Tube vs solid state amp measured with REW

[Ken57]

I have both a tube amp (Mastersound SET 300b) and a solid state amp (Arcam A32), with Klipsch Forte 4 speakers. The Mastersound sounds much better; more clear, very lifelike. But when I measure with REW the frequency response and THD are about the same (with some small differences in harmonic content, about half a percent). Is there any other measurement parameter that causes one amp to sound better than the other? Is what I hear not truly reflected by the measurements?

 

[Keith_W]

What are you measuring? The output from the amp? The output from the speaker? And also, what level are you measuring at? Enough to clip the amp?

 

[fpitas]

A pet theory of mine is that SET amps "help" horns by limiting peaks, basically soft clipping. Horns are capable of dynamic peaks that most cone drivers can't touch, and on some music that may become hard on the ears.

 

[Ken57]

What are you measuring? The output from the amp? The output from the speaker? And also, what level are you measuring at? Enough to clip the amp?

I'm measuring with a calibrated microphone in front of the speaker, at regular listening levels (probably not clipping).

 

[Blumlein 88]

The Forte 4 has a pretty up and down uneven impedance curve vs frequency. I would expect the output impedance of the SET to alter the frequency response enough to make it sound slightly different. I would think your REW FR plots would show this. Even a couple tenths of a db over an octave or two is audible. Won't look like much on the graph unless you zoom in. So about the same FR could well not sound the same. Some smoothing to get a handle on what your ear hears might help too. I might try pyschoacoustic smoothing or 1/6th octave smoothing. Your ear is closer to 1/3rd octave smoothing at lower frequencies and 1/5th or so at the higher range.

 

[Keith_W]

Try measuring at different levels and see if the FR and harmonic content changes.

 

[Blumlein 88]

This is from Stereophile's testing of your Mastersound. This variation is enough to be audible. Your speaker probably has wider impedance variations than the Stereophile loudspeaker simulated load. This will cause even larger FR differences than Stereophile is showing.

Mastersound 300 B S.E. integrated amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

 

[Ken57]

Yes, I'm seeing these sorts of variations. I'm using a software equalizer to flatten this out. There is also a lot of room variations.

I'm seeing a few tenths percent increase in 2nd order harmonics, and a few tenths reduction in third order harmonics, compared to the solid state amp. Is that significant? Or not audible?

 

[Blumlein 88]

Yes, I'm seeing these sorts of variations. I'm using a software equalizer to flatten this out. There is also a lot of room variations.

I'm seeing a few tenths percent increase in 2nd order harmonics, and a few tenths reduction in third order harmonics, compared to the solid state amp. Is that significant? Or not audible?

What are the levels of those distortions?

 

[staticV3]

But when I measure with REW the frequency response and THD are about the same (with some small differences in harmonic content, about half a percent). Is there any other measurement parameter that causes one amp to sound better than the other?

Try playing a track that makes this difference exceedingly obvious, once with your tube Amp and once with the SS Amps, then record both with a mic at a fixed position.
Bonus points if you leave the room before the track starts playing.

Then load both recordings into @pkane's Deltawave and let it analyze the difference.

If there is an audible difference, then the mic will catch it.
If the mic doesn't catch anything, then it was probably just placebo.

 

[GXAlan]

Look at my 300B SET review. Do the sweep at different levels. You don’t need a high resolution sweep. You can use the REW signal generator to digitally adjust the volume. You don’t need to turn the volume knob.

Record breaker: Raphaelite CS30-MKII tube amplifier review and measurements

Raphaelite CS30-MKII 300B integrated tube amplifier review: A New Performance Record This is a review and detailed measurements of Raphaelite CS30-MKK 300B single ended tube amplifier. It is available on eBay for $1449 + $310 shipping to California + tax. There are some better deals from...

www.audiosciencereview.com

 

[Ken57]

for tube:
2nd: 0.2% - 0.8%
3rd: 0-0.2%

solid state is a little less 2nd and a little more third. But is this meaningful in terms of hearing?

 

[Blumlein 88]

for tube:
2nd: 0.2% - 0.8%
3rd: 0-0.2%

solid state is a little less 2nd and a little more third. But is this meaningful in terms of hearing?

Probably not. 2nd harmonic is not as bothersome. With test tones you might be able to hear it. With music most likely not.

 

[GXAlan]

for tube:
2nd: 0.2% - 0.8%
3rd: 0-0.2%

solid state is a little less 2nd and a little more third. But is this meaningful in terms of hearing?

That’s not a lot of distortion but as you saturate, you will get more distortion. Try increasing the volume and remeasuring.

 

[Balle Clorin]

This is from Stereophile's testing of your Mastersound. This variation is enough to be audible. Your speaker probably has wider impedance variations than the Stereophile loudspeaker simulated load. This will cause even larger FR differences than Stereophile is showing.

