file True Lightweight Amp performance at 4/8 ohm stereo

9 years 3 months ago #12861 by jsg
There's no reason why switch-mode convertors can't do lots of power. They control the motors in electric trains, and are even used to convert between AC and DC at the UK-France undersea grid link (gigawatt range).

When coming off a single phase, one issue is that the mains supply momentarily stops giving you power 100 times a second. This means you need reservoir capacitors and, give or take, you need the same amount as for a linear amp (I know there are arguments about this, but they are quibbles really).

So a small, light amp still has to fit the same contingent of caps as a big heavy one. Capacitors themselves get better in terms of energy density, and may improve rapidly if some of the electric car reserarch goes mainline, but for now, I would hope to see a *lot* of caps in a lightweight amp.

My cheap synq units (class D) do not really have enough caps for me to be confident that they can deliver their rated output for longer than it takes them to discharge - fine for a peak, but not for what you're thinking of, Lev. I believe the big Matrix amps are better, but haven't seen inside one.

I think you are right that reservoir draining will be less of a problem at 8 ohms, because you are drawing less current, but you get lower rated power. You may as well just over-spec the amps - or contact "Joe's heavy duty locomotive power systems ltd" :)

Ars est celare artem

Please Log in or Create an account to join the conversation.

9 years 3 months ago - 9 years 3 months ago #12862 by saul

jsg wrote: There's no reason why switch-mode convertors can't do lots of power. They control the motors in electric trains, and are even used to convert between AC and DC at the UK-France undersea grid link (gigawatt range).

When coming off a single phase, one issue is that the mains supply momentarily stops giving you power 100 times a second. This means you need reservoir capacitors and, give or take, you need the same amount as for a linear amp (I know there are arguments about this, but they are quibbles really).

So a small, light amp still has to fit the same contingent of caps as a big heavy one. Capacitors themselves get better in terms of energy density, and may improve rapidly if some of the electric car reserarch goes mainline, but for now, I would hope to see a *lot* of caps in a lightweight amp.

My cheap synq units (class D) do not really have enough caps for me to be confident that they can deliver their rated output for longer than it takes them to discharge - fine for a peak, but not for what you're thinking of, Lev. I believe the big Matrix amps are better, but haven't seen inside one.

I think you are right that reservoir draining will be less of a problem at 8 ohms, because you are drawing less current, but you get lower rated power. You may as well just over-spec the amps - or contact "Joe's heavy duty locomotive power systems ltd" :)

perhaps the most influential post ever

Please Log in or Create an account to join the conversation.

9 years 3 months ago #12863 by levyte357

jsg wrote: There's no reason why switch-mode convertors can't do lots of power. They control the motors in electric trains, and are even used to convert between AC and DC at the UK-France undersea grid link (gigawatt range).

When coming off a single phase, one issue is that the mains supply momentarily stops giving you power 100 times a second. This means you need reservoir capacitors and, give or take, you need the same amount as for a linear amp (I know there are arguments about this, but they are quibbles really).

So a small, light amp still has to fit the same contingent of caps as a big heavy one. Capacitors themselves get better in terms of energy density, and may improve rapidly if some of the electric car reserarch goes mainline, but for now, I would hope to see a *lot* of caps in a lightweight amp.

My cheap synq units (class D) do not really have enough caps for me to be confident that they can deliver their rated output for longer than it takes them to discharge - fine for a peak, but not for what you're thinking of, Lev. I believe the big Matrix amps are better, but haven't seen inside one.

I think you are right that reservoir draining will be less of a problem at 8 ohms, because you are drawing less current, but you get lower rated power. You may as well just over-spec the amps - or contact "Joe's heavy duty locomotive power systems ltd" :)



Ah, love it when experts speak..

Would say also "many" expensive lightweight amps don't have enough caps either..

Now to delete all that useful info, before anyone else sees it.. :lol:

\"When in Vegas, do as the vegasians do\".

Please Log in or Create an account to join the conversation.

9 years 3 months ago #12864 by saul
smiley36 yes

Please Log in or Create an account to join the conversation.

9 years 3 months ago #12865 by jsg

saul wrote: smiley36 yes


Of course if was just the cost of a few caps, people would put more in. The real truth is that insufficient caps "throttle" the total power throughput by forcing early clipping. So the output stages and power supply carry less current and run cooler.

An interesting experiment would be to get an amp, max it into it's lowest rated load, and measure the average mains current. Then desolder the reservoir caps one by one and see that current fall (be sure to keep + and - rails matched). By some companies' measures, the power rating would be the same until you took out the last pair of caps, at which point the amp would only be useful for industrial techno.

Ars est celare artem

Please Log in or Create an account to join the conversation.

9 years 3 months ago #12866 by levyte357

jsg wrote: The real truth is that insufficient caps "throttle" the total power throughput by forcing early clipping. So the output stages and power supply carry less current and run cooler.


Years ago on SP, I got a right royal roasting for basically saying same thing..

How times change... LOL..

\"When in Vegas, do as the vegasians do\".

Please Log in or Create an account to join the conversation.

9 years 3 months ago #12879 by levyte357

Sinfinity wrote:
Im sure I met at least five of the people pictured above at the freespeakerplans recent meet. smiley1


I'm sure some of those people are SP moderators. smiley2

\"When in Vegas, do as the vegasians do\".

Please Log in or Create an account to join the conversation.

9 years 3 months ago #13123 by ΚΔΠШΔЯ
Replied by ΚΔΠШΔЯ on topic True Lightweight Amp performance at 4/8 ohm stereo
Lev, i like your avtar smiley32

Please Log in or Create an account to join the conversation.

9 years 3 months ago #13124 by mykey-

levyte357 wrote:

saul wrote: smiley36

no i was just laughing at what might happen if this was on SP


Yes, all of the closet FFA, Lab Gruppen,PKN, MC2, Powersoft, Camco sellers would be assembling post haste.

:lol: :lol: :lol: smiley32

Please Log in or Create an account to join the conversation.

9 years 3 months ago #13125 by nickyburnell
Replied by nickyburnell on topic True Lightweight Amp performance at 4/8 ohm stereo

levyte357 wrote:

Sinfinity wrote:
Im sure I met at least five of the people pictured above at the freespeakerplans recent meet. smiley1


I'm sure some of those people are SP moderators. smiley2



Funny, I've thought that too.

Please Log in or Create an account to join the conversation.

Powered by Kunena Forum