Be aware that Sallen & Key filters use positive feedback for FR shaping, and have a distortion peak right where the filter has the highest reactance (the frequency corner). If the opamp is a modern ultralow distortion device (not an antique like the 5532/5534), you can get away with this, but there are other active-filter topologies that have considerably less distortion.
My main misgiving about opamps is the output stage typically runs in Class AB for heat-dissipation reasons, and to me, it doesn't make sense to run any part of the signal chain in Class AB unless absolutely necessary. True, there's lots and lots of feedback, but there's less at high frequencies, where crossover distortion is most troublesome.
If more op-amps had the option of bypassing the internal output section with an external Class A discrete stage (like the really old ones with compensation pins), that would be interesting. (Force-biasing opamps into Class A with an external current source can have very odd effects on distortion and slew rate ... been there, done that.)
The Amity and Karna amplifiers are balanced Class A PP triode from input to output, and have an intrinsic forward-path distortion of less than 0.1% at 10 watts or less. They sound very different than SET amplifiers, but don't sound much like pentode or transistor amps either. The sound is actually kind of hard to describe.
They also have the unusual ability to slide from Class A1 (negative grid bias) to Class A2 (positive grid bias) to AB2 with no "glitches" or wrinkles in the waveform. This gives them a peak capability of 30 watts, and can drive 2-ohm loads, which is pretty decent for a 300B-type amplifier.
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The Marchand modules can be adjusted for different slopes and have variable dampening - you can also run the opamps in class A if you feel there is a sonic benefit
http://www.marchandelec.com/ftp/xm1man.pdf
These sound great in ab http://www.futurlec.com/Linear/LM4562NApr.shtml
There are other options like discrete opamps ect, or you can roll your own - in the low range below 1k or so I find the TDM is versatile and sounds transparent
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LM4562NA - LM4562 High Fidelity Audio Op-Amp
if you listen to CD or SACD chances are you listen to opamps
if you listen to CD or SACD chances are you listen to opamps
I don't. CDs is a dead format.
I listen to Spotify a lot, which I should try to avoid except they have so much new music that it is kind of addictive. I have owned a lot of different microphone amps and preamps, and the ones mostly based on opamps have been the least exciting to listen to. If that has had to do with design or the opamps is difficult to guess. I modified a microphone amp (Studio Projects VTB-1) once with better opamps and the sound became remarkably better. Now I use a red Golden Age Pre-73 microphone preamp, which is not based on opamps, and it sounds a lot better. A popular mod for the Pre-73 is instead to upgrade the transformer, to make it more similar to the original made by Rupert Neve that so many studios have used.
I listen to Spotify a lot, which I should try to avoid except they have so much new music that it is kind of addictive. I have owned a lot of different microphone amps and preamps, and the ones mostly based on opamps have been the least exciting to listen to. If that has had to do with design or the opamps is difficult to guess. I modified a microphone amp (Studio Projects VTB-1) once with better opamps and the sound became remarkably better. Now I use a red Golden Age Pre-73 microphone preamp, which is not based on opamps, and it sounds a lot better. A popular mod for the Pre-73 is instead to upgrade the transformer, to make it more similar to the original made by Rupert Neve that so many studios have used.
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I don't. CDs is a dead format.
I listen to Spotify a lot, which I should try to avoid except they have so much new music that it is kind of addictive.
All the music on Spotify is listening to opamps
- I know opamps mostly sound crappy but they don't all have too
All the music on Spotify is listening to opamps
Not necessarily: Optical out, descrete DAC, non-opamp crossover.
And if I find something I like I can download it in .flac.
Hi folks, sorry for getting back to Ariel once again, but as I watched characteristics of certain drivers, I run into a Scan Speak's 15W/8434G00 in hope it could replace the "no where to find" Vifa P13WH-00-08.
Those two got some different characteristics, but when you compare SPL graphs it is very interesting:
http://i318.photobucket.com/albums/mm404/acamilicko/vifa_zpsf595f93e.jpg
http://i318.photobucket.com/albums/mm404/acamilicko/scanspeak_zps6fa0e854.jpg
http://i318.photobucket.com/albums/mm404/acamilicko/vifa-and-scan_zps56846d13.jpg
Wondering if this Scan Speak deserves a try?
Because of lower Fs, would it need longer TL channel (taller enclosing)?
Or to just forget about Ariel if original Vifa could not be found?
Thanks,
Alex
Those two got some different characteristics, but when you compare SPL graphs it is very interesting:
http://i318.photobucket.com/albums/mm404/acamilicko/vifa_zpsf595f93e.jpg
http://i318.photobucket.com/albums/mm404/acamilicko/scanspeak_zps6fa0e854.jpg
http://i318.photobucket.com/albums/mm404/acamilicko/vifa-and-scan_zps56846d13.jpg
Wondering if this Scan Speak deserves a try?
