Mr. Lion's DIY Thread

[g0ldl10n]

Ok, fine. Move the frequency-limited goal posts.

-3 at 8Khz? Sounds great for 1950s car radio restoration projects.

Okay, clearly I was too harsh, the roll off begins at ~4kHz, and the -3dB cutoff looks about 13-14kHz, and "only" a -10dB dive just before 20kHz, like 18kHz or so, and launches straight back up around 18.5-19kHz in a wild fashion to nearly the 0dB point in the ultrasonic region.. this response causes some strange listening tests when comparing to other OPTs, and or frequency responses for that matter.

 

[LobalWarming]

Okay, clearly I was too harsh, the roll off begins at ~4kHz, and the -3dB cutoff looks about 13-14kHz, and "only" a -10dB dive just before 20kHz, like 18kHz or so, and launches straight back up around 18.5-19kHz in a wild fashion to nearly the 0dB point in the ultrasonic region.. this response causes some strange listening tests when comparing to other OPTs, and or frequency responses for that matter.

Minor anomaly in an octave with zero musical value. Unless you listen to a lot of Bactrian camel tunes.

What does the FR look like for the various rectifiers?

 

[g0ldl10n]

Minor anomaly in an octave with zero musical value.

This is not true - well, I guess that yes, a frequency above 20kHz all by itself is of no musical value, but with our amps circuit amplifying our signals, it most certainly imparts negatively into the audible band - very aburpt/aggressive roll-offs, even in the ultrasonic region will impart amplitude and phase shifts back into the audible region.

Nelson Pass, you may have heard of him before? One of the most highly regarded audio amp designers in history (in case you haven't), I will just quote something from him on this.

"Although human hearing is generally very poor above 20,000 Hertz, ultrasonic frequency roll-offs produce phase and amplitude effects in the audible region; for example, a single pole (6dB/octave) roll-off at 30 kHz produces about 9 phase lag and 0.5 dB loss at 10 kHz."

 

[LobalWarming]

This is not true - well, I guess that yes, a frequency above 20kHz all by itself is of no musical value, but with our amps circuit amplifying our signals, it most certainly imparts negatively into the audible band - very aburpt/aggressive roll-offs, even in the ultrasonic region will impart amplitude and phase shifts back into the audible region.

Nelson Pass, you may have heard of him before? One of the most highly regarded audio amp designers in history (in case you haven't), I will just quote something from him on this.

"Although human hearing is generally very poor above 20,000 Hertz, ultrasonic frequency roll-offs produce phase and amplitude effects in the audible region; for example, a single pole (6dB/octave) roll-off at 30 kHz produces about 9 phase lag and 0.5 dB loss at 10 kHz."

Yes, I understand out of band effects on phase... I will explain camel humour at another time. Tough crowd.

I won't nag you anymore about the difference between rectifiers in class A well regulated circuits since you prefer to deflect to other more obvious anomalies.

 

[g0ldl10n]

What does the FR look like for the various rectifiers?

I won't nag you anymore about the difference between rectifiers in class A well regulated circuits since you prefer to deflect to other more obvious anomalies.

Well, I can't answer these questions outside of what internet searches will tell me and you, as I have not had the time to do these specific measurement tests myself yet.

I can say, frequency response alone (which is definitely not the whole picture, even in the non-musical regions, unless ofc the freq responses in said non-musical region are so abrupt, they end up impacting the musical regions, obviously) between a fully passive power supply and a regulated power supply in my circuit, which again, obviously will change things considerably so, in the musical and non-musical regions due to the active gyrator loads, versus entirely resistive loaded amp, are fairly the same. That said, undesirable traits in our amps such as ringing isn't going to show up here, waveform tests such as one described using a squarewave will though.

However, IMD and noise floor, especially caused by mains (60Hz and 120Hz, again,  obvious) are both significantly improved. Other tests that require the AD3s scope and waveform generator have not been done yet, otherwise, I would have shared the results, obviously.

 

[LobalWarming]

Well, I can't answer these questions outside of what internet searches will tell me and you, as I have not had the time to do these specific measurement tests myself yet.

I can say, frequency response alone (which is definitely not the whole picture, even in the non-musical regions, unless ofc the freq responses in said non-musical region are so abrupt, they end up impacting the musical regions, obviously) between a fully passive power supply and a regulated power supply in my circuit, which again, obviously will change things considerably so, in the musical and non-musical regions due to the active gyrator loads, versus entirely resistive loaded amp, are fairly the same. That said, undesirable traits in our amps such as ringing isn't going to show up here, waveform tests such as one described using a squarewave will though.

However, IMD and noise floor, especially caused by mains (60Hz and 120Hz, again,  obvious) are both significantly improved. Other tests that require the AD3s scope and waveform generator have not been done yet, otherwise, I would have shared the results, obviously.

Got it. Just toying with your objective sensibilities.

Probably not going to discover visibly measurable and audible FR differences between rectifiers. But that you and others perceive a difference between them, despite a firm, well regulated power supply is more than a little concerning to me.

Look forward to your further explorations until you discover the only way to rectify the issue is with DC-to-DC power from a 15 kWh in-home flow battery installation charged by sophisticated photons from the south of France.

 

[Isaacc7]

Got it. Just toying with your objective sensibilities.

Probably not going to discover visibly measurable and audible FR differences between rectifiers. But that you and others perceive a difference between them, despite a firm, well regulated power supply is more than a little concerning to me.

Look forward to your further explorations until you discover the only way to rectify the issue is with DC-to-DC power from a 15 kWh in-home flow battery installation charged by sophisticated photons from the south of France.

I’ve been lurking in DIY sites for over a decade and picked up some knowledge over that time. One thing that comes up over and over is how things in theory or in simulations often times have bugaboos once they are actually built. That is especially true when it comes to low level stuff. Sometimes there are surprises. Big ones are measurable and usually can be sussed out. If it turns out there is an audible difference between rectifiers that can’t be seen with various measurements it’s bound to be caused by some sort of weird field effect, magnetic coupling, resonances, etc. etc. etc. that just aren’t worth tracking down. I suspect the amp will sound great regardless

 

[LobalWarming]

I’ve been lurking in DIY sites for over a decade and picked up some knowledge over that time. One thing that comes up over and over is how things in theory or in simulations often times have bugaboos once they are actually built. That is especially true when it comes to low level stuff. Sometimes there are surprises. Big ones are measurable and usually can be sussed out. If it turns out there is an audible difference between rectifiers that can’t be seen with various measurements it’s bound to be caused by some sort of weird field effect, magnetic coupling, resonances, etc. etc. etc. that just aren’t worth tracking down. I suspect the amp will sound great regardless

I like weird field effects and magic coupling... but maybe this isn't the thread for such topics.

 

[triod750]

You might all be right but these efforts from the kitten is worthwhile as a step in the learning process. He might find something interesting and if he doesn't it's interesting too.

 

[Isaacc7]

Any progress? Have you been able to get your amps to where you think you're done? I've never done a scratch build but I can imagine the temptation to keep experimenting could be overwhelming lol.