Bubo
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Posts posted by Bubo
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2 hours ago, Dave A said:
Do you have any similar information on poly caps?
After I finish my slice of carrot cake and PG tips tea
I may dive back in........
On my long list of things is setting up a test rig for caps just for fun
Resistors is another one that easier to demonstrate noise and design.
My thought is to send a tone through the cap and measure using an oscilloscope on the in and out and comparing
Within frequency range, you may be able to characterize a cap the same way you would characterize an amplifier using test tones,
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Capacitor Comparison using Bass guitar and test measurements
Found no real differences in test or audible
Instrument repair tech
https://www.talkbass.com/threads/capacitors-and-tone.1442449/
The musician boards seem keen on which caps to use with instruments
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At different frequencies electrolytic capacitors have different capacitance. Suppose it is 50 uF 16V capacitor (type K50-16), then the measurement results are (using russian E7-14 RCL tester):
1) At 100 Hz - 57,31 uF 2) At 1 KHz - 38,20 uF 3) At 10 KHz - 3,56 uFSo my question is - which frequency the manufacturer had in mind?
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At a frequency where its ESR is negligible compared to its capacitive reactance. Look up its ESR in the datasheet and see if it explains the anomalous results at higher frequencies. – Brian Drummond Mar 4 '17 at 11:23
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1Special electrollytics should be used when high frequencies are applicable, such as with switch-mode circuits. – skvery Mar 4 '17 at 11:40
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Hard to find info about K50-16 russian capacitors, but I have noticed, that for similar types like (K50-15) here it is clearly mentioned test condition: "Capacitance tolerance (25 °C, 50 Hz), %". So I suppose I should use 50 Hz test frequency (in my case only 100 Hz available, but it is closer to truth). – Ernestas Gruodis Mar 4 '17 at 12:37
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Why measure an electrolytic? If it's new and bought from a reliable source just use it. If it's old then don't use it. How much do you value your time? – Andy aka Mar 4 '17 at 14:29
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If its good, why to replace? But how do you know if its good? So this raises the question how to test it properly. – Ernestas Gruodis Mar 4 '17 at 14:42
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You have your question backwards. Instead of asking what conditions you should reference, you should instead start from the conditions which you wish to deal with. If your cap is a filter on the output of a bridge capacitor with a 50 Hz line frequency, 100 Hz is the nominal condition of interest. If you are using the cap as a blocking cap in an audio amplifier, then your audio frequency range is what's important, If you don't know how your cap will be used, it is impossible to tell what test condition is appropriate. – WhatRoughBeast Mar 4 '17 at 15:28
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Yes, I understand. Just want to test as it was tested at factory conditions - at specific test frequency, as they did. Its like testing radio tubes - at some written conditions in datasheet. – Ernestas Gruodis Mar 4 '17 at 17:00
The answer to a slightly different question, which is "what is the standard measurement parameters for electrolytic capacitor capacitance?" is as follows:
Modern electrolytic capacitors use a standardized measurement method to determine their capacitance. This method is 20°C and 0.5VAC at either 100 or 120Hz (which is derived from the traditional common usage of electrolytic caps, which was to smooth the output of a bridge rectifier. That ripple is going to be 2*50Hz or 2*60Hz, depending on the country). The exception is photoflash capacitors, which typically have their DC capacitance measured.
Virtually all electrolytic capacitors will cease being capacitive at all before 100kHz, and beyond that, will be inductive. This is universal to all electrolytic capacitors. Generally, an electrolytic capacitor will gain about 10% capacitance if the DC capacitance is measured. It will lose about 10% by 1kHz (or more in the case of your capacitors - but they say they are designed for DC and ripple applications, so they are probably not optimized for anything above 120Hz).
But to actually answer your question, "at what test frequency should electrolytic capacitors be measured?" They should be measured at the frequency of interest for your application. That's the frequency they should be measured at. Why would you ever measure their capacitance at anything except the frequency of most interest to your planned use?
Which makes me wonder - why are you even doing this? It sounds like you are trying to verify if a capacitor is within spec. There is no reason to do that however, and you are just wasting your time if you are.
The failure mode of electrolytics does not involve a reduction in capacitance, so measuring it and comparing that value to what it was designed to have is not useful.
Beyond that, virtually every electrolytic capacitor, including those russian ones, have pretty awful tolerance. They can vary from -20% to +80% the rated value. So even if loss of capacitance WAS a valid way to determine if an electrolytic had gone bad or not (which it isn't), then a capacitor that reads the right value might have began life at +80% that value, and has lost nearly half of its capacitance, but you'd never know. Not that this ever happens though.
