JayGilb
Major Contributor
Time to buy a panther figurine taking a dump.
The TV we had when I was a kid was a box of tubes. It was hot, smelly, took a long time to "warm up" and wasn't reliable. TV repair shops were commonplace.I had a box of tubes when I was a kid. As soon as transistors were even vaguely usable, I threw the tubes in a lake.
Amps that are designed to look like warming ovens, like these from PrimaLuna, are powerfully suggestive. I can't imagine how they could fail to sound warm while you sit there admiring the looks while listening to Dire Straits.I've wondered for awhile if the 'warm' sound some claim from tubes is caused by PSU noise and ground hum....
looks like a bread toaster oven
Time to buy a panther figurine taking a dump.
There does not exist one single technical reason to use tube power amps nowadays. They are poor in distortion, poor in S/N, poor in output impedance, thus sensitive to load complex impedance characteristics. Their value is only for vintage gear collectors, it is like to drive BMW 327 today, in contemporary traffic.Human ears are just not very sensitive to distortion. We are much more sensitive to frequency response.
Also mains intermodulation/banding that you can see on the measurements. I'm always surprised that nobody talks about this as power supply rejection ratio in push-pull valve amplifiers degrades dramatically once the output stage starts working and shifting away from the centre of its operation so cancellation can no longer occur...I've wondered for awhile if the 'warm' sound some claim from tubes is caused by PSU noise and ground hum. Many of the tube products tested here have a problem with 60 Hz spikes and other noise at low frequencies. Hum and noise tend to be intended in a lot of these 'audiophile' electronics.
Thanks for the subject and object review! It is also a mystery to Mr John Atkinson . Maybe if he reads your review now that he understands that it was his colleague's faultI don't know if they are or are not replaced. I do know I measured lower distortion than the spec (although power rating is different). And my measurements agree with that of Stereophile.
I'd say the same about any Class A/AB amp. We choose them because of non-technical reasons since, if engineered, the sonics will be the same as any other engineered amp.There does not exist one single technical reason to use tube power amps nowadays. They are poor in distortion, poor in S/N, poor in output impedance, thus sensitive to load complex impedance characteristics. Their value is only for vintage gear collectors, it is like to drive BMW 327 today, in contemporary traffic.
I guess in this case the reviewer preferred higher distortion though. It could probably do with a bit more negative feedback although it's disconcerting to see the response peaking (if only by a dB) at 70kHz, although having said that there's probably room in there for a dominant pole somewhere too...I'd say the same about any Class A/AB amp. We choose them because of non-technical reasons since, if engineered, the sonics will be the same as any other engineered amp.
Nah... It is distortion in Italian. Read it as: "dis tor tino!"@amirm unless you have coined a new phrase you misspelled distortion in this graph.
Kevin Deal hasNot sure why 3 people voted it 'Great'!
I will state with 99% certainty that more feedback won't help (the response curves show that stability is already questionable), the problem is in the open loop performance as well as grounding. And included in that 99% is my confidence that they made design errors stemming from a cut and paste approach. As Morgan Jones would say, "Heavily designed, lightly engineered."I guess in this case the reviewer preferred higher distortion though. It could probably do with a bit more negative feedback although it's disconcerting to see the response peaking (if only by a dB) at 70kHz, although having said that there's probably room in there for a dominant pole somewhere too...
No... its really the responsibility of whomever sends the device in but unless there is irrefutable evidence provided by the sender as to the condition of the tubes then a review shouldnt take place.that is too much to ask of Amir. And is he supposed to measure the new tubes in isolation as well to ensure they are good and matched samples. There can be a relatively wide margin of error in tubes, vintage or newly made.
And what about transport? Big power tubes don’t take kindly to being shipped all over the place. Vibrations, drops and such can cause degradation even if the tube is intact and well packed.
My advice for Amir is just to not bother reviewing tube amps at all. Maybe tube preamps. But power amps. Not worth the trouble.
Irrefutable evidence? Here are the company specs for SNR:No... its really the responsibility of whomever sends the device in but unless there is irrefutable evidence provided by the sender as to the condition of the tubes then a review shouldnt take place.
S/N Ratio | 84 dB |
Measurements should only be made in the original condition, and if you replace it with a completely different NOS tube as you say, then it has been modified.CLEARLY, @amirm should've tried exotic NOS tubes that cost $1,500 each right?