Nic,
You are not the only one who want to have good looking enclosures.
And you know what standard I would and would not accept.
There are discussions in the background as to how to make this happen.
Just bear with us for now.
At least we need to find out first how good the 2109 is, before deciding what to do.
I still need to solve the background noise issue in post #135.
Even though I know pretty well where it's from and how to improve, it still needs to be proven.
Hopefully before end of April, when PCBs and new parts arrive......
Patrick
You are not the only one who want to have good looking enclosures.
And you know what standard I would and would not accept.
There are discussions in the background as to how to make this happen.
Just bear with us for now.
At least we need to find out first how good the 2109 is, before deciding what to do.
I still need to solve the background noise issue in post #135.
Even though I know pretty well where it's from and how to improve, it still needs to be proven.
Hopefully before end of April, when PCBs and new parts arrive......
Patrick
Had the chance to listen extensively to the DAO these days at Patrick's...
Just to have the amplifier standing on the workbench in front of you is quite an experience... this thing just
oozes quality! It's a real gem of a headphone amplifier, and I wasn't disappointed listening to it either.
With some well known tracks that I had brought along it was clearly evident that the DAO is a capable design...
very transparent without ever sounding bright or harsh, with exemplary separation of instruments and very good
microdynamics. All those tiny events in the music are rendered effortless and perfectly placed in 3D space.
Very interesting also to play with the Meier Crossfeed that was installed... never felt the urge to try this in one
of my amplifiers, but now I would strongly recommend to try one of the three circuits that P. will be offering.
The only little hickup was the aforementioned background noise, but it's identified and adressed.
Very convincing I have to say, and I am looking forward to be part of the first group of builders!
Thanks Patrick!
Just to have the amplifier standing on the workbench in front of you is quite an experience... this thing just
oozes quality! It's a real gem of a headphone amplifier, and I wasn't disappointed listening to it either.
With some well known tracks that I had brought along it was clearly evident that the DAO is a capable design...
very transparent without ever sounding bright or harsh, with exemplary separation of instruments and very good
microdynamics. All those tiny events in the music are rendered effortless and perfectly placed in 3D space.
Very interesting also to play with the Meier Crossfeed that was installed... never felt the urge to try this in one
of my amplifiers, but now I would strongly recommend to try one of the three circuits that P. will be offering.
The only little hickup was the aforementioned background noise, but it's identified and adressed.
Very convincing I have to say, and I am looking forward to be part of the first group of builders!
Thanks Patrick!
Looking forward to it. Only tonight I put a folder together to start gathering the reading material for the build - first in there were your articles. I try to do this for the complete builds I do - it makes it very easy to go back later and find a schematic, or a note that I made during the build etc.
Fran
Fran
Something that I have forgotten for long, and finally get to remember to post.
The HAGS circuit published here is essentially a differential input version of the CEN EQ stage published by Thorsten L.
http://www.diyaudio.com/forums/anal...design-high-end-tone-control.html#post2965376
My most sincere apologies to Thorsten for my negligence in not making the acknowledgement in the original article.
It is effectively a transconductance amplifier with an IV resistor at the output, before the complementary source follower.
Thorsten's circuit has single ended input and output, and is inverting.
To overcome that, HAGS uses a Curl type complementary JFET diff pair input stage.
The negative input can be connected to Gnd in case of single ended signals (as a non-inverting amplifier).
It can of course also be used as a fully differential input, single ended output converter / amplifier.
And it is a simple exercise to make this fully differential input & output.
As we found out, the TL431 as in the CEN EQ is causing almost all of the background noise in the DAO amplifier chain.
This will be dealt with in the Beta test, and we are confident of the improvement measures.
Patrick
The HAGS circuit published here is essentially a differential input version of the CEN EQ stage published by Thorsten L.
http://www.diyaudio.com/forums/anal...design-high-end-tone-control.html#post2965376
My most sincere apologies to Thorsten for my negligence in not making the acknowledgement in the original article.
It is effectively a transconductance amplifier with an IV resistor at the output, before the complementary source follower.
Thorsten's circuit has single ended input and output, and is inverting.
To overcome that, HAGS uses a Curl type complementary JFET diff pair input stage.
The negative input can be connected to Gnd in case of single ended signals (as a non-inverting amplifier).
It can of course also be used as a fully differential input, single ended output converter / amplifier.
And it is a simple exercise to make this fully differential input & output.
As we found out, the TL431 as in the CEN EQ is causing almost all of the background noise in the DAO amplifier chain.
This will be dealt with in the Beta test, and we are confident of the improvement measures.
Patrick
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For those who wants to understand more about John Curl's input stage, here the link to Pavel Macura's analyses :
Distortion in JFET input stage circuits
Patrick
Distortion in JFET input stage circuits
Patrick
I just ordered this on eBay France (lower shipping cost for some reason) for my ongoing Aleph-H build: B2412B 2 Full Aluminum Enclosure Mini AMP Case Power Amplifier Chassis SN | eBay
Maybe it's suited for the DAO amp as well?
Maybe it's suited for the DAO amp as well?
Just an update.
While waiting for WK to organise parts for the Beta tester (he is 150% loaded till August !!!!!!!), I have been looking at one aspect of the DAO SE specifically, namely the attenuator for volume control.
One of us has done a comparison recently, between a pot with carbon tracks (e.g. ALPS RK27), pot with conductive plastic (e.g. Vishay P11A), switched attenuator series type, and switched attenuator ladder type. The switch used for the experiment was no fancy ones, just 6P4T 2-deck selectors.
https://www.monacor.ch/itemcard.php?itemno=RS-246
The clear winner was switched ladder with Dale resistors.
