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.
This is a review and detailed measurements of the vintage Dynakit Dynaco Stereo 70. It is on kind loan from a member who bought it used online and repaired it. Previous owner hand upgraded it but could not get it working. Given that it is 60 years old, one can forgive the rust and dust...
audiosciencereview.com
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...
