Q&A on Elektor Projects (Session #1 - March 18th, 2014)

THIS EVENT HAS ENDED!We would like to thank you all for attending, and we hope you enjoyed the session as much as we do :)For those who couldn't be there, don't panic! We will be announcing a second round very soon... stay tuned!

THIS EVENT HAS ENDED!

We would like to thank you all for attending, and we hope you enjoyed the session as much as we do :)
For those who couldn't be there, don't panic! We will be announcing a second round very soon... stay tuned!

Some of the most interesting questions regarding the Q-Watt Audio Power Amplifier are posted below.

Welcome to the first session of this question-and-answer series, where we will be solving any doubt you may have regarding Elektor projects. It will take place Tuesday, March 18, 2014 at 4:00 PM (CET). Don't miss it!

- How can I join the session? Is it free?

The Q&A's on Elektor projects are completely free of charge, and of course you're invited to be a part of them, from wherever you may be!

To attend, you only have to register in our web service, this will take you less than one minute! Only the name and e-mail address are required.

CLICK HERE TO REGISTER FOR FREE >>>

- How can I post a question?

Elektor.LABS users can simply post their questions in this site. You may need to login first, and then click on create contribution (right here, or below also). Becoming an Elektor.LABS user is free for Elektor members, just fill in your login details for your Elektor account in the login window.

If you are not a member, you can ask questions as well. Simply use the textbox on the registration form. Please note that we will be giving preference to the questions coming from Elektor members over other attendees.

- Which projects will be discussed this time?

The UltiProp Clock (main project)
The Q-Watt Audio Power Amplifier
...and any other electronic doubts you may have (but of course only after finishing with the featured projects mentioned above!)

- Sorry, but I still have doubts...

Should you have any other question, please just let us know using the contact form in Elektor.LABS, and don't miss to specify that it's related to the Q&A on Elektor projects.

Elements du projet

The UltiProp Clock (JPG, 102.83 KB)

The Q-Watt Audio Power Amplifier (JPG, 62.64 KB)

Presented by (the incomparable) Jan Visser :) (JPG, 269.61 KB)

Discussion (4 commentaire(s))

Pascal Hibon il y a 8 ans

The text sais that this session would be recorded and posted onto the youtube channel. Does anyone have a link to this recording?

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ClemensValens il y a 8 ans

Unfortunately, this video has been lost somehow :(

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Jules il y a 10 ans

Ou trouver un fournisseur pour le boîtier et les accessoires de mesure de cet appareil ?

marc schreiber.

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Jaime G.-Arintero il y a 11 ans

Here are some of the most interesting questions regarding the Q-Watt Audio Power Amplifier we got from the attendants during the session...

Q: Can we use it for Carnival in Rio?
A: Of course you can!

Q: Can you say something about proper ground interconnections - for amp input, amp output and power supply ground references.
A: Input, feedback loudspeaker ground and power supply should form a star ground to give the best quality. That's why this amplifier is stricktly a mono design.

Q: Does that mean that a separate power supply should be used for each amp in stereo mode?
A: Yes!

Q: Would the bridge config need a negative Power rail, since the speaker no longer has a ground connection?
A: The amplifier has a symmetrical power supply!

Q: I'm thinking about a full-bridge motor drive which does not need a symetrical PSU - I do not see why driving a LS coil should be different in principle to this.
A: A bridged audio amplifier can work on a single ended power supply with each output having half the power supply voltage. The DC voltage between the two halves is then of course 0.

Q: I would like to see an hifi audio amp design in a future edition which works from a COTS 5V or 12V single-sided PSU to avoid need for legally and safety dubuois home-build mains work. Might require a switch-mode voltage step-up within the design.
A: Let's call this food for thought, but many high power car amplifiers work on a battery voltage of 12V!

Q: Yes, I guess they must work bridge-mode with a step-up to drive the watts. They do not seem to bother much about distortion from any I've heard!
A: Probably true for most of them and the better ones are bloody expensive...

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Pascal Hibon il y a 8 ans

The initial post said that the session would be recorded. Can anyone point me to that recording? I'm very interested to hear and see what was discussed !
Thanks,
Pascal

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JohnHind il y a 11 ans

1. Would it be possible to design a modern audio amplifier by adapting switching power supply practice so as to avoid the need for specialised high-voltage dual-rail power supplies? Maybe a class-D in which power conversion and amplification are part of a unified circuit which can run off 5v USB power?

2. Could the dual-rail requirement be eliminated simply by floating the speaker coil without grounding one side? Particularly this should be feasible with an active design such as in the last edition of Elektor where there is one amplifier per speaker and the amplifier is in the speaker enclosure.

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DaGreatRV il y a 11 ans

1. I think it would be possible, you can see something similar in class G and H amplifiers. They adjust the powersupply voltage to save power when a high output voltage swing isn't needed. At low volume for instance. A full bridge class D amplifier is almost a 2 quadrant switched power supply, it can sink and source current on the two wires of your speaker. But that would require that the speaker is not grounded to the case/speakerbox if you are going to supply a unipolar voltage to the amplifier. Just an idea for your 5V system. You could make a 2,5V return rail for your speaker. That would have to be able to sink and source(hint: they are used in DDR termination voltages, though I doubt they can handle audio's low frequency and irregular waveform without modification.) Also your speaker has to float to prevent a short circuit. The drive signal would have to be biased with the return rail to prevent a DC potential across your speaker. Edit: AC coupling the output could work, that would prevent a DC bias across your speaker. But that would require a capacitor that displays ideal behavior at high voltages and currents. So that might not go as easy as planned. Another method would be to go to a different two quadrant solution. One that can swing between sourcing a positive voltage and sinking a negative voltage, with only using a unipolar supply. I can't think of a proper topology at this moment, but I imagine it will look a bit like a Buck mixed with a Cuk. Than you can still ground the other side of your speaker. I really doubt there is a commercial part availible that does this, so you'll get to do some developing ;). 2. The signal you send to your speaker only makes sense because it is referred to a certain voltage. That goes for your source and the amplifer in your speaker. Speaking of that speaker, if you float one side you can draw a replacement schematic that puts a GigaOhm resistor in series with your speaker. So you'll hear nothing. You could argue that putting a capacitor on the floating end could work, but it really doesn't. Because that gigaOhm range resistor is still in series with your system. This would result in the same thing. Even if you could manage to do this, sending a signal without a return path(thanks Kirchhoff ;)) you would still be referenced to nothing and that is an undifined potential, thus undefined sound. In short: Nope.

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