Mastersound 300 B S.E. integrated amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

View attachment 336836

Wow this was big bass loss , would need some bass room gain to compensate for such a loss. This should show up clearly in the room response. 2db less bass will be very audible.
I compared my SS amplifier with my Cayin 300b both by in room measurements and on the speaker terminals . I got 1-2 db deviation in different frequency areas. Mostly due to the output impedance. ( Cayin has a way more flat/correct response than Mastersound). Both SS and 300b sounded good to me.
The tube amps gives can be richer sounding impression. 2 order harmonic distortion does give a different more rich sound, The tube amp may also highlight some frequency areas, and you may like that, and maybe the faulty bass response of the Mastersound actually fits your room and speakers. Quite a lot of distortion can be accepted by the ears before sounding bad.
This is how a good 300B amp can measure.
(With my tube selection the distortion was much lower too)

Cayin A-300B integrated amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

Try listening for 2 months to the SS and se if you then like the tube amp when you switch back.

How a bout posting the REW plots?

 

[Ken57]

Wow this was big bass loss , would need some bass room gain to compensate for such a loss. This should show up clearly in the room response. 2db less bass will be very audible.
I compared my SS amplifier with my Cayin 300b both by in room measurements and on the speaker terminals . I got 1-2 db deviation in different frequency areas. Mostly due to the output impedance. ( Cayin has a way more flat/correct response than Mastersound). Both SS and 300b sounded good to me.
The tube amps gives can be richer sounding impression. 2 order harmonic distortion does give a different more rich sound, The tube amp may also highlight some frequency areas, and you may like that, and maybe the faulty bass response of the Mastersound actually fits your room and speakers. Quite a lot of distortion can be accepted by the ears before sounding bad.
This is how a good 300B amp can measure.
(With my tube selection the distortion was much lower too)

Cayin A-300B integrated amplifier Measurements

Sidebar 3: Measurements

www.stereophile.com

Try listening for 2 months to the SS and se if you then like the tube amp when you switch back.

How a bout posting the REW plots?

Here's the REW response with the Klipsch Forte 4 speakers. The volume wasn't matched exactly, but they look about the same to me. Also, the distortion is low with both under 1% 2nd harmonic so I'm not sure why the tube amp sounds better. (Unless it's just wishful thinking since I paid more for it!). Most of the variation in the graph is probably the speaker and room.

 

[Blumlein 88]

Here's the REW response with the Klipsch Forte 4 speakers. The volume wasn't matched exactly, but they look about the same to me. Also, the distortion is low with both under 1% 2nd harmonic so I'm not sure why the tube amp sounds better. (Unless it's just wishful thinking since I paid more for it!). Most of the variation in the graph is probably the speaker and room.

There is plenty of deviation between those two to be audible. If it happens to be what you like with the 300B amp, then good. There are differences in the low end, and up down differences in the lower midrange and midrange. So these will not sound the same.

Here is a measurement based review of the Forte 4 by Erin.

Klipsch Forte IV Review

Klipsch Forte IV Review

www.erinsaudiocorner.com

If look at his impedance curve you can see how parts with high impedance are near peaks in response with your 300B amp. You can also see his Klippel based response has a good similarity to what you have above 500 hz.

 

[GXAlan]

Here's the REW response with the Klipsch Forte 4 speakers. The volume wasn't matched exactly, but they look about the same to me. Also, the distortion is low with both under 1% 2nd harmonic so I'm not sure why the tube amp sounds better. (Unless it's just wishful thinking since I paid more for it!). Most of the variation in the graph is probably the speaker and room.

Speakers are remarkably consistent if you don’t move the microphone.

You can tell REW to do curve math to digitally volume match. The key is making sure you don’t move the mic or speaker and you, physically, are in the same position both times. (Ideally outside the room).

 

[Blumlein 88]

Speakers are remarkably consistent if you don’t move the microphone.

You can tell REW to do curve math to digitally volume match. The key is making sure you don’t move the mic or speaker and you, physically, are in the same position both times. (Ideally outside the room).

While true when one amp as 3+ ohms of output impedance connected to a speaker with a roller coaster impedance curve you will see the differences in his graph. I do believe he said he did not move the microphone.

 

[Balle Clorin]

In the REW plot menu in the rightmost side you can move the curve up and down and overlay the curves perfectly. This will show that the tube amp peaks in the midrange and have less bass in part of the range

The colouration that the tube amp gives can be pleasing , especially with simple music, on complex dense music on higher volume level my tube amp could not keep up with SS. In the end I left tubes since it was too variable with different music. It was great fun for 12 years . I just wish I could have had my DSP room correction preamp before, that made a difference larger than SS vs tube …


Ps take a look at these effects of tube rolling…
Post in thread 'Tube Rolling: Does it Make a Difference?'
https://audiosciencereview.com/foru...g-does-it-make-a-difference.28583/post-994574

Amp is Cayin A-300 with 300B tubes.

Post in thread 'If "Tube Sound" Is a Myth, Why Tubes?'
https://audiosciencereview.com/foru...be-sound-is-a-myth-why-tubes.8656/post-461534