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March Audio

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#62
As much as this might be a fun research project....

Isn't capacitor tweaking really last century's battle?

When it comes to capacitors, I usually think, "Why bother? Go active DSP and make your tweaks in software."

When it comes to electronics, I think, "Why bother? Do the voicing in the FPGA, DSP, or wherever it is you're doing signal processing.."

Delving into the voodoo nuances of capacitors seems like a retrograde research project akin to learning alchemy.*

*this being said by someone who owns a turntable, but uses a ADC-software-defined-DSP-based phono stage...FWIW :)
Totally agree. I spent a lot of time playing with passive XO for my speaker project, playing with different caps. Going to dsp made a significant improvement. Ditch the caps! :)

In now have access to a VNA so could analyse them but why bother :)
 

Wombat

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#63
I would like to propose/recommend that a separate category be created for the purpose reporting measurements and testing results of higher-end audio capacitors. Not listening tests, but purely bench tests using measuring equipment to determine if any meaningful differences can be found between mid-priced audio capacitors vs higher-end “boutique” audio capacitors. You could start with some of the higher-end capacitors that have received the highest ratings on this site: http://www.humblehomemadehifi.com/Cap.html and then compare them with some of the mid-level audio capacitors.

I realize capacitors don't actually qualify as "equipment" but I think there would be a great deal of interest and benefit in doing these tests. Logistically, shipping capacitors back and forth would also be much easier.

Party pooper. ;)
 

Wombat

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#65

MiamiBoy

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#66
Amir, I do appreciate you receiving my request so agreeably especially considering it is coming from a new guy on this forum in his very first post.

I realize I should have first asked whether you are aware of and able to perform such tests that would go beyond what is normally found in manufacturer’s datasheets? If not, then “what would be the point?” But if you are and those test results might either support or refute the glowing reviews and exorbitant prices then I think it would be of value and in keeping with the mission of this site.

No need to make this a wide and deep testing effort across many capacitors of different types. Keep it limited to just film caps and to only three or four of the most high-end ones made by the manufacturers you previously mentioned. Then perform the same tests on some lower cost film caps for comparison.

If you do decide to move forward with this then please ask for cap donations as I may even have a few spare caps that would qualify. I may even be purchasing some higher-end Mundorf caps soon that I could route your way for testing if your tests are non-destructive.

Cheers,
Henry
 

amirm

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#67
Hi Henry. Your suggestion was fresh and potentially a learning exercise for all of us concerned.

The testing component makers do is devoid of audio application. While I like to first replicate those parametric tests, I also like to then move into system level test with them.

As far as instrumentation, I am fully capable. :) I have a 500 Mhz scope, 3 Ghz spectrum analyzer, my audio analyzer and its high accuracy signal generator, various LCR meters, etc. So tools is not the limitation.

Being able to borrow caps would be great and remove a barrier to getting started.

Do you have a specific project in mind for the caps you are purchasing? If so, we could make that the test bench for the first trial.
 

MiamiBoy

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#68
Amir,

I am not technical, so clarify for me, if the tests are performed “out of circuit” doesn’t that mean they would not be application specific or are you able to replicate circuit parameters of a specific application scenario so that the test results would apply to that application?

In my specific case I own two Cary CAD-805AE SET mono amps that each have three coupling caps. They “couple” three different tubes in the amps connected between the plate of the first tube to the grid of the second tube and so on. (The three tubes are 6SN7, 300B and 845/211.)

The amps have the standard coupling caps which are ClarityCaps mfd ESA .22uf 650vdc. Cary offers two upgrade cap options for the amps. One is the new Mundorf MCap SUPREME EVO SilverGold .22uf 2% 1000vdc just released in 2015. The other cap upgrade option for this amp is the Jensen Copper Foil/Paper-in-Oil/Pure Silver Lead-Out Capacitors. When/if I move forward with the upgrade I will most likely go with the Mundorfs.
 

amirm

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#69
Ah yes, ideally we would have your amp here, measure it with ordinary caps and then measure it using upgraded caps.

Measuring the components by themselves may be revealing but may also be boring and uninteresting.

At 80 pounds your amp is too heavy and delicate to send back and forth. So we need to think of another test harness.

I could do the same thing but with a solid state amp or DAC.
 

