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Class D Switching Power Amplifiers and Power D/A conversion

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Old 8th November 2006, 08:28 AM   #11
t. is offline t.  United Kingdom
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Interesting thread, I have built both the Amp3 and Amp6, the Amp3 died a while ago but the Amp6 is still going strong.
Both of these amps was plenty loud enough in my system, with the Amp6 I use 2.2uf Auricap coupling caps, 1000uf Blackgate NX for decoupling on the pcb, MBR10100 schottky diodes and 10,000uf Siemans Sikoral cap in the psu.
The sound is not bad but I feel my UCD180 easily beats it, power isn't an issue in my system.
The UCD uses MBR10100 schottkys, DNM T-network psu capacitors, LM4562 input op-amp and no coupling caps, theres a few other mods added to the pcbs.

Only higher powered Tripath based amps I've heard are commercial ones, unless theres any other mods worth trying with the Amp6 I'll stick with the UCD
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Old 8th November 2006, 12:49 PM   #12
KeithC is offline KeithC  United Kingdom
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Default Re: I would love to build tube gear...

Quote:
Originally posted by ptwining
I would love to build tube gear, hardly cheap, but amazingly seductive!

If I had my 'druthers I'd rather be building big SET's. But, I don't have the expertise. Next best thing (my father built tube amps when I was a kid that I have never forgotten) is the UcD's.

Maybe this winter I will diligently try to electrocute myself building tube amps - but there is so much more to learn than assembling genius devices like the UcD's.

There is a threshold in DIY that one has to cross - one that I have miles to go befiore I even approach. I am currently reading the Navy Tube Manual (posted here somewhere) so that when I die I'll know what killed me.

I'm told willingness is everything...

Regards,
Tom

Tell you, Tube amps are easier to build - component count is typically lower, and components are bigger.

Just as long as you mind the HT - those of us that started in the '60s were used to building units with dangerous voltages, and to me it is an un-natural act to touch a component when power is on. Guess that for those brought up on low voltage devices the converse may be true.

For myself, over the last 14 years I have moved from EL34 pp, to solid state class A, to class D, and now I have started playing with tubes again (just ordered an el cheapo Aria 12w 6P1, and a Zen Taboo sep).
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Old 8th November 2006, 01:39 PM   #13
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For me, at least, it's the accessibility of the t-amps. I'm an art guy, not an engineer, but I do enjoy noodling around soldering in different components, on that elusive quest for more bass. Every session results in a little better sound. Very rewarding as hobbies go.

The UcD modules are already at a pretty high state of tweaking, although I know there is more that can be done. But it is intimidating. The cheap little Tripath amps just shout "tweak me."

Plus if you blow one up, what's the big deal?

In my own case, I'm on a quest for the ultimate boombox, and that stipulates long battery life. Even the smallest UcD module is way overkill for this app.

--Buckapound
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Old 8th November 2006, 04:57 PM   #14
soongsc is offline soongsc  Taiwan
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I recall someone actually like the Tripath better than a Ucd after he changed the output inductors.
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Old 8th November 2006, 05:12 PM   #15
t. is offline t.  United Kingdom
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Well those output inductors would have to make a big difference for me to change my mind
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Old 8th November 2006, 05:28 PM   #16
PWatts is offline PWatts  South Africa
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The output inductor is CRITICAL for any switched amp. Particularly ones that only takes the feedback from before the filter or fully open-loop ones, but they're pretty much restricted to bitstream types (I'm not calling it digital since there's no such thing as a digital amp; the conversion process is just done differently).

Fancy inductors, especially foil types, will do more harm than good since their parasitic capacitance is very high. Not an issue at audio frequencies but when it comes to attennuating the carrier it's a whole different matter. Bruno has a good paper on it. Gapped toroids can work well if implemented properly, although a good alternative are the small SMD coils from CoilCraft - they've some very small ones that can pass as much as 8A linearly. Unfortunately they're hard to fit in a commercial amp that's not designed for them.

