Sound Quality Vs. Measurements

[fas42]

You've got a thing for shiny yellow metal, I can see that, Wave ...

Frank

[benb]

I'm sure it gives perfectly accurate reproduction of this.
Mozart - Horn Concerto No. 4 in Eb major - Rondo, Allegro - YouTube

[fas42]

It's all been done before ...

Tommy Dorsey - The Music Goes Round and Round - YouTube

Frank

[fas42]

I know that piece I just referred to by heart, just about -- it's on my one of my primary test CD's -- and "explains" why I go to the efforts I do. On YouTube, via PC monitors, it sounds pretty bloody awful - a quaint, historical document of a type of music that was played once, scratchy, poor tone, just experiencing an acoustic "cartoon" ...

Well, I want a bit more than that, and get it too: on a good system it turns into a full blown, full blooded musical soundscape; all the instruments sound like they're being played by real people, the voices sound like they're coming from flesh and blood, there's a real sense of space, and all that old-fashionedness, curiousity shoppe "cuteness" subjectively disappears ...

Frank

[dvv]

Originally Posted by DF96

...

If you are smarter than him, why not design your own circuit?

Exactly what I also asked Nige a month or so ago. After a point, reworking anything becomes tedious, expensive and low yield work which is simply not worth it.

If you want more, then it's better and more efficient that you start from scratch and do it the way you think it should be done.

[nigel pearson]

Hello Mr Wave , nice to have you back .

DF 96 . Agreed about messing about with 0 V reference points on amplifiers . I was thinking strictly the connection between the PSU capacitors . I can not remember an amplifier where at least to the eye it didn't look a no brainer to beef up the connection if a PCB . Reading Douglas Self on this I thought it had all been simplified . Tried what he suggested and got nowhere . It should be said I wasn't getting bad results anyway . It just didn't go anywhere applying strict rules . I concluded that the amount of copper matters most . I also found that returning the output Zobel to the star point often was worse ! Doubtless a bit of extra effort would have solved that ? Intriguing that for no obvious reason instability crept in ( the return wire was in free air and I did bend the wire to reduce inductance etc ) . Previously it was returned via amplifier ground by a less substantial wire ( tried it all ways if wondering ) . It was bad enough to kill a tweeter at one point !

I wonder sometimes when people say they heard a big difference going from lets say 2 x 10 000 uF to 2 x 68 000 uF would it be they reduced ripple in the 0 V reference ? That ripple not obvious if lets say 30 mA standing current ? My brother always said he could hear hum modulation with the Quad Valve amps . His point being Quad used common mode rejection of a valve op-amp arrangement to reject noise . He though it audibly obvious when approaching clipping . Drums lost tightness . He went on to say valve amps are low power and have acceptable distortion right up to clipping . Thus one gets perhaps 6 dB more usable power . That is fine if the bass is tight . Other than that he thought it an inspired design , not least it rejected the cheap all electrolytic PSU . A Siemens cinema amp was like that . Highly regulated supply to the drivers ( EF 41 x 2 ? ) . Very raw DC to the EL34's at 820 V ( 240 V ) !! I loved that amp especially with over driven National EL34's , its owner uses Siemens which are fine . 100 W @ 10% distortion , 9 dB feedback , 500 mV input sensitivity . 10 W 1.3% 1W 0.2 % . Thus up to 8W it was DIN 45500 . It would have no real distortion for speech . For explosions I can only imagine it was excellent when getting near clipping . The only defect was obviously low damping factor and that paper veil to the sound ( Pentode sound I feel ) . The transformer had a section which would drive 8 R . Probably to do exactly what I did , a bench test .

Dvv . Absolutely . I build most stuff Dead Bug style . Usually that works fine . The tricky bit is transferring it to PCB . A bit of Dead Bug plus PCB works . In the UK we have Silver DIP for cleaning cutlery . I have a hunch it would clean wires . I would wash them in detergent and then water afterwards . My Son has just qualified in forensic chemistry ( no job yet , it would help if he looked ? It adds to the diploma in Computer Science . I told him he can stay at college until 40 , his mother thought I was joking . It makes me feel better saying it , The course in electronics he almost past was cancelled because the tutor couldn't live on the salary ! We never once talked electronics I am relieved to say , he didn't need to . He plays classical guitar so why not music next ? Some degree in music would not go unnoticed by his dad ) . Not a vast leap to tackle this question Chris . He is obsessed with silver for medical uses .

