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Take the blind challenge! 300B SET vs. Straight Wire with Gain

Choose ALL of the statements that apply.

  • I prefer #1 (over 3)

    Votes: 20 45.5%
  • I prefer #2 (over 5)

    Votes: 7 15.9%
  • I prefer #3 (over 1)

    Votes: 9 20.5%
  • I prefer #4 (over 6)

    Votes: 22 50.0%
  • I prefer #5 (over 2)

    Votes: 18 40.9%
  • I prefer #6 (over 4)

    Votes: 13 29.5%
  • I hear no difference between 1 and 3

    Votes: 14 31.8%
  • I hear no difference between 2 and 5

    Votes: 18 40.9%
  • I hear no difference between 4 and 6

    Votes: 9 20.5%

  • Total voters
    44
  • Poll closed .

atmasphere

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To get around the problems, challenges with tube amps and their inability to power bass drivers:
A three-way speaker where you can plug in and drive the bass element /drivers with class D amplification, then drive the midrange woofer and tweeter with a tube amplifier. I don't understand why this solution is not more common, for those who now want a tube amp in their solution?

___
Another note. I filled out the survey now. It was interesting to see the other results. More discussion about it will hopefully come after May 4. That is after the voting has ended, that is.:)
I think a lot of people do exactly that.

Personally I think SETs went away for a good reason...
 

solderdude

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you can't get the amp to really do what its meant to do.
And what is it meant to do with the current available speakers ?
Not what it was meant to do in the early days.
We are talking about a 300B tube amp connected to speakers that audibly modifies the sound.
I'm not saying feedback is bad!! But it can have bad effects if poorly applied.
Every design, feedback using or not has bad effects if poorly applied. I do not see the value of such comments.
Nearly every audio design currently available aside from some niche products uses feedback in fact it would not work properly without it.
Even if the open loop bandwidth is 10Hz.
Perhaps you might want to retract this particular statement?
No I don't because there is a limit as to what even overall feedback can do when the transformer rolls-off.
Again, its highly unlikely that the SET has an audible treble rolloff
It appears the discussed amp does
Regarding the bandwidth thing again- many tube amplifiers are full power to 100KHz (H/K Citation 2 and Citation 5 for example). 50KHz is very common (Dynaco, Marantz, ARC and more). I'm just wondering why you think this would be audible in the treble range.

I don't at all. Where do you get the idea from. Just saying that the amp in question is doing that and that bandwidth limiting it is often seen in tube amps.
so when loaded with a resistor. Don't know the circuit, don't know why. It is measurable, audible and correctable and load dependent.
Nothing good about it.
Personally I think SETs went away for a good reason...
Yep, we are in agreement here.
 

Thomas_A

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Did the following thing:
Used @danadam level matched uploads, added an approximate of the treble + bass difference found by @pkane to the files that needed it and created ZIP files.
For those who like to hear the difference between the original and the SET amp without the subbass (-1dB) and treble (20kHz-4dB) roll-off, as that roll-off should be almost completely eliminated, leaving the added harmonics, IM, noise and hum as the only things that can differentiate the files.
Maybe @pkane can check if I did the job correctly ? My ears tell me I did but am just as prone to bias as the next person.
It was harder, naturally, and I first went for the C-2 pair, but it was a bit busy music so I got a bit tired. There is a small difference in bass resolution, I think. The B-2 is a bit calmer and the timbre of the bass is a bit different.

Skärmavbild 2023-04-27 kl. 22.54.25.png
 

atmasphere

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And what is it meant to do with the current available speakers ?
Not what it was meant to do in the early days.
We are talking about a 300B tube amp connected to speakers that audibly modifies the sound.
If the SET owner has any sense, he will use a speaker that is designed for them. There are plenty around; most SET owners have pretty good guidance on finding them.
Every design, feedback using or not has bad effects if poorly applied. I do not see the value of such comments.
Nearly every audio design currently available aside from some niche products uses feedback in fact it would not work properly without it.
Even if the open loop bandwidth is 10Hz.
The 'value of such comments' is setting the record straight. In many cases in audio today feedback is poorly applied. I explained why.

No I don't because there is a limit as to what even overall feedback can do when the transformer rolls-off.

