How do you know how good your diy amp is?

fastasulike · 17th December 2009, 10:15 PM

After spending a lot of time and effort on an amp project to get it to look presentable and more importantly, make some sound that at least passes as music, how do you or could you quantify or evaluate its performance?

I know you could take it along to a friends place, or cheekily take it for comparison when auditioning some 'new' replacement, but are there any tests that would, in theory, be telling of its abilities?

I would think that it would also help to have some sort of reference product for comparison also.

woodturner-fran · 17th December 2009, 10:38 PM

Simply put: comparison to known standards ......

Fran

Conrad Hoffman · 17th December 2009, 10:42 PM

Obviously I listen to it, but I also do a suite of measurements. Large and small signal response, response and wave shape into various loads, THD and a spectral plot on the PC. I like to see music on the output and very little music on the supply rails. I want to see no sticking to the rails when it clips. I want the bias to be stable with temperature and have no chance of thermal runaway. I want full output at 20 kHz with no tendency to short the supplies together. I don't normally include protection because I figure if I built it, I can fix it if I'm stupid enough to blow it up. But, if it has protection, I want to verify that it works as intended without working on the music when it shouldn't. I also check very carefully for RF from the supply and look at how HF or RF can affect the input.

CH

MikeHunt79 · 17th December 2009, 11:03 PM

I just listen to it, and if I like what I hear, I'm happy.... The annoying thing is that I always try and think of ways to improve the sound, despite already thinking the sound is good...

Bigun · 18th December 2009, 02:00 AM

If there's no smoke after several days of enjoying the sound then I take a break. Come back to it later and then if I still like the sound, it's good to go.

I have zero interest in measurements, having already done all the measurements in Spice

MJL21193 · 18th December 2009, 02:07 AM

Spoken like a true disciple.

Glowbug · 18th December 2009, 02:17 AM

Quote:

If there's no smoke after several days of enjoying the sound then I take a break. Come back to it later and then if I still like the sound, it's good to go.

I'm of that school.

If it doesn't explode...

eyoung · 18th December 2009, 02:26 AM

I have an o'scope and a freq generator , if i can't see it and I like what I hear then it's good to go. Frequently you will hear someone say they heard an amp they liked despite distortion measurements.

Keep listening and reading,Find what you like and stick with it.

Happy listening(holidays), Elwood

jez · 18th December 2009, 11:04 AM

Build one channel and test it for THD, stability, square wave response, clean clipping, bias stability etc. You can't really do all this with spice 'cos the real world is a very different place!
If all is well then I build the other channel and listening can begin...
Some amps that have measured great can fail this last test by a long way!

osscar · 18th December 2009, 11:13 AM

I am just looking at the screen of different frequency signals form - let say from 10Hz - 30000Hz and also measure gain (with analog microvoltmeter) on different frequencies - like 20Hz, 200Hz, 1KHz, 5KHz, 10KHz, 20KHz. The main instrument is the ears

17th December 2009, 10:15 PM	#1
fastasulike diyAudio Member Join Date: Nov 2009	How do you know how good your diy amp is? After spending a lot of time and effort on an amp project to get it to look presentable and more importantly, make some sound that at least passes as music, how do you or could you quantify or evaluate its performance? I know you could take it along to a friends place, or cheekily take it for comparison when auditioning some 'new' replacement, but are there any tests that would, in theory, be telling of its abilities? I would think that it would also help to have some sort of reference product for comparison also.

17th December 2009, 10:42 PM	#3
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	Obviously I listen to it, but I also do a suite of measurements. Large and small signal response, response and wave shape into various loads, THD and a spectral plot on the PC. I like to see music on the output and very little music on the supply rails. I want to see no sticking to the rails when it clips. I want the bias to be stable with temperature and have no chance of thermal runaway. I want full output at 20 kHz with no tendency to short the supplies together. I don't normally include protection because I figure if I built it, I can fix it if I'm stupid enough to blow it up. But, if it has protection, I want to verify that it works as intended without working on the music when it shouldn't. I also check very carefully for RF from the supply and look at how HF or RF can affect the input. CH __________________ I used to be an audiophool like you but then I took an arrow to the knee.

18th December 2009, 02:00 AM	#5
Bigun diyAudio Member Join Date: Jan 2009 Location: K-W Ontario Blog Entries: 2	If there's no smoke after several days of enjoying the sound then I take a break. Come back to it later and then if I still like the sound, it's good to go. I have zero interest in measurements, having already done all the measurements in Spice __________________ "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

18th December 2009, 02:26 AM	#8
eyoung diyAudio Member Join Date: Aug 2007 Location: Sunny SC,USA 15 min south of Charlotte NC	I have an o'scope and a freq generator , if i can't see it and I like what I hear then it's good to go. Frequently you will hear someone say they heard an amp they liked despite distortion measurements. Keep listening and reading,Find what you like and stick with it. Happy listening(holidays), Elwood __________________ "when you open your mind to the imposible, soon you will find the truth...."

18th December 2009, 11:13 AM	#10
osscar diyAudio Member Join Date: May 2009 Location: Riga, LV	I am just looking at the screen of different frequency signals form - let say from 10Hz - 30000Hz and also measure gain (with analog microvoltmeter) on different frequencies - like 20Hz, 200Hz, 1KHz, 5KHz, 10KHz, 20KHz. The main instrument is the ears __________________ Leach amp LM 3875 F5 LM1875 Le Monstre Leach amp2 OPA549 OBH8SE


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17th December 2009, 10:38 PM	#2
woodturner-fran diyAudio Member Join Date: Jan 2006 Location: Ireland	Simply put: comparison to known standards ...... Fran

17th December 2009, 11:03 PM	#4
MikeHunt79 diyAudio Member Join Date: Aug 2003 Location: Bristol, UK	I just listen to it, and if I like what I hear, I'm happy.... The annoying thing is that I always try and think of ways to improve the sound, despite already thinking the sound is good...

18th December 2009, 02:07 AM	#6
MJL21193 Account disabled at member's request Join Date: Mar 2007	Spoken like a true disciple.

18th December 2009, 11:04 AM	#9
jez diyAudio Member Join Date: Jan 2004 Location: n.e england	Build one channel and test it for THD, stability, square wave response, clean clipping, bias stability etc. You can't really do all this with spice 'cos the real world is a very different place! If all is well then I build the other channel and listening can begin... Some amps that have measured great can fail this last test by a long way!

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