Same goes for capacitors - and I've measured it. Plain Rifa "box" MKP caps sounds and measures much better than audiophile film caps due to the smaller size and hence lower ESL.

My day job is dedicated to class-D amps, and although I don't agree with all Bruno's statements, I'm 100% behind him when he says that for the filter one shouldn't believe audiophile hype, and rather stick to lowest possible ESL for the cap and capacitance for the coil. As a bonus it saves space too.
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Old 8th November 2006, 06:48 PM   #17
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by t.
Well those output inductors would have to make a big difference for me to change my mind
It seems like they did. Different cores and windings were tried, and it seem he was quite satisfied with a molypermalloy core with only 13 winds to get the right inductance. Seems that it made lot of difference in revealing detail slightly better than the Ucd he had.


Quote:
Originally posted by PWatts

The output inductor is CRITICAL for any switched amp. Particularly ones that only takes the feedback from before the filter or fully open-loop ones, but they're pretty much restricted to bitstream types (I'm not calling it digital since there's no such thing as a digital amp; the conversion process is just done differently).

Fancy inductors, especially foil types, will do more harm than good since their parasitic capacitance is very high. Not an issue at audio frequencies but when it comes to attennuating the carrier it's a whole different matter. Bruno has a good paper on it. Gapped toroids can work well if implemented properly, although a good alternative are the small SMD coils from CoilCraft - they've some very small ones that can pass as much as 8A linearly. Unfortunately they're hard to fit in a commercial amp that's not designed for them.

Same goes for capacitors - and I've measured it. Plain Rifa "box" MKP caps sounds and measures much better than audiophile film caps due to the smaller size and hence lower ESL.

My day job is dedicated to class-D amps, and although I don't agree with all Bruno's statements, I'm 100% behind him when he says that for the filter one shouldn't believe audiophile hype, and rather stick to lowest possible ESL for the cap and capacitance for the coil. As a bonus it saves space too.
I quite agree for small signal caps. do manufacturers publish ESL data? How would you measure capacitance of a coil?
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Old 8th November 2006, 07:32 PM   #18
t. is offline t.  United Kingdom
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Quote:
Originally posted by soongsc


It seems like they did. Different cores and windings were tried, and it seem he was quite satisfied with a molypermalloy core with only 13 winds to get the right inductance. Seems that it made lot of difference in revealing detail slightly better than the Ucd he had.



Interesting, if I can get some of these coils I'll compare again and post my honest results
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Old 8th November 2006, 08:43 PM   #19
Pano is offline Pano  United States
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You have to be careful with the cores. Some high permeability cores will saturate and distort the signal well into the audio band.

Fewer coils do seem to help the sound, though.
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Old 8th November 2006, 08:49 PM   #20
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I own both Ucd180ad and Tripath Ta2022 2x50W 8ohm. I've too a couple of t-amps and a Tripath TA0102a 2x100W 8ohm amp.

Low power Tripath chips can't compete with higher power ones: I have Fostex FE206E 96dB sensitivity and t-amps sound loud enough to shake windows, but with high power tripath chips higher and lower dynamic extension are dramatically improved, while sound quality and detail is similar to t-amps, but with more solid sound.

Please, don't ask who's the winner between Tripath and UCD. More useful to discussion is to tell what are good experiences with both.

UCD is unbeatable for clean sound and timber fidelity of instruments (I listen to classic music only): it is like a good valve amp but quieter. I identify this amp with solo violin sonatas and Bach.

Tripath high power amps are unbeatable for dynamic extension, transients and detail: they go lower and higher than UCD and in between it looks like there are more sounds. When the bass section of an orchestra is sounding loud with thick basses, you can still hear distinctly a violins pizzicato at right volume, and the sudden hit of a timbals or drums still detaches from this loud background with great force.

I use UCD when I want fidelity, Tripath when I want live emotions.


P.S.

I'm the guy with 106 MPP cores, 60 perm, 13 turns I calculated with a software that they don't saturate.
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