It appears the discussed amp does
Was the SET revealed as a particular selection? I thought that was not happening until the 4th.
I don't at all. Where do you get the idea from. Just saying that the amp in question is doing that and that bandwidth limiting it is often seen in tube amps.
so when loaded with a resistor. Don't know the circuit, don't know why. It is measurable, audible and correctable and load dependent.
Nothing good about it.
You have said several times comments like this one (and including the one in the paragraph above; emphasis added):
All people that reported talked about the treble roll-off as a give away.
And this one:
That would make the tube vs original sound a lot more realistic (with the roll-off removed)
And this one:
Yes, the distortion is there but that what could be perceived as 'tube sound' (usually typical treble roll-off) might not be caused by the distortion components in the test files but the more obvious treble roll-off.
At least that's what seems to trigger most listeners, they mention the treble roll-off as indicator and not increased distortion.
So the increase in distortion effect might be 'masked' by the treble roll-off.
I don't think I know of a tube amp that has audible 'bandwidth limiting', as you put it, in the treble range. I could easily be mistaken (it happens a lot) but this has led me to believe this is what you think of tube amplifiers. If so, then you are mistaken. If not so, then I am mistaken.

I'm of the opinion that tubes need to go away. That will happen when people understand why. Saying that they roll off the highs isn't a reason though, because they don't do that. My concern here is accuracy.
 

Cbdb2

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I previously explained a common problem with feedback if the GBP is insufficient (and in most cases of amplifiers made, it is). Here's another: if the feedback is applied to a non-linear node (such as the base of a transistor in a differential pair or the cathode of an input tube) the feedback signal will be distorted by the non-linearity of the device. This in turn contributes to higher ordered harmonics, inharmonic distortions and IMD. These things are audible.
A differential pair is very linear if used properly.
 

solderdude

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If the SET owner has any sense, he will use a speaker that is designed for them. There are plenty around; most SET owners have pretty good guidance on finding them.
Yeah right a SET owner that selects a speaker to go with a speaker that was designed for them.
When have you ever read in the spec sheet of a SET amp it was designed for this or that speaker(s) ? (You don't how would your customers know ?)
When have you ever read in the spec sheet of a speaker it was specifically designed for this or that SET amp ?
A lame excuse and honestly don't think anyone really can match (impedance dependent) amps to speakers neither by ear nor using measurements.
At best they may like or prefer a combination and post their findings. It is never about technical excellence but a particular coloration they like.

In many cases in audio today feedback is poorly applied. I explained why.
In far more cases it seems to work just fine. Of course this is design dependent and not just 'caused by feedback'.

Was the SET revealed as a particular selection? I thought that was not happening until the 4th.
It was kind of clear to most that actually listened to the files... due to the excessive treble roll-off.

I don't think I know of a tube amp that has audible 'bandwidth limiting', as you put it, in the treble range.
The discussed (budget) SET amp does it seems in a resistive load. A design issue. Maybe, given the fact that with a lot of speakers the designer wanted the amp to not sound 'sharp' and decided he'd roll-off some treble ? Who knows why and what was done to sell as many as they can. After all that is why brands sell devices.. to make money.

That amp is in no way related to any of your designs unless they simply copied it without your consent... somehow I don't think this is the case.:)

I'm of the opinion that tubes need to go away. That will happen when people understand why. Saying that they roll off the highs isn't a reason though, because they don't do that. My concern here is accuracy.

I'm not... and you certainly are not either. Why should you want your main income to go away ? Why not just build the class-D designs only ?

When people enjoy faffing around with tubes why should they go away ?

Tube amps, when well designed, can be quite accurate.
Here too.... it's the design not the active components used by nature.
This you know very well otherwise you would not be building nice looking and good performing tube amps would it, and you would not be building OTL tube amps.

We are discussing a budget SET amp here and not the performance of any of your designs.

I assume you listened to the files and could clearly tell the SET from the original file and you can used the tube goodness and voted contra the majority of votes as a result ?
You were tagged and asked for your opinion.
 
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solderdude

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It was harder, naturally, and I first went for the C-2 pair, but it was a bit busy music so I got a bit tired. There is a small difference in bass resolution, I think. The B-2 is a bit calmer and the timbre of the bass is a bit different.

View attachment 281879
There is still some difference in FR in the compensated files though. The biggest chunk of the roll-off had been compensated. Audacity EQ only allowed some 1dB steps at specific frequencies. It will indeed be harder to tell because the treble roll-off is compensated for (for the biggest part) and the tube distortion will be contributing relatively more in this particular comparison. With OP's speakers attached it will differ yet again and the SET amp in question will be the brightest amp for sure in a comparison.
 

