Current feedback high speed headphone amp with diamond output buffer

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Current feedback high speed headphone amplifier with diamond output buffer...

This is my first real attemt to build an amp which I have simulated first.

DC - 20 MHz but less I suppose. All SMD!
 

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diyAudio Retiree
Joined 2002
kilometers Per hour

Here's some Gain Bandwith products for some of the most popular op amps among
the DIY builders:

OPA627 16MHz

OPA604 20MHz

AD8610 25MHz

AD825 41MHz

OPA627 >50MHz

I think Per is probably in the neighborhood of a reasonable bandwidth. It sounds like a good idea to me.........
 
Re: kilometers Per hour

Fred Dieckmann said:
I think Per is probably in the neighborhood of a reasonable bandwidth. It sounds like a good idea to me.........
What? :yikes: :wave:

If you (not Fred) check the shematics you have a "speed adjuster" so you can tune in the speed you like but the main purpose is to get a stable amp.

Don't forget that we have a bunch of guys here which like current feedback opamps with speed of > 100 MHz => GHz transistors.
 
Re: Speed

Upupa Epops said:
...ultrawide frequency band is not in some cases the best solution.
Maybe so, but I (or anyone else) can adjust that. Faster isn't automaticly better but building the prototype will give us the answers but I have a hunch about linearity and high speed. Normally this is positive.

Pcb's are ordered in case any wonders...
 
Re: kilometers Per hour

Fred Dieckmann said:
Here's some Gain Bandwith products for some of the most popular op amps among
the DIY builders:

OPA627 16MHz

OPA604 20MHz

AD8610 25MHz

AD825 41MHz

OPA627 >50MHz

I think Per is probably in the neighborhood of a reasonable bandwidth. It sounds like a good idea to me.........

Fred, there's 2 OPA627. The 16MHz one is correct, but the other... maybe an OPA637?
 
Re: Peranders

ACD said:
This is serious!
Please explain to me the advantages of having audio gear that are able to reproduce 20MGHz and up.....
The harmonics are "long gone" at that frequency!!!!!
Sorry, Jan, I can't. First of all it's a thrill technically to scream out 20 MHz with gain from plain BC-transistors.

Hugh (and his many customers) on the other hand thinks that his rather slow AKSA amp is sounding good so there you have the opposites. I will come back later and tell you if 20 megagigaherts(!) is good or bad soundwise.
 
Re: Re: Speed

peranders said:

Maybe so, but I (or anyone else) can adjust that. Faster isn't automaticly better but building the prototype will give us the answers but I have a hunch about linearity and high speed. Normally this is positive.

Pcb's are ordered in case any wonders...

Yes, inherently fast and stable is good, but impulse response unfortunatelly tells nothing about intermodulation with D/A HF residuals. We have compared "unlimited" buffer-preamp (about 6MHz/-3dB) with filtered version (about 140 kHz/-3dB) and the final judge was clear - everyone of 10 listeners preferred the bandwidth limited version. Cleaner, less agresive, non-harsh, more details, more natural sound.
 
I would say, that this is one nice CFP amp.

The bandwidth is just fine.

Of course you need to limit the bandwidth with a LF filter in the input. ... lets say to 200KHz, but with this large bandwidth his amp has nearly the same distortion spectrum at 20k as at 1k. I think this is one parameter we all would like to get....

The ear is very sensitive to harmonics in its "window"....

Sonny
 
Re: Re: Re: Speed

PMA said:


Yes, inherently fast and stable is good, but impulse response unfortunatelly tells nothing about intermodulation with D/A HF residuals.
Listen up guys which remove the output filter of DAC's! The garbage from a DAC _can_ be audiable. If you happen to have a unit which produces unwanted (out of band) signals you should block these signals instread of creating circuits which can make them pass further in the chain.

PMA said:
We have compared "unlimited" buffer-preamp (about 6MHz/-3dB) with filtered version (about 140 kHz/-3dB) and the final judge was clear - everyone of 10 listeners preferred the bandwidth limited version. Cleaner, less agresive, non-harsh, more details, more natural sound.
The reasons for this "bad" sound can be that high frequency residuals produces audiable "garbage".

My theory is to have a fast circuit BUT limit the incomning signal with a plain LP-filter at a sufficiently high frequency.

The amp we talk about here has also a input filter as every amp have which I have designed. This is just common pratice I think.

The design is very easy to adjust when in comes to speed and current consumption.
 
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