Amp Guts Photos - Official Thread - Lets see those pics

[agedhorse]

Haven't listened to hundreds of different op amps, but likely dozens. Much of my auditioning takes place with AKG K702 headphones or my true 3-way fEARful cabinet. Both are more revealing than standard bass gear. I also have Q-tuner pickups in my Rapture 5 and Lane Poors in my Hamer 12-string, which means that my basses produce more upper overtone content than most, certainly much more than a P-bass with the treble rolled off. Under these conditions, it is easy to hear the difference in sound between an ADA4627-1 and a TL072. Through a single 15" with a low bandwidth bass amp and a muddy sounding bass, not so much....

I don't believe that for a minute, and I've done a TON of intensive testing with double-blind players. The results were that there was no perceivable difference every time I ran testing with the same circuit, different ICs. Zero perceived difference no matter how much I wanted there to be.

I think this is a case of "believe what you like" and be happy that it works for you.

 

[agedhorse]

To clarify, I was not asking, or suggesting, that you design a bass amp specifically for me. What I was saying is that it would be interesting to hear something like a D-800 or WD-800 with a "pure direct" option which bypasses unnecessary op amp stages. The idea is that you push a button, and it sends the signal directly from the input stage to the power amp sort of thing. I meant that in terms of a test article, an experiment, to see if any differences would be audible by people who were interested in giving it an audition. If having several op amps in the signal path actually makes a difference to the sound, such a test should, in principle, be revealing.

There's a lot more than several op-amps in the path, there's intentional voicing and textural elements essential to the amp's core character. If that's what you want, use an active DI that outputs line level balanced and you are done.

 

[Mr. Foxen]

I tend to run with if I can't hear any difference from an opamp in the circuit, probably doesn't need to be there.

 

[fdeck]

I'm reminded of Madman Muntz.

Invalid Link Removed

 

[agedhorse]

I'm reminded of Madman Muntz.

Invalid Link Removed

Studied him in school

 

[12bass]

There's a lot more than several op-amps in the path, there's intentional voicing and textural elements essential to the amp's core character. If that's what you want, use an active DI that outputs line level balanced and you are done.

That misses my point. Forget about anything you've designed. The point is to set up a test where one can compare a circuit with a simple input stage feeding a power amp with another that runs the signal through multiple op amp stages (say twenty, without any significant filtering/coloring), then see if it is possible to reliably perceive the difference. If it is impossible to hear any difference, this would speak to the notion that op amps do not affect the sound in any way.

 

[12bass]

I don't believe that for a minute, and I've done a TON of intensive testing with double-blind players. The results were that there was no perceivable difference every time I ran testing with the same circuit, different ICs. Zero perceived difference no matter how much I wanted there to be.

I think this is a case of "believe what you like" and be happy that it works for you.

I know that I've heard differences and that those observations were reliable and repeatable. If anyone wants to setup an ABX test, I'd be happy to participate. Although I'm quite confident in my perceptions, I'm open to having my them falsified in a controlled test.

My background is in philosophy, with a special interest in epistemology and the philosophy of science, as well as some psychology relating to sensation and perception and the various sources of human cognitive bias. I care very much about the truth and I am in favor of objective testing methods whenever possible (though accurately quantifying some aspects of how something sounds may be somewhat difficult).

I've made before and after measurements with my Echo Gina24 after replacing the original NJM2068 op amps with LM4562s and there was a significant measured improvement performance with analog loopback using RMAA which corresponded with what I heard. Further, in many cases, my expectations for improvements have been frustrated, such that a given replacement sounded subjectively worse even though I wanted it to be better. So, that puts some limits on the role of expectation bias.

 

[Jeff Scott]

We're all happy for you and your tests, 12bass.

Now, give it a rest, thanks.

 

[12bass]

We're all happy for you and your tests, 12bass.

Now, give it a rest, thanks.

An excellent way to promote civil discourse on the internet.... thanks!

 

[BoogieZK]

I know that I've heard differences and that those observations were reliable and repeatable. If anyone wants to setup an ABX test, I'd be happy to participate. Although I'm quite confident in my perceptions, I'm open to having my them falsified in a controlled test.

My background is in philosophy, with a special interest in epistemology and the philosophy of science, as well as some psychology relating to sensation and perception and the various sources of human cognitive bias. I care very much about the truth and I am in favor of objective testing methods whenever possible (though accurately quantifying some aspects of how something sounds may be somewhat difficult).

I've made before and after measurements with my Echo Gina24 after replacing the original NJM2068 op amps with LM4562s and there was a significant measured improvement performance with analog loopback using RMAA which corresponded with what I heard. Further, in many cases, my expectations for improvements have been frustrated, such that a given replacement sounded subjectively worse even though I wanted it to be better. So, that puts some limits on the role of expectation bias.

Are you trying to say that LM4562 THD 0,00009% and 55MHz bandwidth is a performance difference with NJM2068 you can detect with your ears?

20kHz hearing range is 0,007% of the NJM2068 bandwidth capability. 0,004% for the LM...

What you heard is more likely the PL2000E audiophiliac high grade Specification.
Also called placebo effect. No disrespect.

