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Testing amps

hopeless said:
I think, in the end, you are dealing with clipping. The spec sheet is nice and all, but it's invalid as soon as you hook up speakers.

I wouldn't expect either speaker to be particularly reactive, but it's possible your amp doesn't like them. In such a case, clipping will come on early.
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Agreed. Watts/Chanel is not a complete measure of an amplifier's capability. There are some speakers my 50 to 60 watt units drive better than my 125W/C AVR, though all can blow me out of the room. The 50-60 watt units (Sansui 5000a, Adcom 535, NAD 3xx units) are what I actually use for two channel music.
 
If you are only going to use it once, why don't you take the money and just buy a new AVR? If it has the same problem, return it and then figure out what else might be causing your issues?
 
I see that that AVR sold for about $350 when new, and I don't know what you have invested in yours, but spending too much money doesn't make sense. There are a lot of very cool old Yamaha AVR's that we all know deliver some power. Many of these can be purchased for pretty little money.

If you want to measure the power, another way to go is to get a cheap ADC. Or audio interface as they are called. A focusrite Solo, or 2i2, or a lot of other low cost interfaces for less than $100. I see them on Craigslist all the time. Get one 8Ohm resistor that can handle the watts, build a voltage divider network and plug into the ADC. Use the scope in REW to see the clipping, measure RMS with a DVM.

Same setup as this thread, but instead of measuring distortion, use the scope in REW.

https://www.diyaudio.com/community/threads/howto-distortion-measurements-with-rew.338511/
 
Asmodeus2112 said:
I see that that AVR sold for about $350 when new, and I don't know what you have invested in yours, but spending too much money doesn't make sense. There are a lot of very cool old Yamaha AVR's that we all know deliver some power. Many of these can be purchased for pretty little money.
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That was not a lot of cash even in '96. If I recall correctly, I spent about $900 on a 75W/C Carver at about that time passing up more Watts/Channel for less money in return for being able to better drive my speakers.
AVR's that do not have HDMI are in general pretty common on the used market. In addition to the Yamahas mentioned by Asmodeus perhaps something from Marantz.
 
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Here's the EU specs(from HifiEngine) for the same model:

  • Tuning range: FM, MW

    Power output: 65 watts per channel into 8Ω (stereo)

    Surround output: 60W (front), 60W (center), 60W (rear)

    Frequency response: 10Hz to 40kHz

    Total harmonic distortion: 0.05%

    Damping factor: 30

    Input sensitivity: 3mV (MM), 200mV (line)

    Signal to noise ratio: 80dB (MM), 85dB (line)

    Channel separation: 55dB (line)

    Output: 200mV (line)

    Speaker load impedance: 4Ω to 16Ω

    Video Connections: composite

    Dimensions: 430 x 158 x 312mm

    Weight: 8.8kg

    Accessories: remote control

    Year: 1996
 
Actually, you don't even need an external ADC, just plug into the sound card on a computer from the voltage divider. The reason to use a sound interface is to get a low noise level to measure distortion, but to just see a sine wave clip a computer sound card is fine. Also, you can use the frequency generator in REW.
 
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Hi all. Many posts under the bridge here - thanks to everyone for jumping in. I will try to address them.

First of all, this amp will go pretty loud. But it will not cleanly go as loud as I think it should with that kind of wattage and headroom. That is an uninformed suspicion only, which gives me the idea to run an experiment to get the facts. The result will be either: 1. the amp works and my expectations are too high/ears too crappy, 2. the amp is not putting out rated power and should be replaced perhaps with a real power amp such as a 200-300 watt Crown ($300-500). If the latter, I can run the same experiment to determine safe levels for the various 6-8ish ohm speakers.

I both love and fear the idea of recycling some Nichrome device for this. Probably not quite as dangerous as a microwave-oven-magnetron spot welder.

On clipping and amp compatibility: Not sure why the spec sheet is invalid when speakers are hooked up. If an amp is FTC-compliant rated 120 watts into 8 ohms 20-20KHz with 2dB of headroom, that is a statement of fact, and further it indicates a powerful amp that should be capable of loud clean sound. Also the amp exhibits the same behavior with at least 4 different speakers. If the amp doesn't like them it is defective or out of spec, and that is what I'm trying to figure out.