[dvv]

Yessir, designing it is half the fun, building it is the other half. It should be a child of love

[DF96]

Originally Posted by nigel pearson

DF 96 . Agreed about messing about with 0 V reference points on amplifiers . I was thinking strictly the connection between the PSU capacitors . I can not remember an amplifier where at least to the eye it didn't look a no brainer to beef up the connection if a PCB . Reading Douglas Self on this I thought it had all been simplified . Tried what he suggested and got nowhere . It should be said I wasn't getting bad results anyway . It just didn't go anywhere applying strict rules . I concluded that the amount of copper matters most . I also found that returning the output Zobel to the star point often was worse ! Doubtless a bit of extra effort would have solved that ? Intriguing that for no obvious reason instability crept in ( the return wire was in free air and I did bend the wire to reduce inductance etc ) . Previously it was returned via amplifier ground by a less substantial wire ( tried it all ways if wondering ) . It was bad enough to kill a tweeter at one point !

You have just illustrated the point for me. Tinkering is as likely to make something worse as to improve it, unless the tinkerer is smarter than the original designer and has taken the time to fully understand the original design.

You need to think about what the purpose of the output Zobel is. Is it to tame the source impedance of the amplifier, or to tame the speaker/cable load impedance? If the latter (as I believe) then it should be across the speaker connection. Understand the design before trying to change it!

[dvv]

Originally Posted by DF96

You have just illustrated the point for me. Tinkering is as likely to make something worse as to improve it, unless the tinkerer is smarter than the original designer and has taken the time to fully understand the original design.

You need to think about what the purpose of the output Zobel is. Is it to tame the source impedance of the amplifier, or to tame the speaker/cable load impedance? If the latter (as I believe) then it should be across the speaker connection. Understand the design before trying to change it!

I'll drink to that.

Sometimes, it takes me weeks to even understand the original design schematic. Fiddling around without understanding it is more likely to cause trouble than to improve anything.

[nigel pearson]

That's is sort of where I got to DF 96 . I have seen it dogmatically stated otherwise . I repeated the experiment many times since and felt it to be an exception to the rule I found . As I terminate the speakers at the star point if my own design your answer works well with observation . I didn't accept the evidence of one thing to be the law for the other occasions . Intuitively if the star point doesn't work it should . It must be slightly more ideal or at least neutral . This was an amp with horrible hum problems amp I was looking at ( if sensitive speakers it would be obvious ) . I laid out the PSU differently as it was a dog's breakfast . It stayed the same . The preamp and amp had cascaded LM317's . Obviously an attempt at something . The transformer had two brass alignment capacitive nuts in the epoxy . I discovered that rotating the transformer affected a cure . Obviously the designer had spotted all of this . The best null was turning the transformer on end . Alas space didn't permit that . I drilled new fixing holes . I was then left with a choice . Minimum hum or nicest sound ? Nicest sound came when the hum was a little higher but less scope harmonics ( pointy bits ) . Neither was bad either way and perhaps 20 dB better than before ? It is very hard to say if my new PSU layout was better , it certainly looked neat . The amplifier sounded much better . Again the muddle that noise created was gone . I suspect the design had been set years before and new technicians just didn't check these things , not least where the transformers were made ? I got rid of 1 x LM317 and 1 x LM337 also . I replaced that with a cheap RCL filter . The R acting also as a fuse . The L was iron cored as that is all I had handy . As the LM317/337 had done most of the work I see no reason for the iron core to matter ? Certainly sounded great ( noticeably so with the choke , 22 000 uH as it insisted on saying ) . Iron cores used without the LM317 seem to ring on the scope . I did have slightly better RF hiss with the choke so kept it .

As for tinkering . I had to as it was that or the dustbin . I looked in my files for the graphs . Unfortunately this one time I didn't keep any , they were good reading .