What is "current rush"? I would have thought that high rail capacitance would be very useful for a Class B chip.
It is pertinent to show that the transistors are mounted directly underneath the op amp, this is the main reason behind the package as a whole being.. just on warm, and the dual package op amp.. warm.
Cheers / Chris
Cheers / Chris
Current rush means that you are forcing current to the OpAmp continuously and the OpAmp in Class B itselfs needs current on transient basis not on continuous. Example of this is a LM1875, claimed to have better sound when used with modest rail capacitance. Also - all modern (high speed/high bandwidth) OpAmps have bypassing requirements in their datasheets described as small capacitance (0.1 uF) directly to the chip power pins.
Don't you think, that after 40 years of usage of transistors by tens if not thousands of engineers all over the world, they would have added a simple transistor and a resistor to an opamp's supply lines ON DIE if it brought such incredible improvements? Your baseless vague babble does zero to make you credible.
I have a suggestion to you. Write Texas Instruments and Analog devices and propose your circuit to be included in their next range of high-end opamps. Then, post their reply 🙂
There is still plenty of time for engineers to investigate this, and add an NPN with a resistor to the + rail and a PNP with a resistor to the - rail. It would save me an hour or two of construction. 🙂
Op Amp manufacturers have investment to see their product sold... so its a fairly proprietary driven industry, maybe it needs to be more community driven, rather than customers we become contributors. A bit like the present silliness of proprietary software vs Linux where there is more to gain where everyone is encouraged to contribute Actually examining a few op amp internal schematics, and for DIY Audio to contribute discussion to TI or Analog or Nat Semi -on their next design would be very healthy for everyone, High on my list would be the best sounding op amp.
Cheers / Chris
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My thoughts on all this.
Without controlled listening tests (double blind etc, two identical CD players, one modded one not) we can't really say whether anything audible happens or not.
I do know that seemingly unmeasurable differences between opamps (different device types) is obviously audible and not easily explainable even when all precautions in implementation are factored in.
I feel sure Chris's mod can only "deteriorate" the technical performance of a given opamp but whether it sounds "better" or more "pleasing" for that is down to an individual to decide.
If the sound does change, we don't know why and the reasons behind it.
If it works for Chris that's fine. It's long accepted that "blameless" performance isn't always the best sounding.
Without controlled listening tests (double blind etc, two identical CD players, one modded one not) we can't really say whether anything audible happens or not.
I do know that seemingly unmeasurable differences between opamps (different device types) is obviously audible and not easily explainable even when all precautions in implementation are factored in.
I feel sure Chris's mod can only "deteriorate" the technical performance of a given opamp but whether it sounds "better" or more "pleasing" for that is down to an individual to decide.
If the sound does change, we don't know why and the reasons behind it.
If it works for Chris that's fine. It's long accepted that "blameless" performance isn't always the best sounding.
Thanks Mooly
This is what I have been encouraging, for people to listen and provide opinion. I know there is much concern over subjective opinion, vs oscilloscopes Audio Precision Ones and Sims ..but a lot so far has been heavy going technical, Which quite correctly has its place.
Maybe it would be nice to hear those contributing to DIY Audio who use their ears, to contribute their opinion. I am sure there will be lots more technical discussion,which is good too.
Cheers / Chris
This is what I have been encouraging, for people to listen and provide opinion. I know there is much concern over subjective opinion, vs oscilloscopes Audio Precision Ones and Sims ..but a lot so far has been heavy going technical, Which quite correctly has its place.
Maybe it would be nice to hear those contributing to DIY Audio who use their ears, to contribute their opinion. I am sure there will be lots more technical discussion,which is good too.
Cheers / Chris
If the OpAmp is really oscillating in high-freq. region, you cannot draw any sane conclusion on just listening test. If it sounds brighter because of this, you will hear that and say - "I hear more detail".
Something more - having best performance current set up to 6 ma says something. If you look through some datasheets or measure it yourself, you will find out that most OpAmps have quiescent current of 2 - 6 mA. Coincidence?