Thomas_A

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There is still some difference in FR in the compensated files though. The biggest chunk of the roll-off had been compensated. Audacity EQ only allowed some 1dB steps at specific frequencies. It will indeed be harder to tell because the treble roll-off is compensated for (for the biggest part) and the tube distortion will be contributing relatively more in this particular comparison. With OP's speakers attached it will differ yet again and the SET amp in question will be the brightest amp for sure in a comparison.
I was thinking of that and the match is within 0.25 dB (?) or so in frequency response up to 10 kHz from the previous difference comparison. It may be the frequency response difference that reveals it and not distortion. Difficult to tell without having it matched within 0.1 dB
 

Sokel

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Actually, they do. SET owners are very much aware of the limitations of their amps, so they are very careful about speaker selection.
That's true according to what I see around,and these speakers cover a range of big to enormous,mostly horns.
 

solderdude

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Actually, they do. SET owners are very much aware of the limitations of their amps, so they are very careful about speaker selection.
They are aware and choose the speakers based on their preference combined with that particular amp or recommendation of others.
They choose what they prefer/like but do not do this based on 'accuracy' as in signal fidelity but think it is.

Some people really like some peaking here or there in their rooms and their ears or some roll-off in lows or highs and this is something 'wire with gain amps' simply cannot provide without resorting to tone controls/EQ.
They love the search for their 'preferred sound'. They, in general, do not search for accuracy but rather seek enjoyment.
These are not necessarily the same thing but can be.
The same people also often do not believe in (digital) EQ and believe that choosing 'the right' components (incl. speakers and amps) is the way to go and call that 'synergy' where in reality you never see them measure the results. They do not believe in measurements at all in most cases but rather trust their ears.

And this, in the end, to me is a good thing. In the end it is all about enjoyment of sound. Others want 'accuracy' and want to hear what the final product (the recording) should sound like, as similar as the recorded wave form as possible. This too is an option.

And as with everything in life it is not always black and white. There are all sorts of grey in between. I believe both extremes and everything in between should be available and people are free to enjoy whatever they want.

A viewpoint is only 'correct' when that is ones viewpoint and multiple viewpoints exist.
In the science part there is only signal fidelity though.
That can be measured but to be thorough requires more than just a few standard measurements and tests.
 
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Keith_W

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And as with everything in life it is not always black and white. There are all sorts of grey in between. I believe both extremes and everything in between should be available and people are free to enjoy whatever they want.

Yup, I agree. "Audio science" only tells us about science. It has nothing to do with preference.
 

DanielT

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I think a lot of people do exactly that.

Personally I think SETs went away for a good reason...
Well, if you start going that way, you might as well power the midrange and tweeter drivers with solid state amps.;)

Having said that, I understand the attraction of tube amps mainly for people who are knowledgeable in electronics. Tinkering with, DIY, tube amps seems to these people to be attractive. And why not, it's a hobby as good as any. Something that DIY tube dudes will never get around is that sensible output transformers are expensive.
But you can then ask the question:What is it that can be considered expensive with a hobby? Still cheaper with DIY tube amps than fixing with vintage cars (in most cases I'm guessing). Joining a book club is cheaper than ...and so on. :)

Speaking of fiddling with tube amps. Even for example Amir, who as far as I know is not actually a tube dude says:

I love the simplicity of tube amps like this. There is just so little to them. If I were less busy, I wouldn't mind playing with one to get it to optimal performance.
Dynaco Dynakit ST-70 Power Amplifier Audio Review.jpg



 
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atmasphere

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Yeah right a SET owner that selects a speaker to go with a speaker that was designed for them.
When have you ever read in the spec sheet of a SET amp it was designed for this or that speaker(s) ? (You don't how would your customers know ?)
When have you ever read in the spec sheet of a speaker it was specifically designed for this or that SET amp ?
A lame excuse and honestly don't think anyone really can match (impedance dependent) amps to speakers neither by ear nor using measurements.
At best they may like or prefer a combination and post their findings. It is never about technical excellence but a particular coloration they like.
I suspect you're placing too much value on spec sheets in this case; SETs producers tend to be weak in that department anyway. A person buying an SET will be advised by the manufacturer, dealer and SET community to use a speaker that's easier to drive. Its not a weak excuse at all- I've seen this sort of advice offered a lot on other forums over the last 30 years. I've seen many speakers advertised as being suitable for SETs. I can give examples if you like.

There are simple rules for matching SETs to speakers WRT impedance and measurements and you can do it by ear. You make sure that the speaker's impedance is not low in the bass, so speakers that are 4 Ohms in the bass are out. In fact 4 Ohm speakers should be avoided, as in an SET this is pretty sure to truncate the bottom octave off the amplifier's power response. Otherwise the speaker should be higher impedance; 16 Ohms is preferred but 8 is fine; The impedance curve does not have to be flat as long as the impedance bumps tend higher; there won't be any ill effects as long as the amp can manage the bass impedances. Beyond that the efficiency of the speaker is paramount. Efficiency is far more useful spec (as opposed to sensitivity) since the amp behaves as a poor power source rather than a voltage source.