 

[12bass]

Are you trying to say that LM4562 THD 0,00009% and 55MHz bandwidth is a performance difference with NJM2068 you can detect with your ears?

20kHz hearing range is 0,007% of the NJM2068 bandwidth capability. 0,004% for the LM...

What you heard is more likely the PL2000E audiophiliac high grade Specification.
Also called placebo effect. No disrespect.

I'm aware of the placebo effect and expectation bias, and a vast array of other cognitive and perceptual biases. I'm also not sure why the LM4562 sounds and measures better, but it does.

 

[beans-on-toast]

I'm aware of the placebo effect and expectation bias, and a vast array of other cognitive and perceptual biases. I'm also not sure why the LM4562 sounds and measures better, but it does.

I’ve always wondered why some amps have something special going on that makes you feel good when you use them. I’ve found that this goes beyond component tolerances.

Geoff Emerick was evaluating a recording console and he didn’t like what he was hearing on some of the channels. It turned out when the designers were troubleshooting and measured the response there was a bump at 54kHz on those channels. A problem was identified with some transformers. He couldn’t hear this but he could perceive that something was wrong. High bandwidth frequencies are important, even if you can’t distinguish them.

In recent years, great strides have been made in the development of portable brain PET and MRI scanners. At a lower level, there are also
inexpensive brain wave sensors and apps available that can be used to record how your brain is reacting to what you are listening to or seeing.
For example, MindWave

Imagine using brain waves to help evaluate and improve the performance of an amp during development. Research in this area has been going on for some time. Audio circuit design that includes what makes you emotionally feel is not far fetched.

We talk about our hearing but it is our brain that interprets what the auditory sensors detect. Our brain takes us beyond what we hear, it also generates emotions, such as happy, sad, or irritation like Geoff Emerick experienced, that go with the sound. It comes as a package.

 

[Rockbobmel]

I thought this was an amp porn thread?

 

[BoogieZK]

I'm aware of the placebo effect and expectation bias, and a vast array of other cognitive and perceptual biases. I'm also not sure why the LM4562 sounds and measures better, but it does.

I’ve always wondered why some amps have something special going on that makes you feel good when you use them. I’ve found that this goes beyond component tolerances.

Geoff Emerick was evaluating a recording console and he didn’t like what he was hearing on some of the channels. It turned out when the designers were troubleshooting and measured the response there was a bump at 54kHz on those channels. A problem was identified with some transformers. He couldn’t hear this but he could perceive that something was wrong. High bandwidth frequencies are important, even if you can’t distinguish them.

In recent years, great strides have been made in the development of portable brain PET and MRI scanners. At a lower level, there are also
inexpensive brain wave sensors and apps available that can be used to record how your brain is reacting to what you are listening to or seeing.
For example, MindWave

Imagine using brain waves to help evaluate and improve the performance of an amp during development. Research in this area has been going on for some time. Audio circuit design that includes what makes you emotionally feel is not far fetched.

We talk about our hearing but it is our brain that interprets what the auditory sensors detect. Our brain takes us beyond what we hear, it also generates emotions, such as happy, sad, or irritation like Geoff Emerick experienced, that go with the sound. It comes as a package.

It does? Or brainwaves... this is not a scientific way, it's the voodoo way.

 

[beans-on-toast]

It does? Or brainwaves... this is not a scientific way, it's the voodoo way.

Mind control from outer space will bias the results of brain wave scans.

 

[beans-on-toast]

I thought this was an amp porn thread?

Amp porn that makes you happy is all in your mind. You can only imagine how it sounds.

 

[Roxbororob]

Glad to be tagging along!

 

[seamonkey]

Haven't listened to hundreds of different op amps, but likely dozens. Much of my auditioning takes place with AKG K702 headphones or my true 3-way fEARful cabinet. Both are more revealing than standard bass gear. I also have Q-tuner pickups in my Rapture 5 and Lane Poors in my Hamer 12-string, which means that my basses produce more upper overtone content than most, certainly much more than a P-bass with the treble rolled off. Under these conditions, it is easy to hear the difference in sound between an ADA4627-1 and a TL072. Through a single 15" with a low bandwidth bass amp and a muddy sounding bass, not so much....

It looks like you op amps are on sockets
Is there an opportunity here for you to record samples of different op amps in one or more of your amps?
Ones where you clearly hear a difference.
I'd be interested to hear, but not really to find what sounds best but just to hear what the differences are and if they can be applied to other situations.

 

[metron]

I'll attempt to participate in this thread. Here is a rare '79-'80 Ampeg B15S gut shot with a somewhat recent cap job. This one is among the last of these amps. I read in the Ampeg book that the B15S was made through 1977 but the pot codes in this one are dated spring 1979.

 

[Mark Reccord]

I'll attempt to participate in this thread. Here is a rare '79-'80 Ampeg B15S gut shot with a somewhat recent cap job. This one is among the last of these amps. I read in the Ampeg book that the B15S was made through 1977 but the pot codes in this one are dated spring 1979.

View attachment 3548411

Why are the caps wrapped with appears to be heat shrink?