advertisement


Pass Labs INT-60 vs Accuphase/Luxman etc.

No problem!



I’ll leave it to those better informed than me, but one thing to remember is that efficiency can, and does, vary fairly significantly between class-A designs.

There are specific types of class A amplifiers and the efficiency is perfectly predictable when we know what type they are.
 
Okay, then I'm wrong but, sorry. :oops:
But I don't get it why they
a.) called Int 60 (the Int 30 has 30 watts class A too, the Int 25 has 25 watts class A as far as I know)
b.) How could the idle be doubled if the class A part is the same?

The Int 30 was measured by Stereo in Germany: 90 watts dynamic headroom, idle 134 watt, the Int 60 was measured by Stereoplay Germany: 88 watts dynamic headroom, idle 240 watt.

Please can you or someone else explain me how that could be.

For comparison:
Accuphase E 560: 30 watt class A, idle 157 watt

The power delivered in class A is very much not the only factor determining the heat produced and power consumed at idle.
The total power the amp is capable of very much comes into it. An amp capable of 200WPC that delivered the first 10W in class A would dissipate about 208W in heat when idling, roughly the same as a 45WPC "pure class A" design.
This is due to the much higher voltage needed for the higher power delivery being present at the same time as the high bias current needed for class A operation. Watts = Volts X Amps

Be aware that class A power is quoted into 8 Ohms unless stated otherwise and halves for each halving of load impedance.... total power roughly doubles as always with halving load impedance.

All the above assumes conventional push pull operation.
 
Thank you, that is very helpful but still I don't understand why the Int 30 and the Int 60 have such a big difference in idle (134 watt vs. 240 watt).
Both have 30 watt class A part both have around 90 watt dynamic power @ 8 ohm. Even the E560 which has 30 watt class A too @ 8 Ohm and has 60 watt dynamic power @ 8 ohm differs not that much from the Int 30 (157 watt vs. 134 watt).
 
Thank you, that is very helpful but still I don't understand why the Int 30 and the Int 60 have such a big difference in idle (134 watt vs. 240 watt).
Both have 30 watt class A part both have around 90 watt dynamic power @ 8 ohm. Even the E560 which has 30 watt class A too @ 8 Ohm and has 60 watt dynamic power @ 8 ohm differs not that much from the Int 30 (157 watt vs. 134 watt).

The maths doesn't lie but marketing people.... "dynamic power"? What the hell is that supposed to mean? Sounds rather like the old "total music power" scam. In fact the bigger and better the power supply (and class A means well hefty!) the less extra there will be for peaks. The very fact that it is class A means sweet FA available for peaks anyway by and large. I would expect a 30W class A amp to give virtually nothing more on peaks. A regulated power supply guarantees no extra! All this is in fact a good thing as it means an amp that can usually get towards doubling power into half the impedance and means it will likely drive awkward loads better.

Usually when an amp actually can give significantly more power for very brief transients it is a mark of a weedy power supply! It will also be class A/B. Idling or at low to medium ish volumes the weedy PSU will sit at a voltage higher than it can sustain under real load. The smoothing caps (also known as reservoir caps for a good reason!) hold this charge. If a brief big transient comes along it takes a certain time for the caps to discharge to a mean level more accurately reflecting the capabilities of the PSU and so for a few milliseconds ISH an amp rated at say 30W may give say 45W. It would likely only manage say 37W into 4 Ohm even though it gives 30W into 8 and would be comparatively poor at driving awkward loads. Such an amp could be expected to be more likely to get "harsh and shouty" or "loose grip" as volumes get up and is IMHO why you see some people claiming that high power amps sound "better" etc than low power units even when only using say 10W... THEY DON'T! What they are hearing is the sound of a usually cheap amplifier with a weedy PSU and often over eager protection circuitry joining in to save the cheap output transistors likely to be used in such an amp!

Edit: I should add that it can be argued that the above with "weedy PSU's" can be advantageous when certain cost V max loudness V reliability compromises must be made and relatively easy to drive speakers are in use... such as in most budget integrateds etc.
 
Is there such a thing as a class A single ended solid state amplifier ?

There sure is. TdP designed one for Alchemist that was sold as "The Mono" (monoblocks obvs) and made a similar but much bigger and twice the price one under his own name. Both of these ran from high voltages and used output transformers. Pass has many DIY designs for them and EWA (Colin Wonfor) do some.

In the case of some of the Pass designs and such things as the Sugden class A amps and the JLH 10W class A they are kind of "pseudo single ended".

