- Posted by Dave Davenport (A) on June 30, 2004 at 07:43:44
In Reply to: Re: sneak preview of the RAKK dac posted by akltam on June 30, 2004 at 02:37:57:
Hi Alan,If you notice there is a relatively open area where the capacitors are above the outputs. As part of our evaluation in one of our early prototype models we installed Black Gates instead of the tantalum capacitors. Comparing one-on-one between a RAKK DAC with the tantalum capacitors versus a RAKK DAC with the Black Gates, both Kevin and I preferred the tantalum capacitors. I had expected the BG to sound superior and was surprised at the result, but then that is why we did the experiment.
I have done a lot of component comparison over the last couple of years since I started on the Line Stage odyssey and have found one underlying principal: There is no one type component that sounds best in all cases. Results are impossible to predict because they are circuit and location dependant. I have never found that a crappy component sounds good, rather some good components sound better than other good components in some locations.
During the development of the Raleigh Audio Line Stage, which was the base for the RAKK tube output, I evaluated resistors. It was an extensive test that took several hundred hours of critical listening. First I placed all of one type resistor in all locations. Then all of another type, then another and another... Metal film, carbon film, metal composite, wire wound, carbon composite, tantalum etc. The best sounding was the tantalum resistor. But I didn't leave it at that. Starting with all tantalum resistors I focused on one single location. With tantalum resistors everywhere else I cycled all of the resistors through this one location. I found that in this one location a different type of resistor sounded better than the tantalum. Then with this new "best" resistor in that location and tantalums everywhere else I moved on to the next location and cycled all of the resistors through that location. When I had finished, there was not a tantalum in sight. I ended up with a mix of Kiwame, Mills and Caddock resistors. This is not to say that a tantalum resistor would not sound best in some location in some circuit.
There are similar results with capacitors. For example, I found that the Solen capacitor sounded the best for the filter in the Minimal Reactance power supply. But the Solen was not the best sounding in the parafeed capacitor location.
So feel free to experiment, and your results may be different from ours because your preferences may be different from ours, but understand that the tantalum capacitors that we chose (there are different types of tantalum capacitors) are not “expedient” or a compromise but rather were chosen because they sound better.
Dave
Follow Ups:
- For the passive Transformer output .... - akltam 17:01:56 07/02/04
(1)
- In Reply to: Re: sneak preview of the RAKK dac posted by Dave Davenport on June 30, 2004 at 07:43:44:
would the analog power supply for the DAC be a very important contributor to its performance ?
I incline 'minimalist' design. I came to this idea that in the passive transformer output, the DAC is in fact driving the output closely and thus the quality of the power supply will be important. What do you think ?
Alan
- Re: For the passive Transformer output .... - Dave Davenport 18:35:04 07/02/04
(0)
- In Reply to: For the passive Transformer output .... posted by akltam on July 02, 2004 at 17:01:56:
I don't know, but I suspect that the power supply would have the same effect on either the passive output or the active output because the load is about the same.
Dave
- Re: For the passive Transformer output .... - Dave Davenport 18:35:04 07/02/04
(0)
- Re: sneak preview of the RAKK dac - AnandR 09:41:38 07/02/04
(4)
- In Reply to: Re: sneak preview of the RAKK dac posted by Dave Davenport on June 30, 2004 at 07:43:44:
Dear Readers/Asylum lurkers,
I hope you all sincerely wish Dave & Kevin the best with this Dac because what they have done is some serious Research and Development (R&D). Trust me it takes A LONG time to come up with resistors and capacitors that sound good since you have to evaluate them one at a time. Finding the proper operating point on my headphone amp took me a while and I can definitely see the effort done in making this DAC project.
Hmm...maybe when I get tired of my Philips 963SA, I'll use it as a transport and build the RAKK DAC!Too many projects, too little time (to borrow a little from Gary Dahl),
Anand.
- RAKK dac project history - KevinC 11:30:46 07/02/04
(3)
- In Reply to: Re: sneak preview of the RAKK dac posted by AnandR on July 02, 2004 at 09:41:38:
Thanks Anand for the support!
I haven't really given any info on the origin of this project and I should, because it shows you what we were thinking and gives credit to those who remain otherwise unmentioned.
For almost a year, a Lundahl transformer user and friend in Vancouver, Ian Langs, has been on my case to develop a DIY DAC kit. On one of the many phone calls where he gently harrassed me about the project, I broke down and gave in, promising to call a contact at Burr Brown and see if they had an evaluation board for their new PCM 1792/1794 DAC products. I had already purchased an Analog Devices AD1853 eval board and wasn't all that enchanted with what I heard, so this was the other latest generation current output candidate. It turned out that they did have them, but only for loan, so I begged one for a month. When I got it I removed the nasty little opamps from their sockets to get access to the output connections and attached a quickie discrete FET differential amplifier (designed by me and built by Doug Bergen) to each differential current output, hooked up a simple choke loaded low voltage supply for the digital stuff and listened. What I heard fairly blew me away! There was more of everything I associated with music and less of everything I associated with CD sound. I had to grudgingly admit that Ian had driven me to something very good.
