Class A amplifier

[SIY]

I don't have any measuring instrument.

Is that why you keep saying stuff that's either demonstrably wrong or has no evidence supporting it?

 

[voodooless]

I don't have any measuring instrument. I can't even open the glued sealed cabinet to access it amp circuit This website doesn't support upload of wav files. Orelse I can give this. Output of Serum soft synth plug in.

That looks like a minim phase square wave. But that's not on speakers I think you can zip audio files if you want to attach them.

 

[kongwee]

That looks like a minim phase square wave. But that's not on speakers I think you can zip audio files if you want to attach them.

Ok. Take note, it goes very loud. Can make you go crazy if you keep repeating it. It is very short wave life. Edit them if you need to do.

 

[voodooless]

Ok. Take note, it goes very loud. Can make you go crazy if you keep repeating it. It is very short wave life. Edit them if you need to do.

So this is what that looks like on an actual speaker:

LS50 with Dirac, so a coaxial. If you try this with a normal 2-way, it will look way worse.

And then you worry about your amplifier...

 

[kongwee]

So this is what that looks like on an actual speaker:
View attachment 183904
LS50 with Dirac., so a coaxial. If you try this with a normal 2-way, it will look way worse.

I dunno why you talk about speaker when it is all about the amp. Speaker output is another issue too. There are two tone in the file just to take note. Open wave editor you can see the slight different visually. Even the tone itself have a bit different wave form due to Serum algorithm to make the tone sell, not for measurement.

 

[voodooless]

I dunno why you talk about speaker when it is all about the amp.

Because speakers mess it up anyway, especially in the case of normal multiway systems.

Speaker output is another issue too. There are two tone in the file just to take note. Open wave editor you can see the slight different visually. Even the tone itself have a bit different wave form due to Serum algorithm to make the tone sell, not for measurement.

Class D square waves look just fine.

 

[kongwee]

Waveform from my speaker to SM58 mic.

 

[kongwee]

Class D square waves look just fine.

It is very fine. 460kHz wide bandwidth. Gryphon Class A on spec is 450kHz, you know the cost.

 

[SIY]

I dunno why you talk about speaker when it is all about the amp.

No politer way to put this: that is absolutely nuts.

 

[Gorgonzola]

But as we've seen distortion on class A amps is not at audible levels even though it does not compare well to e.g Hypex or Neurochrome. Although I suppose it might be with a really badly implemented class A design but it would have to be shockingly bad.

As usual, we hear what we want to hear, or what we expect to hear. There's no escaping that.

I consider the non-audibility of distortion at low levels is moot despite the likes of ABX testing. Such testing being "science", but like all current science, not "settled", i.e. not necessarily ultimate truth.

 

[solderdude]

It is very fine. 460kHz wide bandwidth. Gryphon Class A on spec is 450kHz, you know the cost.

What's the fastest signal the amp will be fed when listening to music ?
For what would one need 450kHz power bandwidth ?
What will your speakers produce ?
Would that be a square-wave ? (Vinyl, tape or digital are all band limited so are recording microphones)

 

[voodooless]

It is very fine. 460kHz wide bandwidth. Gryphon Class A on spec is 450kHz, you know the cost.

What's the bandwidth of your DAC? speakers? Or your ears?

If you want to fill all of the 460 kHz bandwidth of a square wave, you'll need to generate it using at least a 920 kHz sample rate.

 

[kongwee]

What's the fastest signal the amp will be fed when listening to music ?
For what would one need 450kHz power bandwidth ?
What will your speakers produce ?
Would that be a square-wave ? (Vinyl, tape or digital are all band limited so are recording microphones)

Spectral amp. 1.8mHz +- 3dB but quite noisy amp for ASR standard. You got to listen what the highest bandwidth amplifier can do. Keith Johnson will want you listen with 2C3D setup thou. Listen it before goes into history. Don't need to own one.

What's the bandwidth of your DAC? speakers? Or your ears?

If you want to fill all of the 460 kHz bandwidth of a square wave, you'll need to generate it using at least a 920 kHz sample rate.

My speaker dunno. It is equator audio q8. The company go bust. DSP crossover goes mHz.

Decade ago, DAC for CD liked to go 64 or 128 oversampling.

 

[voodooless]

Spectral amp. 1.8mHz +- 3dB but quite noisy amp for ASR standard. You got to listen what the highest bandwidth amplifier can do. Keith Johnson will want you listen with 2C3D setup thou. Listen it before goes into history. Don't need to own one.

