened to them for many hours, at high volume, without strain (this is not to say that I've never experienced "harsh and bright" before, but the fix was never in the amp). Would a no-feedback amp sound softer, less bright? Maybe. But without the fatigue, the discomfort over time or at volume, without something to show that the negative feedback amp is distorting the input signal, that's just another preference.

My preference? I love percussive notes to attack aggressively and decay naturally. I love to hear the natural, organic sibilance of human mouths and voices in sensitive microphones. I love the ring and shimmer of cymbals, the karannng! of a Rickenbacker guitar through a Vox AC-30 Top Boost. I know exactly what all of that sounds like up close and personal, I know that it sounds a bit more like the real thing to me through systems that many audiophiles would call bright or analytical, and I know that I can and do run my negative feedback systems long, loud and hard....and I'm not tired.

That's the effect I'm judging.

Tim

 

[Occam]

In addition to the diy constant power chipamp, previously mentioned, Joe Rassmussen also had a multi-driver speaker project, Elsinore, designed specifically to be driven by a constant power amp, as well as conventional voltage amplifiers.
http://www.customanalogue.com/elsinore/elsinore_index.htm
I've not heard in myself, but it is an open source project
FWIW

 

[Duke LeJeune]

In addition to the diy constant power chipamp, previously mentioned, Joe Rassmussen also had a multi-driver speaker project, Elsinore, designed specifically to be driven by a constant power amp, as well as conventional voltage amplifiers.
http://www.customanalogue.com/elsinore/elsinore_index.htm
I've not heard in myself, but it is an open source project
FWIW

Thanks for the link, Occam. Very thorough design, Mr. Rasmussen takes a lot of things into account that imo really matter - electrically, acoustically and psychoacoustically. He and I have chosen somewhat different solutions, but I think we have a lot of common ground as far as what the problems are that need to be addressed.

Are you aware of anyone using his speaker to compare different amplifier types?

 

[andy_c]

Thanks for the link, Occam. Very thorough design, Mr. Rasmussen takes a lot of things into account that imo really matter - electrically, acoustically and psychoacoustically. He and I have chosen somewhat different solutions, but I think we have a lot of common ground as far as what the problems are that need to be addressed.

Are you aware of anyone using his speaker to compare different amplifier types?

Rasmussen is a total crank, so it doesn't surprise me that other cranks would endorse his bogus crap.

 

[andy_c]

My modelling software assumes an amplifier with negligible output impedance, and suggested .8 cubic feet tuned to 62 Hz for a F3 of 75 Hz as being a "maximally flat" alignment. Hardly inspiring bass performance.

It's pretty obvious that you have no clue what the meaning of "maximally flat" is, and that you are just bullshitting here.

 

[Duke LeJeune]

Rasmussen is a total crank, so it doesn't surprise me that other cranks would endorse his bogus crap.

I take it you disagree with Rasmussen about something. Care to elaborate?

It's pretty obvious that you have no clue what the meaning of "maximally flat" is, and that you are just bullshitting here.

So if I understand correctly, you feel (rather strongly it seems!) that I'm mis-using the term "maximally flat."

There is a tab on my box modelling program for generating a "maximally flat" alignment. I input the woofer's parameters and selected that tab, and posted the box size, tuning frequency, and F3 that the program calculated.

If you see something wrong with that, let me know.

Or let me know your definition of the term.

 

[steve williams]

It's pretty obvious that you have no clue what the meaning of "maximally flat" is, and that you are just bullshitting here.

Andy

you know that talk such as this is contrary to our TOS.

Please challenge the post and not the poster

 

[cnpope]

Until you try an amp without negative feedback, it seems impossible for you to judge its effect.

I hope this isn't too much off-topic, but what puzzles me in some of these vigorous debates about the alleged bad effects of negative feedback is that if you consider all the stages of amplification and processing that the original sound source will have been subjected to, by the time it emerges from the output sockets of the CD player, then it has probably been through many stages, typically op-amps, with huge amounts of negative feedback. So the total number of dBs of feedback will have been colossal. Whether or not the final power amplifier in the living room has negative feedback is not going to alter the previous history of huge feedback that the signal has undergone. Is a final amplification with no feedback supposed to undo all the "bad" effects of the previous amplification stages?

Chris

 

[theguesswho]

Atmasphere said, If you measure the sound pressure level then you will know for sure. Until then its just speculation."

Ralph, can you post a video of your spl meter during a playback of what you consider a dynamic album?

Wendell

 

[Phelonious Ponk]

Atmasphere said, If you measure the sound pressure level then you will know for sure. Until then its just speculation."

Ralph, can you post a video of your spl meter during a playback of what you consider a dynamic album?

