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What is THD?

jderry78
10-11-2005, 10:32 AM
Sorry if this is a stupid question. But what does 10% THD mean?

John C. Kosick
10-11-2005, 11:15 AM
Total Harmonic Distortion......... see link (2nd. par.)


http://www.yamaha.com/yec/customer/FAQs/faq13b.htm

jderry78
10-11-2005, 12:17 PM
so 10% is what? Not so GOOD?

d6500k
10-11-2005, 05:53 PM
so 10% is what? Not so GOOD?
Correct. Quite bad in fact.

Doug k

maicaw
10-11-2005, 06:15 PM
so 10% is what? Not so GOOD?an amp putting out that much THD into high quality speakers would probably risk damaging them - you may have misread the spec-normally it's 1000 times less - it normally would be as shown in that faq A typical specification might read 100 watts RMS into 8 ohms from 20Hz-20KHz at .01% THD] - the human ear may not be able to hear under 2% THD (per the faq)- (I don't really believe that statement) but speakers will go crazy trying to acoustically reproduce it (heavy metal speakers excepted)

John C. Kosick
10-12-2005, 08:28 AM
The specs. for your model does say 10%. That is a very high % for 'THD'. I checked this link below, and 10% seems to be a common number in most/some of the lower priced 'HTIB' units. I have a Yamaha TSS-1 and it also has a 10% THD spec., but I'm still happy with the sound I get from this unit.
I guess it all depends on your hearing, and what you want to spend on a system. If you look at the specs. of the other 'higher priced' units, you will see 'THD" specs. around .08%.........if you can believe those numbers. Unless you are an 'audio engineer', how could you check their accuracy?????
If you are happy with the audio from your unit, I wouldn't be concerned.................... :)

http://www.bhphotovideo.com/bnh/controller/home?O=pagination&A=nextPage&Q=&catId=2520&compareCatId=2520&shs=&ci=2520&ac=&al=&bl=&sb=ps&sq=asc&fi=all&pn=2

jderry78
10-12-2005, 08:52 AM
Thank you for your reply, I think the sound of my system is exceptionally good, was just surprised that the $500.00 price I paid for it be have such a high THD. But you are right as long as I love it thats all that matters. Thank you again for your time and responses, they are greatly appreciated. :bowdown:

John C. Kosick
10-12-2005, 12:32 PM
There seems to be a big difference in 'THD' between these two units.
Perhaps 'RMS power' and 'speaker impedance' are big factors in the determination of "THD". Your unit has 6ohm speakers, the other unit has 8ohm speakers.
These two units seem to be very similar. Perhaps someone here can explain the BIG difference in these two units. I'm not an audiophile, so I have no idea. The internal components in the receiver should be the same......... so maybe its the RMS power/ speaker factor............. FWIW........

maicaw
10-12-2005, 01:37 PM
I guess it all depends on your hearing, and what you want to spend on a system. If you look at the specs. of the other 'higher priced' units, you will see 'THD" specs. around .08%.........if you can believe those numbers. Unless you are an 'audio engineer', how could you check their accuracy?????A lot of old-timey radio/electronics shops and hobbyists have THD analyzers suitable for measuring down to 1/2% or so - I recall Heathkit and Eico among the kit makers had them -simple devices - If you are curious it shouldn't be too hard to find somebody with one of the old inexpensive ones - Of course Tektroniz and H-P made the pro models - but those are very expen$ive and way too accurate. --
BTW Some of the old Western Electric vacuum tubes (300A's etc) used today in very expensive modern vacuum tube amps - were originall manufactured in the 1930s for use in the copper (16ga) land-line Blue(ABC), Red(NBC) and Purple(Mutual) (and green and yellow!) radio network feeds that had hundreds of "repeaters" strung across the country - each one of which added its THD - consequently the THD and IM of each individual repeater/amplifier was unmeasureable by the standards of that era. - [they weren't actually repeaters (2-way amps) -there was an unbelievably klutzy arrangement of voltages and relays that reversed every amp to send audio in the other direction on the same wires]The WEAF stations and network would become known as the (Click link for more info and facts about NBC Red) NBC Red network; the WJZ stations and network would be dubbed the (Click link for more info and facts about NBC Blue) NBC Blue network, which later became the (Click link for more info and facts about American Broadcasting Company) American Broadcasting Company @ http://www.absoluteastronomy.com/encyclopedia/n/nb/nbc2.htm

John C. Kosick
10-12-2005, 02:26 PM
Can you see anything in the specs. of these two similar units that would dictate a big difference in the 'THD' numbers???
I would think the receivers would be very similar in construction....... namely quality of parts. Therefore the receiver shouldn't be a factor....... or am I wrong there.

Any ideas.....

John C. Kosick
10-12-2005, 03:10 PM
I couldn't find too many articles on "THD"...... :confused:
I did find this one though.......... FWIW...... :rolleyes:
* Speaker quality seems to be a big factor (dynamic impedance).

http://www.rocketroberts.com/techart/amp.htm

** Who ate all the 'beer nuts'........ NUTS...... :(

maicaw
10-13-2005, 12:55 AM
Each of the dozen or so topics he discusses can show up as distortion - -Class of amp - power supply - clipping -impedance,- RMS power - etc..etc.. ---and all of course are argued by audiophiles - like progressive and interlaced and LCD and plasma - and contrast and viewing angle are by videophiles- The thing he mentioned in passing "even good speakers can have THD up to 10%, especially at low frequencies" - - the conversion from acoustic source to electrical signal (mic) and the conversion back to acoustic (speaker) - might be the primary source of distortion in todays audio reproduction systems. -particularly with small HT speakers -also someone here can probably verify that even pro microphones also have higher distortion than good amps - Akira mentioned in another thread how the recording engineer's job/artistry is to coax the symphonic sound of 100 instruments from a few 6" speakers - naturally it's impossible - so the recorded sound is manipulated to reproduce a believeable sound that matches in perception - the actual physical performance. (hope I got that right!)