Because of lower Fs, would it need longer TL channel (taller enclosing)?
Or to just forget about Ariel if original Vifa could not be found?
Thanks,
Alex
So, what is the output impedance of these Amity and Karna amplifiers?
Is it ~ 0.5 Ohm? 1 Ohm? > 1 Ohm? More?
Because if it is 1 Ohm or more, I would argue that much of the difference in their 'sound' vs. that of other amps (e.g. low-output impedance transistor amps heavily biased into class A) may actually be explained by the frequency response deviations caused by the amp's output impedance interacting with the loudspeaker's impedance curve.
Marco
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I think it would be ~0.5ohm. That is if my math is correct. plate resistance of two 300Bs in parrallel is ~400ohm. The OPT of the Karna is 6.6k/8ohms, so 400/825 ~ 0.5ohm. Granted this is a dirty measurement cause it isn't accounting for the cathode resistor and inductor's resistance in parrallel, but its close.
Hi Lynn
With OPAMPs whether they are class A or AB depends on their load. If you keep the load above about 20K ohms they will stay in class A. You just have to keep in mind their bias of about 500 micro amps. If you draw less current than that they will remain class A. If you draw more current they will go out of the class A region and move into class B. Never use their capability of 600 ohm loads.
myhrrhleine.
Thank you for that reply. I think that is a constant problem in some of these conversations, the absolutes that are given even though they are not always true. I am glad at least that Lynn is not advocating for SE tube amps, I understand his desire to use vacuum tubes however. I am not going back to that approach, I have been there and done that and have moved on. We can agree on enough other material and learn from each other so I continue to read this thread. I however would not build this latest speaker, I do not see any reason that this has taken 7 years from what I am hearing. A competent speaker designer could have done this basic design in short time. This is nothing that has not been done many times before by many others. Only the devices have changed over time, that is all I see in the basic speaker design, nothing revolutionary or particularly innovative from my perspective.
Thank you for that reply. I think that is a constant problem in some of these conversations, the absolutes that are given even though they are not always true. I am glad at least that Lynn is not advocating for SE tube amps, I understand his desire to use vacuum tubes however. I am not going back to that approach, I have been there and done that and have moved on. We can agree on enough other material and learn from each other so I continue to read this thread. I however would not build this latest speaker, I do not see any reason that this has taken 7 years from what I am hearing. A competent speaker designer could have done this basic design in short time. This is nothing that has not been done many times before by many others. Only the devices have changed over time, that is all I see in the basic speaker design, nothing revolutionary or particularly innovative from my perspective.
Not necessarily: Optical out, descrete DAC, non-opamp crossover.
And if I find something I like I can download it in .flac.
All opamps all the time - You have a discrete DAC and the file is provided to you in a format that was all discrete from the mike to the file
??
All opamps all the time - You have a discrete DAC and the file is provided to you in a format that was all discrete from the mike to the file
A first-class speakers should swiftly determine any foul use of opamps during the recording process.
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And I think we have a bunch of folks that are crossing their compression drivers over about an octave too low. But I'll leave it at that, tried to help with that a while ago
sure, name one please. A first class speaker? What opamp in what configuration and device used where in the chain?
POOH,
In agreement on the crossover point on the compression drivers. I wouldn't use these large format drivers anyway, nothing larger than a 1" exit for me on compression. I have been a proponent of a mid-range cone driver for a long time. even horn loaded mids with a cone, I have done it for years.
In agreement on the crossover point on the compression drivers. I wouldn't use these large format drivers anyway, nothing larger than a 1" exit for me on compression. I have been a proponent of a mid-range cone driver for a long time. even horn loaded mids with a cone, I have done it for years.
Good to see that POOH/Magnetar and Kindhornman are in agreement, and thanks for your contribution to the discussion.
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I speak of my own of course.
Any serious DIY speaker builder would agree that their own speaker is the best in the world.No, but seriously, I have very sensitive driver down to 250Hz. The bigger the horn the more sensitive it is, so this is pretty revealing. Not my graph but with a similar horn: http://usr.audioasylum.com/images/1/12755/6681_on_Azura_AH-10.JPG
In a A/B comparison I am sure it would show a difference between material recorded on opamps and material that is not.
Obviously it can't do everything great. As someone once wrote: "When you are spending $50,000 on a speaker, you would think that it would do EVERYTHING right. But this is not the case. Engineering always involves a series of trade offs. So even if you have fifty thousand to spend, you still need to be prepared to weigh what tradeoffs you can live with. Just as you wouldn't buy a Porsche 911 to haul furniture, expensive loudspeakers cannot do everything either." - Patrick Bateman
Your loss!
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