Wendell

He did say that, but I wasn't speculating as to whether or not it was loud, I was listening and it was loud. If I can get it up to louder than I care to listen to it, loud enough to obliterate the noise floor in my room and render conversation an unrealistic expectation, and not experience any of the alleged ill effects of negative feedback, then it's a pretty safe assumption that the alleged ill effects of negative feedback are insignificant if there at all.

This says nothing about the quality of systems without negative feedback, but it does speak directly to the reason for designing them. There's a lot of that in the high end, in my view -- elaborate, very expensive (and very often immeasurable and unquantifiable) solutions to problems we were blissfully unaware of until they were pointed out to us. At that moment, some of us immediately begin to hear them. Usually those of us who don't believe in expectation bias.

Tim

 

[Atmasphere]

I hope this isn't too much off-topic, but what puzzles me in some of these vigorous debates about the alleged bad effects of negative feedback is that if you consider all the stages of amplification and processing that the original sound source will have been subjected to, by the time it emerges from the output sockets of the CD player, then it has probably been through many stages, typically op-amps, with huge amounts of negative feedback. So the total number of dBs of feedback will have been colossal. Whether or not the final power amplifier in the living room has negative feedback is not going to alter the previous history of huge feedback that the signal has undergone. Is a final amplification with no feedback supposed to undo all the "bad" effects of the previous amplification stages?

Chris

Of course not. All we are trying to do is create a more neutral presentation of the signal that arrives at the input to the preamplifier/amplifier.

One of the more interesting and historic tape machines on which a lot of material has found its way into the recorded media is none other than the Ampex 351 tape machine. Old hat, but still sought after... its record circuit is zero feedback FWIW. But my favorite media, the LP, so far is set up so that if you want to record in stereo, you will have to run some feedback between the cutterhead and the preemphasis or you don't get any channel separation out of the cutter (at least that is true of my cutter system- some other systems might be different in that regard). Interestingly enough though, the cutterhead (Westerex 3D) of our setup has some Power Paradigm characteristics in that it is better off if the amplifier driving it exhibits a constant power characteristic, even if feedback is used. We run a zero feedback amplifier on the head itself, but the feedback required through the feedback module so far is unavoidable. Maybe we will get there some day though. As it is, we have the first LP cutter system that runs a zero feedback transformerless tube amplifier to drive *** cutterhead. I'm interested to see how far we can push it.

Atmasphere said, If you measure the sound pressure level then you will know for sure. Until then its just speculation."

Ralph, can you post a video of your spl meter during a playback of what you consider a dynamic album?

Wendell

I'll have to get a meter. We usually have one a shows, which is how I know this. On that meter I have seen 115 db peaks plenty enough (if you want to hear a dynamic LP, try the 2nd track on side one of the Verdi Requiem of the RCA Soria box set). Other exhibitors at shows often complain about us because sometimes they can only hear our system in their room when we turn it up. But even though the system comes off relaxed, we do have to watch it as people often won't even come into the room if there is any volume at all. Ears get abused at shows....

 

[cnpope]

Of course not. All we are trying to do is create a more neutral presentation of the signal that arrives at the input to the preamplifier/amplifier.

One of the more interesting and historic tape machines on which a lot of material has found its way into the recorded media is none other than the Ampex 351 tape machine. Old hat, but still sought after... its record circuit is zero feedback FWIW. But my favorite media, the LP, so far is set up so that if you want to record in stereo, you will have to run some feedback between the cutterhead and the preemphasis or you don't get any channel separation out of the cutter (at least that is true of my cutter system- some other systems might be different in that regard). Interestingly enough though, the cutterhead (Westerex 3D) of our setup has some Power Paradigm characteristics in that it is better off if the amplifier driving it exhibits a constant power characteristic, even if feedback is used. We run a zero feedback amplifier on the head itself, but the feedback required through the feedback module so far is unavoidable. Maybe we will get there some day though. As it is, we have the first LP cutter system that runs a zero feedback transformerless tube amplifier to drive *** cutterhead. I'm interested to see how far we can push it.

Hmmm...OK, I knew of course that that was not the claim, but my ironically-phrased question was based on what for me is a genuine puzzle; if a typical music source (such as a CD) has passed through many stages with huge amounts of negative feedback, why is there supposed to be such a big advantage in not having feedback in the final stage of amplification in the living room?

Your description of the OTL-driven LP cutter sounds really intriguing. Do you have plans to market the LPs? It would be a very interesting experience to be able to listen to the outcome of such a unique process.

Chris

 

[Atmasphere]

Hmmm...OK, I knew of course that that was not the claim, but my ironically-phrased question was based on what for me is a genuine puzzle; if a typical music source (such as a CD) has passed through many stages with huge amounts of negative feedback, why is there supposed to be such a big advantage in not having feedback in the final stage of amplification in the living room?

