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I have built eight Class D amps over the last year or so and found the original hifimediy 180W T4 module the best and warmest sounding of all the Class Ds. There is a new T4 module out - V1.3. Not convinced it is as warm as the original but excellent sounding regardless. He is my latest Tripath D. Current I still have two Ds (is that a double D?). The other is a 250W IRS2092 gate controller based module. But here is the T4.
To ensure maximum current throughput from rec bridge to first cap I soldered the rec bridge directly onto the cap and doubled the wiring from tranni (500VA) to the rectifier. Two 8000uf caps provide smoothing. Small and large polies in the PS to suppress any noise.
| retro-thermionic |
Follow Ups:
I have the IR reference board amp out in the garage.
Any PS advice? Voltage or a specific transformer?
Too much is never enough
Which board do you have? Stick strictly to max voltage I broke one going over Volts.
Only drive these with a DC linear PS. They really shine.
| retro-thermionic |
I'll have to go look. I printed the entire 'helps' from the WD site, too.
I worked for 'em for 15+ years making all sorts of power devices and the guys over at the audio section 'comp'd' me an amp. I'd like to make it work.
If it helps, this board will run in bridge or half-bridge mode?
Too much is never enough
Now I'm lost. Not sure where I can help.
| retro-thermionic |
Bridge rectifiers usually need some heatsinking, mounting it on top of a capacitor may not be best for longevity.
Regards
13DoW
A HS can be added to the bridge.
| retro-thermionic |
but running 16,000 uF on 48V rails (maximum allowed) is only 18 joules of storage for a 360 watt amplifier. You might want to bump that a bit. Or a lot.
By comparison, my ARC SP20 preamp has 23 joules. :)
Thanks for the nice comment.
| retro-thermionic |
There is another 10,000uf on the amp module. Infact you can just connect a tranni direct to the board. But the suggestion by the seller is to run them on DC.
The way this one is setup it will provide about 160W. My speakers are Beyma 15" concentrics at 99db efficient. So I only need a few watts for good volume.
| retro-thermionic |
Infact you can...
Sorry, not familiar with the word "infact".
So I only need a few watts for good volume.
Which is the case for most speakers. I find that power supply stiffness really does count at any power level. Even with preamps. :)
:-)
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Agree, in my 250W Class D I have two 47,000uf Mundorf M-Lytic caps. These caps are massive and ultra low ESR. I went to discharge one with a 100ohm resistor and could draw a blue blame a 1cm long off the cap for about three seconds.
| retro-thermionic |
my 1981 Threshold Stasis 3 amp with 100 watts/channel had. It used 50,000 uF @ 65V rails for 105 joules.
Caps are cheap. Use them liberally for improved resolution and dynamic punch. I learned that lesson long ago from Frank VanAlstine's Dyna modifications.
Back in '76, I boosted an Audire One's power supply from 20,000 uF to 80,000 uF and installed a new bridge. The difference was significant . :)
Not sure if you have read the article which claims your diodes or rec bridge has to deliver 100A short pulses to keep the first cap charged. And that the wiring from bridge to first cap is generally never heavy enough. In this build I soldered the rec bridge direct to the first cap to ensure no loss even through heavy wiring. I also doubled wiring from tranni to bridge.
But I hear and understand what you are saying. And agree.
| retro-thermionic |
is not what I've read - it's what I've heard.
Weak power supplies, regardless of the wiring used don't cut it.
Very nice detailed job. Great work!
Enjoy
charles
Thanks mate for the nice comment. I feel anything less dumbs down the art.
| retro-thermionic |
I have a Topping TP-60, very nice older tripath amp. Uses dual-mono power supply setup, very solidly made. Have a look at the picture. This is a lot of amplifier for $200 retail. Detailed, somewhat tubey-sounding (slightly sweet) with good bass extension and control (within the limited amount of power provided- this is not a giant Krell, Pass or Levinson arc-welder)
Big analog amps have considerable constant current consumption, they need much larger capacitor reservoirs than a switching amp which has almost no idle current drain. Even preamps with energy-consuming shunt regulators will want big capacitor banks. Switching amps are a different animal, and while they do need current reservoirs the requirements are different. With a switching amp you want some ampacity but more importantly you want the lowest source impedance power supply you can get at the frequencies that the switch uses. That doesn't always translate to giant electrolytics.
