How do I determine my amp's output impedance?

[JMFahey]

A current amp does not care if you short the outputs, so none is incorrect.

dave

Don´t know what a current amp is, I bet you don´t either.

By dictionary:

current adjective
cur·​rent | \ ˈkər-ənt
, ˈkə-rənt\
Definition of current

(Entry 1 of 2)
1a archaic : running, flowing
b(1) : presently elapsing the current year
(2) : occurring in or existing at the present time the current crisis current supplies current needs
(3) : most recent the magazine's current issue the current survey
2 : used as a medium of exchange
3 : generally accepted, used, practiced, or prevalent at the moment current fashions current ideas about education

I mean, if you are writing in English, that is.

Glad to talk with you but please write your doubt or question in English so we can go on.

 

[GM]

I've got one in the shop, it's called an arc welder.

Anyway, those definitions don't apply to electrical devices.

Voltage Vs current source amps: Voltage source vs. current source amplifiers | Audiogon Discussion Forum

GM

 

[Bayou Self]

@GM
longer wall mostly windows, desk centered against wall, speakers on either side

 

[planet10]

Don´t know what a current amp is, I bet you don´t either.

a current amp is one with a very high output impedance. A voltage amp strives for zero output impedance, a current amp infinity.

In practise higher impedance than the speakers.

I have had a current amp in-house and have followed the exploits of Nelson with the F1 & F2, and helped Joe with his.

Have you read ESA’s book on the subject? Or even followed his thread?

dave

 

[mp9]

I was under the impression that I needed a more sensitive (greater than 92 dB) speaker to get the effortless sound I'm looking for from my little amp. Unless i am mistaken, the Markaudio drivers are between 85 and 90 dB. Maybe if I go for the FH XL with the FE168EZ? Or does that driver also require a high output impedance amp?

Reason behind Mark Fenlon giving us the 92db (91.73db) A12p driver.

My pair are still waiting for a box (FHXL JANE variant), but play plenty loud sitting on a shelf driven by a 45 triode tube 1.5Wpc SET amp.

 

[planet10]

My real world measurements put the A12p closer to a dB more sensitive than the A10p but it can also move more air.

dave

 

[GM]

@GM
longer wall mostly windows, desk centered against wall, speakers on either side

Arg! FWIW, the sound wall should be well damped. OK, a little confused now; is this primarily a sitting at the desk system or sitting further away where?

GM

 

[GM]

92db (91.73db)......but play plenty loud sitting on a shelf driven by a 45 triode tube 1.5Wpc SET amp.

Please define 'plenty loud' and from how far away because with typical recordings the amp runs out of steam with a 92 dB/m eff. driver at ~74 dB/m average, which is lower than many folks watch the evening news.

GM

 

[Bayou Self]

GM,
Primarily a "sitting at the desk system", but I would like to have a bigger sound than a desktop bookshelf system--already have that!

 

[mp9]

Please define 'plenty loud' and from how far away because with typical recordings the amp runs out of steam with a 92 dB/m eff. driver at ~74 dB/m average, which is lower than many folks watch the evening news.

GM

Good question GM, IDK, when I get a chance I am willing to do a little experimenting for you, take some crude measurements with music playing using my old RatShack sound level meter and get back to you on that.

Will add, I generally try to keep listening levels ~80 - 85db on the upper end to limit hearing damage. My rooms are also on the small side.

 

[mp9]

Please define 'plenty loud' and from how far away because with typical recordings the amp runs out of steam with a 92 dB/m eff. driver at ~74 dB/m average, which is lower than many folks watch the evening news.

GM

Not having a problem hitting 90db - 92db peaks in the small room with the drivers on a desk aimed up at the wall and powered by the 1.5wpc 45 type tube SET amp. It sounds plenty loud to me. With more complex music, above 94db and I'm detecting some "polite" clipping easily dealt with by turning the volume down a notch. Again, small room and IDK how accurate the old RatShack "analog readout" sound level meter is.

 

[GM]

Well, if hitting driver eff. 1 W peaks, the average is 15-20 dB lower or are you only listening to highly compressed music, i.e. no obvious dynamic headroom? What I usually refer to as 'Muzak'/elevator music.

GM

 

[Bayou Self]

GM,
Could you please elaborate? Thanks.

Arg! FWIW, the sound wall should be well damped.

 

[gabdx]

wow.... again , 20 posts, and no one is telling him how to either

calculate the amp output Z

measure the amp output Z

Measuring input impedance and calculating output impedance calculation calculate audio amplifier op-amp how to measure impedance voltage gain total loudspeaker speaker microphone resistance resistor bridging matching test load loudspeaker source resi

just don't mess up

 

[mp9]

Well, if hitting driver eff. 1 W peaks, the average is 15-20 dB lower or are you only listening to highly compressed music, i.e. no obvious dynamic headroom? What I usually refer to as 'Muzak'/elevator music.

GM

GM, this is a very preliminary observation, my A12p drivers aren't even in a box yet. I suspect I'll use the 3wpc 2A3 to drive them when they are and I do expect it to be sufficient power.

Btw, I listen to many genres of music, prefer new music, rock, rap, hip hop, alternative, classical, some jazz, sorry no muzak or easy listening.

 

[mp9]

wow.... again , 20 posts, and no one is telling him how to either

calculate the amp output Z

measure the amp output Z

Measuring input impedance and calculating output impedance calculation calculate audio amplifier op-amp how to measure impedance voltage gain total loudspeaker speaker microphone resistance resistor bridging matching test load loudspeaker source resi

just don't mess up

...about time, Thx.

 

[mp9]

highly compressed music,

GM

YouTube

 

[GM]

GM,
Primarily a "sitting at the desk system", but I would like to have a bigger sound than a desktop bookshelf system--already have that!

Hmm, AFAIK none of the BLH/BVR speakers are going to have the driver high enough for desk ear levels unless spaced up, but then horn loading is compromised.

Sound wall = where the speakers are.

GM

 

[GM]

Good question GM, IDK, when I get a chance I am willing to do a little experimenting for you, take some crude measurements with music playing using my old RatShack sound level meter and get back to you on that.

Will add, I generally try to keep listening levels ~80 - 85db on the upper end to limit hearing damage. My rooms are also on the small side.

Thanks, but of importance to me is how compressed the music you listen to is with 1.5 W, knowing that folks into tubes often will overdrive them [intentionally or otherwise] because they like its euphonic distortion.

TV, online/youtube, vast majority of CDs have little dynamic headroom, so one can get by with low eff. speakers, low power amps.

Do you have the calibration curve for the analog RS SLM? Mine apparently grew legs and left for someone who will use it more often than every decade or two .

GM

 

[GM]

sorry no muzak or easy listening.

Again, it's just what I call very low dynamic headroom music, which sadly is much of what's available today is.

GM