A consistently more musical sounding valve imho
SET amp owners thread
- Thread starter bonzo75
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A consistently more musical sounding valve imho
the tube is cheap, but the rest of the amp is not. Mostly you need really high voltage to let that tube sing (maybe an interstage coupling is necessary) main transformer, choke, interstage transformer, and output transformer. that can get really expensive...ouch
Good exsample for not so expensive
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A good driver tube for GM70 is the 6N6p…no need for an interstage transformer. But it has to be very robust overall amp to deal with high voltages…I think my Amplifon ran at 1300 or even 1400V but it made a true 40 watts Class A1 from one tube.
I find this is where some manufacturer’s cut costs , if you are going to design a circuit incorporating IT’s then it is imperative that it is of similar or same quality as the OPT .
I bought four NOS military spec GE 211’s from Billington Export Ltd. UK for £325.00 each
Have you heard the older tango ones? I have 300b with old tango transformer and i think it sound quite good..
The 6bl7 is a good driver for that voltage monster, you can build 2 watt se amp with that tube...that kick the gm 70 in the grid(ass)
Yes I heard them. IME 300B with old Tango transformers is one of the two great sounding Wavacs, other is stereo 805.
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The trick is to direct couple to the grid of any power triode if you really want to see what it can do.
SET power is the most expensive kind of audio power available...
The Veblen Effect is in full force!
Not at all, you might find some great locally made point to point wired SETs. You will just have to do more research
Not sure what this is supposed to mean.
Since there are PP amps and class D amps out there now that compete with SETs on any metric an audiophile might find important, then the cost certainly comes into play.
The tubes are out.of reach.
The iron is expensive.
The speaker in finicky to the amp.
It seems like a guessing game. I'm pretty bitter I have close to $20k into my 845 and its not very good. Then I ask about 211 and told good tubes are unobtanium. I don't want that hastle. I want a readily available tube at a cost of say $1000 to retube the amp. And the tubes should last 3000 to 5000 hours. Thats why I got the Blade. Its darn reliable to readily available quality tubes that cost about $600 to retube.
The iron is expensive.
The speaker in finicky to the amp.
It seems like a guessing game. I'm pretty bitter I have close to $20k into my 845 and its not very good. Then I ask about 211 and told good tubes are unobtanium. I don't want that hastle. I want a readily available tube at a cost of say $1000 to retube the amp. And the tubes should last 3000 to 5000 hours. Thats why I got the Blade. Its darn reliable to readily available quality tubes that cost about $600 to retube.
You can do that with 211 just don’t feel bad when you read on the forum there are better tubes. Depends on the type of audiophile you are. You can also check with Oliver Sayes and his used amps.
Cost does but on the right metrics. Kind of like saying your amplifier is the most expensive amp per pound (lb.) of transformer
There are several problems you or anyone playing with SETs has to face.
The first is the efficiency of your loudspeakers. That's why there are so many more horn speakers around now, with the resurgence of SETs since the 1990s. The problem is you really only have about 20-25% usable power. So if you really want to hear what the SET can do, the speakers have to be efficient, and more so than most people care to admit.
So the second issue is most speakers made (about 99%) are not compatible since most SETs don't use feedback. Any tube amp with no feedback tries to exhibit a constant power character, regardless of load. Of course they don't succeed but that's what they try to do. Most speakers are actually designed for the amp to be a constant Voltage source instead! For a tube amp to do that it must employ feedback. More:
Voltage vs Power Paradigms
This is a big part of the 'guessing game' to which you refer! You literally just have to try it out and see if it works. Your speakers sound great if they have enough power and I've heard them on SETs at shows (where the room was tiny and the volume low), but IMO/IME you need an amp with a good 50-60 Watts in most rooms if you want things to go well.
The next problem is SETs really can't make bass. This is because the load line of the tube's operating point becomes elliptical (not good for the tube...) at lower frequencies due to the output transformer having insufficient inductance. IOW the limitation is baked into the output transformer. No SET can make full power at the bottom end of their frequency response because the output transformer simply won't allow it. For a 7 Watt amp to do that, the output transformer would be the size of a small refrigerator. Most high efficiency speakers don't make full bandwidth to 20Hz anyway so you may not notice this limit if you run powered subs, but it will affect how the amp sounds at higher power levels because the distortion caused by the bass affects the sound of the amp.
Some SETs have more distortion due to how the power tube is driven. Since triode power tubes have very low mu (gain; for example a 300b is typicaly a value of 2) and high input capacitance on their grids, most power triodes are quite hard to drive. The best way to drive them as a result is either direct-coupling (the best way) or by using an interstage driver transformer. Quite often the driver tube needs to be pretty gutsy although less so if direct-coupling is employed.
Obviously the power tubes themselves are a problem as you point out. There can be tremendous differences between the garden variety of power tube and the more exotic (good) stuff.
Another common problem is as the output power is increased in any design, the output transformer has to be increasingly compromised. IOW bass gets a lot harder to make if you also want the highs right. This is why the 2A3 supplanted the 300b and the type 45 supplanted the 2A3. The smaller amps sound better because they have more bandwidth. The tubes themselves all have similar bandwidth otherwise.
You're trying to make this all work on speakers that are only 96dB in what looks like it might be an average listening room. My speakers are 98dB so very similar; I've found I need 50-60 Watts to really get that to work. Smaller amps simply sound more strained even though I'm not pushing them anywhere near clipping (and my speakers are 16 Ohms, an easy load).
So if you take the example of a 20 Watt SET, in your room you'll be pushing it hard if you want lifelike levels. Since their usable power is so low, you could get better sound with a PP amp of less power because PP amps tend to have more like 90-95% usable power. Usually when PP amps are compared to SETs, important things like class of operation, the actual output power, the kinds of tubes used are all ignored.
That still doesn't quite make sense to me. But if I take the example you state right here, it sounds like SETs are the most expensive kind of amplifier power based on weight vs output power, which IME is mostly correct. Tube amps have always been expensive power, which is why there were so many horn speakers in the old days when tubes were the only game in town. I think, generally speaking, that the metrics aren't important; Watt for Watt, SETs are the most expensive kind of amp you can own; for how much weight the amp has vs output power this is generally true too. If we talk about which are the good stuff when it comes to the power tubes, the SETs are still more expensive.
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