Pure Class A Push Pull

doctor r

It all comes down to the heat issue and failures associated with the high biasing. It does not matter if it is in PP or SET the wasted energy that is not immediatly being used for sound reproduction has to be handled as heat dissipation.
Rick

megasat16

Of coz, Heat is No. # 1 issue with the Class A amp failure. But in the beginning, the small signal transistors were not reliable as today and many failures were due to thermal runaway from the small to mid transistors in the predriver stage of Class A PP amps.

There is pre-driver stage complexity in SS that is different from Tubes for the Class A amps. That's why you have many Tube amps come in Class A but only a handful of SS in Class A.

Anyway, heat is an issue for Class A and all the real Class A amps dissipate a lot of heat sitting idle and it's very damaging for all kinds electronics including Tubes.

mhardy6647

Thermal runaway was a feature of the very early germanium transistors. Those were indeed used in early soiled state "hifi" (the fi of those units was none too hi) but were very rapidly replaced with silicon devices.

Nothing harder to implement about Class A except dealing with the heat. It is absolutely true, though, that the little teeny-tiny junctions in the power transistors are moderately delicate.

heiney9

FTGV wrote: »

But does it have complimentry pairs of output devices(push-pull).If not it has to be SE thus Class A

Yes, it absolutely has complementary pairs and the chassis in no way shape or form could support 100wpc @ 8ohm and 160wpc @4 ohms. Single ended shouldn't even be able to produce more watts a 4 ohms. The chassis and heat sinking are about 1/2 of my Aleph and that gets damn hot @ only 30 wpc SE so you think something 1/2 the size could dissipate 100 wpc SE class A???? Not physically possible on Earth......maybe Mars!!!!

H9

heiney9

Doctor R wrote: »

It all comes down to the heat issue and failures associated with the high biasing. It does not matter if it is in PP or SET the wasted energy that is not immediatly being used for sound reproduction has to be handled as heat dissipation.
Rick

megasat16 wrote: »

Of coz, Heat is No. # 1 issue with the Class A amp failure. But in the beginning, the small signal transistors were not reliable as today and many failures were due to thermal runaway from the small to mid transistors in the predriver stage of Class A PP amps.

There is pre-driver stage complexity in SS that is different from Tubes for the Class A amps. That's why you have many Tube amps come in Class A but only a handful of SS in Class A.

Anyway, heat is an issue for Class A and all the real Class A amps dissipate a lot of heat sitting idle and it's very damaging for all kinds electronics including Tubes.

Funny how Pass class A amps have less then a .01% rate of failure over a 10 year life span. Class A amp failure is for amateurs.

H9

BlueFox

heiney9 wrote: »

Funny how Pass class A amps have less then a .01% rate of failure over a 10 year life span. Class A amp failure is for amateurs.

All this talk the last few months about Pass Labs Class A amps resulted in my looking into their gear as a possible upgrade, or nice small room 35W/ch system.

Anyway, they certainly are expensive enough to be reliable for 10 years. Does Pass equal Bryston's 20 year warranty on analog gear?

heiney9

BlueFox wrote: »

20 year warranty on analog gear?

They don't put it in writing, but if you look on the internet I have never heard a bad word and I've never encountered anyone who had to pay for a repair. Nelson has said several times it's very rare their gear breaks.

I can unhesitatingly recommend the gear and their exemplary customer service. I read one account of a customer sending in a 10 year old pre-amp in original box and packing for a check up. It had a 100% bill of health. No charge for the check-up and they got all new box and packing even though they didn't need it!

H9

heiney9

SundayForever wrote: »

The new Hyperbolic Conversion Amplification Circuit does away with this problem, allowing your Yamaha MX-800/U to deliver superior performance constantly, without switching or cut-off, over its entire power range.

It's BS................like you're BS. Take your spam and stick it!

H9

megasat16

heiney9 wrote: »

Funny how Pass class A amps have less then a .01% rate of failure over a 10 year life span. Class A amp failure is for amateurs.

H9

You need to read between the lines (or the posts above the posts) to make sense of what "in the Beginning means". That's when small signal transistors were having reliability issues and failure from thermal runaway for the Class A amps. Of coz, it is design dependent. You can bullet proof even the most fragile transistors but it was the beginning so everyone was still learning.

And yes, everyone was amateurs in the beginner. But later along the line, they need to learn and understand.

You would think that Mr. Pass would have perfected his designs after 30 yrs?

megasat16

heiney9 wrote: »

Yes, it absolutely has complementary pairs and the chassis in no way shape or form could support 100wpc @ 8ohm and 160wpc @4 ohms. Single ended shouldn't even be able to produce more watts a 4 ohms. The chassis and heat sinking are about 1/2 of my Aleph and that gets damn hot @ only 30 wpc SE so you think something 1/2 the size could dissipate 100 wpc SE class A???? Not physically possible on Earth......maybe Mars!!!!

