I find HP equipment hard to fix and easy to replace. You were just cheated, Grey. I bought 2 HP 3580's over the years and 2 HP 3581's and 1 HP 3563 without any problem. They should be cheap on E-bay, now.
Joshua_G said:
Joshua,
Be carefull. You may now say it's only for audio, but once you have such an instrument you will quickly have needs for higher frequency. Like looking at oscillating stages, power supply noise, and so on.
For audio work, go for 20MHz at the minimum.
I have a Tek scope that has a 20MHz BW limit switch which I have activated a lot of the time for general audio work so there's less noise at low levels, but when checking for oscillations or verifying square wave responses I need to go to full BW.
Jan Didden
PMA said:
So far I've gotten away with a 5MHz scope, and those are dirt cheap today.
Magura 🙂
The Tek 465 is a reasonable minimum. 20MHz is the very minimum.
I have, over the decades, used 5MHz (Eico), 20 MHz, 80MHz, and now 350MHz. I like more, but 100MHz (or more) is necessary for high frequency oscillations that can happen sometimes.
I have, over the decades, used 5MHz (Eico), 20 MHz, 80MHz, and now 350MHz. I like more, but 100MHz (or more) is necessary for high frequency oscillations that can happen sometimes.
Sorry! Typo. Like so many that I make. Every time I re-read one of my responses I see a typo or a better way to express whatever I wanted to say. It is almost always too late to change it. 24 hours or more is best for re-reading.
I share the same problem. 30 minutes is too short for those with an "esprit de l'escalier". 😉
dimitri said:
Hi Dimitri,
There is no single criteria like THD20 < 0.001% at full power, especially when it is a lumped number without spectral distribution of the harmonics.
I know it is frustrating, but the truth is that THD20 below some number is neither necessary nor sufficient for extremely high sound quality in an amplifier. This does not mean that it is not important and useful. John and I both agree that, for example, we like to see 7th at -100 dB or below.
Part of the problem is that there are many other things that can affect amplifier sound quality that are not of a nonlinear distortion nature, such as frequency and transient response, amplifier mis-behavior, and nonlinear distortion that shows up under peculiar load conditions that may not be there in a standard THD-20 test. Don't ignore the possibility of parasitic oscillation bursts, either.
The other thing is that there are many amplifiers that sound great that have 0.01%, or 0.1% THD-20 if it is of a soft, low-order nature. Once again, this is not a reason to throw out THD-20, but is a cautionary note to take care in interpreting it.
On the other hand, if you do have THD-20 below 0.001% as measured under a large number of conceivable conditions of load and power level down to very low power, then there is very little wiggle room for the presence of much of any nonlinear distortion of any kind in the amplifier. BTW, if possible, this THD-20 number should hold under conditions of output stage thermal variations where transient thermal mis-tracking may cause higher output stage distortion (this is tough to measure).
Once again, if you built this amplifier with poor quality capacitors whose sonic degradation did not show up as nonlinear distortion, the amplifier still might not sound great.
Cheers,
Bob
Bob Cordell said:
Hi Bob,
Does this imply that (by whatever means) you cannot measure the 'sonic degradation' introduced by such caps at all?
Cheers,
Edmond.
Many thanks to all who commented about the scope.
I'm going to replace the one I ordered with Regol DS1102E 100MHz, unless you may tell me why I Should go for 200MHz one.
I'm going to replace the one I ordered with Regol DS1102E 100MHz, unless you may tell me why I Should go for 200MHz one.
Joshua_G said:
Hi Joshua,
This scope looks like a very good choice for the money.
Alex
P.S. AFAIK Rigol is OEM for Agilent
will a 100Msps digital scope have as much HF resolution as a 30MHz analogue scope?
Or will it be no better than the resolution given by a 10MHz analogue scope?
Or will it be no better than the resolution given by a 10MHz analogue scope?
I would like to tell my hf oscillation story that happened over 15 years ago.
When Dick Marsh developed his new caps along with Bas Lim at Reliable Capacitor, he was VERY adamant to put them in every audio product he could talk people into.
I, already, used Reliable Cap RT .1 uf devices (film and foil polystyrene) but that was not good enough for him, as he had 'improved' the cap to be better at high frequency bypassing with much better ESR.
So, without my knowledge, Michael Percy was asked to replace my REL RT caps with Dick's new REL caps of the same value for a 3'rd party customer in a VENDETTA phono stage.
Well, the caps didn't fit well in the same spot, so the leads were left slightly long.
Guess what? It oscillated, but at a frequency higher than could be seen with a 20MHz scope.
Michael Percy contacted me and I fixed it, without replacing the new high frequency caps. Without at least a 100MHz scope, I could not have seen the problem, and with my 350MHz scope, the problem was obvious.
When Dick Marsh developed his new caps along with Bas Lim at Reliable Capacitor, he was VERY adamant to put them in every audio product he could talk people into.
I, already, used Reliable Cap RT .1 uf devices (film and foil polystyrene) but that was not good enough for him, as he had 'improved' the cap to be better at high frequency bypassing with much better ESR.
So, without my knowledge, Michael Percy was asked to replace my REL RT caps with Dick's new REL caps of the same value for a 3'rd party customer in a VENDETTA phono stage.
Well, the caps didn't fit well in the same spot, so the leads were left slightly long.
Guess what? It oscillated, but at a frequency higher than could be seen with a 20MHz scope.
Michael Percy contacted me and I fixed it, without replacing the new high frequency caps. Without at least a 100MHz scope, I could not have seen the problem, and with my 350MHz scope, the problem was obvious.
x-pro said:
glad you said this.
it applies to audio too.
i mean 5x sampling minimum for audio.
AndrewT said:
I personally hate digital scopes. Low rez (often 8bits) and sampling/aliasing artifacts make some measurements difficult. People forget how much the brain can fill in with analog and how much needs to be filtered out with digital. Yes one can learn to do it, that's not the point.
On the scope issue can anyone compare the picoscope vs. Rigol software? Picoscope lists Labview support which is a plus.
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