The time has come to talk about the overall aim of my DAC developments - a modular DAC platform for DIYers and audio systems integrators. By this word 'platform' I mean this isn't going to be presented as a single end-to-end design that you can order up from a friendly reseller. Nor is this an 'open source' design, although it is open to anyone to use or adapt with no restrictions. Rather this is a DIYer's DAC architecture a series of interconnected modules that are subsystems from which an audiophile grade DAC can be assembled.
When I say 'audiophile grade' what I mean is this is a design optimized for aural satisfaction, not for the numbers. To be even more specific, its been optimized to give the highest perceived dynamics (within the limitations of the chosen DAC chip) rather than the lowest THD+N and flattest FR. If you're looking for ODAC-type measurements, feel free to move along now That's not to say measurements have been ignored, rather they're very much in the...
Posted 6th October 2013 at 02:27 AM byMITsound (Dedicated satellite/sub combo)
Tried out fmod high and low pass filters to feed inputs on a 300B integrated and Nait 5 , used to drive mid&treble horns, and 15" trace Elliot woofers , respectively. All mounted on large(ish) open baffle. 6db highpass @ 900hz leaves out enough bass and eq's a "hump" in the mid's response. Instead of a series cap for the highpass leg of this "filtered rca splitter", would I parallel another cap from hot to neutral to create a low pass? This is being done with 3 rca sockets in a project box per channel as I don't wish to mod the original amps and to ease cap swapping which past speaker level crossovers have proven irresistible for me to avoid revising. I do wish to maintain 1st order filtering, for the sake of fixing a couple of minor "humps" and "knees" in these drivers' responses. Bear in mind I'm very new to the electrical side of audio. Any help welcome.
To try to recreate the Magister experience I hooked up the Magnums to the little ECL86 amp mentioned previously. I was greeted again with enormous deep bass, but not as happy over all, a rather lumpy frequency response, and a big question, what's going on... So I hooked up my Hybrid amp and the Magnums sounded a bit more normal, but the bass was considerably reigned in, disappointingly.
I think the Magnums like being back against the wall, they seem happy there and the in room response is now quite civilised with a nice boom free sound and bass is only there when it should be.
Still confused, had the ECL86 on the bench to measure to try and find out what's up. The frequency response looks a bit rolled off to the bottom, so no help there, but the treble peak is looking quite promising, explaining the "prominent" treble. After some wriggling the little amp surrendered its output impedance, all be it with significant 50Hz artefacts.
I recently got some Goodmans Magnums K2, and SLs, in my quest for lovely bass, experienced when I had some Magisters, 6 months ago, but in a smaller box. Like the Magisters the plastic cover of the woofer had started to de-laminate. The K2 had suffered more, so embolden by having 2 pairs of speakers with apparently identical woofers, I decided to have a go at fixing them.
For whatever reason I decided to attack them with my hot air gun. The black material is softened quickly but so did the dust cap glue, so I took that off, and then I just tried to push the soft plastic back on to the cone, and it stuck, a bit at a time with my finger. I then put some hotmelt glue around the edge of the lamination to try to give it some more support. Then I heated up the edge of the lamination and around the back of the dome and put it back on... No idea if it will hold but it was quite easy to do.
The woofers between these K2s and SLs are different, the resonance of the SL...
Posted 11th September 2013 at 01:31 AM bywlowes Updated 29th November 2014 at 08:44 PM bywlowes
This is another personal build diary. Don't expect to see any new engineering.. just my take on a lot of other people's innovation... Sept 2013 Concept complete and chassis design kicks off.
I had really good results over the past 2 years building/tweaking and enjoying a Lampizator inspired TDA1541a DAC with 6n2p tube output. It was prototyped to death and now that I understand it I want a clean, reference build.
Inspired by Lampizator, I am shamelessly using his case design and level 6 output. This means:
-dual mono power supply,
-5C3S rectifier tubes,
-6n2p tubes mounted inverted for easy wiring,
-200u polypropylene filter caps
-separate B+ tranny for each channel
Like many, I have followed ecdesigns and Oliver Mai projects. I decided to use Oliver's Red Baron PCB and Salas shunts. Really nicely done and contains all the stuff that makes for a great tda1541a without all the...
