Anyone deliberately dial in 2nd harmonic?

DrewP · 15th November 2009, 07:13 AM

Much as the binkum in the Wikipedia "valve sound" article grates due to its poor/selective/non-existent quoting of references, the regularly touted pleasing nature of second harmonic distortion is interesting.

Once one moves away from a global loop feedback circuit to a design with zero feedback then the possibility to dial in second harmonic distortion deliberately raises its head.

For instance, in the PP el84 amp I'm working on, simply by increasing the negative bias voltage on the input tube (6CG7) from 5v to around 10v I slide along the load line from a point where the lines are pretty evenly spaced to a point where there's a decent wad of 2nd harmonic being produced.

So, while in theory accuracy is what we strive for, do any of you deliberately engineer second harmonic into your designs?

(I'm not saying that I intend to, merely curious to see if anyone does)

SY · 15th November 2009, 10:36 AM

Yes and no. This is one of those deals where lots of people do it but either don't know that's why they like it better or won't admit it.

greenvalve · 15th November 2009, 11:19 AM

I've been playing around with this for a while. I've found that dialing in a little extra 2nd harmonic can make 'dry' speakers, like many metal coned drivers, sound more listenable.

An interesting arrangement is to use starved filaments and at the same time using 0V bias. Here is Steve Benchs work... DHT with starved filaments.

Using the 01A as a driver with fil of 3.2v, anode 60v and bias 0v is a surprisingly enjoyable listen, albeit high distortion. The imaging is spectacular, likely because of the directly grounded cathode and no cap in the signal path on the grid or cathode of the tube.

Magura · 15th November 2009, 12:06 PM

Quote:

Originally Posted by SY

Yes and no. This is one of those deals where lots of people do it but either don't know that's why they like it better or won't admit it.

This is according to my understanding, a key point to why quite many people claim to prefer tubes, in particular SE. If you take a look at the Zen articles, you will find, that those amps are very popular. They sure are the SS pendant to a SE tube amp.

As for the last part, yes most guys would rather admit to have problems satisfying their woman , than that they actually like distortion.
However, in the tests I have performed, it was evident that many actually prefers some distortion, over say 0.0002% THD.

Magura

pointy · 15th November 2009, 12:50 PM

there are other things.............clarity of the audio image and speed of followers, good local feed back etc. so sometimes there must be a pay off between them to get what you like best from your speaker drives.

greenvalve · 15th November 2009, 01:52 PM

Quote:

Originally Posted by Magura

As for the last part, yes most guys would rather admit to have problems satisfying their woman , than that they actually like distortion.
However, in the tests I have performed, it was evident that many actually prefers some distortion, over say 0.0002% THD.

Magura

Hey now, what are you insinuating? Lets just say the mature man is confident in his ability... to appreciate distortion.

Curly Woods · 15th November 2009, 02:24 PM

Quote:

Originally Posted by greenvalve

Hey now, what are you insinuating? Lets just say the mature man is confident in his ability... to appreciate distortion.

SS guys are the ones that need "feedback" to know that they are men

A little distortion never hurt a tube man

Eli Duttman · 15th November 2009, 03:47 PM

IMO, it's a matter of distortion spectrum. That's why I strongly advocate the use of 12AT7s in PP designs. The NET HD spectrum is an ear pleasing "waterfall" of 2nd > 3rd > 4th ... The 12AT7's bias towards 2nd order products meshes very well with the internal even order product cancellation inherent to PP "finals".

IM distortion is an altogether different matter. As IM products are unrelated to the desired signal, they are EXTREMELY irritating. Therefore, getting the IM distortion of a circuit as close to zero as can be is a good thing. To a degree, music masks HD and underscores IMD.

Curly Woods · 15th November 2009, 04:06 PM

Quote:

Originally Posted by Eli Duttman

IMO, it's a matter of distortion spectrum. That's why I strongly advocate the use of 12AT7s in PP designs. The NET HD spectrum is an ear pleasing "waterfall" of 2nd > 3rd > 4th ... The 12AT7's bias towards 2nd order products meshes very well with the internal even order product cancellation inherent to PP "finals".