Regarding the cheapness, of both the original and a used similar replacement, both are definitely true. However I could get into the same situation as I am now, with uncertain power and performance, and not sure how far I can go without endangering the speakers.

The EU spec is interesting but ultimately immaterial (another poster mentioned it earlier in the discussion also). The rating differences probably are for a rebadged lower model, or relate to the power supply and the greater line voltage. In any case this is a US spec unit and the published specs are regulated by the FTC parameters.

And on the measurement, I need to think about that solution a little more. It seems doable - will do some reading.

One thought to close with: It is possible I am just looking for an excuse to buy the Crown.
 
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C Hart said:
Hi all. Many posts under the bridge here - thanks to everyone for jumping in. I will try to address them.

First of all, this amp will go pretty loud. But it will not cleanly go as loud as I think it should with that kind of wattage and headroom. That is an uninformed suspicion only, which gives me the idea to run an experiment to get the facts. The result will be either: 1. the amp works and my expectations are too high/ears too crappy, 2. the amp is not putting out rated power and should be replaced perhaps with a real power amp such as a 200-300 watt Crown ($300-500). If the latter, I can run the same experiment to determine safe levels for the various 6-8ish ohm speakers.

I both love and fear the idea of recycling some Nichrome device for this. Probably not quite as dangerous as a microwave-oven-magnetron spot welder.

On clipping and amp compatibility: Not sure why the spec sheet is invalid when speakers are hooked up. If an amp is FTC-compliant rated 120 watts into 8 ohms 20-20KHz with 2dB of headroom, that is a statement of fact, and further it indicates a powerful amp that should be capable of loud clean sound. Also the amp exhibits the same behavior with at least 4 different speakers. If the amp doesn't like them it is defective or out of spec, and that is what I'm trying to figure out.

Regarding the cheapness, of both the original and a used similar replacement, both are definitely true. However I could get into the same situation as I am now, with uncertain power and performance, and not sure how far I can go without endangering the speakers.

The EU spec is interesting but ultimately immaterial (another poster mentioned it earlier in the discussion also). The rating differences probably are for a rebadged lower model, or relate to the power supply and the greater line voltage. In any case this is a US spec unit and the published specs are regulated by the FTC parameters.

And on the measurement, I need to think about that solution a little more. It seems doable - will do some reading.

One thought to close with: It is possible I am just looking for an excuse to buy the Crown.
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Specifications are not valid in actual use because the testing is done into an 8ohm resistor which is nothing like a speaker load. An 8 ohm speaker is only 8 ohms in passing. It varies with frequency and port tuning. You also have other nasty stuff happening as well, phase angles and back EMF. Welcome to the jungle. Most receivers really aren't designed to drive speakers, they are designed to look good driving those resistors. Most people don't understand that, seeing specifications as gospel. There are times that your 120 watt receiver will only be able to deliver a fraction of that power into a real speaker load. This is why a lot of amplifiers sound gutless.they can't feed the power the speakers demand.

The problem with audio is that you are always working with bad information. Or, probably more accurate, information in a context you aren't likely to understand. You are expecting separate amplifier performance from a receiver. Not gonna happen.
 
hopeless said:
Specifications are not valid in actual use because the testing is done into an 8ohm resistor which is nothing like a speaker load. An 8 ohm speaker is only 8 ohms in passing. It varies with frequency and port tuning. You also have other nasty stuff happening as well, phase angles and back EMF. Welcome to the jungle. Most receivers really aren't designed to drive speakers, they are designed to look good driving those resistors. Most people don't understand that, seeing specifications as gospel. There are times that your 120 watt receiver will only be able to deliver a fraction of that power into a real speaker load. This is why a lot of amplifiers sound gutless.they can't feed the power the speakers demand.

The problem with audio is that you are always working with bad information. Or, probably more accurate, information in a context you aren't likely to understand. You are expecting separate amplifier performance from a receiver. Not gonna happen.
Click to expand...