Something more - having best performance current set up to 6 ma says something. If you look through some datasheets or measure it yourself, you will find out that most OpAmps have quiescent current of 2 - 6 mA. Coincidence?
Yes quite aware of quiescent current, I have seen no evidence of oscillation or brightness in listening, however a better appreciation of stereo and spatial improvement that that brings.
Cheers / Chris
Well go ahead and don't ignore the advice I gave you: Start contributing and send your suggestion to TI and AD. Comment on this please. Are you going to do this? I'd surely like to read their responses if you get them at all. Maybe they will even hire you and in the future we'll get to see a line of audiophile "Chris Daly" opamps from them.
Not unless all those opamps were destined for such audio circuits, I think.
Without picking on this or other particular engineering comment here, don't you think that the obvious presumption that the OP design should be within conventional design guidelines and thus constrained by linear, text-book operation is too narrow?
Probably, the post would be ignored in the musical amplifier forum but I don't see this as anything to get indignant about, included here with audio amplification. Some of you may have recollections of expensive 1970s equipment that did far worse jiggering about with audio than here, to achieve "improvements" in stereo sound when few even raised an eyebrow. It was just business.
DBX comes to mind as one respected manufacturer; with sub-harmonic generators, dynamic companders and there were stereo enhancers among all manner of gadgetry that was popular in its day. What is so sacrosanct about fitting this or any other novel use of parts in or externally to an audio amplifier? Surely we need only determine whether it does do anything to audio and leave the sonic evaluation to the guys who merely listen with their ears.
I don't endorse this gadget, but I can't see any merit in rubbishing someone's scheme because it does not fit conventional industry guidelines or perhaps offends some notional professional ethics.
Let's not forget the zillions of dollars spent in synthetic music generation and effects amplifiers used in musical instruments. This is a legitimate industry employing professional audio designers/engineers, no?
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As the concept is not new, the implementation seems interesting. Usually, transistors are added this way to the power rails to help with power filtering and this method can be seen as "virtual battery", "capacitance multiplier", etc. Great for Class A amps, saves $$$ for caps 🙂
My understanding is that this, implemented to the power legs of the OpAmps, aim at reducing the DC reactance of the power rails and rejecting some of the parasitics on the power rails themselves.
I don't see the bypass caps on the schematic, but I think they still have to be implemented after the transistors. Also - the current should be chosen for the specific OpAmp to be used. If the LME47910 has 5 mA of Is, AD8610 has half of that.
My understanding is that this, implemented to the power legs of the OpAmps, aim at reducing the DC reactance of the power rails and rejecting some of the parasitics on the power rails themselves.
I don't see the bypass caps on the schematic, but I think they still have to be implemented after the transistors. Also - the current should be chosen for the specific OpAmp to be used. If the LME47910 has 5 mA of Is, AD8610 has half of that.
Thanks Magic Box
to cic.asia@analog.com
date Wed, Dec 14, 2011 at 9:12 PM
subject AD 825
Dear Madam / Sir
I have been purchasing AD825 from you. I am very pleased with the product. I am selling small quantity from my eBay store. I have been modifying the entry to the + and - rail by adding transistors in a unconventional manner involving a NPN connected with a 2k4 resistor between its collector and base, and emitter feeding V+, and a PNP connected with a 2K4 resistor between its collector and base, and its emitter to V- that in my opinion and in my many happy customers opinion improves stereo spatial information. I have published detail of this improvement at my blog website opamp - opamp construction I have contributed these ideas to DIY Audio with whom I have been a forum member since 2004. The forum are apparently at a loss to explain what occurs relative to an AD825, and have encouraged me to contact you directly.
Can Analog Devices assess measured and aural perceived difference particularly in a Stereo installation with this idea ?,
I look forward to your contact
Yours Sincerely
Chris Daly
Ferrite beads can sometimes suppress HF oscillations where other measures fail.
http://www.vishay.com/inductors/multilayer-ferrite-beads/
http://www.palomar-engineers.com/Ferrite_Beads/ferrite_beads.html
Don
http://www.vishay.com/inductors/multilayer-ferrite-beads/
http://www.palomar-engineers.com/Ferrite_Beads/ferrite_beads.html
Don
They are still not win-win situation I suppose. Adding induction so close to the chip will probably have some negative influence.
