Posted 14th October 2013 at 06:57 AM byabraxalito Updated 27th November 2013 at 01:42 AM byabraxalito
Here's my first stab at an affordable yet screened passive filter using off-the-shelf inductors. Its a 17th order quasi-Chebyshev using 8 equal valued series L and 9 shunt caps achieving slightly better than 50dB rejection at 24.1kHz.
Update - this might be the first and last filter I build with these Coilcraft inductors. (If anyone's interested, the part no. is LPS6235-335). Reason being - on trying to order more, the price got hiked more than 100%. Originally these were attractive because on Taobao there was a source selling well below the manufacturer's list, but that seems to have dried up. At the list price in USD, there are other alternatives potentially better value. However none with the same inductance (3.3mH). The key feature is the Q - the Coilcrafts have a Q around 40 at 20kHz - this is very hard to beat in such a small package. As a reference, my pot-core hand-wound inductors have a Q about 160 but they're huge in comparison, so these tiny inductors are actually...
After the Magisters went I started missing them. Much irrational thought later I decided that I needed some Dovedales. It may be some left over residual memory of some super 8s I had when I was young, they were very nice despite the lack of tweeter (retrospective young thought). The big Dovedale woofers look similar with the green felt, bit nervous of those strange pink domes though... Anyway, eventually "won" some with mint drivers slightly tatty boxes. Long story short the rubber had got stiff, but not yet brittle.
Sulk, got the Magnums... (must have bass now). After much research and thought, the Dovedales don't seem to be a standard size for foam, and I had got to the point of contemplating cutting away some of the cone to fit a flat foam. I was tidying up the garden when I found a 700 inner tube I had changed recently.
At this point I thought what have I got to loose, so gave it a good wash, (lots of washing up liquid applied neat), chopped out the valve...
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 3rd January 2014 at 03:14 AM 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.