[werd]

Hi werd
almost 80% of power comes from the transformer,and about 20% from capacitors,capacitors are there to filter out the hum from the rectifier ,this had been a lesson for me when dealing with class-a amplifiers,and the filter needed to be big...

Hello

Well then you want a really big transformer

[dlaloum]

Actually the AVS thread is still current, but started a while ago. It seems the necro worked.

BTW, it was my own posting from a week ago in AVS. Perhaps I should have stated that.

I came this forum, looking at the Hypex Ncore class D amps. Looking for some more power (possibly) to occasionally listen to some really loud music from about 2.5 to 3 meters away. Perhaps I should just slide the chair closer. It was instructive to go through the exercise, but I am not looking at 900 watt amplifiers; our house is already heated.

I seriously considered the Ncore's - needed more power as the Gallo Ref3.2's I have seemed to find the 150W (RMS 8 ohms) I was feeding them insufficient - even biamping with an additional amp for the woofer didn't help.

So I experimented by purchasing a twin pair of Crown Drivecore XLS2500's one for the low end, one for the high end (or I could run them both bridged as a left and right monoblock set ...)

The difference was VERY noticeable - I do NOT run at high loudness levels - typical is around 75db to 80db - but the difference was an immediately obvious improvement.

Why not try the Drivecores as a "economy" class D tryout for serious power - if it provides a good improvement then trying a set of Ncores would show you whether you need the additional refinement brought by the big $ versions.

I am gobsmacked by how good my system now sounds - but I have yet to try an alternative at a higher price bracket.

bye for now

David

[Folsom]

Hi werd
almost 80% of power comes from the transformer,and about 20% from capacitors,capacitors are there to filter out the hum from the rectifier ,this had been a lesson for me when dealing with class-a amplifiers,and the filter needed to be big...

Uh... They don't filter much, rectifiers shouldn't hum, and they're actually to keep a constant voltage. They provide current when they try to keep up the voltage.

However, as already stated, you can't provide enough capacitance typically for many of the big inefficient amplifiers that operate on constant current, so yes a lot of juice comes from the wall. But even to keep the voltage up you need a lot of capacitance.

In small amplifiers you can literally have enough voltage and current to run not plugged in for a few seconds for a pittance. You've got more current than you'll ever need, but since the capacitors don't discharge much relatively, they aren't inefficient. The big question is if the unit can dump the current when needed, based on many factors including your source.

[G Georgopoulos]

Hello

Well then you want a really big transformer

For sure,bass always causes power supply(and transformer)voltage drops,it's not about mids and highs but bass,if you dont have a good regulation transformer, power supply wont recover from bass soon enough to power mids and highs,capacitors actually cause a voltage drop when charging from the transformer so capacitors wont recover the ps charge,it's the transformer that makes a difference here,the bigger the better,what do you think?

[S Clark]

What happens when you put the TDA7297 on them? I've driven Piega Premium 5.2's to moderate levels without issue. They're not efficient.

They do rather nicely for most listening, but just can't do large orchestral pieces with any degree of realism. .  So far, I still need the Moscode HR401. 

[Folsom]

For sure,bass always causes power supply(and transformer)voltage drops,it's not about mids and highs but bass,if you dont have a good regulation transformer, power supply wont recover from bass soon enough to power mids and highs,capacitors actually cause a voltage drop when charging from the transformer so capacitors wont recover the ps charge,it's the transformer that makes a difference here,the bigger the better,what do you think?

A well designed smaller amplifier will stagger capacitors some, so you won't see a drop in the mids/highs. This isn't possible with constant current power supplies to the same degree. I'd argue that you might get a benefit from a few high end caps near the transistor, but I haven't tried it.

Capacitors charge/discharge 90 degrees out of phase. For this reason whatever voltage drop they incur won't matter. Worst case scenario at high volumes the amp doesn't get as loud as the voltage at 120v would predict. Not a surprise, everyone knows amplifiers aren't 100% efficient. The only thing you have to worry about is inrush current from the capacitors being discharged too much. In general no design should be predicting full discharge of a capacitor bank post rectification. If that's happening your amp will sound stupid. SOO in general the inrush shouldn't be that bad.

When to use a really big VA transformer? When you've got a constant current power supply! That's the simple answer. You can use a 330va for a chip amp, but you may never hear the difference between it and a 250va or 160va depending on your capacitor setup.

