Is there any good option for an amplifier that is flat from DC to like 50 Khz

[vintologi]

I am trying to find an amplifier that is good for accurately measuring the frequency response of speakers and ideally it should also be good for regular use.

Cheap but not quite what i am looking for: Topping Mini 300

Hypex NC400 is down to 10hz at least but not so great otherwise. I also don't feel like doing some DIY amp project any time soon.

 

[staticV3]

Specifically for measurements I'd definitely consider the B100:

Topping B100 Amplifier Review

This is a review and detailed measurements of the Topping B100 "monoblock" amplifier. It was sent to me by the company and costs US $299. I was surprised by the desktop/low profile of the amplifier. I expected something a lot taller/chunkier especially since this is a class B amplifier and not...

www.audiosciencereview.com

Three gain settings, with Low being Unity gain add flexibility and repeatability.

Bandwidth is high.

Noise and distortion are at the bleeding edge.

The only question mark is the <4Ω compatibility.

People have reported triggering the protection with infrasonic soundtrack material, not sure if the speaker loads and test tones that you want to use would be more or less taxing than that.

 

[vintologi]

Specifically for measurements I'd definitely consider the B100:

Topping B100 Amplifier Review

This is a review and detailed measurements of the Topping B100 "monoblock" amplifier. It was sent to me by the company and costs US $299. I was surprised by the desktop/low profile of the amplifier. I expected something a lot taller/chunkier especially since this is a class B amplifier and not...

www.audiosciencereview.com

Three gain settings, with Low being Unity gain add flexibility and repeatability.

Bandwidth is high.

Noise and distortion are at the bleeding edge.

The only question mark is the <4Ω compatibility.

People have reported triggering the protection with infrasonic soundtrack material, not sure if the speaker loads and test tones that you want to use would be more or less taxing than that.

Obviously not good for testing low frequencies.

Decent frequency response above 10hz at least.

It would be great if i don't end up having to buy multiple amplifiers for different testing scenarios but i am not getting my hopes up for that.

 

[NTK]

Most well designed audio amplifiers have some type of DC protection, since outputting DC to loudspeakers as signal is never useful. That said, Purifi amplifiers are DC coupled, but the DC protection threshold is set at 12 V, 2.5 Hz detection filter.

 

[vintologi]

Most well designed audio amplifiers have some type of DC protection, since outputting DC to loudspeakers as signal is never useful. That said, Purifi amplifiers are DC coupled, but the DC protection threshold is set at 12 V, 2.5 Hz detection filter.

View attachment 527315

I guess i would be able to remove that protection circuit if needed.

I am pretty sure 12v @ 5Khz is going to be a lot worse than 12v @ 0.2 hz for good full-range speakers so what they are doing doesn't really make sense imo.

 

[TurtlePaul]

If you want to test to 50 khz, definitely get one of those class AB tanks like a Bryston, McIntosh, Benchmark, etc.

 

[Robin L]

This has potential. -.6 db @ 50 kHz, nearly 400 watts @ 4 Ω, stable into 2 Ω. Not cheap but not a ripoff.

Apollon 1ET6525SA ST Amplifier Review

This is a review and detailed measurements of the Apollon 1ET6525SA ST Purifi based class D stereo power amplifier. It was kindly loaned to me by a member and costs 1,190.00€ (USD $1,348). Apollon designs are unique a step up from some of its competitors. Even the power switch feels nice and...

www.audiosciencereview.com

 

[Bwaslo]

The Dayton APA150 might work for you. https://www.parts-express.com/Dayton-Audio-APA150-150W-Power-Amplifier-300-812?quantity=1
I've used one for calibrating microphones to 90kHz.
If you really need the bottom f3 to be lower and don't mind voiding wartantee, I suspect you could increase the value of an input coupling capacitor. The rolloff appears to be 6dB/octave, likely just from a single coupling capacitor.

 

[SSS]

Look for a vintage CROWN DC-300A. As the name says it works from DC to 100 kHz.

 

[Speedskater]

For 50 kHz definitely a Class A/B amp. Class D amps aren't great much above 20 kHz.
For DC you can bypass the input capacitor, but then you lose protection.
For near DC, you can replace the input capacitor with a very large cap.

