Output impedance

For most of the current equipment, I believe they are very low. Typically around 50 Ohms.

Joe

Do you want to know this for the pre or power amp?

quote:

Originally posted by DaveBk:
Do you want to know this for the pre or power amp?

I believe output impedance is only quoted with respect to preamps and and source equipment line cd players and phonoamps. I have never seen output impedance quoted for a power amp, Instead, power amps have their input impedance quoted instead. Generally, you want the ratio of input impedance over output impedance to be as high as possible, and as a general rule, the ratio should be at least 10 or more, and preferably around 100. For Naim power amps, the input impedance for poweramps is about 20,000 Ohms and the output impedance for CD's and preamps is around 50 Ohms, so the ratio is 400. For valve/tube amps, the figures are typically 100,000 Ohms for the poweramp input impedance and 800 Ohms for the preamp, so the ratio is around 125.

Generally, there are little electrical compatibility problems matching a transistor preamp to a valve poweramp. However, there could be problems matching a valve preamp to a transistor poweramp.

This is a very general comment.

Thank you Joe. It is power amplifier output impedance i would like to know in order to calculate the damping factor with my loudspeakers.

When Hi-Fi World magazine review Naim amps they often quote a damping factor of around 15 which they describe as "low".

Regards, Chris

quote:

Originally posted by Christopher_M:
When Hi-Fi World magazine review Naim amps they often quote a damping factor of around 15 which they describe as "low".

Regards, Chris

I would be very surprised if Naim amps have such a low damping factor. A damping factor of 15 is very low, even for valve let alone transistor amps. A figure of a few hundred is more typical. At the other extreme, I've seen some transistor amps (such as Soulution of Switzerland) quote a damping factor of 10,000 which is exceptional

Joe.

quote:

Originally posted by joesilva:

I would be very surprised if Naim amps have such a low damping factor.

Joe

I may be barking up the wrong tree, but could the low damping factor be due to the fact Naim power amps don’t contain an inductor in the output stage. This is the reason that Naim advise the use of a specific type/minimum length of speaker cable to ensure stability. Damping is performed by the speaker cable.

quote:

Originally posted by fatcat:

quote:

Originally posted by joesilva:

I would be very surprised if Naim amps have such a low damping factor.

Joe

I may be barking up the wrong tree, but could the low damping factor be due to the fact Naim power amps don’t contain an inductor in the output stage. This is the reason that Naim advise the use of a specific type/minimum length of speaker cable to ensure stability. Damping is performed by the speaker cable.

I'm no electronics engineer, but if the damping is performed by the speaker cable, then theoretically the longer the speaker cable, the greater the damping. But that does not make sense as the damping ultimately depends on the amp to put a brake on the speaker drive units over-shooting. The longer the speaker cable, the more difficult that would be for the amp to achieve.

Fewer output devices creates lower damping factor as multiples in parallel lower the impedence. I much prefer the fewer output device approach as dynamic matching is a non issue. Damping factor is still plenty hign with any direct coupled SS transistor amp and other factors can have as much or greater effect on percieved bass control and speed. If you've ever heard a 300w amp that sounded slow, you'll understand. All of those have very high damping factors.

I measured Ri for my NAP200 once and I think it was around 250mOhm @40Hz. Which leads to a Df of around 30 for an 8Ohm load. In all magazine tests I can remember DF is also around 30 for most Naim amps (150, 200, 250, Nait). No really high, but sufficient

quote:

Originally posted by yeti.fro:
I measured Ri for my NAP200 once and I think it was around 250mOhm @40Hz. Which leads to a Df of around 30 for an 8Ohm load. In all magazine tests I can remember DF is also around 30 for most Naim amps (150, 200, 250, Nait). No really high, but sufficient

Thanks Yeti.

quote:

When Hi-Fi World magazine review Naim amps they often quote a damping factor of around 15 which they describe as "low".

To say a bit more, HFW would then conclude that the particular Naim amp under test would have full bass. At which point I draw my own conclusion that the amp will work well with speakers that are highly damped (or 'over-damped' which I think is their phrase). Amongst others I place n-Sats, Kans and SBLs in this category. Experience has shown that the Naim amps I've owned or heard in a dem (and that HFW have tested) have indeed worked very sweetly with these speakers, especially SN and SBLs.