Look at SMPS supplies, they use itty bitty transformers. Transformers are fit to application. The only reason to stay larger without wanting to meet thermal efficiency for the constant current amplifiers is that if you get too small they generate common mode noise. 

[Folsom]

Well maybe we can change that near future,  (PM for details)

They do rather nicely for most listening, but just can't do large orchestral pieces with any degree of realism. .  So far, I still need the Moscode HR401.

[G Georgopoulos]

Look at SMPS supplies, they use itty bitty transformers. Transformers are fit to application. The only reason to stay larger without wanting to meet thermal efficiency for the constant current amplifiers is that if you get too small they generate common mode noise.

Hi Salis
+1 
i have actually used smps in linear amplifiers(tiny beasts)and they provide
the power needed,however some noise that is inherent can be easily
filtered out...

[werd]

For sure,bass always causes power supply(and transformer)voltage drops,it's not about mids and highs but bass,if you dont have a good regulation transformer, power supply wont recover from bass soon enough to power mids and highs,capacitors actually cause a voltage drop when charging from the transformer so capacitors wont recover the ps charge,it's the transformer that makes a difference here,the bigger the better,what do you think?

What ever it takes to get a good voltage source off the secondary. That means big power with nice shiny thick windings. I am not bagging out on SMPS I've heard some nice stuff but it's not cheap.  Speaker crossovers are about the worst load for an amp ironically.  The whole thing wants to amplify bass. Especially in the 4ohm loads. Getting it to respond to high frequencies is punishing for an output especially tubes. At least they don't have to deal with ramped up feedback closing In on DC. 

Hey if you want it to sound good you gotta give er a lil.

Big

[dlaloum]

The Pro Crown's put out plenty of current from their SMPS, and are (relatively) dirt cheap - benefits of mass production?

440W @ 8ohm, 775W @ 4ohm and 1200W @ 2ohm - seems to indicate a heap of current to me!

[OzarkTom]

They do rather nicely for most listening, but just can't do large orchestral pieces with any degree of realism. .  So far, I still need the Moscode HR401.

Are you getting one? The Moscodes were one of my favorites back in the 80's, I sold a bunch of them. If you have noticed the new PS Audio amp will be $8K and similarly  the same design, tube input and mosfet output. George Kaye has been building them going on 30 years, I would love to try his latest one.

[Quiet Earth]

[RDavidson]

As he turns up the volume, horrible oscillating humming can be easily heard and yet he ignores it.

[werd]

Mcfly's kid 

[S Clark]

Are you getting one? The Moscodes were one of my favorites back in the 80's, I sold a bunch of them. If you have noticed the new PS Audio amp will be $8K and similarly  the same design, tube input and mosfet output. George Kaye has been building them going on 30 years, I would love to try his latest one.

No, I've had one for a couple of years.  After building the LS9's, I started watching for either a used Moscode HR401 or a McCormack.  Neither came available quickly, but the Moscode came up first.  I sent it to George and upgraded caps and resistors and have been very happy with it.  I've also got an old Moscode 300 that I'll get around to getting repaired since it's still a very nice amp with upgrades- way down on the to do list. 

[werd]

No, I've had one for a couple of years.  After building the LS9's, I started watching for either a used Moscode HR401 or a McCormack.  Neither came available quickly, but the Moscode came up first.  I sent it to George and upgraded caps and resistors and have been very happy with it.  I've also got an old Moscode 300 that I'll get around to getting repaired since it's still a very nice amp with upgrades- way down on the to do list.

Love those Gr 's. What's are those blue thinger majingies?

[OzarkTom]

Lucky dog, Clark.

For supper power, two Crown 2500 amps bridged will give you 1550 Wpc. And bi-amping with 4 of those would give you 3000 Wpc. That should be plenty of headroom.

[Russell Dawkins]

A convenient calculator for power needs. Headroom requirement not addressed, but it's a start:
http://www.sengpielaudio.com/calculator-efficiency.htm

[Guy 13]

A convenient calculator for power needs. Headroom requirement not addressed, but it's a start:
http://www.sengpielaudio.com/calculator-efficiency.htm

Hi Russell.
There's lot of good information in your link.
Thanks.

Guy 13

[dlaloum]

Yep quite a few handy converters/calculators and good explanations