Wombat

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#71
Are there tests that can expand on Cyril Bateman's efforts? Will the tester understand capacitors as well as Cyril in order to effectively interpret the results? Cyril made specialised equipment for his tests. It is not something to be undertaken lightly as lack of rigour can only provide fuel to the existing subjective beliefs re caps. There are several shoddy cap tests/comparisons on the WWW which are regularly used to back-up subjective opinions.

Inserting a component into a system and measuring a change may lead to a conclusion that the component caused the difference when it was possibly the result of another component/s being unduly very sensitive to the change due to it being outside of design considerations. Such testing, measurement and analysis is not a casual activity.

However, the transfer function of negative-gain simple passive circuits(pre-amps, crossovers) could be measured with various caps to see if the measured output differences were above the minimum detectable levels for hearing.
 
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watchnerd

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#72
Are there tests that can expand on Cyril Bateman's efforts? Will the tester understand capacitors as well as Cyril in order to effectively interpret the results? Cyril made specialised equipment for his tests. It is not something to be undertaken lightly as lack of rigour can only provide fuel to the subjective beliefs re caps.

Inserting a component into a system and measuring a change may lead to a conclusion that the component caused the difference when it was possibly the result of another components being very sensitive to the change due to it being outside of design considerations. Such testing, measurement and analysis is not a casual activity.
If the outcomes are really that sensitive to the test harness, what does that say for real world applications?
 

Wombat

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#73
If the outcomes are really that sensitive to the test harness, what does that say for real world applications?
Ask audio circuit designers about sensitivity to parasitic oscillations, interference pick-up and layout problems.
 

watchnerd

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#74
Ask audio circuit designers about sensitivity to parasitic oscillations, interference pick-up and layout problems.
Sure those are real. But they're application specific.

If capacitors exhibit different sonic characteristics in different circuits, what's the point of the test harness?
 

Wombat

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#75
Sure those are real. But they're application specific.

If capacitors exhibit different sonic characteristics in different circuits, what's the point of the test harness?

A test harness would have to be 'invisible' or known compensation applied for reliable results.

I can't give an electronics education in a forum post.
 

amirm

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#76
Are there tests that can expand on Cyril Bateman's efforts? Will the tester understand capacitors as well as Cyril in order to effectively interpret the results? Cyril made specialised equipment for his tests. It is not something to be undertaken lightly as lack of rigour can only provide fuel to the existing subjective beliefs re caps. There are several shoddy cap tests/comparisons on the WWW which are regularly used to back-up subjective opinions.
Well, we certainly could try to expand on his work. Looking at his measurements, he is using a lower distortion generator than what is built into my Audio Precision analyzer. On the other hand, my analyzer is digital so I can easily deal with noise and I could get an ultra-low-distortion oscillator. The downside of those and same is true of Cyril's is that they are fixed frequency so can't do sweeps and such with them.

What would be a lot easier and superior to any work done before is to measure a complete digital audio product like a DAC. Then we don't have to worry about fidelity of the signal generator. Not sure what percentage of scenarios this includes though.

Overall your message is well taken that it may take work to get a proper test harness in place.
 
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#77
Limited technical knowhow and chops here, but, like many I suspect, here to learn and maximise my limited resources. Particularly interested in phono preamps should they eventually be on the test bench - seems to be a glut of budget preamps on the market given renewed vinyl interest, and it'd be interesting to see how they stack up against one another.

Enjoyed lurking/ browsing/ learning thus far, many thanks.
 

Wombat

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#78
Limited technical knowhow and chops here, but, like many I suspect, here to learn and maximise my limited resources. Particularly interested in phono preamps should they eventually be on the test bench - seems to be a glut of budget preamps on the market given renewed vinyl interest, and it'd be interesting to see how they stack up against one another.

Enjoyed lurking/ browsing/ learning thus far, many thanks.
Me, too. This is one of the most hyped items in the broader audio catalogue. No rocket science design required, inexpensive components yet astronomical price range.
 
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#80
Thanks, Amirm. Yes...

Art USB
U-Turn Pluto
Musical fidelity V90
Rega Fono MM MK2 or 3
Pro-Ject Phono Box S (Pro-Ject have a confusing number of preamps, though this seems to have decent price/ performance)
Schiit Mani
Graham Slee Communicator
Behringer PP400

Game for anything, really...
 
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