One of the things I read is that tube amps and fullrange drivers pair up really well. When I read about amplifier measurements they are usually done on a dummy resistor load and measured directly through the electrical contacts. However actual frequency response curves driving a speaker and measuring the sound through a microphone is almost non-existent. The closest I find is this article by Nelson Pass comparing a current source vs a voltage source amp.
http://www.firstwatt.com/pdf/art_cs_amps.pdf
On review sites like 6moons I constantly read about how they test speakers on different amps but their descriptions are always subjective with no data.
Would anyone know a place that has frequency response curves(or other relevant data) comparing a tube amp and a solid state amp on a given speaker? Especially if the speaker is a Fostex full range type speaker.
http://www.firstwatt.com/pdf/art_cs_amps.pdf
On review sites like 6moons I constantly read about how they test speakers on different amps but their descriptions are always subjective with no data.
Would anyone know a place that has frequency response curves(or other relevant data) comparing a tube amp and a solid state amp on a given speaker? Especially if the speaker is a Fostex full range type speaker.
There's a reason for that. Each individual driver you attach to a given amp will produce a different plot. A manufacture cannot possibly know all of the possible drivers a DIY'r might hook up to his amp. All you are really looking at when you measure an amp through speakers and a microphone is the speakers. Not what you want.
Bob
I am not looking for manufacturer figures but independent plots. While a manufacturer doesn't know what is being hooked up, people that take independent measurements do know.
I agree that I would only be hearing the speakers but that's the point. I want to know what the difference is between two amps given that they power the same set of speakers. In other words the only variable I would change are the amps. This would basically be identical to what Nelson Pass did in the link I posted previously. Are you saying his measurements are useless?
This is a good question and I see your point to make the only difference being the amp to see if there are differences that are measurable.
Seems easy enough. I have done this for class AB vs class D amps and see differences in bass extension and treble detail and sometimes with harmonic distortion.
You need to find someone with several types of amps and a good set of speakers that can resolve the differences, and a willingness for that person to put their favorite amp to a test based on quantitative data, not listening impressions. The problem is that many folks with expensive tube or class A amps won't make the measurement, and if they did, they may find that the measurements don't support the price difference so you won't see the results.
I have only seen one person with a fancy class A amp willing to listen to the difference between his beloved amp and a highly modified TPA3116D2 amp and then tell us about it.
The class D amp won the listening test btw. I recall it was done with A7.3 driver.
Seems easy enough. I have done this for class AB vs class D amps and see differences in bass extension and treble detail and sometimes with harmonic distortion.
You need to find someone with several types of amps and a good set of speakers that can resolve the differences, and a willingness for that person to put their favorite amp to a test based on quantitative data, not listening impressions. The problem is that many folks with expensive tube or class A amps won't make the measurement, and if they did, they may find that the measurements don't support the price difference so you won't see the results.
I have only seen one person with a fancy class A amp willing to listen to the difference between his beloved amp and a highly modified TPA3116D2 amp and then tell us about it.
The class D amp won the listening test btw. I recall it was done with A7.3 driver.
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cspirou, what I can do for you is to measure my Fostex FE-208 Sigma in a BLH with solid-state amplifier and with SE tube amp based on 300B.
Is this the measurement you asked for?
Is this the measurement you asked for?
"closest I find is this article by Nelson Pass comparing a current source vs a voltage source amp."
Amplifiers: Solid State amps verses Valve amps
Amplifiers: Solid State amps verses Valve amps
Rutcho,
Wonderful! Your measurements are fantastic - thanks for the database and we can trust your set up. Do you have a class D amp like the TPA3116D2 to test while you are at it?
That would be perfect!
A lot of my questions are derived from this article.
Amplifiers: Solid State amps verses Valve amps
He mentions that solid state amps are more voltage driven and tube amps are more current driven. Nelson Pass showed the difference with his own amps but I have never ever seen the tube vs solid state comparison in numbers.
Edit:
Looks like I got ninja'd by adason.
Hi xrk971, could you steer me toward that thread, e.g., what to search on? Thank you very much in advance.
Timely thread
This thread is amazing for it's timing. I just went through this on my system.
My home-brew tube amp sounds wonderful connected to my TB 1778's, front horn loaded. Previously hooked up to a well known Class A solid-state amplifier ; said amp knocked me back in my chair like the old Maxell commercial.
Basically, I reversed positions, the class A amp now drives the ribbon tweeter, while the tube amp is on the full range driver. All is well.
This thread is amazing for it's timing. I just went through this on my system.
My home-brew tube amp sounds wonderful connected to my TB 1778's, front horn loaded. Previously hooked up to a well known Class A solid-state amplifier ; said amp knocked me back in my chair like the old Maxell commercial.
Basically, I reversed positions, the class A amp now drives the ribbon tweeter, while the tube amp is on the full range driver. All is well.
All full Stereophile amplifier reviews have amplifier frequency response for a typical speaker load.
Full range drivers are pretty benign in impedance. You can look up lots of reviews on their web site.
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Sorry but you got it upside down.
Transistors are current driven, Tubes and (Mos)Fets are voltage driven.
Thanks! I just checked stereophile to look for reviews. It seems like they use resistors at 2,4 and 8 ohms as well as a simulated speaker.
Dan D'Agostino Momentum monoblock power amplifier Measurements | Stereophile.com
While I can see that the simulated speaker looks much more realistic than the resistive loads, I am a little suspect about how accurate of a representation it is. The curves look like they are flat to 10Hz. Frequency response curves for real speakers roll off and rarely go down to 10Hz. Seems like you can only get curves like that by measuring through the electrical contacts.
Even so, as long as they use the same simulated speaker load I can get an idea of the amp to amp behavior.
I managed to find a measurement comparing a solid state amp with a tube amp through headphones.
Classic Tube Amp Sound
While not exactly what I was originally looking for, headphones are essentially full range speakers and similar arguments can be made. The distortion with tube amp seems extremely minimal. Although there are some things I can see that don't really make this the same comparison.
I. The impedance of the headphones are 300 ohms which produces a rather large damping factor, not as comparable with 8ohm-16ohm drivers.
II. The Schiit Valhalla tube amp used for the comparison is an output transformerless amp. Typical speaker amps use output transformers for impedance matching, which is a big source of distortion.
Even so, I feel a bit more informed about using tube amps and I won't worry as much about claims of the sound being massively distorted. Still looking for a site with tube vs SS data on full range speakers. Let me know if any of you find it.
Classic Tube Amp Sound
While not exactly what I was originally looking for, headphones are essentially full range speakers and similar arguments can be made. The distortion with tube amp seems extremely minimal. Although there are some things I can see that don't really make this the same comparison.
I. The impedance of the headphones are 300 ohms which produces a rather large damping factor, not as comparable with 8ohm-16ohm drivers.
II. The Schiit Valhalla tube amp used for the comparison is an output transformerless amp. Typical speaker amps use output transformers for impedance matching, which is a big source of distortion.
Even so, I feel a bit more informed about using tube amps and I won't worry as much about claims of the sound being massively distorted. Still looking for a site with tube vs SS data on full range speakers. Let me know if any of you find it.
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