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Class D guitar amp
Class D guitar amp
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Old 9th February 2019, 04:40 PM   #11
Khron is online now Khron  Finland
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Most class-D amp chips contain four half-bridges. Some can be configured as 4x single-ended amps. Most, if not all, are 2x BTL, and most (if not all) of those can also be configured as PBTL (parallel bridge-tied load).
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Old 9th February 2019, 06:00 PM   #12
pettol is offline pettol
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In just one day I get all this good information - Thanks a lot guys!

So hard to know what power you need, with the logarithmic scale and all...

Yeah, I think the stereo boards I've been looking at are 2xBTL. And PBTL is for lower impedances if I've understood things correctly.
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Old 11th February 2019, 07:48 PM   #13
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by pettol View Post
So hard to know what power you need, with the logarithmic scale and all...
True guitarists always need more power. At least, they think they do.

I have a nominally 15-watt '65 Princeton Reverb reissue valve guitar amp that I have never managed to turn up to full volume, because it's too @$!~% loud.

I now live in an apartment, and I have a 2-watt valve guitar amp I built for use at home, and it's too loud - I ended up using it at jams, not at home.

Most recently I built a little single-ended amp with an estimated power output of 200 mW - 250 mW (one fifth to one fourth of a watt). That's about right for playing guitar in my apartment during the day, but connected to the stock Eminence speaker in my 'Princeton, it's too loud to overdrive at night.

If you had been building a 100 W valve guitar amp rather than, say, a 20 watt one, there would be considerable penalties to deal with: the 100 W amp would cost far more, and weigh far more, than the 20 W version.

The good news is that, using a modern solid state class D power amp, and a modern switching power supply, you don't suffer a huge weight or cost penalty for the unnecessary 80-odd watts.

A MI manufacturer called Matrix Amplification has already run with the same idea. Here is one of their guitar amps,with valves in the preamp and a 420 watt class-D power amp: Vintage British 800


-Gnobuddy
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Old 12th February 2019, 03:17 PM   #14
shanx is offline shanx  Canada
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Running 40 W into even 2x12 cabinet is a LOT of volume!
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Old 12th February 2019, 08:20 PM   #15
kevinaston1 is offline kevinaston1  United Kingdom
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Reliable connections for multiple filters?

Not from my experience. A few years back, our workshop received a warranty repair; a German 1kW class D amplifier, the customer complaint was that "it did not sound right".

On switching it on, the workshop radio died. At the same moment, Steve, the radio mic technician popped his head around the door to ask who had just fired up a high powered transmitter.

The fault was dry joints on the output filter inductors and capacitors; the amplifier was fine.

Kevin
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Old 14th February 2019, 06:11 AM   #16
pettol is offline pettol
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Thanks for the information!

I'm not too worried about the switch. I'm quite experienced in soldering (I build guitar effects) and I would etch daughter a pcb for the filters. But the agian, if the switch fails... Anyway, it seems like it's overkill.

Just to confirm; as suggested by FauxFrench, would just desoldering the components of the filter of one channel be safe for a mono application? Instead of a dummy load that is.
It seems to be what they do with the mono chip TDA7498MV (isn't that a special application of the TDA7498 rather than a separate chip?).
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Old 14th February 2019, 01:10 PM   #17
Printer2 is offline Printer2  Canada
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The TDA7498MV is a mono chip.
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Old 14th February 2019, 05:33 PM   #18
pettol is offline pettol
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Yeah, I know. It's just that the design is so similar to the regular one (all the pins are there for instance). And I wonder if a separate production process for a mono chip can be justified economically...
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Old 14th February 2019, 07:30 PM   #19
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by pettol View Post
I wonder if a separate production process for a mono chip can be justified economically...
Most likely, quality control at the fabrication plant catch some chips that happen to have one dead channel. Those will be marked differently, and sold as "mono" amplifiers.

Years ago, I was told that much the same thing was true of Intel CPUs labelled and sold with varying clock speeds. During testing, the ones that happened to work at the highest clock speeds were separated, and their prices marked up substantially. Die hard gamers were willing to pay a lot more for the fastest CPU they could get their hands on.


-Gnobuddy
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Old 15th February 2019, 06:09 AM   #20
pettol is offline pettol
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Quote:
Originally Posted by Gnobuddy View Post
Most likely, quality control at the fabrication plant catch some chips that happen to have one dead channel. Those will be marked differently, and sold as "mono" amplifiers.
You're probably right! And the same goes for the low(er) power TDA7498L.
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