The failure mode of electolytic caps is that their electrolyte dries out. This does not have a meaningful impact on their measured capacitance. What it does do, however, is cause ever increasing ESR, until eventually the ESR is so high that they are no longer useful as capacitors. Even then, they will have the 'right' capacitance. So I can think of nothing useful being accomplished by verifying the actual capacitance value.
Now, if you don't know the value of a capacitor, because the label has fallen off, the lettering rubbed off, or whatever, then that's when you can do something useful by measuring the capacitance. Or if you need to verify the capacitance at a specific frequency of interest.
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Capacitor Self-resonant Frequency and Signal Integrity
https://resources.pcb.cadence.com/blog/2019-capacitor-self-resonant-frequency-and-signal-integrity
Frequency dependent capacitor for AC sweep analysis in LTspice
Capacitor AC Response
The frequency dependent impedance of a capacitor is called capacitive reactance.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/accap.html
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I have to believe that the Cap mfgs must run frequency and DC leakage tests for their products to characterize them.
And that the equipment mfgs must bring in the top 10 meet or exceed spec caps to test and listen to in the design.
Thanks to Deang for his measurements
This is the spec sheet from Nichicon's premium "audio" capacitor Muse
Measurement made at 120HZ
Not sure I understand Tangent of loss spec, loss across cap uniformity at tested frequencies ?
http://www.nichiconcapacitors.com/pdf/e-ukz.pdf
https://www.nichiconcapacitors.com/product/nichicon-kz-muse-1000uf-25v/
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1 minute ago, jdmccall said:
In light of all preceding, which is "best": an amp rated 70W into 8 Ohms / 140W into 4 Ohms, or an amp rated 275W into 8 Ohms and 400W into 4 Ohms? Which, if either, would sound cleaner and more dynamic driving speakers that dip to 4 Ohms at some frequencies? .....asking for a dumb guy I know.
The 75 W amp looks like a more robust design on one metric
The second amp may have problems with peaks
You also have to look at SN, THD etc....
YMMV
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This is a review of a headphone amp, not hard to extrapolate to an amp
Charts with the measurements
Review and Measurements of Massdrop THX AAA 789 Amp
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Perhaps the question is: Is a more Robust Amplifier more desirable ?
A. Yes
It can handle a greater number of variances off of the ideal load.
Greater power reserves and the ability to deliver without distortion
The same goes for performance at higher and lower frequencies
When the Engineers design an Amp, they should and most likely Characterize it in the lab with a variety of load conditions, inputs and faults. To see how the Amp handles them, compared to the design.
"High Current" to me is more of a Marketing Slogan
I stumbled across the THX Lab tests they use to characterize Amps once, I wish I had saved it.
Might have been over 200 measurements under varying conditions to characterize the amp and determine if it was in tolerance to meet THX defined loads
QuoteWe refer to the THX controller as both dedicated surround sound processor/preamplifiers, and the processing section of integrated receivers.
There are two distinct halves to the certification of a THX Controller. The first is the actual performance metrics, shown in the table at right. As you can see, it goes well beyond any review you’ve ever read, including our own best. What is absolutely key here is that these are not simply “minimums” a product must meet, but many are actually design considerations. For example, the line level outputs must not only meet a certain voltage capability, but their output voltage must be a certain level relative to an input signal, be it analog or digital.
https://hometheaterhifi.com/editorial/what-it-means-and-how-to-use-it/
The THX Controller
Metrics Tested on THX Controllers:
Reference Output Voltage
Voltage Gain
Input Impedance
Gain Control Range
Gain Tracking of the Master Gain Control
Overload Source Voltage
D.C. Bias Current at the Input
Maximum Output Voltage of Low-Level Outputs
Output Source Impedance
Polarity
D.C. Offset at the Output
Frequency Response Deviation
Signal Time Delay
Noise Output Voltage
Input Level Indicator (Clipping Indicator)
Video Path Switching
Video Level
Sync Level
Bar Tilt
Pulse/Bar Ration
K-Factor (K-2T)
Frequency Response Amplitude (0.5 to 4.2 MHz)
Group delay (0.5 to 4.2 MHz)
Chroma Gain
Chroma Delay
Differential Gain
Differential Phase
Noise
Video Conversion
Harmonic Distortion and Noise
Difference-Frequency Distortion
Dynamic Range
Digital Data Sampling Rate Support
Input Mode Control and User Interface Design
Input Mode Switching
Automatic Detection of Data Types
Output Modes and Post Processing
Equalization and Tone Controls
Signal Headroom
Bass Management
Filter Characteristics
LFE Channel Level Scaling
Loudspeaker Position Time Synchronization
Auto Calibration
Auto Setup
Output Levels
Dialogue NormalizationAnother key element that THX requires for receivers and SSPs is the reference setting for volume control. When a system is calibrated according to the manufacturer’s instructions, “0.0 dB” on the volume control corresponds to reference level playback. In turning the volume down, the volume level is expressed in -dB, or how many dB below reference level you are.