IM distortion is an altogether different matter. As IM products are unrelated to the desired signal, they are EXTREMELY irritating. Therefore, getting the IM distortion of a circuit as close to zero as can be is a good thing. To a degree, music masks HD and underscores IMD.

Thank you Eli. People rarely discuss IMD and its affect on music reproduction.

Allen Wright · 15th November 2009, 04:15 PM

Take any "tube output" Chinese made CD/SACD player. Put in a test disc and measure the audio distortion before (very low) and after the tube - VERY high, and mostly 2nd h!

Yet some people just love the sound of these sonic attrocities.

But the worst I have ever seen/heard is a German CD player based on a Playstation mechanism, with a EL34 as an output amp, with something like a 100k anode load R.

Over 25% 2nd harmonic! And when I corrected it - the owner demanded it be put back as it was!

Chocolate sauce is chocolate sauce...and some peole can't get enough of it!

Regards, Allen

15th November 2009, 07:13 AM	#1
DrewP diyAudio Member Join Date: Jan 2002 Location: Canberra, Australia	Anyone deliberately dial in 2nd harmonic? Much as the binkum in the Wikipedia "valve sound" article grates due to its poor/selective/non-existent quoting of references, the regularly touted pleasing nature of second harmonic distortion is interesting. Once one moves away from a global loop feedback circuit to a design with zero feedback then the possibility to dial in second harmonic distortion deliberately raises its head. For instance, in the PP el84 amp I'm working on, simply by increasing the negative bias voltage on the input tube (6CG7) from 5v to around 10v I slide along the load line from a point where the lines are pretty evenly spaced to a point where there's a decent wad of 2nd harmonic being produced. So, while in theory accuracy is what we strive for, do any of you deliberately engineer second harmonic into your designs? (I'm not saying that I intend to, merely curious to see if anyone does)

15th November 2009, 10:36 AM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Yes and no. This is one of those deals where lots of people do it but either don't know that's why they like it better or won't admit it. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

15th November 2009, 03:47 PM	#8
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	IMO, it's a matter of distortion spectrum. That's why I strongly advocate the use of 12AT7s in PP designs. The NET HD spectrum is an ear pleasing "waterfall" of 2nd > 3rd > 4th ... The 12AT7's bias towards 2nd order products meshes very well with the internal even order product cancellation inherent to PP "finals". IM distortion is an altogether different matter. As IM products are unrelated to the desired signal, they are EXTREMELY irritating. Therefore, getting the IM distortion of a circuit as close to zero as can be is a good thing. To a degree, music masks HD and underscores IMD. __________________ Eli D.

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15th November 2009, 11:19 AM	#3
greenvalve diyAudio Member Join Date: May 2007	I've been playing around with this for a while. I've found that dialing in a little extra 2nd harmonic can make 'dry' speakers, like many metal coned drivers, sound more listenable. An interesting arrangement is to use starved filaments and at the same time using 0V bias. Here is Steve Benchs work... DHT with starved filaments. Using the 01A as a driver with fil of 3.2v, anode 60v and bias 0v is a surprisingly enjoyable listen, albeit high distortion. The imaging is spectacular, likely because of the directly grounded cathode and no cap in the signal path on the grid or cathode of the tube.

15th November 2009, 12:50 PM	#5
pointy diyAudio Member Join Date: Mar 2009	there are other things.............clarity of the audio image and speed of followers, good local feed back etc. so sometimes there must be a pay off between them to get what you like best from your speaker drives.

15th November 2009, 04:15 PM	#10
Allen Wright R.I.P. Join Date: Dec 2001 Location: Schaffhausen Switzerland	Take any "tube output" Chinese made CD/SACD player. Put in a test disc and measure the audio distortion before (very low) and after the tube - VERY high, and mostly 2nd h! Yet some people just love the sound of these sonic attrocities. But the worst I have ever seen/heard is a German CD player based on a Playstation mechanism, with a EL34 as an output amp, with something like a 100k anode load R. Over 25% 2nd harmonic! And when I corrected it - the owner demanded it be put back as it was! Chocolate sauce is chocolate sauce...and some peole can't get enough of it! Regards, Allen

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