It all starts with the power supply...
David @Frank Harvey Hi-Fi, Coventry
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It does indeed. It does not really matter if you have tubes or solid state stuff after that in the chain. Neither are going to make a significant difference if the power supply section is rubbish.
This is why most of the well respected manufacturers of amplifiers wind their own power supply transformers.
Tom Evans Audio being just one of those.
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How can you read the quality of the PSU in the amp's specs? Is it in doubling the wattage when impedance is halved?
To put it differently: when driving current-hungry speakers (say Magnepans, with a flat 4 Ohm impedance), are you better off with an amp that delivers 150 W into 8 Ohm, 200 W into 4 Ohm and 240 W into 2 Ohm or with one that pumps 30 W into 8, 60 W into 4 and 120 W into 2 Ohm?
The Magnepans are unusual in that there impedence is largely resistive with minimal capacitance or inductance, so in this case the answer is simple, more power is better all other things being equal.
In my example, do I go for the first or the second amplifier? (Is doubling watts better? Or just the more watts into 4 Ohm, the better?)
The easier (more resisitive) the load that is also close to 8Ohms at all frequencies - it will be the former where its poor(er) damping factor (higher output Z) won't matter too much.
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Extremely important! It does not take much to figure out when you look at the topology of an output stage that the power supply is all important. I have seen AV amplifiers rated at 100WPC and I would not have put some of the power supplies in a stereo amplifier rated at 35WPC.
How did you deduce that the 'former' amplifier had a poorer damping factor?
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Ignoring the comments about winding your own mains transformers (why on earth would you?), the PSU question is quite interesting.
For low power sections (pre amp, DAC, early stages of a power amp etc) a stabilised supply makes very good sense. There are many ways to do this and one or two designs which have a cult following for low noise and high stabilty, google 'Jung super regulator' for a popular design.
Strangely, none involve winding your own transformer (or braiding your own mains cable)...
For the power stages of an amp, it gets more complicated. Ideally a stabilsed supply would make obvious sense, but it needs to react quickly to transients (it almost needs to be an amp in itself), and high wattage linear stabilised supplies are a performance to cool. Most (I believe) amps use simple bridge rectifier / large storage caps for their output stage power supplies. This is actually where a switch mode supply, or class D with feedback come into their own (interestingly, an amp with switch mode supply isn't that different from class D when you think about it)
So yes, PSUs do matter, but a big transformer, big diodes and big caps get you to where you need to get for output stages, and a decent regulated supply for the low level stages. No magic, just basic engineering.
150W into 8Ohms
200W into 4Ohms
Without resorting to calculating the output Z looks pretty average but probably uses less than average negative feedback. IMO these figures would suit the mentioned speakers better at higher volumes
30W into 8Ohms
60W into 4Ohms
Implies extremely low output Z if you get a virtual doubling of power with half the load impedance with likely high levels of negative feedback to keep the damping factor so high. DF is the ratio of Z load divided Z source where Z is the impedance. The impedance "seen" by the amplifier will be a complex one which will vary with frequency, cable chraracteristics including length, Xover components & voice coil temperature so will vary from low to high power. An amp with such characteristics would suit difficult loads if not to particularly high volume.
Now this interest me because im going to get a tripath thats rated at 160w+160w but that is only if you can get a 36v 5amp power supply because it come with a 26v 4amp supply now is this rue for all amps if you up the power supply do you up the watts of the amp ?
Interesting, whilst I totally understand what you are saying, I would have thought that these variations would have been pretty small compared to the more obvious limitations of power supplies, output devices and the rest. You live and learn......
I think of a power amp as being split into three sections per channel: input buffer, output section & PSU (Class D includes a little bit more). I'd speculate that the output & PSU's being the most important - in that their design is going impact the SQ the most. As for your question - it probably depends but upping the current capability will usually mean more headroom for transients without dropping the rail's voltage so much. I think the specification is called transient recovery time which was one of the more difficult DC PSU measurements I've had to do in the past. That 160W per channel will not be obtained from 36V 5A supply for starters - that implies 100% effeciency that not even class D can achieve. The true continuous ouput power maybe a lot lower but hell, even 80W is only 3dB lower.
Buying class D amp modules is going to be great fun for those into DIY audio more than those just trying to save money. The latter group would be better off buying 2nd hand IMO. So, if you are going for Tripath modules, go for decent PSUs! I don't know if Tripath shares class D's general attribute of dumping current back into the supply rails but designing PWM amps involves a little more than fitting OEM amp modules into a case. Get the PSU right & you'll get the SQ to challenge class A but with less heat for a lot more power.
I must take the case off my Primare A34.2 sometime - it's got SMPSs - my DAC generates more heat!
There are other ways to look at the subject. Some people like low watt valve amps when partnered with easy to drive speakers. At the other end of the spectrum, amp manufacturers such as Naim & Cyrus sell accessory PSUs. Some will argue that the PSUs should be better to start with whilst the manufacturer's will surely point out that their products are built to price points but give their customers the option of spreading the costs of better SQ over time. I personally prefer the idea of buying a product without worrying over whether to improve it with yet another box unless the it's an internal module swap.
Psu and also other components like capacitors are critical to providing a sound that is neutral, i am talking of elna capacitors, torroidal transformers, the cheap budget amps used to have a frame type of psu, probably poorly shielded, this affected the amps dynamic range, its drive, and also colours the sound, reading old amp reviews will provide a classic example of a amp based on a budget, and therefore the sound is limited to a fixed budget.
marantz ken isshiwata used to take the budget amps like the pm series then add some exotic components like copper shielding a few choice capacitors and a upgrade to a better psu to torroidal amps.
the result is a amp that is tonally different than standard
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Hi busb this is the amp im getting http://www.ebay.co.uk/itm/Class-D-Amp-2-Channel-2x-40W-Tripath-Audio-Pow...
for the money it should run most speakers but if i upgraded the power supply i should get better sq and have more headroom for speaker selection ?
I was just thinking aswell are pc power supplies any good for powering amps and if so how would i go about connections as i can get the amp board without casing and power supply for peanuts
No you can’t.
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