You don't understand. Your square wave will not use any of that bandwidth because it cannot contain any of the harmonics above the bandwidth of the sampled signal. You can have a 10 MHz amplifier all you want, if you generate a square wave with 44.1 kHz sampling, the highest harmonic will be at about half that at most, so 22 kHz. No amount of oversampling will change that.

My speaker dunno. It is equator audio q8. The company go bust. DSP crossover goes mHz.

Speaker is speced to 22kHz -3dB, so that is all the bandwidth you'll ever need. I'm pretty sure the DSP will just run on 44.1 or 48 kHz given the age of these things. So no, they don't do mHz..

 

[solderdude]

Spectral amp. 1.8mHz +- 3dB but quite noisy amp for ASR standard. You got to listen what the highest bandwidth amplifier can do. Keith Johnson will want you listen with 2C3D setup thou. Listen it before goes into history. Don't need to own one.

You probably mean 1.8M(ega)Hz instead of m(illi)Hz
Why does one have to listen to an amp with the highest BW it can do ?
What would be the difference between an amp BW limited to 100kHz or 1.8MHz when it never gets fed anything above 50kHz.
In fact, depending on the DAC one uses a high BW can give lots of problems.

 

[gene_stl]

Only poorly designed loudspeakers present the amplifier with very low impedance loads. (another good reason to multi amp)

Square waves should be band limited otherwise they are not a fair test unless you want to know how much excess slew rate and GBW product you have. If you don't know what that is maybe you shouldn't be taking part in a discussion like this.

I have a stereo friend here in St. Louis who has a Krell amp. It has a huge number of output devices. And somehow the design is so good that it blows them up in multiples. Since he has had it it has spent WAY more time in the shop than in his system. He hooks it up and it blows up. IMO it's a complete POS and I don't care WHO designed it. None of these classic audiophool boolsheet amps perform as well as a Neurochrome let alone outperform them.

There are getting to be too many trolls here from the audiofool sites. Repeating audiophile platitudes. Experience spending money at the yacht club audio store is not very useful experience. It won't win any arguments here. Take some college courses in electronics or acoustics or both. Build some amp kits. Work at the repair bench. Actually manufacture and sell a non snake oil audio product. Or even just gin together a decent audio system DEVOID of snake oil or over priced crap that you bought because some asshole dealer said it sounds great.

I have only ever bought one piece of gear because a dealer recommended it. A Dyna PAT 4 in 1969. It sounded terrible. I got rid of it and built another.
Sounded exactly the same. Got rid of that and got something better (That had tubes) But I never took a dealer suggestion ever again. And the guy involved was not a bad guy actually. He wasn't even an audiophile. He was a retailer that happened to be in the stereo business. He just never really listened to music.

 

[kongwee]

You don't understand. Your square wave will not use any of that bandwidth because it cannot contain any of the harmonics above the bandwidth of the sampled signal. You can have a 10 MHz amplifier all you want, if you generate a square wave with 44.1 kHz sampling, the highest harmonic will be at about half that at most, so 22 kHz. No amount of oversampling will change that.

You probably mean 1.8M(ega)Hz instead of m(illi)Hz
Why does one have to listen to an amp with the highest BW it can do ?
What would be the difference between an amp BW limited to 100kHz or 1.8MHz when it never gets fed anything above 50kHz.
In fact, depending on the DAC one uses a high BW can give lots of problems.

All you need to listen to 2C3D setup. Nothing much to say if you don't listen. Keith Johnson already opened the door of wide bandwidth. Look at this look just fine again. The transistor actually switching into 1.2mHz and no more reading. It is 500 times more bandwidth than you need in audio.

This is typical of Spectral amp.
SPECIFICATIONS

DMA-250 S3 Stereo Reference Amplifier

Power Output:
(continuous)

• @ 8 ohms - 200 Watts RMS
  @ 4 ohms - 360 Watts RMS
  @ 2 ohms - 545 Watts RMS

Output Current:

• 60 Amps peak per channel

Frequency Response:

• ±0.1 dB, DC-150 KHz
  ±1 dB, DC-1 MHz
  ±3 dB, DC-1.8 MHz

Distortion:
Static:

• Less than 0.015% from DC to 100 KHz, typically 0.005% @ 200 WRMS/8 ohms

Dynamic:

• 8 Tone Cluster Test 20 KHz @ 500 Hz separation; 0.01% 8 ohms; 0.015% 4 ohms

Speed:
Rise Time:

