simple class D amp

[latala]

I have at last obtained 2 off Sinclair X10 modules these require new output devices can any 1 give me details on recommended devices
V max is 12 volts I am looking for low saturation High speed,High gain and complimenary devices
Regards Trevor

[davefromnj]

Originally posted by Gorilla
Class D amplifers have two sub-catorgories; Carrier based and self oscillating. Carrier based usally use a triangle waveform to pulse width modulate the audio signal. Feedback can be added with degrees of success. Self-oscillating amps rely on some sort of positive feedback to achieve modulation. The UCD or SODFA amps are examples of this.

If you want something simple in concept try a PWM amp without feedback. Later if you wanted feedback could be added. More challenging would be a DIY UCD. The topology is almost unparalleled in terms of its component count simplicity but is more diffcult to understand.

Search the forum there are plenty of examples round.

This UCD amp sounds interesting... I've built PWM Class D amps, but only with triangle generators. I've never heard of UCD.


Do the UCD amps sound any better? What is the advantage of the UCD amp, if any?

[corvus56]

Hi, these old fashioned stuff from Clive Sinclair looks good to me. As a beginner in Class D i am interested in a simple and discrete circuit with a few (say not more than 10 tansistors - i am not able to work with IC, only with discrete components) like the Sinclair Z-12. I am looking for this circuit diagram at the net and here - but bad luck.

Can anyone of the gurus help me and post the circuit of the sinclair z-12 amp or a link to it?
That woud be really kind - THX in advance.

[Ouroboros]

Originally posted by davefromnj



Do the UCD amps sound any better? What is the advantage of the UCD amp, if any?

The main advantage is that the NFB is after the output filter. They are also very stable into a wide range of load impedances.

[Ouroboros]

Corvus, don't even think of looking at the dreadful X10 circuit! It's very simple to make a UCD-style amp using simple components. Look at the UCD reference circuit in the Philips/NXP application note. This circuit doesn't have the performance of the Hypex designs, but it is still likely good enough for you to be impressed by what such simple circuitry can do.

[corvus56]

Thank you for the tech tip about the Philips UcD Amp ... but thats really nothing for me (Layout absolut critical around the MosFets and so on i read in some threats). I am not able to do that PCB and SMD work in my small kitchen.

I am just looking for a small class D amp circuit in the 5-10W class like the Sinclair Z-12 - only with discrete components made. It is NOT for HiFi purpose - only to understand how the basic princip class D can work ... or not ;-).

This small 1.5W 9V class D amp i tried is too complex for me - i constructed it twice in "ugly design technique" and it will not work.

Plz help me with the Z-12 circuit or so ... (that piece would be commercially sold, i think it will work on a fair level)

[rjb]

From memory the Z-12 was a conventional analogue amp, not a class D.

They made two class D, the x-10, and the X-20. I have one of the later, and somewhere the circuit diagrams. About 10 transistors.The X-20 sounded nice with my speakers of the time, but strongly radiates RF up to the Aircraft bands, because it has no output filter.

I would not recommend trying to duplicate either. And certainly do not build one without a good output filter. You will have Police knocking on your door! And aircraft falling through your roof. :-).

Another design was published in old Wireless Worlds, (Doug Self???) with a critique that was not flattering.

However I like a good class D, such as those from 41Hz, second only to class A

[latala]

I have designed and made a simple class D amplifier
the unit uses 2 off simple and inexpensive chips a dual op amp and a quad comparitor as well as 2 gp silicon output transistors
the switching frequency is 100 khz .The circuit has been breadboarded and made up on vero there are a no of options available that use an output filter or not
The sound quality is reasonable and all-though it does not have a minimum component count the advantage is that the amplifier is in discrete sections and each section can be made to work without damge to any other section during development
I am sorry to say that due to the late hour I am unable to post tonight ! There is about 3 hours more work to do before I am prepared to show my scheme !
I make no great claims re distortion figures etc for this but any reasonable amature will be able to construct a class D amplifier in a few hours that will be able to give a pleasent sound result
The unit works with a voltage supply of 12-30 volts dc the power bieng in the region of 7 watts into 8 ohm at 30 volt supply
Please hold on for a week and I will post then !
I have waited since 1964 since i saw the first X10 advert
best regards For now Trev

[RiskCord]

The main advantage is that the NFB is after the output filter.

Sounds like you are implying that it is not possible to build a carrier based Class D amp with NFB after the output filter... which is not absolutely true...

I'm designing a carrier based amplifier with a dual feedback loop, both feedback signals taken after the filter... we'll see how it goes!

[corvus56]

@latala - THX in advance for posting the circuit diags of your simple class D amp.

I found the circuit diags of the X-10 from Radionics (the Sir Clive company) but without component values and i post it here for completeness. This very first class D amp is capable of 2 Wrms, not more (they suggested 10 wpeak - but with 12V Supply @ 4 ohms it is not reacheable). Thats why they made the successor X-20, who shoud deliver 20 watts peak.

Shure will i use these LC-RF filters at the output - i am afraid from airplanes falling throug my roof ;-) and of course from the police !