Topic: I miss the WNA discussions! Suggestion ..... (Read 2,653 times)
FritzS Deputy Dawg Sound of Blue Danube member is offline
Sound of Blue Danube
Joined: Feb 2005 Gender: Male Posts: 1,173 Location: Austria
I miss the WNA discussions! Suggestion ..... « Thread Started on May 2, 2006, 10:50am »
Dear Mike, really I miss the WNA discussions with you
I hope a follower comes back as "phoenix out of ash"!
But no-one reply to my suggestion for modification. I think with an J-FET input OP and small modifications it can comes back as a great headphone amp! Another idea I have for the output DC protection - it's a symbiosis from some DIY projects. I will post this ASAP.
My experience is a J-FET input OP sounds better than a bipolar input OP - AnalogDevice OP's sounds better than BurrBrown - the AD OP275 sounds better than NE5532N or OPA2134
rickcr42 el Rickamundo (admin) Where anything goes member is offline
Joined: Feb 2009 Gender: Male Posts: 4,514 Location: Connecticut,USA
Re: I miss the WNA discussions! Suggestion ..... « Reply #1 on May 2, 2006, 5:16pm »
I have been using the OP275 for years and I noticed this chip is a love it or hate it part with no nuetral fence sitters.Better was the single opamp version,the OP176 but this has been out of production for years as has (I think) the "clone" SSM chip (SSM is the Analog Devices designator code for "PRO Audio" parts).
Will operate at low voltages though better at the full +/- 15VDC and really does need a dicrete "current pump" or monolithic buffer on the output even though alone it specs fairly high in the current delivery area. no speacial bypassing requirements,stable in just about any well layed out circuit (and even poorly layed out circuits ),dynamic,good bass ......
All in all a very civilised easy to use part that is close to "plug-and-play" replacement for any dual opamp using a standard pinout but like I said,hated by many while loved by others.
Quote:
My experience is a J-FET input OP sounds better than a bipolar input OP
The real strength of a bipolar input opamp is the first stage current delivery to the next stage and input noise levels which better JFET opamps.not as important at low gains but move into the 30-60dB gain range and you will wish you had a bipolar opamp
Even better is a discrete Dual JFET front end to a bipolar opamp.The easy way to squeeze one in to a circuit that has zero room on board is to remove the input cap,make a small perf board with the new input circuit which will now have the input cap on board then use the pad positions formaerly occupied by the cap as the in/out to the new "front end" board. A dual jfet is tiny,the size of an 8-Pin DIP opamp so even when you add the rest of the parts you can get the board footprint into the 2x2 inch area for a stereo board-------just another option
At least I made you THINK,never a bad thing no matter what the topic{=}{/=}{=}{/=}
rickcr42 el Rickamundo (admin) Where anything goes member is offline
Joined: Feb 2009 Gender: Male Posts: 4,514 Location: Connecticut,USA
Re: I miss the WNA discussions! Suggestion ..... « Reply #2 on May 3, 2006, 5:07pm »
So how long will this sub forum be able to stay topical Mike ?
seems like with WNA closing the doors and you no longer supporting the products at your previous enthusiastic level the amps will become an asterisk,an "also ran" in the not too distant future.
I must also say it is kind of strange to design then announce a "WNA lll" will be offered then when interest is peaked pretty much say "never mind".
Is there a chance in hell of maybe just purchasing/weasling/begging the rights to the basic amp architecture and pc board layouts ?
that way there is continuity and no one that bought in is left hanging AND would add value to the amps on the used equipment market.
Otherwise two years down the road any attempts to sell one of the amps would bring a "WNA ? Who and what in the hell is that ? anyone ever hear of this obscure amp ?"
At least I made you THINK,never a bad thing no matter what the topic{=}{/=}{=}{/=}
rickcr42 el Rickamundo (admin) Where anything goes member is offline
Joined: Feb 2009 Gender: Male Posts: 4,514 Location: Connecticut,USA
Re: I miss the WNA discussions! Suggestion ..... « Reply #3 on May 3, 2006, 6:53pm »
seems best really otherwise you would have to add a sub forum for every short run amp on the planet and that just does not work.General DIY gets my vote
At least I made you THINK,never a bad thing no matter what the topic{=}{/=}{=}{/=}
PinkFloyd Rock Grotto (admin) Born again Caveman member is offline
Joined: Dec 2004 Gender: Male Posts: 11,532 Location: Far from the modding crowds
Re: I miss the WNA discussions! Suggestion ..... « Reply #4 on May 3, 2006, 7:50pm »
Quote:
seems best really otherwise you would have to add a sub forum for every short run amp on the planet and that just does not work.General DIY gets my vote
OK, will let this forum run for a while and gradually move any technical / interesting parts of it over to the DIY section.