What to do now.... After some consideration I invited Dave Davenport of Raleigh Audio to join me in this project, because I was excited about it, wanted it to happen soon, and value his design and listening expertise. Dave is a 30 year veteran of IBM who has substantial project management skills and is an inveterate perfectionist when it comes to the design details. It helps, too, that he has 30 years of electronic design and development experience. ;=)) Without Dave, I would still be working on the circuit board design!
At the same time Dave worked on adapting and refining his differential parafeed line stage circuit and power supply to use as an active output stage while I came up with a way to use the LL1674 as an alternative passive output stage.
We set a very aggressive timeline and worked together to explore different configurations and parts and settle on the best of these for the RAKK dac. It helped, too, to have the listening skills and encouragement of the Piedmont Audio Sunday School group. Lots of listening tests later Dave and I are nearly ready to ship the product.
It has been a great project. In particular, it isn't often that you can undertake a project and discover that the medium you once disdained as second rate ain't second rate at all. I think that those of you who try the RAKK dac will agree that it "unlocks" the sonic potential in CDs, which will, afterall, be the dominant recorded music medium for some time to come.
Thanks for reading my uncharacteristically long post!
Kevin Carter
K&K Audio
www.kandkaudio.com
- Uncharacteristical long post! - Bas Horneman 05:18:52 07/05/04
(2)
- In Reply to: RAKK dac project history posted by KevinC on July 02, 2004 at 11:30:46:
Kevin,
I should gently harass you to make more of these posts! The internet is a PERFECT medium for such a thing. And inmates generally LOVE these type of stories. I also soothes the pain of having to wait for your products!
Cheers,
Bas
To infinity and beyond!!!
- PS...when is part 2? - Bas Horneman 05:21:11 07/05/04
(1)
- In Reply to: Uncharacteristical long post! posted by Bas Horneman on July 05, 2004 at 05:18:52:
of your project history? ;-)
To infinity and beyond!!!
- Re: PS...when is part 2? - KevinC 07:35:58 07/05/04
(0)
- In Reply to: PS...when is part 2? posted by Bas Horneman on July 05, 2004 at 05:21:11:
Actually, Bas, it's probably guys like you who will be writing Part 2 after you get your kits (soon), build them, and inevitably modify them to personalize and improve them. I look forward to that. Then maybe Dave and I can proceed to Part 3!
Kevin Carter
K&K Audio
www.kandkaudio.com
- Re: PS...when is part 2? - KevinC 07:35:58 07/05/04
(0)
- PS...when is part 2? - Bas Horneman 05:21:11 07/05/04
(1)
- Uncharacteristical long post! - Bas Horneman 05:18:52 07/05/04
(2)
- RAKK dac project history - KevinC 11:30:46 07/02/04
(3)
- Re: sneak preview of the RAKK dac - akltam 18:10:57 06/30/04
(1)
- In Reply to: Re: sneak preview of the RAKK dac posted by Dave Davenport on June 30, 2004 at 07:43:44:
I have little doubt that for a project like this, you use the best components to your ears.
But, maybe it is pyshcological that I like to see a big cap right next to the receiver chip and the DAC. I never saw a commerical product (CD, SACD) that put a 1000uF cap for power supply next to them. I saw 100uf (may be 220 Uf at max, extremely rare). And these little values is only good for theory. For the sake of my reference, what value uF of Black gate did you use for test ?
Rdgs.
Alan
- Black Gate cap - KevinC 18:34:56 06/30/04
(0)
- In Reply to: Re: sneak preview of the RAKK dac posted by akltam on June 30, 2004 at 18:10:57:
47uf 16v FK series Black Gate
Kevin Carter
K&K Audio
www.kandkaudio.com
- Black Gate cap - KevinC 18:34:56 06/30/04
(0)
- Re: sneak preview of the RAKK dac - MaciekP 11:34:47 06/30/04
(1)
- In Reply to: Re: sneak preview of the RAKK dac posted by Dave Davenport on June 30, 2004 at 07:43:44:
by the way, did you use the N, NX Black Gates and gave them at least 100 hours?
Maciej
- Re: sneak preview of the RAKK dac - KevinC 13:01:40 06/30/04
(0)
- In Reply to: Re: sneak preview of the RAKK dac posted by MaciekP on June 30, 2004 at 11:34:47:
We used the FK series and listened after 72 hours of active break-in.
Kevin Carter
K&K Audio
www.kandkaudio.com
- Re: sneak preview of the RAKK dac - KevinC 13:01:40 06/30/04
(0)
This post is made possible by the generous support of people like you and our sponsors:
You can not post to an archived thread.
[
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]