I appreciate your interest and advice. While I have been proven wrong many times and learn something new every day about it, I'm not a noob to audio. Your point about possible impedence issues is valid. I would counter that a significant audible difference in output that results in clipping because of varying speaker impedence of music signals is not something I have seen. These components are not at all exotic and should interact benignly.

But for other comments we will have to agree to disagree. I am not a spec-only guy but do I expect conformance to spec as a minimum from a Japanese maker of quality electronics, whether on a power amp, integrated amp, or hifi receiver.
 
C Hart said:
I appreciate your interest and advice. While I have been proven wrong many times and learn something new every day about it, I'm not a noob to audio. Your point about possible impedence issues is valid. I would counter that a significant audible difference in output that results in clipping because of varying speaker impedence of music signals is not something I have seen. These components are not at all exotic and should interact benignly.

But for other comments we will have to agree to disagree. I am not a spec-only guy but do I expect conformance to spec as a minimum from a Japanese maker of quality electronics, whether on a power amp, integrated amp, or hifi receiver.
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It will meet spec if operating to spec, driving an 8 ohm resistor as advertised. Put all the faith in it you will. Not a noob either, 25 years in the industry, mid-fi to high end. I've seen "competent" Japanese receivers hooked up to an oscilloscope playing test tones into a speaker load. Some feel the need to grasp for straws. I have that up decades ago.
 
Hello C Hart, do you have a spl meter. I am asking this because I believe you are getting close to the clipping limits of that amp.
How loud are you trying to achieve. The L166’s are 89db/1W @ 1 meter so if your are reading about 110 db @ 1 meter that is about your max on peaks. Be careful as the 066 tweeter is non replaceable as no parts are available unless purchased used.
A lot of the budget AVR’s from that era looked good on paper but in real world conditions did not exactly live up to it
 
There’s a guy on YouTube that tests our car amps. On a SMD amp dyno. It would be cool to see the same thing done with home audio gear.

I have no interest in car audio anymore, and yet I still love watching them “dyno” amps.
 
powerman said:
The L166’s are 89db/1W @ 1 meter so if your are reading about 110 db @ 1 meter that is about your max on peaks. ...
A lot of the budget AVR’s from that era looked good on paper but in real world conditions did not exactly live up to it
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hifiengine has the L166 listed at 76dB, which I found elsewhere but also found the 89dB (New JIS) figure listed for the L166 Horizon at Audio-database. Unless the Horizon is significantly different at least one of these numbers is irrelevant.
If the 89dB is a stretch for the receiver then anything less is a bridge too far far for a (the) budget unit. AVR's stuff a lot into one box and the lower the price point the more extreme the compromises. It's a stretch to consider budget AVR units "hifi" despite what marketing may say.
 
@powerman thanks for the input - yes I do have an SPL meter. I don't have a reading yet because I don't want to crank it up without some power data, but I hope to achieve 105dB peak with 95dB continuous, which should be within spec for both.

I am aware of the JBL limits and your concerns are very well taken. A previous owner blew the 066s and replaced them with slightly tougher 035tia's but it's still a worry. The woofers (122A) are the weak link - not as robust as I would like and alnico which is more power-sensitive than ferrite. I do hear you on the AVRs but this one is really more audio receiver than AVR. It has very minimal AV capability and is really an audio receiver that will do 5 channels powered (plus I'm only using the front). And that is part of what I want to find out.

How did I get to 95dB: By the numbers, the L166 should be 10 watts to 99dB and 100 watts to 109dB. With 2dB headroom the amp should do clean peaks of ~180 watts. However, the woofer will take only 50 watts continuous, so that gets me down to ~95dB as an upper limit.

@elitopus me too! I watch those waiting for smoke. I think that test box uses load resistors also. Maybe I'll have a dyno video when this is all done.
 
@Guido57 yes that 76dB is an early wacky JBL attempt to quantify what you get at a typical listening position. 89dB is actually correct especially since this speaker design could not be more ordinary.

A couple of posters made the point of cheapo AVRs - it is certainly correct. I too have seen tests that show how crappy they are. Part of the fun in the exercise is figuring out if this is one of them. And maybe justifying that XLS800.
 
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