 

[Cbdb2]

Why do you need DC to test speakers? Use a battery or a DC power supply.

 

[vintologi]

The Dayton APA150 might work for you. https://www.parts-express.com/Dayton-Audio-APA150-150W-Power-Amplifier-300-812?quantity=1
I've used one for calibrating microphones to 90kHz.
If you really need the bottom f3 to be lower and don't mind voiding wartantee, I suspect you could increase the value of an input coupling capacitor. The rolloff appears to be 6dB/octave, likely just from a single coupling capacitor.

View attachment 527331

It's decently cheap at least (220$) and has a volume control.

I guess the downside is S/N ratio not being the best but for what i mainly need it for that might not actually matter much.

 

[dguillor]

Lots of AB amplifiers have wide bandwidth. It’s more difficult for a class D amplifier to have wide bandwidth because they need to filter the switching frequency.

 

[vintologi]

Lots of AB amplifiers have wide bandwidth. It’s more difficult for a class D amplifier to have wide bandwidth because they need to filter the switching frequency.

Is there any good option currently available?

 

[Mr. Swordfish]

Look for a vintage CROWN DC-300A. As the name says it works from DC to 100 kHz.

My recollection is that the original DC-300 would pass DC, but the DC-300A, which was designed for audio instead of controlling lathes, added circuitry that blocked DC.

I used to loan mine to an outfit that used it to produce 50hz 110v AC to test gear the Japanese market. Still around somewhere...

 

[Oddball]

I am trying to find an amplifier that is good for accurately measuring the frequency response of speakers and ideally it should also be good for regular use.

Cheap but not quite what i am looking for: Topping Mini 300

Hypex NC400 is down to 10hz at least but not so great otherwise. I also don't feel like doing some DIY amp project any time soon.

What do you need to amplify down to 10hz? Passive sub or what? Nothing goes that low except for such things - in huge boxes, and they need 2kW or so to make it happen.

So not sure what is the point?

 

[kyuu]

Yeah, I don't understand the notion that you need to test a speaker down to DC. With very few exceptions, always very large subwoofers, there isn't anything under 10Hz. You're limiting your options and risking damage to your equipment for nothing.

 

[dguillor]

Is there any good option currently available?

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[SSS]

My recollection is that the original DC-300 would pass DC, but the DC-300A, which was designed for audio instead of controlling lathes, added circuitry that blocked DC.

I used to loan mine to an outfit that used it to produce 50hz 110v AC to test gear the Japanese market. Still around somewhere...

All three versions the DC-300 DC-300A DC-300A-II pass DC as to the specs in the service manuals and customer manuals. I own the DC-300A and it does pass DC. I admit that the frequency response up to 100 kHz was measured at low wattage like 2W.

 

[Shiva]

Take a look at the Cherry Ultra...

Cherry Ultra Amplifier Specifications​

The Cherry Ultra is the top-of-the-line stereo amplifier from the Digital Amplifier Company, designed for high-fidelity audio with a focus on power, precision, and low distortion.

Key Specifications​

• Power Output: 400 watts per channel into 8Ω, 675 watts per channel into 4Ω. It is bridgeable for mono operation, delivering up to 1350W into 8Ω.
• Power Supply: Features a massive 1500W (or 1800W in some sources) toroidal transformer for high headroom and dynamic transients.
• Total Harmonic Distortion (THD+N): Exceptionally low at 0.005% (1kHz) and 0.009% across 20Hz–20kHz at 10W.
• Signal-to-Noise Ratio (SNR): 116dB, contributing to a very quiet background.
• Gain: 27.4dB.
• Frequency Response: 1Hz to 60kHz.
• Output Impedance: 0.045Ω at 1kHz, providing strong speaker control.
• Inputs: True balanced XLR inputs (RCA-to-XLR adapters included).
• Efficiency: Highly efficient Class-D design, consuming less than 30W at idle and less than 5W in standby.
• Physical: Measures approximately 17.0" x 14.3" x 4.6" and weighs 42 lbs.