• Less than 400 nanoseconds

Settling:

• 1.5 microseconds to -40dB

Slew Rate:

• 600 volts/microsecond

Noise:
Signal to Noise:

• 97dB

Crosstalk:

• -102dB @ full power 8 ohms

Input:
Impedence:

• 10K ohms

Sensitivity:

• 1.5 volts / nominal output

Power Supply:
Line Voltage:

• 100 volts, 120 volts, 240 volts (factory set)

AC Voltage Range:

• ±10%

Maximum Consumption:

• 1600 Watts

Quiescent Consumption:

• 250 Watts

Operating Temp:

• 0° to 50° Celsius range; 32° to 122° Fahrenheit

Protection Features:
DC Protection Servo:

• 0.5 volt range

Current Limit Onset:

• 40 Amps

Thermal Threshold:

• Protects at 85° Celsius, 185° Fahrenheit

AC Main Fuses:

• 2 @ 2.5A 3AG Slo-Blo for 100 - 120 VAC

Size and Weight:
Dimensions:

• 19" (48.22cm) W
  7 1/4" (18.4cm) H
  18" (45.8cm) D

Weight:

• 64 lbs, (29.0 KG) Net
  Warranty
  3 Years Parts and Labor

Lot of the spec are worst than AHB2 other than Frequency Respond and speed. It is one of the top well engineered amp in the world. If really choosing for reference, I will definitely choose Spectral.

 

[SIY]

All you need to listen to 2C3D setup. Nothing much to say if you don't listen. Keith Johnson already opened the door of wide bandwidth. Look at this look just fine again. The transistor actually switching into 1.2mHz and no more reading. It is 500 times more bandwidth than you need in audio.

This is typical of Spectral amp.
SPECIFICATIONS

DMA-250 S3 Stereo Reference Amplifier

Power Output:
(continuous)

• @ 8 ohms - 200 Watts RMS
  @ 4 ohms - 360 Watts RMS
  @ 2 ohms - 545 Watts RMS

Output Current:

• 60 Amps peak per channel

Frequency Response:

• ±0.1 dB, DC-150 KHz
  ±1 dB, DC-1 MHz
  ±3 dB, DC-1.8 MHz

Distortion:
Static:

• Less than 0.015% from DC to 100 KHz, typically 0.005% @ 200 WRMS/8 ohms

Dynamic:

• 8 Tone Cluster Test 20 KHz @ 500 Hz separation; 0.01% 8 ohms; 0.015% 4 ohms

Speed:
Rise Time:

• Less than 400 nanoseconds

Settling:

• 1.5 microseconds to -40dB

Slew Rate:

• 600 volts/microsecond

Noise:
Signal to Noise:

• 97dB

Crosstalk:

• -102dB @ full power 8 ohms

Input:
Impedence:

• 10K ohms

Sensitivity:

• 1.5 volts / nominal output

Power Supply:
Line Voltage:

• 100 volts, 120 volts, 240 volts (factory set)

AC Voltage Range:

• ±10%

Maximum Consumption:

• 1600 Watts

Quiescent Consumption:

• 250 Watts

Operating Temp:

• 0° to 50° Celsius range; 32° to 122° Fahrenheit

Protection Features:
DC Protection Servo:

• 0.5 volt range

Current Limit Onset:

• 40 Amps

Thermal Threshold:

• Protects at 85° Celsius, 185° Fahrenheit

AC Main Fuses:

• 2 @ 2.5A 3AG Slo-Blo for 100 - 120 VAC

Size and Weight:
Dimensions:

• 19" (48.22cm) W
  7 1/4" (18.4cm) H
  18" (45.8cm) D

Weight:

• 64 lbs, (29.0 KG) Net
  Warranty
  3 Years Parts and Labor

Lot of the spec are worst than AHB2 other than Frequency Respond and speed. It is one of the top well engineered amp in the world. If really choosing for reference, I will definitely choose Spectral.

Uh huh.

 

[JSmith]

Spectral amp

Any real measurements instead of a spec sheet typed up by the manufacturer? Would be interested to see same.


JSmith

 

[kongwee]

Any real measurements instead of a spec sheet typed up by the manufacturer? Would be interested to see same.


JSmith

No one test the amp, but this forum has these info:

Basic Measurements of Spectral DMA 260

Hi, Here are some basic measurements of a Spectral 260 power amplifier that I bought as a pre-owned unit approximately two years ago and had it checked by a local electronics expert who used an AP analyser from what I can see.

www.audiosciencereview.com