H9

I don't know about Monarchy amps but the way you are criticizing the amps from the size of the heatsink, chassis, and power ratings is a bit scary.

If you want to know whether it's true PP Class A or not by easily gauging at the power supply transformer and capacitor banks first. If it's using like 600W toroid and claiming 150W output, it might well be true Class A regardless of the size of the chassis, or heatsink, etc. Smaller heatsink will have negative effect on the amplifier reliability due to higher temperature it needs to dissipate.

Do you have Monarchy amps and compare the temperature against your Aleph 30?

BlueFox

megasat16 wrote: »

Of coz, ...

Out of curiosity, why do you use "coz" instead of typing 3 more letters for "course"? Every time I read it I go through some mental translation to understand the context.

megasat16

Coz I am lazy! But you are right, it meant of course!

RuSsMaN

Class A solid state guys are HILARIOUS.

BlueFox

megasat16 wrote: »

Coz I am lazy! But you are right, it meant of course!

Yes. That is what I thought, but in this context it means "because".

megasat16

RuSsMaN wrote: »

Class A solid state guys are HILARIOUS.

We like to be Hilarious. :biggrin:

BlueFox wrote: »

Yes. That is what I thought, but in this context it means "because".

Yes, true that.

So, are we getting a handle on the issue now?

When I typed "of coz", it really means "of course" and when I typed "coz", it means "because".

lyle64

i have a set of rta 11tl i hear good and bad reviews does any one have a sound unbiased opinion-also found a pair of polks rt400 i have never seen these before so i bought them - they seem to be a good speaker though the tweeters seem a little over powering yet good bass response - has any one have any info on these

megasat16

lyle64 wrote: »

i have a set of rta 11tl i hear good and bad reviews does any one have a sound unbiased opinion-also found a pair of polks rt400 i have never seen these before so i bought them - they seem to be a good speaker though the tweeters seem a little over powering yet good bass response - has any one have any info on these

Hello Lyle64, Welcome to the forum. I am not familiar with rta 11tl but I think there are people here with lots of info on these speakers.

But you need to create a new thread under the speaker sub-forum.

http://www.polkaudio.com/forums/forumdisplay.php?f=15

Click on "Post New Thread" and ask the same question so people can see and response to your questions properly.

FTGV

heiney9 wrote: »

Yes, it absolutely has complementary pairs....
H9

Then the outstage must be PP Class A not SE.

heiney9

megasat16 wrote: »

I don't know about Monarchy amps but the way you are criticizing the amps from the size of the heatsink, chassis, and power ratings is a bit scary.

If you want to know whether it's true PP Class A or not by easily gauging at the power supply transformer and capacitor banks first. If it's using like 600W toroid and claiming 150W output, it might well be true Class A regardless of the size of the chassis, or heatsink, etc. Smaller heatsink will have negative effect on the amplifier reliability due to higher temperature it needs to dissipate.

Do you have Monarchy amps and compare the temperature against your Aleph 30?

James you need to read my posts a little better......they claim they are SINGLE ENDED Pure Class A. It's a marketing misnomer that annoys me, that's all. My brother had a pair, now they are with a friend of ours and another forum member just bought a pair. And no they don't get as warm as the Aleph.

The other thing your missing from my posts is C.C. Poon admitted they aren't single ended, remember the quote about the Mosfet's being up in the Mhz range and being so fast that switching distortion is a non-issue? You had a good laugh at that quote a few weeks ago. How can a single ended amp have switching distortion? How can a push/pull Pure class A (your description of pure class A) have switching distortion? Simple, it can't.

The amps sound great, so in the end who really cares. I'm just using that example in these threads to reinforce my point that manufacturer's take liberties with these terms all the time and many times it's simply not true. So we can all come up with our definitions, but in the end some manufacturer's stretch those already loose definitions into something completely different or take liberties and make their products appear to be something they aren't.

Point being it can become hard to classify what the true meaning of Pure Class A is and that if manufacturer's are going to take liberties using that term, the definition gets watered down and pretty soon everything is being called class A.

I've stated that atleast 3 times now, so I hope it's sinking in because I really don't want to explain it for a 4th time.

H9

heiney9

FTGV wrote: »

Then the outstage must be PP Class A not SE.

But that's NOT how they market it. They market it as a Single Ended Pure Class A amp. Also what I'm saying is because of the size of the chassis and heatsinks and the rated output and the fact that C.C. states the use of their MHz mosfets blah, blah, switching distortion is a non-issue.

