What Class Amp is the LeAmp,Class D?

ABEX · « **on:** 20 Apr 2003, 02:38 pm »

What Class Amp is the LeAmp,Class D?

And what differentiates it from other amps in it's Class as far as design?

TIA

mbarnes · « **Reply #1 on:** 20 Apr 2003, 05:11 pm »

Le Amp (1) is Class AB. It uses a TDA 7294 amplifier chip.

Le Amp II is a Class A Gain with a Class AB output stage. Many amplifiers on the market today simply call these CLASS A. The gain stage uses Toshiba JFETs and the output uses Toshiba Bipolar.

NealH · « **Reply #2 on:** 20 Apr 2003, 07:13 pm »

"mbarnes", I am not aware of many amplifier companies that employ class "AB" output topology yet claim they are class "A" output designs. Can you back up this claim with some examples or evidence? You very well may be correct but looking over approx. 20 popular amplifiers on the market today I see no evidence of deception. I did notice that a couple of amplifiers operate in class "A" up to a point then gradually transfer to class "AB" operation. But this was made clear in their websites. Neverthe less, maybe this is what you are referring to. Still, I would not say there are many fitting this operational description. Maybe first we need to know your definition of "many".

ABEX · « **Reply #3 on:** 20 Apr 2003, 07:52 pm »

Great!
I was initially thinking of getting the Outlaw amps until I heard they were class D.I would not buy a ClassD amp unless it were for driving a Sub ,but It might be an alternative to for using as Bass Drivers for a Vertical amping setup.

Thx!

ABEX · « **Reply #4 on:** 20 Apr 2003, 07:59 pm »

The intial reason for posting this question was due to this statement that was made at AA and was wondering about the design which came under scrutiny from this post.
===================================
Gepeto wrote:

Switching power supplies are less reliable than linear, owing primarily to much higher component count and high operating voltages (switchers with power factor correctors step up the rectified line voltage to ~400VDC) in the primary converter circuits.
Switchers also require a lot more AC input filtering to keep conducted noise from exiting the power supply down the input power cable. They generate more RFI as well, sometimes hard to tame in other circuit design that is powered by them. This RFI can possibly have some effect on other equipment in your system.

Upsides are small size/lighter weight/lower cost (those huge transformers in linear supplies cost a lot) and switchers with power factor correctors do a good job of looking like a resistive load to the power line which your utility company likes.

IMHO, switching power supplies have no useful purpose in any high end audio equipment. Switching power supplies are great in computers and other non-audio equipment.
G.
Crank it up...

http://www.audioasylum.com/forums/amp/messages/16352.html

ABEX · « **Reply #5 on:** 20 Apr 2003, 08:05 pm »

Other designs that use switching amps are from and sources of info can be found at the following:

http://www.acoustic-reality.com/us_realitysa.htm

http://www.powerdesigner.com/InfoWeb/design_center/articles/Amplifiers/amplifier.shtm

ClassD Amps:

http://www.e-insite.net/ednmag/archives/1995/052595/11df3.htm

mbarnes · « **Reply #6 on:** 24 Apr 2003, 04:36 am »

I have a Bedini 203 amp. It claims to be a Class A but only the input section is Class A. On my Plinius amp, it claims Class A but according to the literature, it is Class A up to 50 watts. The amplifier is rated at 250 watts. It switches into Class A/B above 50 watts.

It is my understanding that many high-end audio amplifiers work exactly the same way.

As for switching power supplies, saying that having more parts makes the product less reliable is simplistic. Switching power supplies have more parts and are more complex to design. However, that doesn't make them less reliable. Most power supplies suffer more from aging capacitors than anything else.

Switching power supplies do require filtering components but so what? In the end, they can deliver more power with less weight and provide power that is more consistant and higher bandwidth. Switching power supplies do not saturate at high power the way standard powers supplies do.

Let's look at the facts. Most commercial amps suffer more because they have inadequate power supplies than for any other reason. Power supplies are the most expensive part of an amplifier. Switching power supplies allow us to achieve a high quality power source in a smaller package, with less heat and for less money. The sound benifit is mostly a result of providing sufficient power to the amplifier.

We had many people come by and hear our Le Amp II at the audio show. The sound was very highly praised. I have replaced the old power supply in my Bedini amplifier with a 800 V/A switching power supply and it has breathed new life into the amplifier.

ABEX · « **Reply #7 on:** 24 Apr 2003, 09:34 am »

Just so you know MB.I am not bitching and am impressed without even hearing it by what I have read about amps and based on the little of what I know about amps.
At the price and quality of parts it is quite an accomplishment in comparision of whatelse is out there.I know I have not been impressed with the amps I have went to audition in the past year.