Metrics Tested on THX Amplifiers:
Reference Output Voltage
Voltage Gain
Output Current
Output Source Impedance
Overload Restoring Time
Stability with Capacitive Load
Harmonic Distortion and Noise
Modulation Distortion
Difference-Frequency Distortion
Noise Output Voltage
Phase Response
D.C. Offset at the Output
Hum
Crosstalk
Acoustic Noise Level
Mechanical Noise
Input Sensitivity
Input Impedance
Output Impedance
Load Impedance Range
Voltage Output Capability
Current Output Capability
Transient Output Capability
Transient Overload Recovery Time
Asymmetrical Clipping
Frequency Response
Phase Response
Phase Margin
Time
Total Harmonic Distortion
Intermodulation Distortions
SMPTE IM Distortion
IHF IM Distortion
DIM 30 Distortion
Noise
Hum
Radiated Interference
Conducted Interference
CrosstalkMake no mistake: THX Ultra power amplifiers tend to be very powerful. We’ve never seen one with less than 100 watts/channel continuous RMS, full band, all channels driven, BUT because of the “practical sum” THX has defined for themselves, even seemingly modest receivers under $1,000 can get THX Select2 certification and provide a satisfying experience for a lot of people who can’t afford a stack of THX Ultra power amps (we’ll talk about Select- vs. Ultra-Certification a little later).
Metrics Tested on THX Speakers:
Axial Frequency Response Analysis
Directional Characteristics
Sensitivity
Impedance
Harmonic Distortion
Low Frequency Cut Off
Phase Angle
Stray Magnetic Flux
Maximum Output Level
Acoustic Noise Level
Polarity
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If I win the lottery.....
A barn Conversion
So I can pack it full of gear that is wired so I can listen to all of it.
Pair of Jubes
Would probably need a larger TV in the middle.
I once saw listed a pair of Altec Bass horns, exponential?, standing about 8 ft tall and 2ft wide, guess about 8 ft deep, 1 or 2 driver.
I want a pair of those for watching The War of the Worlds 1953
Jeff Wayne - The Eve of the War (Official Audio) ft. Richard Burton, Justin Hayward
208,407 views
•Jan 30, 2020
https://www.youtube.com/watch?v=Poii8JAbtng
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I was looking at a Marantz 8000 surround receiver the other day
15 years old ask was $200
Superb built in DAC and performance measurements, 100Wpc
I like to use the older surrounds as Stereos with built in DAC etc
Some of these have superb tuners
You would have to have a phono pre amp
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The reasons young people are flocking to vinyl is:
No quantization error if analog source
No loudness wars, won't fit on vinyl
No psycho acoustics added to trick the ear for low bit rate and $2 ear buds.
Guttenberg interviewed a friend who masters music, asked which mastering is the best, answer, the version for vinyl.
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Excellent and to the point.
Last time I stopped by a Magnolia Center, I had them play one track with Poe using their totl Marantz
and switching between speakers, most expensive to least expensive (monkey coffins)
Her voice was unintelligible on most, difficult on a few and clear on the Klipsch R series book shelf
Sales mgr was upset and stopped the test. Put on something was mostly rock instrumentals turned up.
My understanding is that Magnolia isn't allowing people to bring their own music as of 1-2 years ago.
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Altec produced a lot of great products
The 19 was considered their best home speaker by many
The cabinet with 2 connected chambers is a different design philosophy than the LaScala
19 = 2 drivers, better driver alignment
LaScala 3 drivers, fully horn loaded. 19 is 2-way so one less crossover point to manage
LS probably better for vocals with crossover at 400hz vs 1200Hz
19 goes to 30Hz, LS bottoms out at 50Hz
If I had room I would own a pair of 19s in addition to all my other gear.
I have always loved the LS for female vocals.....
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The no brainer improvement on the Fortes would be the addition of a protective metal cage over the rear radiator, black.
Would the tweeter be better if sweeter sounding but rolled off after 17khz ? take one of the horns from the better reference and use it as the tweeter ? Would the Forte 4 be better with no tweeter, just two drivers ? A larger, fuller range mid horn ????
If the Tweeter is eliminated, a larger horn becomes possible, and or dual woofers.
The Forte is a compact combination of frequency range 30-20Khz, and woofer mid driver alignment. would be better of tweeter aligned too.
Alignment is something Altec and JBL seemed to focus on.
What would be the benefit of more height ?
I am suspect of MDF, prefer Birch Cabinets.
Cross bracing and damping are cheap and easy real estate to add, no brainers.
What effect would porting have on sound quality if any, would it defeat the radiator ?
