Do you ever buy tubes ..you talk tubes, but all you buy is SS..
You see now, if your reading is so selective, how selective is your hearing? And what do you select for measurements?
This is the root of the problem, about listening Vs measurements.
I still need to hear your take on these..... ?
http://www.diyaudio.com/forums/lounge/200865-sound-quality-vs-measurements-106.html#post2868163
http://www.diyaudio.com/forums/lounge/200865-sound-quality-vs-measurements-106.html#post2868163
I find it insulting to imply that 'engineering is boring'. I find it fascinating, and have done so for the last 50 years. It is 'solving problems', however, you have to be aware what the problems are. IF you are in an 'ivory tower' perhaps you don't realize this, and think that what was put forward as OK, for example in autos, 50 years ago, is just as good, today, and you can 'prove' it by some 'blind test' like putting you in a 50 year old car, blindfolded, sitting on a blanket, going to and from the store and comparing the experience with a newer, similar vehicle. In audio this is like the double-blind test between amps.
Your inapt car analogy aside, I didn't imply this, I said it. Engineering (we're talking audio electronics here) does not lead to a good story or golden ear affectations. There's no resorting to unmeasurable or unquantifiable phenomena. As a story, it's boring. Doesn't sell magazines or impress the audio salesmen and their clientele.
Yup, and someone might just prefer the ride in a 1971 Valiant over a Bentley. I have several friends for whom this is a fact.
Everything presented in the specs looks like several other good amps with lots of feedback, for instance the rising distortion vs. frequency with different loads. IMHO they went to the limit on supply and ground bussing, supply regulation and EMI/RFI prevention. There are just TOO many parts in that thing way anti-zen.
I think that the history of audio engineer is fascinating, and I have an almost complete library devoted to it. I have found EVERY 'breakthrough' in audio useful, however, many of my associates found them often 'just more work' or 'who cares?' That is why I am still here, and they fell away over time.
Thanks Scott,
There are 3 graphs, 3 different amplifiers, all three look different , is there a good better best between the 3? sonic character? what are we looking for ?
True dat .........
The road to perfection is steep and narrow, too steep and narrow for the uncommitted. Maestro Curl is committed!
So do I. Well, most of it. But I don't buy much new audio gear, do you?
Dentists, bankers and lawyers do.
As regards his suggested input grounding scheme, yes very definitely sub-optimal. As regards his almost total reliance on single tone THD testing rather than IMD (perhaps multitone) and listening then again, sub-optimal.
<edit> Here's an interesting article for those who want to learn a bit about measurements on DACs (rather than amplifiers):
http://www.hit.bme.hu/~papay/edu/DSP/comDAC.htm
Last edited:
Hi,
There is a 220K resistor to ground, if you look closer. Resistive load. Q.E.D.
Ciao T
the 2'nd LTP stage is loaded on a current mirror, that can't be called resistive load.
There is a 220K resistor to ground, if you look closer. Resistive load. Q.E.D.
Ciao T
Hi,
Well, I have been always happy using passive preamps. But I always use gear with low output impedances and designed so it is happy to drive a 10K volume control and amplifiers that have a high and linear input impedance (Fet, Tube) and use very low capacitance cables.
BUT, many transistor amplifiers (Op-Amp's too) using bipolar inputs have appreciable base current modulation and worse, many potentiometers have a severely non-linear wiper/track interface. An example of a op-amp that is bipolar and explicitly addresses this problem is the LM3875/86 etc. range from Nat Semi (extra EF before the input diff pair)...
Equally, much commercial gear uses output stages that have a miniscule Class A range in their outputs and hence cause crossover distortion into lowish load impedances (they use tons of NFB to push this problem way low, but it is not eliminated).
Here a little experiment for anyone to try.
If you have a bipolar Op-Amp, add a set of J-Fet followers with a CCS tail before the bipolar inputs and a FET Buffer on the output running at enough current for full level into 600 Ohm. Then compare this to the Op-Amp alone with a 50K or 100K volume control and 10K load...
Ciao T
Well, I have been always happy using passive preamps. But I always use gear with low output impedances and designed so it is happy to drive a 10K volume control and amplifiers that have a high and linear input impedance (Fet, Tube) and use very low capacitance cables.
BUT, many transistor amplifiers (Op-Amp's too) using bipolar inputs have appreciable base current modulation and worse, many potentiometers have a severely non-linear wiper/track interface. An example of a op-amp that is bipolar and explicitly addresses this problem is the LM3875/86 etc. range from Nat Semi (extra EF before the input diff pair)...
Equally, much commercial gear uses output stages that have a miniscule Class A range in their outputs and hence cause crossover distortion into lowish load impedances (they use tons of NFB to push this problem way low, but it is not eliminated).
Here a little experiment for anyone to try.
If you have a bipolar Op-Amp, add a set of J-Fet followers with a CCS tail before the bipolar inputs and a FET Buffer on the output running at enough current for full level into 600 Ohm. Then compare this to the Op-Amp alone with a 50K or 100K volume control and 10K load...
Ciao T
Why would anyone use a bi-polar on a 100K pot? There are plenty of FET amps with non-linear input C too (easily measurable distortion even on 10K).
- Status
- Not open for further replies.