In tyhe end the main thing is the sound quality it can deliver and all else being secondary,although I am glad it is not a Cl.G amp which Outlaw is trying to sell.

Here is a note I remember seeing that might help even further that you might beable to answer concerning the capabilities of the LeAmpII--

---------------------------------------------------------------------
What specs should one look for to identify high-current amps?"

*There are a bunch of things:
1) The maximum current which the amplifier is rated to deliver.
2) The minimum load impedance which the amplifier is rated to drive.
3) The number and capacity of the output devices used.
4) The amount of filter capacitance.
5) The size of the power transformer.

#1 & 2 & 3 indicate the PEAK current which an amplifier can deliver, without damage of current limiing.
#4 indicates how long that peak current can be sustained.
#5 indicates the maximum CONTINOUS current which an amplifier can deliver.

"Do manufacturers generally include an amperage rating into different loads?"

*No. Not necessary. Ohm's Law tells us that.

mbarnes · « **Reply #8 on:** 24 Apr 2003, 10:01 am »

The units we built now do not have the final heat sinks. Our custom heatsinks will be better than what we are now using. We have rated the amp at 180 watts into 8 ohms and 360 into 4.

We did testing and we were easily over 200 watts into 8, 400 into 4 and we tested 800 into 2. This is not our rating -- it was part of stress testing.

We will rate the unit down to 2 ohms. This is a function of the heatsinks more than anything else.

We are using a total of 6 output devices. There are 3 JFETS for the input and 3 Bipolars for the output. All devices--including the drivers are Toshiba parts.

Capacitors for switchers are different so I hesitate to give you the output values on these. As it is a swticher, the size of the transformer is not related. The power supply is conservatively rated 800 V/A.

You can do your calculations if you like. We have set the output voltage at 67 volts.

Quote from: ABEX

Just so you know MB.I am not bitching and am impressed without even hearing it by what I have read about amps and based on the little of what I know about amps.
At the price and quality of parts it is quite an accomplishment in comparision of whatelse is out there.I know I have not been impressed with the amps I have went to audition in the past year.

In tyhe end the main thing is the sound quality it can deliver and all else being secondary,although I am glad it is not a Cl.G amp which Outlaw is trying to sell.

Here is a note I remember seeing that might help even further that you might beable to answer concerning the capabilities of the LeAmpII--

---------------------------------------------------------------------
What specs should one look for to identify high-current amps?"

*There are a bunch of things:
1) The maximum current which the amplifier is rated to deliver.
2) The minimum load impedance which the amplifier is rated to drive.
3) The number and capacity of the output devices used.
4) The amount of filter capacitance.
5) The size of the power transformer.

#1 & 2 & 3 indicate the PEAK current which an amplifier can deliver, without damage of current limiing.
#4 indicates how long that peak current can be sustained.
#5 indicates the maximum CONTINOUS current which an amplifier can deliver.

"Do manufacturers generally include an amperage rating into different loads?"

*No. Not necessary. Ohm's Law tells us that.

rlinder · « **Reply #9 on:** 24 Apr 2003, 10:44 pm »

If I understand ohms law and the numbers presented correctly the new LeAmp II would have 8.37 amps of current at 8 ohms. Is this correct?

Rich Linder

mbarnes · « **Reply #10 on:** 26 Apr 2003, 06:43 am »

I am not sure I understand your question. However, you need 5 amps to produce 200 watts. We get this knowing that you need 40 volts across 8 ohms to generate 200 watts. Therefore 40 x 40 / 8 = 200. Therefore the answer to how many amps for 200 wats into 8 ohms is 5.

The same amplifier will deliver 400 watts into 4 ohms with 10 amps.

We claim that the amplifer is 180 watts but it will perform like a 200 watt amplifier in every respect. We might rate the unit at 200 watts later. Our voltage is set at 67 volts.

rlinder · « **Reply #11 on:** 26 Apr 2003, 11:50 am »

Is LeAmp II a high current amp? If I understand your previous post, use 8 ohms and 67 volts, and understand ohms law correctly LeAmp II puts out 8.37 amps of current at 8 ohms. I was just trying to see if this assumption is correct. If so this does not sound like a high current design, many of the high current designs are rated at 30 amps or more. Current is generally needed to drive ribbons, which I have, and this is the reason for my question. I am considering purchasing your amp but am frustrated by limited information.

Thank you,

Rich Linder

mbarnes · « **Reply #12 on:** 26 Apr 2003, 05:53 pm »

I believe the term "high-current" is a marketing term and not a technical term when refering to amplifiers. I tend to stay away from hype.