I am familiar with a lot of this since much of this is what we've faced making our OTLs the last 50 years. The main differences are OTLs can make a lot more power and distortion is vastly reduced- usually a couple of orders magnitude lower at any power level the SET can make. If built to a large enough scale, 4 Ohms and below is manageable. We examined SETs very closely back in the early 90s to determine if they were a threat to our business model and concluded rather quickly they were not- and over the last 30 years that's proven correct.

These days class D is the actual threat to tube amplifiers.

In far more cases it seems to work just fine. Of course this is design dependent and not just 'caused by feedback'.


It was kind of clear to most that actually listened to the files... due to the excessive treble roll-off.


The discussed (budget) SET amp does it seems in a resistive load. A design issue. Maybe, given the fact that with a lot of speakers the designer wanted the amp to not sound 'sharp' and decided he'd roll-off some treble ? Who knows why and what was done to sell as many as they can. After all that is why brands sell devices.. to make money.
It will be interesting to see what is what in the great reveal... If the rolled off files are indeed the SET, then we need to look at the load it was driving. If it really was rolled off then yes, that's a serious design issue and one easily avoided. Usually SETs have output taps; so owners are advised to use the one best matching their speakers. If we're talking about a low impedance in the treble region, the 4 Ohm tap might well have solved that.

WRT to why they sell them, its not always to make money. I know a lot of these producers from doing audio shows. Money is often a secondary factor- the main reason most of them (including myself) do it is because they enjoy it and many are motivated to see how well they can push their vision/version of State of the Art.

I'm not... and you certainly are not either. Why should you want your main income to go away ? Why not just build the class-D designs only ?
Actually that's how its working out- our class D is outselling all of our tube amplifiers put together.

We are discussing a budget SET amp here and not the performance of any of your designs.

I assume you listened to the files and could clearly tell the SET from the original file and you can used the tube goodness and voted contra the majority of votes as a result ?
You were tagged and asked for your opinion.
No idea why I was tagged...

All I know is an SET is involved. I didn't listen for a rolloff. Instead I listened to the highs to see if I could tell which was smoother. Its my assumption that the SET would be smoother, but a lot depends on how hard its being driven, since about about 20% of full power, SETs tend to make a lot more higher ordered harmonics. This causes them to sound brighter at higher power levels (and more 'dynamic', but its distortion masquerading as 'dynamics'). So I really can't say based on the files which amp is which- I simply ticked my preferences. One of the files played with a bit of sibilance on my desktop so I ticked its opposite.
Well, if you start going that way, you might as well power the midrange and tweeter drivers with solid state amps.;)

Having said that, I understand the attraction of tube amps mainly for people who are knowledgeable in electronics. Tinkering with, DIY, tube amps seems to these people to be attractive. And why not, it's a hobby as good as any. Something that DIY tube dudes will never get around is that sensible output transformers are expensive.
But you can then ask the question:What is it that can be considered expensive with a hobby? Still cheaper with DIY tube amps than fixing with vintage cars (in most cases I'm guessing). Joining a book club is cheaper than ...and so on. :)

Speaking of fiddling with tube amps. Even for example Amir, who as far as I know is not actually a tube dude says:

I love the simplicity of tube amps like this. There is just so little to them. If I were less busy, I wouldn't mind playing with one to get it to optimal performance.

I've been a big fan of subwoofers since being introduced to the idea of a Distributed Bass Array in the early 2000s. FWIW, my main speakers are powered by class D at home, so I'm doing exactly as you suggest.

The biggest single weakness of the ST70 is the rectifier tube. Due to the power the amp makes, the rectifier is the most likely tube to fail. They should have designed it with dual rectifiers but it was made to a budget target. You can't replace the 5AR4 with solid state since the power supply runs higher than the OPTs are spec'ed for. Triode Electronics sells a transformer that is rated for the right voltages using dual rectifiers, which bolts in place. But then you have to find a place to put the second rectifier tube while maintaining the amp's power supply caps properly. It can be done! The 7199 driver tube is rare; but 6GH8s are common and with an inexpensive adapter socket (available on ebay), are a good replacement that yields lower distortion...
 

solderdude

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Actually that's how its working out- our class D is outselling all of our tube amplifiers put together.
That's a good thing. Much more power thus no more weak bass, less speaker dependency (maybe except for upper treble depending on the design) and normal efficiency speakers can be used as well as lower impedance. In the same way as any decent power AB amp already did for decades.
It will be interesting to see what is what in the great reveal...
It has already been revealed a few times as wire with gain cannot have a treble roll-off and measurements of the amp (using a resistive load) were clearly rolled off which I suspect is by design so the less aggressive sounding one will be the SET.
Furthermore when the files would be created with the OP's speakers (not optimal for SET) the SET amp would have been the brighter/sharper sounding amp.
 
