How to sell amplifiers (cheat the sound)

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See attachment (measurement starts at 20hz and ends at 20khz), a reputable 70 Watts hifi amplifier with tone controls to center shows this kind of response with clear boost of bass and high frequency.

This is common practice in the audio industry.

This explains your big bass and high treble from your beloved SS amp. It is common in CD players, DAC, phono, you name it
 

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Mystified.
Commercial designs boost the 30hz region of 8db in the example, and the treble region to give excitement to the potential buyer. Some amps will behave like this when connected to speakers to give a weighty feeling to the music and you will of course buy the amp which has the most detail sound (boosted treble and boosted bass) and more bass.
 

kevinkr

Administrator
Paid Member
I measured a lot of reputable audio gear back in the day for my employer and I never saw anything like this unless loudness compensation was enabled.I don't know what they do these days, but even with undefeatable tone controls it was usually possible to find the flatest response somewhere near the center of the range. (not always)

Instead of making such a generic allegation all commercial electronics how about some specifics? Also a loop back measurement showing that the measurement system is flat would be a welcome.

Edit: Measurement levels seem to be very low, normally somewhere between -6dBFS and -20dBFS is where I tried to do these sorts of measurements. I question this.
 

wg_ski

Member
2007-10-10 5:21 pm
Probably just undefeatable loudness compensation. Turn up the volume pot and see if it flattens. The loudness may not necessarily be undefeatable - but on modern gear be buried so deep in menus that you give up before you find it. My last car stereo head was that way. Don't even try to find it with the engine running. Even at a light.
 
I measured a lot of reputable audio gear back in the day for my employer and I never saw anything like this unless loudness compensation was enabled.I don't know what they do these days, but even with undefeatable tone controls it was usually possible to find the flatest response somewhere near the center of the range. (not always)

Instead of making such a generic allegation all commercial electronics how about some specifics? Also a loop back measurement showing that the measurement system is flat would be a welcome.

Edit: Measurement levels seem to be very low, normally somewhere between -6dBFS and -20dBFS is where I tried to do these sorts of measurements. I question this.

It is flat, I have other measurements done with it. The sample was at around 10 watts and I use voltage dividers to protect the measuring equipment, this is not a scope, it is a highly precise distortion meter, 192khz 24 bit.
 
Probably just undefeatable loudness compensation. Turn up the volume pot and see if it flattens. The loudness may not necessarily be undefeatable - but on modern gear be buried so deep in menus that you give up before you find it. My last car stereo head was that way. Don't even try to find it with the engine running. Even at a light.

I am not stupid, the volume had no effect on the tests, it is where the amp stands with controls set to 0, it is never flat. I don't mention any company names, but big names are out there. Start testing and you will believe. Use speakers, some tone controls are activated only by a speaker load and not a resistor.
 

wg_ski

Member
2007-10-10 5:21 pm
If it really measures flat into a resistor but "smiley faced" with a loudspeaker I'd like to see how they pulled that off in a modern amp. Only way I could see without using some sort of digital trickery would be a single-ended pentode/ NPN/ Mosfet with only cathode/source feedback. Voltage gain would follow the speaker's impedance curve. Bass would be a spike and highs would rise gradually. Old console stereos with large open-back fullranges used to do that, and many sounded better than they had a right to.

It's not totally outside the realm of possibility to use non defeatable EQ as "standard". I've built amps that way back in the day. It saved the expense of pots that would have been turned up all the way anyway.
 
A lot of people around here have measured a lot of stuff over the years. No one is calling you stupid, but it would help if you could provide a bit more information to substantiate your claims. For example, I might be wrong about this (someone please speak up if I am), but I don't think it would be a violation of any rules here if you were to name the make & model that produced the response you've posted above, and perhaps some others where you've observed this kind of thing.

-- Jim
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
hifi amplifier with tone controls to center

Strange. What kind of tone control is it. Imo, there is no need to cheat with tone control design. Users are free to lower the bass response if they want to. A bass boost may be needed to compensate for the room (so measure the acoustics not the electronics).

Besides, most buyers will boost the LF far beyond acoustically flat anyway. That's why they pay for the tone control. Me, I always defeat the tone control.
 

AngelP

Member
Paid Member
2012-07-12 9:11 am
Stansted
I am a bit mystified, too. "A reputable 70W hi-fi amplifier"? Could you please state which one so perhaps one of our fellow diyaudio members may try to replicate your observations?

Also, as you have seen this as being commonplace could you possibly confirm that the amps you have seen this effect on were all under some sort of software control?
 
With speakers instead it happens ALL the time .... especially because proper methods and equipment to measure is not available to common people ...manipulations take place in various areas of the acoustical spectral ...

Even if one manages to measure anything the answer will be :"its made out of your room "

For reputable brands but for lo fi or cheaper or commercial gear this is quiet common Philips also did it many years ago but there was a legal issue around it ( if my info is accurate enough they lost in court big time ...)

Its ok if for cost reductions or other reasons for a company not to be able to reproduce accurately a music production. There is an issue though if a company is altering the production on purpose...

Kind regards
Sakis
 
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I am a bit mystified, too. "A reputable 70W hi-fi amplifier"? Could you please state which one so perhaps one of our fellow diyaudio members may try to replicate your observations?

Also, as you have seen this as being commonplace could you possibly confirm that the amps you have seen this effect on were all under some sort of software control?

I hate being in the hot spot like you place me there. I will not mention company names. This post was to illustrate how the flat frequency response is cheated by designers of amps when it comes to drive real speakers.

I doubt NAIM for example would do such a thing or NAD. But you will get surprised to actually test your amp connected in your speakers, this is not the speakers that I measured but the reaction of the output stage to a speaker. If the bass is too good and the high has so much details you are almost sure the amp is not flat as it claims or should be honestly.

The bottom point: it is a simple trick to do to fool customers into buying vs a neutral frequency amp
 
dB scale suggests this is measured at a very low level, and the curve indicates a normal loudness function is active.

Johan-Kr

huh no, it was made to around 15 watts, and for that particular example it had the same response into a 8 ohm resistor

what do you mean a normal loudness function??? it is dbv and it is a sweep test, the test starts at 20hz and ends at 20khz.
 
I hate being in the hot spot like you place me there. I will not mention company names. This post was to illustrate how the flat frequency response is cheated by designers of amps when it comes to drive real speakers.

I doubt NAIM for example would do such a thing or NAD. But you will get surprised to actually test your amp connected in your speakers, this is not the speakers that I measured but the reaction of the output stage to a speaker. If the bass is too good and the high has so much details you are almost sure the amp is not flat as it claims or should be honestly.

The bottom point: it is a simple trick to do to fool customers into buying vs a neutral frequency amp

No ...NAim or NAD will do the opposite...IE mess up somewhere in the middle area since their audience focus there related to the musical program that they listen .... One that likes hard rock will be bother with the sound of the electric guitar as priority and bother less on how crisp or clear is the high ...Approach like that allows the British to continue to work with 3MHZ semis :D:D:D:D
 
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