Hope that helps.

Chris

last I asked output impedance was .22 ohms for all amps.

When? All amps?

ATB from George

Year was 2002 and for all power amps.
Things may have changed - shoot Naim an inquiry.
Here's the reply I received.

Hi Ken,

The output impedance across the entire range is 0.22 ohms (yes,
really....

Regards,
Richard
Naim

quote:

Originally posted by kosnibor:
Year was 2002 and for all power amps.
Things may have changed - shoot Naim an inquiry.
Here's the reply I received.

Hi Ken,

The output impedance across the entire range is 0.22 ohms (yes,
really....

Regards,
Richard
Naim

Not far from Yeti's observations then. That means a damping factor around 36 with a 8 ohms load.

Is the damping factor a musical factor?

quote:

Originally posted by munch:
What speakers do you have?
Cant you just play music through them and then sort things out.
Numbers are a bloody pointless
This makes me wont to drink some bleach
Use you ears man.
Stu

Hey Stu, I listen to a lot of music and I like my system the way it is right now. Just want to understand things. The other day, I swapped a pair of 25' Naca 5 for a pair of 8'. I immediately noticed more *punchy* bass notes. I believe it has something to do with the overall damping factor ; a combination of amplifier output impedance, cable lenght and size plus speaker impedance.
Pierre

It may actually be a little bright at that length and actually have a little ring to it. Maybe you like less damping. A bit more mid(ring) can give the bass a punchier sound. Try 12-17' It's stable and vibrant. There's more to this like overall load which may or may not be OK with 8' but a bit more is almost always better. Damping factor and slew rate are of small import in most cases once you have enough current for the purpose and the output impedence is low enough to drive the load in a linear fashion. These #s are well within that for the audio band.

quote:

Originally posted by GFFJ:
Is the damping factor a musical factor?

Certainly not but with large diameter woofers a sufficient amplifier damping factor may be preferable as I understand it.

Naim amplifiers should be ok with large woofers as they can easily move a pair of DBL's.

quote:

Originally posted by js:
It may actually be a little bright at that length and actually have a little ring to it. Maybe you like less damping. A bit more mid(ring) can give the bass a punchier sound. Try 12-17' It's stable and vibrant. There's more to this like overall load which may or may not be OK with 8' but a bit more is almost always better.

I did not hear any brightness or ringing in the last few days.
Does this recommendation of a minimum of 3.5 meters hold true for all post-olive amplifiers?

quote:

Originally posted by cat345:

quote:

Originally posted by js:
It may actually be a little bright at that length and actually have a little ring to it. Maybe you like less damping. A bit more mid(ring) can give the bass a punchier sound. Try 12-17' It's stable and vibrant. There's more to this like overall load which may or may not be OK with 8' but a bit more is almost always better.

I did not hear any brightness or ringing in the last few days.
Does this recommendation of a minimum of 3.5 meters hold true for all post-olive amplifiers?

Yes. It's possible that you're OK but I think Naim knows their product. You're probably not unstable as the new amps seem to be less wire dependant but a slight bit of ring can be hard to detect. Borrow a slightly longer pair, live with it for a few CDs and then put the short ones back. It will probably tell you what you need to know.

quote:

Originally posted by js:It's possible that you're OK but I think Naim knows there product. You're probably not unstable as the new amps seem to be less wire dependant but a slight bit of ring can be hard to detect. Borrow a slightly longer pair, live with it for a few CDs and then put the short ones back. It will probably tell you what you need to know.

I will just cut the 25' pair in half and see what it does. I could use the other half later if I bi-amp with my SN.

cat345, your post interests me because apart from anything, it just goes to show that we all get enjoyment from our Naim systems in different ways!

As I have already demonstrated, I have a very limited understanding of how my system works but I get immense enjoyment of it. You too say you are happy with the sound of your system. It seems that you seek a more rational understanding of how it works, it's not enough for you to know that it does work. But your post makes me ask if it really does work for you?

I could be wrong but I perceive your post as a request for help over speaker choice. I wonder what you would make of a pair of SBLs with your SN in your room. For me, fronted by a CDX2 or better, this is a blistering combination - for the reason I've already outlined.

Of course I may have completely got the wrong end of the stick, in which case I apologise.

Best, Chris