Each of the Heritage speaker lines was a different design philosophy, Forte being radiators.
Heresy has better Horn Woofer driver alignment, tweeter too short
LaScala fully horn loaded, woofer horn 1 ft longer than mid horn etc etc.
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13 hours ago, Mars1 said:
"the list from (3 to 4)..." referring to the speaker
- I like to see a removing of the rear radiator,
- increasing the height to a nice 42 to 43 inches perhaps, maybe little less,
- but increased height nonetheless,
- better wood cabinet,
- better crossover components perhaps as well, and
- front ported: single, dual, triple.
I guess with the front ports it'll be like the Corns and Chorus'. But that's what I like to see.
When I look at any work product to evaluate it
The question I ask myself is:
What would I add to the Product to improve it ?
What would I take away from the product to improve it ?
Ranking the changes can be done by category
- Mandatory to have a sellable product
- World Class cut above the competition
- Nice to have features that have some value
So yes, the question is what would you add or take away from the Forte 3
that should be incorporated into the Forte 4 ?
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On 12/29/2020 at 10:20 AM, wilkic65 said:
They sound fine to me
recap the crossovers horn seals
or change woofer.
Caps have a shelf life, 30 years it's time
New gaskets for the screw on compression driver, they dryrot
Crites and others have the parts.
Leave the woofer alone, rotate makes sense
Wires can be replaced with standard 12GA speaker cable
If you don't want to solder a new wire, you can strip,
splice a section of new wire soldered and shrink-wrapped.
If you are uncomfortable, ask your friends, one of them knows how to solder.
If the cabinets are oil finish, watco natural oil them.
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Question
With the current Forte 3, what would you add, what would take away ?
The list from 2 to 3 was easy....
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18 hours ago, billybob said:
reproduce with accuracy any flaw in a source.
Here it is
You may discover you don't like a favorite band,
or hear the added noise for psycho-acoustics
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On 12/28/2020 at 9:22 PM, jvs1670 said:
That is one comprehensive list, thank you. Also worries me because I think I'm in over my head even attempting most of what you suggest. I'm gonna take a peek inside again but I think I'm going to have to get it looked at when all is said and done. Guess I don't mind spending a few bucks if it can be fixed.
Take the lid off and blow it out with a can of compressed air, unplugged
Think of it as a first kiss and jump in.......
Good solder joints look like shiny Hershey's kisses, broken ones look broken, dull ones are cold joints.
Bulged and leaking capacitors look bulged and you can see if it took a dump on the board.
You can't damage anything by looking, and learning.
Best
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Better than expected, not sure what the message of the film was.
I was expecting the usual "everything is hopeless" and didn't get it thankfully.
Would be good on the big screen, wide panoramic shots,
and might have had the feel of a real WW1 bayonet charge in the theater.
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On 12/25/2020 at 10:33 AM, Bharath Abhishek said:
Hi.. Have recently purchased a HT Setup with Denon x1600 Receiver, R620F towers, R52C centre.. m confused about surround speakers.. should I opt for R14S or R41M...m considering for Upgrading to Atmos with elevation speakers with Polk OWM3.. Suggestions or welcome..
Either will work fine.
I have a small room 5Mx4M approx. and use the surround S style in the rear corners angled in, sitting on shelves. They likely have greater dispersion than the R41s. You can try both and if S style, use the other pair for a bedroom system.
If you have a bigger room in the future, you can use the S for the mid wall speakers
Mine are Klipsch10 years earlier speaker line, but same configs.
YMMV
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48 minutes ago, dwilawyer said:
It may be his best path is a HT Receiver, or pre.
The best way to make 2 speaker sound like 4 speakers, is to add 2 more speakers....
May be fast and cheap to add two low cost rear speakers and experiment with synthetic surround and various delay aka Concert Hall options. Can KGs be had cheap ?
High quality 15 year old Surround Receivers are literally a dime a dozen, I usually pay less than $20 if in good working order. Who cares how much they paid, the market does not want them without the latest chip sets .......
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What we listen too is .5 watt or less
2 Watts is screaming
How an amp sounds at 100W is irrelevant for the high efficiency speakers
The SS amp may have tighter engineering tolerances and less drift, tubes do age as they are consumed.
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Not sure what you mean by ambient ?
Resonance ?
Capacitor Rabbit Hole. Just How Do You Measure?
in Technical/Restorations
Posted
My thought is to send a tone through the cap and measure using an oscilloscope on the in and out and comparing
Within frequency range, you may be able to characterize a cap the same way you would characterize an amplifier using test tones,
I'm no xover guy....but the caps roll off at different freqs, combined with inductors becoming more resistant with frequency
The faster they roll off the steeper the crossover point......
It should be possible to characterize a cap like an amplifier within it's range.