Ian, I think there's a small difference that you overlook and that is that all those sound colorization circuits you speak of, have actually been designed to get those intended results, these are probably repeatable performance designs too and would highly likely constitute of more than just one transistor and a resistor. Your electronic organ will sound the same whether it's number 10 or number 100 of the batch. Don't you agree?
I'm not to judge someone's listening experience, but its the snake-oilish presentation is what irks people. This thread has shown that the author doesn't exactly understand the workings of his circuit either. But everyone is entitled to his/her opinion. I just don't like to see ignorant people go about and ruin their audio gear like this, although that's their own responsibility.
Magic Box
All the information including detailed construction is provided at my blog site, you are similarly most welcome to try it. This is hardly being secretive or deceptive is it ?
Neither are people being ignorant or ruining their audio gear, see my feedback remarks...
"Fantastic product, absolutely love it.
"Excellent product - quick delivery - fast answers - very highly recommended"
"super service, excellent instructions, thanks A+++++"
Great service trusted ebayer, Chris is A1++++
Excellent, Chris is a real gentleman I will recommend him to all I know A1+++++
psst.... don't tell anyone the AD825 is a brilliant CD upgrade... great seller!
Excellent on all counts, item as described, recommended seller AAAA+++++++++++++
Top service as usual. Excellent op amps, excellent soldering, fast shipping. A++
Cheers / Chris
All the information including detailed construction is provided at my blog site, you are similarly most welcome to try it. This is hardly being secretive or deceptive is it ?
Neither are people being ignorant or ruining their audio gear, see my feedback remarks...
"Fantastic product, absolutely love it.
"Excellent product - quick delivery - fast answers - very highly recommended"
"super service, excellent instructions, thanks A+++++"
Great service trusted ebayer, Chris is A1++++
Excellent, Chris is a real gentleman I will recommend him to all I know A1+++++
psst.... don't tell anyone the AD825 is a brilliant CD upgrade... great seller!
Excellent on all counts, item as described, recommended seller AAAA+++++++++++++
Top service as usual. Excellent op amps, excellent soldering, fast shipping. A++
Cheers / Chris
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Yes, the part about swapping out 20 year old opamps for new ones in a SOIC package using an adapter is a good idea, provided the replacement opamp is similar in impedance specs as the one being replaced. This alone will measurably improve the amp performance. But that, in my opinion is as far as it goes. I'm not critisizing the construction documentation either. This is solely narrowed to the transistor/resistor circuit.
Most of the replies are targeted at the false claims on how the modification works. Not to whether there is an audible difference.
If the thread starter has opened with
"I have modified the supply lines to the opamp with a pair of the two component circuits shown, I have no idea why it changes the sound I hear.
Could some members chime in with some hypotheses on why the sound is changed?
Could the supply modification be done in a better way?"
That could have avoided all the argument. Particularly the loss of face of the poster who appears to be trying to fleece his customers by claiming unsubstantiated science for his modification.
If the thread starter has opened with
"I have modified the supply lines to the opamp with a pair of the two component circuits shown, I have no idea why it changes the sound I hear.
Could some members chime in with some hypotheses on why the sound is changed?
Could the supply modification be done in a better way?"
That could have avoided all the argument. Particularly the loss of face of the poster who appears to be trying to fleece his customers by claiming unsubstantiated science for his modification.
Hi Chris
You could save yourself some hassle and just PM Scott Wurcer (of Analog Devices). He's an active member here on diyAudio, often hanging out in John Curl's thread. Not sure about the AD825 specifically, but he is the designer of several highly regarded chips e.g. AD797.
IMHO, he won't be overly interested, but you're more likely to get a useful response here than from an anonymous email to AD.
There's another problem, though. Chipmakers (and discrete semi manufacturers too, for that matter) really don't care about high-end audio anymore. A few decades ago it was different, with a lot of effort being put into making the best sounding stuff. These days, it's such a small niche market, it's not worth pursuing, from a business POV.
Cheers - Godfrey
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