Very neat job there on the build.
Thanks for the nice comments. My Digikey 250W sounds the best of my current Ds and I'm not sure if it is because of the module and audio caps I added or because of the massive PS. Regardless sounds excellent.
| retro-thermionic |
You need a big supply, yes, and linear supplies seem to sound better than switching power supplies. Linear supply like a transformer, diodes and filter caps... and the big-ish caps on the board itself help supply & sink current without the inductance of the wiring between the supply and the amp module. This inductance, though small, is not zero and using caps right near the amp module eliminates it, gives lower source impedance for the DC. Using "audio grade" caps which usually have very low inductance and ESR seems to help too. Of course they are usually bypassed with VERY low ESR film caps which is also useful.
But using good capacitors in the power supply itself is also a good idea, helps keep that source impedance low.
The switchmode amp module itself is, I think, largely responsible for the overall "sound" but won't achieve it's full goodness without the right power supply.
I think a beefy shunt-type regulated supply works somewhat better than an unregulated transformer-diodes-filter cap type supply, but this is quite an additional expense, adds a lot of heat, and provides only a LITTLE better sound if done right.
Here is the inside of my 250W Digikey Class D with massive filter caps - Mundorf M-Lytic, 47,000uf, the better audio caps and 500VAC tranni.
| retro-thermionic |
Agree. And in my latest the PS leads are very short and double thickness. And as I have mentioned the bridge is soldered directly onto the first filter cap.
| retro-thermionic |
There are a fair number of conventional solid-state amplifiers I've seen with the bridge right on the caps like this; sometimes they use copper plates instead of wire on the really large amplifiers.
Does the bridge get hot? I'll bet it doesn't. You are not running this amplifier long term at high RMS power levels, your speakers don't require that. A big peak here, a big peak there maybe. And since these class-D amps are very efficient, you really are not pulling much current through there on average. On demand, yes, but not much the time.
With 15" concentric Beymas at 99db efficient my 1920s tube power amp (Intermezzo) with its 330mW, plays at good listening levels. So I guess I'm pulling less than 2W (lately playing louder) from an amp capable of delivering 160W! The bridge should stay cold.
Same for my 250W Digikey amp - barely idling. I'm finding this may be the best combo;- very high efficiency BIG concentric drivers in big boxes, powerful, fast amps and high res audio from dedicated music severs. But I could be wrong.
| retro-thermionic |
Bleed resistors could be a better fittment than those 'bypass' caps.
Which even if one acribes to the bypass theory..seem a strange choice,
5 cent mylars on Uber priced Mundorfs ?
Out of simple curiousity: Where/Who mfg'd that 'Tripath' chip ?
As Tripath dissapeared over 10 years ago.
Edits: 09/02/16
Putting the polies on filter caps, across diodes and rec bridges and across audio caps is something I have always done. I have read in a number articles how it is good practice and I don't believe they have to be over expensive items.
Should I get to see the bottom of another T4 board I post the chip name. Tripath licenced thier technologies to other chip makers so some chips could aspire to the Tripath design.
One thing I have noticed with Tripath Class Ds (or Class T) is as the load increases the wattage drops. With most Class Ds the bigger the load the bigger the wattage output. Hifimediy make a 4ohm load version called the T2 which is designed for 4ohm loads. This is the give-away that the module is a genuine Tripath. Part of the Tripath design is where they take the feed back point. I understand most Class Ds take the FB from the analogue stage at the end. Tripath moved the FB stage to the switching area. Supposedly better sound by better FB design.
| retro-thermionic |
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