Is bigger better?

[Alex from Oz]

Hi All,

I do most of my listening at relatively low power levels, and currently get by quite well with a 50W gainclone amplifier.
...
my question is, which would be better for my usually quiet listening levels?
...
I really like the relaxed, laid back sound of class A and this is my preferred amplifier mode (after building a few JLH/PASS LABS clones).

G'day swordfishy,

Couple of questions:
1) How efficient are your speakers and what is the minimum impedance?
2) How quiet are your "usually quiet listening levels"?

Speaker efficiency and the desired sound output in dB will determine how much power you will need from an amplifier.

I too prefer quiet listening levels. My lawnmower has a sticker on it that says it's sound output is limited to 74dB. If I started it up in my listening room, personally I would find that to be more than loud enough for comfortable listening. For each additional 3dB of sound output you need to double the power. So it would take 64 lawnmowers running to generate 92dB. 😱

Cheers,

Alex

 

[jackinnj]

I wouldn't get hung up over class of operation... it's pretty irrelevant to how the amp actually sounds... sorry I know some will see red at that 🙂

That belies the number of letters which Nelson got (perhaps the stories are apocryphal) in which folks worried that they were going to hear a thump when the amplifier went from Class A to Class AB.

 

[abraxalito]

Ok thank you. This is more the reply I was looking for.

If classA power is your primary requirement (as it does seem to be), then definitely the 840W is the one to go for. The difference though in headroom between 120W and 200W is just over 2dB. Your concerns about mis-match of the paralleled output devices are not really a worry in practice.

I agree with jez that a well-implemented chipamp could beat this poweramp when listening pleasure rather than measured distortion (and other marketing factors) is the aim.

 

[GregH2]

Ok thanks all. Some good thoughts here.

Tending toward the 840W. If it needs softening I can always look at a valve preamp hopefully.

My speakers are, I believe, a difficult load. This is based on my experience with using several amps with them and the profound lack of bass with some. But honestly, I don't really know.

Sensitivity is 89dB and nominal impedance is 6 ohms.

I hope this doesn't prove to be an expensive, though enlightening exercise in learning just how good the gainclone really is 🙂

I will be sure update you all with an unbiased opinion and comparison with the GC when I get it.

 

[abraxalito]

Tending toward the 840W. If it needs softening I can always look at a valve preamp hopefully.

If it needs softening, I'd make sure I was using the balanced inputs first before changing the preamp. Though of course you might need to upgrade your pre to get a balanced signal to drive into it...😀

I say this because in Mr Self's book, his way of connecting the unbalanced input to the power amp does not sound good to me.

 

[satoru]

Dear swordfishy,

I thought you were wondering why higher power amplifier could sound better even though you are not using the full power at all. Here is my guess:

Transistors' essential characteristics change with the voltage across the corrector to emitter, especially the capacitance between channels. As the output signal goes higher, the voltage available to transistors get lower and Cob goes higher. Also, the hfe dives down when more than 20% of the maximum current is flowing through the output transistors. Higher power amps have higher voltage power supplies (of course), so at the same output power level, they are further away from poor linearity area of the transistors. I could be wrong, but this linearity may be the difference of higher power amps to lower power ones driven close to the maximum.

As a DIYer, you can design an amp with slightly higher power supply voltage while limiting the output current to meet your needs (plus a margin). Hope you'll find time to forge your own design in a near future!

Have you tried a MOSFET amp? It behaves differently when the output approaches the maximum. It may very well satisfy you with lower power design than corresponding BJT design...

For my listening style, 2W is enough and I have a lot of freedom in my design. I can even drive them with batteries. Oh, how do they sound nice during power outages....

Best regards and happy shopping!

Satoru

PS. Oh, forgot to say that all criticisms and pointing out the mistakes are welcome!

 

[GregH2]

If it needs softening, I'd make sure I was using the balanced inputs first before changing the preamp. Though of course you might need to upgrade your pre to get a balanced signal to drive into it...😀

I say this because in Mr Self's book, his way of connecting the unbalanced input to the power amp does not sound good to me.

Thanks for the tip. My current DAC/Preamp does indeed have a balanced output so I will be sure to use them.

 

[GregH2]

Dear swordfishy,

at the same output power level, they are further away from poor linearity area of the transistors. I could be wrong, but this linearity may be the difference of higher power amps to lower power ones driven close to the maximum.

Ok thanks another good reason.

Now it's all becoming clear...

No clipping, ease of driving difficult loads, better transistor operating region...

this is all good stuff and the kind of info I was hoping to find.

 

[Melon Head]

I would seriously consider the option of purchasing second hand gear.
If you are lucky you might be able to get hold of an xa30.5 or possibly an X250.5 etc, at a reasonable price second hand.