I can't see any point in them personally for anything more than a Watt or so and I've only used it for a headphone amp that can drive all cans from 8 to 600 Ohms... and then it was for novelty factor TBH!
Anything a single ended class A amp (oh and for true single ended an amplifier HAS to be class A. It won't work any other way if single ended... not for audio anyhow) can do a push pull one can do better for less money and less heat.
Fans of them will no doubt claim mystical sound quality advantages... take it with as much salt as you require:rolleyes:

The TdP ones are I guess closest conceptually to SET amps but SS single ended is quite different technically in many ways to SET. Most SS ones use considerable negative feedback for starters.
 
The maths doesn't lie but marketing people.... "dynamic power"? What the hell is that supposed to mean?
Sorry I don't know the right term. Is it peak? impulse? or burst? power? I don't know to translate it from German into English. The term dynamic power isn't from Pass or any manufacturer. The specs aren't from a the manufacturer they were measured by Stereoplay (Int 60) and Stereo magazine (Int 30).

https://www.moremusic.nl/reviews/passlabs/INT-60_Stereoplay.pdf

https://www.stereo.de/hifi-test/produkt/pass-int-30-a-283

https://www.i-fidelity.net/testberichte/high-end/pass-int-60/seite-5.html

https://www.stereophile.com/content/pass-laboratories-int-60-integrated-amplifier-measurements
 
Sorry I don't know the right term. Is it peak? impulse? or burst? power? I don't know to translate it from German into English. The term dynamic power isn't from Pass or any manufacturer. The specs aren't from a the manufacturer they were measured by Stereoplay and Stereo magazine.

If we are talking power into 8 Ohms and "peak? impulse? or burst? power?" then as I explained earlier there is no extra power. Sometimes such names are used for a test where the load is only 2 Ohms or even 1 and a short set of say 4 cycles is used as the signal with the idea being that this is long enough to get a measurement but short enough to avoid blowing fuses etc.
 
@Arkless Electronics But even if we ignore burst, peak, whatever.

Int 60: Sinus 74 watt @ 8 ohm @ 1kHz with k=1%, idle 240 watt
Int 30: Sinus 90 watt @ 8 ohm @ 1kHz with k=1%, idle 134 watt

How could that be if both amps work with 30 watt class A? Sorry if I'm too stupid.
 
@Arkless Electronics But even if we ignore burst, peak, whatever.

Int 60: Sinus 74 watt @ 8 ohm @ 1kHz with k=1%, idle 240 watt
Int 30: Sinus 90 watt @ 8 ohm @ 1kHz with k=1%, idle 134 watt

How could that be if both amps work with 30 watt class A? Sorry if I'm too stupid.

I would need more information how they are quoting these figures and on what sort of topologies are in use... they could even be wrong of course! The figures don't "add up". They suggest that the Int 30 has considerably less than 30W in class A, around 10-12W ish more like. They look about right for the Int 60.

It would seem strange for a company to make two integrated amps... both 30W class A... and with the cheaper one actually giving more total power in class A/B but by so small a margin as to not matter;) (the difference between 74W and 90W is diddly squat in practice).
 
Just a heads up, theres a luxman 590 mk 2 going on uk audio mart and is being sold by a dealer, so should have warranty, only 6 months old for less than £5k
 
Jez, the INT-30 was the INT-60’s predecessor (I believe).

Actually, looking at the product lifecycle at Pass Labs, I wouldn’t be surprised if the INT-60 and INT-250 are due for replacement quite soon. Notwithstanding the current environment.
 
Another quick look at those Int 30 figures above and it cannot possibly give 30WPC in class A even if it was incapable of any more by going into class A/B.... not unless it uses some "cheaty" sliding bias arrangement anyway... if the figures are correct...
If everything was theoretically perfect and all done with superconductors and the pre section used no power at all it would have to idle at 120W if it hit a brick wall at 30W... So idling at 134W with all the losses and allowing say 5-10W for the pre amp.... and it goes on to give 90WPC in class A/B? Nah.
 
Just in case anyone is remotely interested... The Arkless Electronics 15W class A monoblocks (prototypes and currently just for my own use but who knows...) I'm listening to as I type are biased to double the required current for 15W into 8 Ohms in pure class A. Into 8 Ohms then it wastes twice as much power as heat as it needs to but is not even remotely approaching leaving class A when it actually runs out of power. It also means it will still give 15W class A into 4 Ohms rather than the expected 7.5W. At 15W It will then move into class A/B into 4 Ohms and go on to produce a smidge less than 30W (no amplifier literally doubles its maximum power into half the load impedance;))
 


advertisement


Back
Top