There is a very comprehensive explanation of different types of switched attenuators by Gold Point :
Stepped Attenuator Types
There is also a large selection of both the series and ladder type attenuators on the market, starting from 10USD and ending somewhere over 1000USD. Or you can just buy a 4-deck, 24-position rotary switch (ebay, Elma Shallco, Seiden, Grayhill, …….) and a bunch of “audiophile” resistors and make your own. The chances are that you will end up with spending about 100USD+ and a volume quite a bit bigger than a normal ALPS RK27 or TKD CP2500, which Mark uses for his DAO. And the major cost driver is of course the 4-deck 20-position rotary switch, unless you go for one of those from ebay.
But then I found these, and I like the idea of using the mechanics of a normal pot as rotary switch:
WiredState Audio Community • View topic - Need advice on a TKD stepped series attenuator
°ëÔ²±ú·¢ÉÕ¼¶RH2702_A100KÖ¸ÊýÒôÁ¿µçλÆ÷27ÐÍË«Áª²½½ø¾«¶È³¬ALPS-ÌÔ±¦Íø
Dact Type SMD Stepped Attenuator 21 Step | eBay
The second one BTW is not from ALPS, but a Chinese invention using (probably fake) ALPS RK27 wipers and mechanical parts.
Actually a clever invention.
The trouble with all these solutions is that they are all of the series type. It is already a squeeze to fit 21 SMD (0805) resistors into the space available, and a stereo pot has only one wiper per channel to offer. If one would accept a series attenuator solution, then the easiest way is to buy a RH2702 and change all the resistors to Susumu 0.5% thin film.
Alps RH2702 Audio Potentiometer - Boards | Kits | Components | Modules | Tools
Susumu Dünnfilmwiderstände - SMD | Mouser
This also allows you to choose the tracking accuracy, thermal coefficient, total impedance, maximum attenuation, pot taper, …. yourself. How nice.
But luckily, you can also build a ladder with one common wiper shared between two contacts :
http://tubecad.com/2011/04/26/Ladder Attenuator.png
And there are two sides on a PCB to mount resistors, right ? The tricky part is to find 0.7mm of space on the backside of the PCBs, which is still possible but requires machining of adjacent components.
We’ll see how far I can get in a few months from now. An ALPS RK27 is on its way.
Patrick
While waiting for WK to organise parts for the Beta tester (he is 150% loaded till August !!!!!!!), I have been looking at one aspect of the DAO SE specifically, namely the attenuator for volume control.
One of us has done a comparison recently, between a pot with carbon tracks (e.g. ALPS RK27), pot with conductive plastic (e.g. Vishay P11A), switched attenuator series type, and switched attenuator ladder type. The switch used for the experiment was no fancy ones, just 6P4T 2-deck selectors.
https://www.monacor.ch/itemcard.php?itemno=RS-246
The clear winner was switched ladder with Dale resistors.
There is a very comprehensive explanation of different types of switched attenuators by Gold Point :
Stepped Attenuator Types
There is also a large selection of both the series and ladder type attenuators on the market, starting from 10USD and ending somewhere over 1000USD. Or you can just buy a 4-deck, 24-position rotary switch (ebay, Elma Shallco, Seiden, Grayhill, …….) and a bunch of “audiophile” resistors and make your own. The chances are that you will end up with spending about 100USD+ and a volume quite a bit bigger than a normal ALPS RK27 or TKD CP2500, which Mark uses for his DAO. And the major cost driver is of course the 4-deck 20-position rotary switch, unless you go for one of those from ebay.
But then I found these, and I like the idea of using the mechanics of a normal pot as rotary switch:
WiredState Audio Community • View topic - Need advice on a TKD stepped series attenuator
°ëÔ²±ú·¢ÉÕ¼¶RH2702_A100KÖ¸ÊýÒôÁ¿µçλÆ÷27ÐÍË«Áª²½½ø¾«¶È³¬ALPS-ÌÔ±¦Íø
Dact Type SMD Stepped Attenuator 21 Step | eBay
The second one BTW is not from ALPS, but a Chinese invention using (probably fake) ALPS RK27 wipers and mechanical parts.
Actually a clever invention.
The trouble with all these solutions is that they are all of the series type. It is already a squeeze to fit 21 SMD (0805) resistors into the space available, and a stereo pot has only one wiper per channel to offer. If one would accept a series attenuator solution, then the easiest way is to buy a RH2702 and change all the resistors to Susumu 0.5% thin film.
Alps RH2702 Audio Potentiometer - Boards | Kits | Components | Modules | Tools
Susumu Dünnfilmwiderstände - SMD | Mouser
This also allows you to choose the tracking accuracy, thermal coefficient, total impedance, maximum attenuation, pot taper, …. yourself. How nice.
But luckily, you can also build a ladder with one common wiper shared between two contacts :
http://tubecad.com/2011/04/26/Ladder Attenuator.png
And there are two sides on a PCB to mount resistors, right ? The tricky part is to find 0.7mm of space on the backside of the PCBs, which is still possible but requires machining of adjacent components.
We’ll see how far I can get in a few months from now. An ALPS RK27 is on its way.
Patrick
Attachments
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Would it be possible to convert this file into a basic pdf, by any chance - for some reason, even with the latest upgrades, I can't get my computer to access this asc file
Sorry, but very interesting ...
I've found that with different music, I prefer different amounts of X-feed (sometimes none with the planar type 'phones) and sometimes with different headphones, slightly different filters (I thought this was me 'being pedantic'!
Sorry, but very interesting ...
I've found that with different music, I prefer different amounts of X-feed (sometimes none with the planar type 'phones) and sometimes with different headphones, slightly different filters (I thought this was me 'being pedantic'!