Your description of the OTL-driven LP cutter sounds really intriguing. Do you have plans to market the LPs? It would be a very interesting experience to be able to listen to the outcome of such a unique process.

Chris

In high end audio there is a tendancy to try and see how good we can get the reproduction. With a lot of media there might be no point, but some recordings are remarkable, and if we can get more accurate reproductions that would be better, at least IMO.

Some of the LPs are already out. We operate the mastering operation for any label that cares to have the job done. We only just got started this year although we've been working on it for years Its been a hellava learning curve

 

[theguesswho]

Hi Ralph, If you are not doing anything today perhaps you can take a trip to Radio Shack to buy an SPL meter.

I dont own a copy of the Verdi records you recommend. Do you have any more common albums that we could compare?

Wendell

 

[Atmasphere]

Hi Ralph, If you are not doing anything today perhaps you can take a trip to Radio Shack to buy an SPL meter.

I dont own a copy of the Verdi records you recommend. Do you have any more common albums that we could compare?

Wendell

The original white label (we are not talking promos in this case) Vertigo British or German pressing of Black Sabbath's Paranoid will bring most systems to their collective knees if you want to play a lifelike presentation... and if played correctly no-one will be screaming at you to turn it down- it is quite well-recorded. Funny- that LP is over 40 years old but its still risky to play it at shows.

The Wagner Ring cycle on Decca (original press) has some amazing passages as well. I like to show off with the entrance of the gods into Valhalla (side six of Das Reingold).

A field recording that has always impressed me is the Nonsuch recording of Village Music of Bulgaria. The energy of the massed female voices on that LP drive many systems crazy, but if the system can hold together without editorial the presentation is awesome.

 

[DaveyF]

Ralph, I haven't listened to my original UK Vertigo pressing of Paranoid in years. I will take your advice and throw it on the table tonight. I have a doubt that my SF Guarneri's will like this music though, LOL.

 

[KeithR]

We're not talking about the effect of amps without negative feedback. We're talking about how negative feedback affects amps. It is alleged here to make them bright, harsh, difficult to listen to at high volumes and/or over long periods of time. I don't ever need to hear a no negative feedback amp to make that judgement. The alleged negative effects, as described here, do not exist in my current speaker and headphone systems and did not exist in past systems; I've listened to them for many hours, at high volume, without strain (this is not to say that I've never experienced "harsh and bright" before, but the fix was never in the amp). Would a no-feedback amp sound softer, less bright? Maybe. But without the fatigue, the discomfort over time or at volume, without something to show that the negative feedback amp is distorting the input signal, that's just another preference.

My preference? I love percussive notes to attack aggressively and decay naturally. I love to hear the natural, organic sibilance of human mouths and voices in sensitive microphones. I love the ring and shimmer of cymbals, the karannng! of a Rickenbacker guitar through a Vox AC-30 Top Boost. I know exactly what all of that sounds like up close and personal, I know that it sounds a bit more like the real thing to me through systems that many audiophiles would call bright or analytical, and I know that I can and do run my negative feedback systems long, loud and hard....and I'm not tired.

That's the effect I'm judging.

Tim

Yeah, but it doesn't work like that Tim- you don't know until you know. You might think your amps (or whatever) are the greatest known to man until you try another one that is better. My experience with amps that don't have negative feedback is that they are more resolved and more natural at the same time-- the feedback is obscuring detail. YMMV.

KeithR

Ps. I don't like soft amps either- Luxman Class A was my recent experience with that

 

[Phelonious Ponk]

Yeah, but it doesn't work like that Tim- you don't know until you know. You might think your amps (or whatever) are the greatest known to man until you try another one that is better. My experience with amps that don't have negative feedback is that they are more resolved and more natural at the same time-- the feedback is obscuring detail. YMMV.

KeithR

Ps. I don't like soft amps either- Luxman Class A was my recent experience with that

In this case, that's exactly the way it works. I'm not speculating that zero feedback amps don't sound different from, or even better than mine. All I'm saying is that the grievous symptoms of negative feedback described in this, and quite a few other conversations, don't exist in my current systems. Are they "brighter" than a system with one of Ralph's amps? Maybe. Without a measurable difference to determine which is more faithful to the input signal, that would just be a matter of taste and perception anyway. But according to the conventional audiophile wisdom (CAW), I'm supposed to be irritated, experiencing fatigue, driven to turn the volume down, driven from the room. None of that is happening. I listen happily for hours on end.

That's all I'm saying. If I listened to my actives powered by four zero-feedback tube amps, I may like them better. Or not. But it wouldn't change any of the above.

Tim