FritzS Deputy Dawg Sound of Blue Danube member is offline
Sound of Blue Danube
Joined: Feb 2005 Gender: Male Posts: 1,173 Location: Austria
Re: I miss the WNA discussions! Suggestion ..... « Reply #5 on May 4, 2006, 7:40am »
Dear Mike, Rick! I think we should begin a new "Open Source" (!!!) project with name "Phoenix Headphone Amp" and create a new headphone amp reconstructing on WNA and you could rename this forum to this name
I will help you to create a new schema - inklusiv a output DC protection and PSU. We could gathering ideas till autumn, winter 2006/07 and then we design a new PCB including all.
I think the basics from WNA schema are common knowledge - the most ideas comes from Walt Jung. I found similar ideas in other projects too!!! So we did not have a problem with copyright.
I have a subscription from audioXpress too an can send you a pullout-copy of a headphone amp project to your private mail-address (if you tell which).
rickcr42 el Rickamundo (admin) Where anything goes member is offline
Joined: Feb 2009 Gender: Male Posts: 4,514 Location: Connecticut,USA
Re: I miss the WNA discussions! Suggestion ..... « Reply #6 on May 4, 2006, 8:10am »
most ciruits are just that-standard designs,but it is the combination of implementation and layout that makes them uniquely someones baby.
My thoughts are if you want to do an amp that step one should be to go "outside the box" and go straight to a true bipolar power supply of +/-24 to +/-30 VDC 500mA per polarity,use a "bootstrap mode" bipolar opamp (AD826,OP37,AD797) with a discrete matched jfet front end (or not) and a bipolar class-A current pump output.
The high PS voltage along with a bootstrap mode opamp means dynamics will be eye popping and the use of a bipolar opamp (not jfet) with a vanishingly low noise floor means you can up the gain at will to crazy levels and still have a huge drive capability in both the voltage (something around 9 volts audio signal level) and current (100-150 ma class-A sliding to AB for higher current peaks AS IF ! )
Be more like the Hydra than the Pheonix,pure kill power
both are not really the same - the article from EDN is a true bootstrap but the TNT is a bit other - here is the VCO/VEO fixed.
The TNT principle is common used in some HiFi amps far back. I know this principle - I remember it was used with solid state transistors in Threshold power amps ....
But both have a drawback - the highspeed OP amps (as used in WNA) will possibly oscillate
rickcr42 el Rickamundo (admin) Where anything goes member is offline
Joined: Feb 2009 Gender: Male Posts: 4,514 Location: Connecticut,USA
Re: I miss the WNA discussions! Suggestion ..... « Reply #10 on May 4, 2006, 6:09pm »
Quote:
here is the VCO/VEO fixed.
for illustration of possibilities only.both ways get you serious voltage drive,maybe enough to even attack the 600-1K ohm AKG cans without going to a "true" power amp or pentodes.Obviously such would require a hig/med/low gain switch if it were to be a universal "any cans" amp or you would lose all possible control of the volume pot and if a potentiometer you always want to keep a dual pot in the "sweet spot" of its range or your inter-cannel tracking will suck big time. Then again,if the output is to the old "standard headphone amp load" there would be 120 ohm resistors inline with the output which would in a way "act" as a gain adjuster by pinching off power to low impedance loads while passing it to high impedance loads
Quote:
But both have a drawback - the highspeed OP amps (as used in WNA) will possibly oscillate
And why I purposely use slow opamps when I must use opamps.There truly is not much need for anything over the mid to upper twenties (or at best mid sixties) at audio frequencies which more forten than not can get a person into trouble unless steps are taken to compensate. These ultra-high-speed opamps operate right at the edge of being their own radio transmitter and no matter where RFI enters (power supply leads,either input node,output hence to the feedback loop) it WILL be amplified as if a signal (it is) and mix with the audio frequencies.
Where this becomes a serious problem is when the event is not detected (scope does not have a high enough range) and the amp is colored by this event. The reasons for the event being an unknown a reasonable person will usually look to the resistors or caps as the fix thinking better parts will make the amp sound better while all along that "brittle/etched" sound they thought to be detail when the amp was purchased,and what is now causing headaches,is in reality oscillations so high in frequency they are not the dominant sound while still imparting their own tonal "stamp" on everything passing through the stage.
