I only test one channel at a time.Is one channel out or one meter stuck ?
I only test one channel at a time.Is one channel out or one meter stuck ?
It kind of depends for me on where all that distortion is. If it's a lot of 2nd harmonic, then I'll stretch to 10%. If it's a lot of 3rd, I'm less willing. (With this amp it's a lot of 3rd)Yeah -- I thought 10% was the hifi cutoff
(actually I am not being entirely facetious -- the old tube manual data for audio power output tubes often, perhaps generally, list power output at 10% THD)
I don't tend to do a lot of square wave testing unless I'm doing feedback compensation or looking for something extremely specific. Lots of nice sounding amps don't make pretty 10kHz square waves, that's more a function of using as much feedback as possible to obtain that specific desired result.As to the contour -- have you looked at any square wave reproduction yet? I am guessing that might not be pretty.
It's a push-pull amp,right?It kind of depends for me on where all that distortion is. If it's a lot of 2nd harmonic, then I'll stretch to 10%. If it's a lot of 3rd, I'm less willing. (With this amp it's a lot of 3rd)
Absolutely true, but given the output impedance, doesn't it seem like there is something funny goin' on with that amp? Is there no NFB at all? Are the outputs triode-wired?I don't tend to do a lot of square wave testing unless I'm doing feedback compensation or looking for something extremely specific. Lots of nice sounding amps don't make pretty 10kHz square waves, that's more a function of using as much feedback as possible to obtain that specific desired result.
I would concur (FWIW, not that I am anything close to expert!) that's perfectly reasonable (and better bandwidth, e.g., than the SE 2A3 amp I listen to, I reckon!).Power bandwidth isn't all that bad. The amp will do:
10.5W at 40Hz/10% THD and 9.2W at 30Hz/10% THD, but then down to 5W at 20Hz 10% THD.
That's not really bothersome for what this amp is and it would be totally fine as a desktop amp.
...
I think that comment is broadly applicable to vacuum tube audio hardware (and I don't mean that snarkily; I am a vacuum tube audio kind of fellow, as y'all know).so it's a tool that has some practical applications.
I think that comment is broadly applicable to vacuum tube audio hardware (and I don't mean that snarkily; I am a vacuum tube audio kind of fellow, as y'all know).
DSC_8376 (2) by Mark Hardy, on Flickr
(speaking of Bottleheads... )
Hmm... $1100 is real money (at least from my perspective) for a ppEL84 amplifier!
Plus there is (or at least, there has been) a whole cottage industry of aftermarket/retrofit/upgrade PC boards/hardware for the SCA-35.I sure would be thinking about the SCA-35 for a lot less money.
Nah, gotta mess around with the priceless artifacts. If you don't, what fun would this be?You also don't feel like you're destroying some priceless artifact by messing around with the Dynaco.
Power bandwidth isn't all that bad. The amp will do:
10.5W at 40Hz/10% THD and 9.2W at 30Hz/10% THD, but then down to 5W at 20Hz 10% THD.
That's not really bothersome for what this amp is and it would be totally fine as a desktop amp.
The output impedance at 1kHz is a whopping 5 ohms, which is totally unacceptable and telling some of the story about why the frequency response looks a little weird.
First and foremost, I am probably the problem here!
I am perversely fascinated by the long threads on various hifi fora (y'all know the one/ones) that gush over 31 dollar preamps, 129 dollar hybrid integrated amps, and 299 dollar all tube integrated amplifiers. These products are offered under a plethora (nay, a surfeit) of brand names and sometimes feature the use of unusual (from a Western perspective) vacuum tubes (some without exact "Western" substitutes).
Now, here's the thing... one comment I read a lot in these threads strikes my cheap/frugal Yankee sensibility as distressing.
Here is an exact quote from one post to one such thread.
I find myself horrified by such an attitude! Now -- yeah, I know, it's their money and they're grown-ups and all... but the notion of just urinating away a couple of hundred dollars (or even 31 dollars) just because something is cheap seems very, very wrong to me.
Believe it or not, my dudgeon isn't directed at individuals -- it's directed at the culture that puts so little value in its own spending power.
Finally -- as you've likely guessed, I am on the cusp of buying one of those damned 31 dollar preamps!
Somebody. Stop. Me.
Thanks for "listening"!
A 6 ohm rated tap with 5 ohms output impedance is even worse.I own this amplifier which sounds terrific - The amplifier is rated as 6 ohm - not 8 ohm or 4 ohm - it sounded poor with the KEF LS-50 - it simply can't drive them - on HE speakers it's a dream.
The tube in there is a 5U4 with fancy packaging. The amp may perform a bit better with a 5AR4 than it does with a 5U4, especially if that's what it's designed for.FWIW: The rectifier tube in the picture you posted is not stock - it is supposed to be a 5AR4. King's recommended tube is the NOS RCA 5U4G.
The tilted treble would be very concerning if I had horn speakers.I am not too concerned by the measurements because if that was really a deal breaker - why the hell are any of you buying tube amplifiers.
A 6 ohm rated tap with 5 ohms output impedance is even worse.
The tube in there is a 5U4 with fancy packaging. The amp may perform a bit better with a 5AR4 than it does with a 5U4, especially if that's what it's designed for.
The tilted treble would be very concerning if I had horn speakers.
The gist of this thread is to test the claims of certain import amps that appear to be a little dubious. This particular manufacturer doesn't really make any claims, so there wasn't a lot to say in this regard, but I still figured I would measure it and see how it did.