You’ve done this? Musical fidelity had amp boosters called superchargers that claimed the same thing…funny thing…no one uses them…
Yes , its actually a known known , its why Bob Carver took on the challenge ...
What do measurements say about SET’s
- Thread starter Rensselaer
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Yes , its actually a known known , its why Bob Carver took on the challenge ...
The output stage of tube amps are literally boat anchors and its always been the gain stages before it that actually produce the sound people are looking for in tubes.You’ve done this? Musical fidelity had amp boosters called superchargers that claimed the same thing…funny thing…no one uses them…
The only exception to this is guitar players because they over crank so dampening effects their speaker cabinet.
Um, hate to disagree again, but you are adding many gain stages and tons of feedback to achieve low distortion. Solid state amplifier designers are for the most part delusional about the high distortion of loudspeakers. No loudspeaker exists on this planet Earth that can resolve even 16-bit audio, let alone 24-bit audio. To resolve 24-bit audio, you need to have distortion down to -140 dB. That’s a pipe dream with modern loudspeakers. Your average very high quality moving coil dynamic loudspeaker achieves maybe -50 dB in the bass (like 8 bits of resolution). Behold the mighty JBL M2, widely used in studios world wide. Ugh, look at the distortion on this really high priced loudspeaker. It’s barely reaching even cassette tape quality. So, why in the world do you need solid state amplification with 0.001% THD when the sound from your loudspeaker is a million times more distorted? Once you factor in the distortion of your listening room, forget about it! You need to understand that the weakest link in the chain matters more than the strongest one when you are hanging on for dear life while climbing Mount Everest.
As a designer of SETs, one of the most important criteria, especially when using very high efficiency horns, is noise level. Ideally, noise and hum/buzz should not be audible any farther than 1 foot or so from the horn mouth, but this can be difficult to achieve. I rely on low noise in my designs so that the signature harmonic distortion character of an SET is not polluted by non-harmonic noise/junk.
These are measurements which are like the ones Stereophile performs - ideally an SET should be this clean.
1kHz / 1w 0-1kHz FFT - note extremely low power supply related noise at 60Hz and it's harmonics.
50Hz / 1W - only harmonically related distortion components are present with extremely low power supply related noise. You can only see the distortion components above the 4th because there is no noise to cover them up, but even so, they are well below an inconsequential -100dB re 1 watt.
"A" weighted noise is almost -101dB, which is exceptionally good and THD is 0.35%. Again, all distortion components above the 4th harmonic are below -100dB (< 0.001%).
These are strictly technical aspects/measurements of which I would argue the noise measurement above is the only relevant aspect for an end user. The total amount of harmonic distortion, I believe, is pretty irrelevant beyond the fact that there should not be any extraneous noise present which interferes with that harmonic structure.
These are measurements which are like the ones Stereophile performs - ideally an SET should be this clean.
1kHz / 1w 0-1kHz FFT - note extremely low power supply related noise at 60Hz and it's harmonics.
50Hz / 1W - only harmonically related distortion components are present with extremely low power supply related noise. You can only see the distortion components above the 4th because there is no noise to cover them up, but even so, they are well below an inconsequential -100dB re 1 watt.
"A" weighted noise is almost -101dB, which is exceptionally good and THD is 0.35%. Again, all distortion components above the 4th harmonic are below -100dB (< 0.001%).
These are strictly technical aspects/measurements of which I would argue the noise measurement above is the only relevant aspect for an end user. The total amount of harmonic distortion, I believe, is pretty irrelevant beyond the fact that there should not be any extraneous noise present which interferes with that harmonic structure.
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What happens when you start to ask it to put out some power? What output tube? Do you start to see core saturation down in the bass as the power goes up?
I am not sure if all speakers are at this level of distortion at this volume level.
This is a 300B/2A3 amplifier, and it outputs the usual expected power with these tubes. The output transformer is over-specified with a rating of 35 watts so bass holds up better than usual for this type of amplifier. I didn't publish higher power graphs because they would be much the same as any other amplifier of this type with the exception that the amplifier has exceptionally low noise / power supply noise which was a goal with this design. Since it is directly connected to horns with a sensitivity of 107dB/w in an electronic crossover system, any noise and/or hum is unacceptable in my very quiet room.
I don't believe that the amount of distortion SETs generate matters with smaller scale music since relatively high distortion is expected in these amplifiers. What does matter is that what distortion there is isn't polluted with noise and power supply related junk. Where SETs are asked to reproduce deep bass which would require power at or beyond their output capability, this will cause high distortion, audible higher up in the midrange and treble, just as with any other over-driven amplifier type. Bass limitations can be addressed to some extent by overly large output transformers with plenty of inductance to hold up at these low frequencies. This obviously costs more in dollars and weight.
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I had a 22w/8 ohm SET. 300B-XLS
I realised it's all about the speakers.
And the transformers (Sowter in this one)
Hum is important as it is very annoying . 0.2mV is ten times lower than the Air Tight 211, so that is a good thing. Frequency response given without db limit is not worth much. Watt at given distortion is kind of typical, what is more important if you have high efficiency speakers are the distortion at 1watt. What speakers are you using the amp with?
By the way the Air Tight 211 is a poor tube amp. Yours are likely better
By the way the Air Tight 211 is a poor tube amp. Yours are likely better
This amplifier (picture in my profile) is driving the high frequency Altec Lansing 802/511 horn in an electronic crossover system, crossed over at 500Hz. The sensitivity of this horn is 107dB/w so the amp has to be squeaky clean to have inaudible hum/noise. I have to stick my ear inside the horn to hear anything. The 1W distortion is shown in the graphs I posted and is a bit under 0.35% at 1kHz and 1w. The 1W frequency response is shown in the graph below:
I'm having trouble with these specs, unless the amp in question is class A2 rather than class A1. The data sheet shows that tube making 5% distortion at full power, about 19 Watts with 1200V on the plate. So how can it make more power with the same distortion, keeping in mind that the Voltage amplifier and driver circuit of the amp contribute distortion as well?
Do you still have this amp?
Yes I still have this amp. Perhaps it has only 19 watts, I don't know. I run both the bass and treble speakers off it for now, and as the compression driver is rated to 8 watts maximum I do not turn up the volume pots beyond 9 O-Clock setting, which is still loud enough.
I am on the waiting list for a Decware 300B Sarah amplifier. It has volume pots on it as well so that one can run directly from the phono stage without a pre-amplifier too (like the Ongaku clone from Soundgate/Japan). I am thinking of finding someone who can make a small passive crossover/splitter to insert between phono stage and amps so that I can bi-amp, 300B to compression drivers, 211's to bass speakers, balanced with the volume variable resistors.
I have some cheap Taiwanese 300b monos strapped directly (active xover) to 110dB compression drivers…there is a bit of hiss but otherwise they are pretty clean too.
Its unlikely you'd damage the compression driver with this amp since most of music power lies in the bass region.
What sort of slope do you need the crossover to have? The more the slope (12dB as opposed to 6dB for example) the more gain you'll need to make up for its insertion loss.
You're very lucky! It would be interesting if you have a schematic of that amplifier.
Not sure, figured that if in front of the amp values would be small and make little difference to power of amplifier. I figure cut off at 500 Hz, 12dB? I really don’t know enough about this so was hoping to find someone else familiar with bi-amping Altec A7’s to help. Need some way to dial in voicing on top too.
Oh, it’s fine, it is just that I ordered a Decware first (but the waiting list is long) and couldn’t wait three years without music. I was going to compare and keep what sounded best, but, I read someone mentioning bi-amping and that got me to thinking…
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