I like slow opamps (when I use them, a discrete/valve type person),filtered to the balls on every single potential RFI entry point,TRUE dual power supplies (followed by shunt regs if the part has a high enough PSRR) a fast STOP (settling time) rather than start (rise time) and to be honest bipolar transistor input opamps that idle at a high current (compared to the new breed of class B idlers)
Radical/old school would be OP37 bootstraped to a SEPP Class-A output stage AC coupled or with an ultra-low turnover DC servo as an option to lose the cap for the capacitor shy (I HATE servoes but they have a place).
No parallel devices,no fet input,no split power buss,no fancy parts,a low impedance feedback network with feedback loop DC shunting (electrolytic to ground in the loop),RF compensation in the loop,at the input and output plus both ps pins.........
that or just build a damn Jensen JT-990 discrete opamp (open source design,free to use) with a beefier output stage and call it a day
While you are at it the other Deane Jensen AES papers are also a very good and very illuminating read,also worthy of a request.
the beauty of the JT-990 papers is not just that anyone can build and actually sell identical copies of the design (true public domain) but there is enough blow by blow content of the actual design to go off and do your own version armed with the information.
Quote:
I disagree - WNA use high speed OP's - Jan Meier use them too - all amps sounds well
never said it can't sound good,only that additional steps are required to make it so and being a K.I.S.S. type (keep it simple stupid) I would rather strart from a foundation of stability then build off it than I would start out making the foundation work THEN try to build of of that.
I regularly use the AD797,OP27/OP37 ands AD744 with output section bypassed and it is a rare day I go with anything over 60V/uS in opamp designs. Why ?
Because each succeeding stage needs to be faster than the previous stage or you introduce slewing distortions and that means you power suppply needs also be much faster than the actual amplifying device.
This last is easy in a shunt regulator (no in series with the voltage) but a shunt reg can have noise issues many times so off the list for high gain duty (mic/phono/tape head) and will stop regulating if the voltage output exceeds the shunt regulation element voltage (can actually be a good thing ).
that the fast opamps can work and can sound fine does not mean additional steps to make them behave has not taken place (in fact says it has) but in the end makes for a more complicated design that in real world use is no faster than the slower device due to the compensation methods.
Mate the fast front end to an output section not quite as fast or marginally faster and you introduced MORE problems.Follow this with a slow amplifier (opamp as preamp box) and you need to introduce filters at the upper end on the power amp or you introduce S.I.D. there ! (and why the final stage of a power amp is always the fastest part of the design and uses power transistors operating in the MHz range)
So slow and easy is my way though I realise it is not new millenium PC or considered SOTA which many times is just folks trying to blaze their own path to be different and not because it betters what has gone before
At least I made you THINK,never a bad thing no matter what the topic{=}{/=}{=}{/=}
FritzS Deputy Dawg Sound of Blue Danube member is offline
Sound of Blue Danube
Joined: Feb 2005 Gender: Male Posts: 1,173 Location: Austria
Re: I miss the WNA discussions! Suggestion ..... « Reply #13 on May 8, 2006, 7:26am »
Quote:
I have been using the OP275 for years and I noticed this chip is a love it or hate it part with no nuetral fence sitters.Better was the single opamp version,the OP176 but this has been out of production for years as has (I think) the "clone" SSM chip (SSM is the Analog Devices designator code for "PRO Audio" parts).
The OP275 is my favorite - but I did not found a similar single OP in DIL8 - the OP275 sounds very analytic, detailed, down to the last details - so I had never heared my old Philips CD650 before
Quote:
I regularly use the AD797,OP27/OP37 ands AD744 with output section bypassed and it is a rare day I go with anything over 60V/uS in opamp designs.
They have the reputation to sound a little dark - but I had not test and heared them ......
Quote:
never said it can't sound good,only that additional steps are required to make it so and being a K.I.S.S. type (keep it simple stupid) I would rather strart from a foundation of stability then build off it than I would start out making the foundation work THEN try to build of of that.
rickcr42 el Rickamundo (admin) Where anything goes member is offline
Joined: Feb 2009 Gender: Male Posts: 4,514 Location: Connecticut,USA
Re: I miss the WNA discussions! Suggestion ..... « Reply #14 on May 8, 2006, 2:56pm »
just did a fking twenty minute EXTENSIVE response and when I hit "post reply" got the damn white page,hit "back" and all gone !!!!!!
Too pissed off to even consider trying to reconstruct my thoughts and posting a response.Maybe later,maybe never,likely the latter since I am not in the habit of repeating myself unless to drive home a point and this is just not that important
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