Posted 7th September 2013 at 09:51 AM byalexcp (My DIY projects)
Updated 17th February 2014 at 05:08 AM byalexcp
I talked earlier about soundcard measurements, and here is some news: Pioneer Hill Software updated SpectraPLUS 5 so that it can now use ASIO.
ASIO (Audio Stream Input-Output) replaces Windows' own MME (MultiMedia Extensions) or DirectSound. As far as I understand, the beauty of ASIO is that it bypasses Windows Mixer and thus doesn't bring any issues associated with sample rate conversion or level adjustment.
The ASIO drivers that came with my E-MU 0204 crash every time (on Windows 7 and WIndows 8). Thankfully, there is ASIO4ALL, which works well for me.
First picture shows two spectra taken with SpectraPLUS: red is the E-MU 0204 output fed directly into E-MU's input; and blue is the output of the E-MU fed into Pete Millett's interface, output of the interface fed to the input of the interface, and then back to the sound card. THD+N is 0.000781% is the first case and 0.001272% in the second.
Posted 6th September 2013 at 04:45 AM byabraxalito Updated 6th September 2013 at 05:10 AM byabraxalito
Here's what I've ended up with in my SDcard DAC for eliminating the pull-up current sources within the TDA1543 - a heavily filtered 3.75V reference. For a single TDA1543 just connect the L and R 870R resistors to the output of this filter instead of the normal connection to 0V. Then the input's fed with the TL431 - I'm using 3k and 1k5 output voltage setting resistors. The first resistor and inductor on the left are my attempt to simulate the output impedance of the 431.
The electrolytics are Sancon 16V types with 0.1R ESR - the 440uF being made of two in parallel. The inductors need to have the right ESR (about 0,1ohm also) for which I had to wind my own 68uH - the ready made ones I have are too lossy Varying these parameters might result in a lumpy frequency response.
Attenuation is -70dB by 20kHz but almost flat to 1.6kHz and output impedance remains low down to DC.
Eliminating the current sources means that pin7 of TDA1543 now goes unconnected....
Posted 6th September 2013 at 12:05 AM byabraxalito
This board is really a fun one to tweak mainly because its so simple and relatively self-contained, so results of mods can be verified very quickly.
In stock form, the sound is fairly typical 1543, nothing unpleasant but an almost total lack of soundstage depth. On recordings with a high ratio of ambient to direct sounds (Nimbus) the acoustic cues are muddied. The flatness of presentation is one of the reasons I was so slow to accept 1543's other virtues during the course of development of my DACs. Soundstage depth is a biggie for me. There's also a lack of 'finesse' on the HF - lack of 'poise' or 'delicacy'.
I started by fixing up the grounding to enforce a star earth on the analog outputs and power supply. Then went on to filter the DAC's supply regulator (7805) with series ferrite beads and additional lytics and ceramics. It later transpired that the beads were being shorted by a parallel track on the other side of the board. I installed filtering prior to...
Posted 2nd September 2013 at 02:55 AM byabraxalito Updated 5th September 2013 at 06:51 AM byabraxalito
Its a TDA1543 SDcard player. Not hooked up yet to my amp but looks to be a really simple and quick way to get analog-like digital sound on the cheap.... The digital part is a dsPIC, it would have been better if it were an ARM (much lower power) but this looks to be a good start. Can't argue with a price of 150rmb, considerably cheaper than the QA550 and it does have an I2S output connector For those who prefer to do their own DAC, the vendor also looked to be selling the pre-programmed dsPIC for 40rmb.
Update - I tried powering this up and no sound . There's most likely a problem with the format or type of SDcard I'm using. There's no I2S signal being sent to the DAC which suggests the dsPIC hasn't recognised what's on the card. But there is activity on the card pins so its definitely attempting to read it.
Update 2 - had a chat on QQ with the designer/seller and he mentioned that the .wav files must be placed into directories and I was trying with just a...