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GXAlan

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It has already been revealed a few times as wire with gain cannot have a treble roll-off and measurements of the amp (using a resistive load) were clearly rolled off which I suspect is by design so the less aggressive sounding one will be the SET.
Furthermore when the files would be created with the OP's speakers (not optimal for SET) the SET amp would have been the brighter/sharper sounding amp.

Optimal/not-optimal is not as clear. The SET does measure with a rolled-off treble against resistor, which is how the blind files were made. On every 2-ch speaker I have, there is a treble boost which actually correlates with my audible experience more. This SET *is* an effects processor but I would say that it is a very pleasant effects processor. I do like it.

My "reference" remains the Marantz SA-10/PM-10 combo.

The PM-10 measures very well into a resistor
and shows less variability than the PM-11s2 into a speaker load

and I've shown that with DSD content, the PM-10 comes closer than the D90 to a straight wire with gain (digital comparison) and when using a microphone to a speaker, the PK Metric shows that the difference might be audible.
 

solderdude

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This SET *is* an effects processor but I would say that it is a very pleasant effects processor. I do like it.

As I do not have the amp nor the speakers but you do and have the ability to measure the 'change' you could run the following experiment.
Apply some counter EQ to the original sound so that there is no roll-off/peaking (basically flat output on that speaker) and compare that recording to the original.

Or the other way around... apply some EQ, the same as you get with the 'effect box amp' and use a normal amp and see if the effect is the same tonally.
It would not be entirely so because the output Z of the amp will have more influence than just FR but would be interested in finding out if it is not just the altered FR that is the reason for your preference or that there really is some 'unknown magic' happening in the amp.
 

atmasphere

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That's a good thing. Much more power thus no more weak bass, less speaker dependency (maybe except for upper treble depending on the design) and normal efficiency speakers can be used as well as lower impedance. In the same way as any decent power AB amp already did for decades.

It has already been revealed a few times as wire with gain cannot have a treble roll-off and measurements of the amp (using a resistive load) were clearly rolled off which I suspect is by design so the less aggressive sounding one will be the SET.
Furthermore when the files would be created with the OP's speakers (not optimal for SET) the SET amp would have been the brighter/sharper sounding amp.
You can get very powerful bass with tube amplifiers if you pay attention to the load impedance where bass energy is made. It is nice to get away from that particular dependency though!

WRT your last comment: Yikes! If the SET was really that bad (rolled off in the audio band with a resistive load), I would regard it as a poor choice for this sort of comparison as its not typical of SETs, unless of the cheap variety that can be had for a few hundred dollars. Most of the SETs I get exposed to (mostly at audio shows) cost 4 figures at a minimum.
 
OP
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GXAlan

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If the SET was really that bad (rolled off in the audio band with a resistive load), I would regard it as a poor choice for this sort of comparison as its not typical of SETs, unless of the cheap variety that can be had for a few hundred dollars. Most of the SETs I get exposed to (mostly at audio shows) cost 4 figures at a minimum.

Yeah, this is the unit. Budget unit that looks pretty.

It’s actually the extremes of very good and very poor performance more to show how subtle it can be at the extremes…

Lots of lessons learned about doing a better blind test in the future like using a real load instead of a resistor and finding longer tracks for sampling.
 

computer-audiophile

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its not typical of SETs, unless of the cheap variety that can be had for a few hundred dollars.
Even in this low-priced segment, there are big performance differences. It depends not least on the circuit and all sorts of little things. There are also very good examples with the 6SN7 cascade in loftin-white circuitry. This circuit can be called the world standard for 300B SET, since it is used in a very similar way by many manufacturers.

Typical representatives of this type can be found e.g. at: Audio Note UK, JE-Labs/Angela Instruments, Sun Audio/Uchida, Reichert, Tambour/Raphael-Audio, Sound Practice/J.C. Morrison and Stoet, just to name a few. Twenty years ago, I had described such an amp as a do-it-yourself project on my former tube audio homepage. It was built quite often and successfully afterwards.
 
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