XPA-1L Questions and Newbie Class A and A/B Query

[jcisbig]

Hey All,

There's lot's of pages of info on the XPA-1L, and I looked through a lot of them but couldn't easily find the answers to my questions. I thought I'd post a couple questions here to get some good answers quickly.

1) In a nutshell, why is Class A generally better liked than Class A/B?

2) Class A seems to generate much more heat than Class A/B. I'm assuming that this is because it's using more electricity? If so, would this most likely represent a significant electricity bill increase?

3) Due to how much heat Class A amps generate, I'm guessing it would be frowned upon to stack these amps?

4) Has Emotiva published what the price of the 1L will be?

5) Are there most likely people out there that would choose an XPA-1L over an XPA-1 based on the increase in Class A power alone? Or would everyone still prefer to have and XPA-1?

Thanks in advance!

[harri009]

Here are some good technical articles

passlabs.com/technical-articles/

[jcisbig]

Those do look like some good technical articles, but a bit too over my head at this point! Thanks for passing those on though!

[stiehl11]

Mar 1, 2013 16:40:02 GMT -5 jcisbig said:

Hey All,

There's lot's of pages of info on the XPA-1L, and I looked through a lot of them but couldn't easily find the answers to my questions. I thought I'd post a couple questions here to get some good answers quickly.

1) In a nutshell, why is Class A generally better liked than Class A/B?

2) Class A seems to generate much more heat than Class A/B. I'm assuming that this is because it's using more electricity? If so, would this most likely represent a significant electricity bill increase?

3) Due to how much heat Class A amps generate, I'm guessing it would be frowned upon to stack these amps?

4) Has Emotiva published what the price of the 1L will be?

5) Are there most likely people out there that would choose an XPA-1L over an XPA-1 based on the increase in Class A power alone? Or would everyone still prefer to have and XPA-1?

Thanks in advance!

1) Because Class A reproduces the entire wave form rather than most of it (for more information see here).

2) Define significant. If you're leaving them idle as opposed to using them at full tilt you will have a different power consumption rate.

3) How much ventilation will they have? How hard will you drive them? How long will you drive them?

4) It will be on the website in the next week. I think the estimate was around $700 (again, estimated).

5) Yes.

[davidas6350]

I'm no expert in this but here's what I understand so far.

1. In a nutshell, class A is always on (better audio quality) and others switched on & off.

2. Yes, I would also assumed it uses more electricity than a class A/B, I don't know how significant though.

3. I have the XPA-1, the 1st two days I got them (while waiting for my racks) I had them stack together and they get a little hot. Now in the racks/shelves with 2.5" space on top they are barely warm. I'm gonna assume, it'll be more significant on the XPA-1L.

4. I haven't seen or heard any offical price.

5. I was waiting for the XPA-1L but pulled the trigger on the XPA-1 about 2 weeks ago when it went on sale. I'm also interested in your last question. I started a thread about figuring out how much wattage is the amps actually supplying to the speakers in a typical home setting but it was going nowhere

[audiofile]

I'm an amp dummmy but here's my take on yor questions:

1. No shortcut in the wavelength produced by the Class A vs. Class A/B.

2. Any amp will generate heat. The amount really depends on load as heat translates into resistance in the electrical circuit. Look at it this way...how much heat to you produce at rest vs. running a marathon? It's all about demand.

3. My XPA-1's are not stacked and have sufficient airflow around them. I'd stack them if I needed to as they will generate more power than my mains will ever demand and I won't worry about them.

4. I have not seen a price but then I haven't been shopping for amps. I have 6 Emo amps now!

5. Yes, I suppose there will be those that will but they may need that power. I may need the power of my XPA-1's some day if I ever change out my main speakers. But, that seems unlikely as I love how things work now.

[wcparks]

In the podcast they said you could stack them basically as high as you want.

[milt99]

well, good luck with that.
I didn't hear that.
I heard them say non-specifically that these would be great to add to your stack or something similar.
If these amps are truly class a and you leave them on, they will run as if you're cranking them that's one of the characteristics of a class a amp, it's always "on".
What I did hear them say that if the amp gets too hot it will automatically switch to class a\b operation.
I'm sure there's more to it than that but anyone who has ever owned a class a amp and I have, knows how hot they are at idle.
Ever see pics of tube amps stacked? FYI, tube amps are class a.

[audiosyndrome]

The similar Pass Labs XA30.5 (35 watt stereo amp) idles at 200 watts. The XA60.5 (60 watt monoblock) idles at 600 watts . Be very careful and think out all aspects of operation if you're going to go Class A.

The 1L front panel switch should be labeled Winter Use / Summer Use rather than A - A/B. ;D

Russ

[AudioHTIT]

Mar 1, 2013 21:36:33 GMT -5 milt99 said:

well, good luck with that.
I didn't hear that.
I heard them say non-specifically that these would be great to add to your stack or something similar.
If these amps are truly class a and you leave them on, they will run as if you're cranking them that's one of the characteristics of a class a amp, it's always "on".
What I did hear them say that if the amp gets too hot it will automatically switch to class a\b operation.
I'm sure there's more to it than that but anyone who has ever owned a class a amp and I have, knows how hot they are at idle.
Ever see pics of tube amps stacked? FYI, tube amps are class a.

These are high bias class A/B amps, they will run in class A up to 30 watts and then become A/B up to 250 watts. So they will not run as hot as a 250 watt class A amp. Also most tube amps are class A/B, though some are class A.

[deltadube]

just really wondering watts is 30watts of class a power going to do for you it does not sound
like alot of power ? i dont know much..

this be a good mono block for my new studio 100s?

thanks

[garbulky]

It's actually 70 watts total for two channels. That'll give you a healthy volume.

[davidas6350]

Mar 2, 2013 4:07:07 GMT -5 deltadube said:

just really wondering watts is 30watts of class a power going to do for you it does not sound
like alot of power ? i dont know much..

this be a good mono block for my new studio 100s?

thanks

Supposedly in a "perfect world," that 30 watts on a 90db sensitivity speakers listening in stereo at 10 feet from the speakers will give approximately 98 db (pretty loud) in SPL reading.

But in the "real world," as my little test showed me on another thread, that's not always the case. So, results will be different for each setup and listening environment.

[richardrc]

I liked my idea of a separate trigger input for class A operation, no reaching and pushing buttons. These amps will probably idle at around 150w. That is quite a lot of heat to dissipate.

[jmasterj]

I'm really interested in the XPA-1L. I was planning to purchase the XPA-2. So I can't wait to find out more about these new mono blocks. Maybe they will change my mind. I think that 30 watts of class A would be plenty power for some high sensitivity, high output speakers.

[frenchyfranky]

I'm very interested to know the idle temperature of the XPA-1L, normally 30watts idle in class A represent at least a medium amount of heating dissipation, enough to be considered. I hope Emotiva will include this important info in the presentation web page.

[crashcarruthers]

I have one system with Vincent SP-T 100 hybrid mono blocks(100 watt) pure class A . They each idle at 138 watts according to my kill-a-watt meter.

[audiosyndrome]

Crash- I do not believe you're making an accurate measurement. A pure Class A 100 watt amp will most likely idle somewhere around 600 - 800 watts.

Or, perhaps your amp is a SLIDING Class A amp where the bias current is adjusted upwards as more power is required. I believe Hyperion has (had) a solid state (100 watt) amp that worked that way.

In any case, there is no way a pure Class A amp idles at 138 watts.

Russ

[arthurz]

I thought with class A there was no difference between idling and full output. Is that incorrect?

[Chuck Elliot]

This is a very good article to understand Class A: www.sound.westhost.com/class-a.htm