I did a search on the Internet to see how the term "high-current" is used by other vendors. I saw terms like "high-current" output devices. "high-current" transformers.

Most power supplies that I have seen in amplifiers and receivers are inadequate for the power they are rated.

As I stated in my last post, to produce 200 watts into 8 ohms, I need to have 40 volts. Once again, that is 40 x 40 /8. This is five amps.

You claim that you understand ohm's law. Then you must know that ohm's law is a relationship between, amps, watts and volts. If one side of the equation changes, then the other part of the equation is also impacted. I tried to show this by stating that an amplifier that outputs five amps (200 watts) into 8 ohms will output 400 watts with 10 amps into four ohms. This assumes that the heat sink and power supply are sufficient.

If I am producing more amps--I am also producing more watts.

We have set our voltage at 67 volts. This is more than is required for 200 watts but we have to account for various losses and we have to accomidate peak music output.

There really is no such thing as an RMS watt. What we have is an RMS volt. An RMS volt is a mathmatical approximation of what voltage is required to simulate a battery power source using an AC circuit.

When we state we are 200 watts, we then need to have 40 volts RMS across 8 ohms. We also have to account for peak music. We use 1.414 x 40 to arrive at 56.56 volts.

A switching power supply doesn't saturate like a normal power supply. None-the-less, we add 6 volts to compensate for this saturation. That would take us to 62. We need to add 7% because of voltage losses using JFETS. This brings us up to 66.34.

We have therefore designed the power supply to provide adequate power to compensate for saturation losses and losses due to the JFETS. We have also compensated for peak music power.

Finally, the total power available is 800 V/A. This would be 1600 V/A for a stereo pair. This is far more power supply than you are likely to find in other amplifiers.

To me, the whole thing is very ironic. We over designed the power supply. This is far more power supply than anyone uses in an amplifier rated at this power or priced anywhere near its price. None-the-less, people want to try to poke at the power supply to find some weakness. The weakness will have to be somewhere else as the power supply is absolutely over designed.

While we have put real volts, amps and watts into Le Amp II, we are not going to use a lot of hype. When $300.00 receivers that promise 120 watts per channel x 5 use a 200 V/A power supply and call it High Current, I think that the term is over used and meaningless.

rlinder · « **Reply #13 on:** 26 Apr 2003, 07:35 pm »

Thank you for the information, I believe I said "if I understand the information correctly" in my first post, I do not claim to know what I am talking about.
Thank you for exposing the falacy of these ratings.

Rich Linder

ABEX · « **Reply #14 on:** 27 Apr 2003, 04:26 am »

Seems like from decade to decade new theory's of what makes a great amp come into the dictum of advertising.I am not really worried about the capability of how many ampres the amp capabile of,but I would like to know where it might benefit in driving a difficult loads.

There is much exageration of Cos. to state ridiculous claims.NAD and HK to name a few and specs are not what makes a good amp.If that were so everyone would be lining up for the next best Japanese amp to come out which will never happen for me.Been there ,saw that.HK's top amp would not drive difficult Planar loads ,but the specs and lit. stated it would.The results were terrible.

So what you have is the LeAmpII's will produce 5,10,15amps into 8,4 and 2ohms respectivey which should be ample.

All in all the parts quality and specs are all top rate and what more can one ask for besides having good synergy between components.

aaird · « **Reply #15 on:** 27 Apr 2003, 01:27 pm »

Well, I heard them in prototype, and I now have no trouble believing the the power output is as Mbarnes says. They could and did play very loud, at least for a short time, with no loss in any obvious sonic range. I do not play music as loud as those went for a while when Mbarnes walked over and turned them up. I should clarify that I heard NO distortion or shrillness or harshness, just too much volume for my listening preferences, during one demonstration of a Jazz piece.

That's why I've already got my Le Amp II's on order.

Andrew

ABEX · « **Reply #16 on:** 27 Apr 2003, 01:54 pm »

What was the sensitivity of the speakers you were listening to?At 180-200 into 8 Ohms there should be enough power to fill any room with sensive speakers ,say 90db\1m and above.

I have no qualms with the power that these amps can produce as I am using an amp that is well under the the rated power of the LeAmpII's .

The extra power is a help as the new speakers I am getting are less sensitive than the ones I am presently using and vertically amping will give plenty of reserve power to drive my speakers.

In whatever setup I choose I will find a happy place for them and for the price they are well worth buying.

As an example I would rather buy these than what Outlaw is selling to an unknowing market.