Sounds to me like high bias A/B. They sound good though.

They also use the term "zero negative feedback".................not even going to touch that can of worms because there is all kinds of controversy and interpretations of what constitutes no NF, just like class A. I use Monarchy as a recent example, but there are many manufacturer's that use these terms in a misleading way. As in any industry, I know it's nothing new.

H9

Ricardo

heiney9 wrote: »

They sound good though.

And this, gentlemen, is all that matters. Who cares if they are class A, B, C , D, E, F, G, H, I or K.

End of the discussion.

FTGV

heiney9 wrote: »

But that's NOT how they market it. They market it as a Single Ended Pure Class A amp.

Certainly some companies are careless with their technical facts in regards to marketing.Despite what they might call it does'nt change the real definition of Class A (which IMO can be either SE or PP).

Sounds to me like high bias A/B.

Maybe?I did some digging and that looks like a nice little pair of mono blocs.However it's hard to say how much of it's 100 watt rating is delivered in Class A.The input stage is single ended but the output is definately PP with 4 pairs of complementry outputs per chassis,so by definition a PP design.I can only guess since it's hard to tell the actual size of those heatsinks.From the pic's they look substantial enough to sustain a reasonable amount of Class A since each of the 4 heatsinks is disipating the heat of only 4 transistors(vs IIRC 6 per HS in your A30).

Ricardo wrote: »

And this, gentlemen, is all that matters. Who cares if they are class A, B, C , D, E, F, G, H, I or K.

Exactly,I have heard excellent examples of Class A,A/B and even C.:eek: Despite what some elitist types may profess there exists no universal best (brand or Class)of amplifier.

End of the discussion.

Not likely since this being an audio forum the horse will still take a pounding despite being plenty dead.

Face

Ricardo wrote: »

And this, gentlemen, is all that matters. Who cares if they are class A, B, C , D, E, F, G, H, I or K.

End of the discussion.

Can you elaborate on Classes I and K? :biggrin:

FTGV

FTGV wrote: »

,I have heard excellent examples of Class A,A/B and even D.:eek:

Fixed.

strider

mhardy6647 wrote: »

Thermal runaway was a feature of the very early germanium transistors. Those were indeed used in early soiled state "hifi" (the fi of those units was none too hi) but were very rapidly replaced with silicon devices.

C'mon, we know you're a tube guy but why you gotta talk crap about SS?

Ricardo

FTGV wrote: »

it's hard to tell the actual size of those heatsinks

3 1/2" by 2", 20 each side for a total of 40 each mono.

And they do sound incredibly good, and can drive the Maggies without getting too hot

megasat16

Ricardo wrote: »

And this, gentlemen, is all that matters. Who cares if they are class A, B, C , D, E, F, G, H, I or K.

End of the discussion.

Oh...you missed a J. :biggrin:

There will never be end of discussion till Brock here agrees Full On Push-Pull Class A can be called a Pure Class A.

The only other way out of this will be paying me the blood money. :eek:

---

On a lighter note, WTF full on means anyway? No one even asked me about "Full on" but someone asked me about "of coz". So, I know people are reading my posts even if they makes no sense. :biggrin:

megasat16

megasat16 wrote: »

If you want to know whether it's true PP Class A or not by easily gauging at the power supply transformer and capacitor banks first. If it's using like 600W toroid and claiming 150W output, it might well be true Class A regardless of the size of the chassis, or heatsink, etc.

In case anyone wonder that can't be right, I am saying the power supply rating for each channel or monobloc configuration. Just thought I should clarify a bit further.

Brock, I researched a little more on the Monarchy but it seems only one version which you are talking about is inappropriately labeled as SE Class A. The current products they are offering now seems to have the Class A name dropped or used appropriately.

Regardless, the believe of Push-Pull always is Class AB is incorrect. Push-Pull (better call complementary pairs) can be A (or real A that doesn't stepped into , or C, or D or G, or H based on how biasing and power supply is designed.

Ricardo

Face wrote: »

Can you elaborate on Classes I and K? :biggrin:

I'd have to google them....

FTGV

Ricardo wrote: »

3 1/2" by 2", 20 each side for a total of 40 each mono.

OK thats a tad shorter than I guestimated from the pics,I thout they would be more like 5"ish high.Are they approx.12" deep?

... can drive the Maggies without getting too hot

Good considering as I understand most Maggies are on the low side sensitivity and impedance wise ,though present a purely resistive load.A true Class A amp should run a bit cooler when working hard (vs when idling) as the current is being used to drive the load instead of being disipated through the heatsinks thus wasted as heat.

They are shall I say "cute" and I would like to hear a pair and their little brother the SM70.