Audio Power Amplifier Design book- Douglas Self wants your opinions

[DouglasSelf]

You may have heard that a new (6th) edition of Audio Power Amplifier Design is planned for later this year. While the basic structure of the book is fixed, the rest is not yet set in stone.

I would be glad to hear of any new topics that you think should be included, or anything else that would make it an improvement on the 5th edition.

 

[Dave Zan]

Main ones that jump to mind.

1. Improved treatment of double differential IPS. The VAS current indeterminacy is barely mentioned. Lot of stuff in DIYaudio on this
2. Better treatment of 2 pole. TPC and TMC. DIYaudio and also Harry Dymond's article and updates.
3. Noise in current mirrors. Samuel Groner has an excellent article that covers this and several other comments on your book.
4. Improved Thermal Trak bias spreaders.
5. Nested feedback and advanced compensation schemes.

I also have a few typos and errors. Do you want them here or in a PM?

Best wishes
David

 

[Samuel Jayaraj]

A more comprehensive coverage on other topologies as compared to Lynn, Voltage Feedback vs Current Feedback, Effect of Rise Time and Slew Rate on sonic impact, more on output stage devices like Vertical Mosfets, Discrete IGBT and the now elusive SIT.

 

[djoffe]

Is the topic of switching power amps, e.g. class D, in its various forms, kind of outside the range of what you think is appropriate for the book? I know that 5th edition had a small chapter on this, but I was curious how much expansion you were planning for this chapter.

A particularly interesting area might be a Beauty and the Beast Amplifier...a class AB amp nestled inside switching amp rails.

Akitika GT-101

 

[Bonsai]

I echo Dave Zan's requests.

I would also add

Thermal compensation - especially triples
Stability of EF3's

I have the original book (I think), so its probably time for me to get a newer edition - looks like that will be the 6th!

 

[Ian Finch]

a) Thermal compensation, sensing of quasi-complementary output stages.

b) Review of a few more novel or interesting designs with appropriate comment.

c) Lateral Mosfets - optimal drive requirements

d) Current Silicon - what is available generally for power amplifiers of all types, what may be acceptable for commercial and premium applications.

Everything else that fits in 1,000 pages

 

[mlloyd1]

Doug:

Thanks for asking. I agree with Dave Zan's comments.
I especially would like your analytical rigor applied to alternate topologies.

mlloyd1

 

[FdW]

Douglas,

After reading the 5th edition (and I liked it very much)?

1) A bit more on different topologies.
2) Selection help on power transistors.
3) Selection help on driver transistors.
4) Different compensation schemes.
5) More about CFB and comparing CFB/VFB.
6) What next? Let me rephrase, now that we have these very good tools, simulation and real, and now that we have these very good designs, how do we progress, where is the next frontier, what needs to be done. This is not about the answers, but more about the remaining questions. Like, what do I need to solve to make a real contribution Give us something to set our teeth in

Regards,
Frans.

 

[rsavas]

Hi Doug,

A pleasure reading your books, articles and your insight into this subject matter.

1) How about some Spice simulations showing the benifits of different topologies, provide models and ckts (web site) for us readers to download and run so we can all learn from.
Since LTSPICE is the only free SPICE simulator that I have heard about, then that would have to be the defacto choice for the masses.
2) Always wondered about the performance of protection circuits employing MOSFETs as the pass element. What the hit on distortion is?
3) Possibly Chip Amps, i.e. LME498xx series. That is if you see things that are missing from what is already documented in App Notes etc. I am currently designing an PA based on LME49830/Alfet AL16X16. Wondering about means of S/S protection, advantages vs costs of using a servo vs simple ecaps for input and feedback. Baker Clamps? If LME49810 is any differentt than LME49830 in this particular application
4) Power Supplies? Separate supplies for front-ends, advantages vs additional cost dis-advantages.
5) Maybe Class "D"? I have been using TPA3100D2 in a small portable stereo that I designed of late. I have an issue with AM RFI, I am using a Si4735 chip, need shielding, remote antenna mounting, etc. I am happy with its sound. It is not Class "AB performance" but for what it does, it is great device for many appluications. Some insight hear would help me out. TI has some newer devices that are being offered to address this RFI issue, I guess that I am not the only person with this issue. To be honest I do not even listen to AM radio, but for a prodcut it is probably important to resolve.
2×50-W into a 4-Ω BTL Load at 21 V (TPA3116D2)
2×30-W into a 8-Ω BTL Load at 24 V (TPA3118D2)
2×15-W into a 8-Ω BTL Load at 15 V (TPA3130D2)

Good Luck & Best Wishes
Rick Savas

 

[Kindhornman]

Mr. Self,
I parrot what others are saying here and would expand on an area of the chip amps that I do not see much in the technical literature. That would be higher power applications using chip amps. How best to implement bridge/parallel circuits using these chip amps for higher power requirements. All the information that I find, most from the former National Semi, has been discredited by most on this diy forum as being poorly implemented and problematic. Many are attempting to use these chips as can be seen by the many gainclone threads but the higher power applications are lacking.

 

[Junm]

How about designing stable solid state output buffers for hybrids with tube inputs.

 

[Bigun]

I think Class D is particularly important. I honestly believe this is the future of audio power amplifiers for the majority of applications. But it's a fast changing field and already it has plenty of people dismissing it because of the poor implementation of the past. Providing clarity on the performance of state of art Class D and how the hobbyist can access it maybe of interest.

Surface mount components are also mainstream. Some hobbyists are afraid to use this technology despite the advantages - parts don't need to be microscopic and they can be mixed with through-hole to take advantage of what both have to offer.

Digital to Analogue is perhaps the Source for most material we will feed into our amplifiers. Perhaps D to A should receive more attention.

p.s. your writings have been a very important guide for me in this hobby - thank you and keep it up !!!!

 

[maiky76]

Hi,

What about some insights regarding headphone amps that could driver equialy well 16 - 600R HP?
M

 

[Johno]

I would like to see more analysis of alternative configurations - particularly the common base with its low noise and low input impedance, eg its application to phono pre-amps and equalisation. Leach has been there I know and Phillips published some application notes in the late 1960's for their then 'state of the art' transistor offerings.

I seem to remember some really clever stuff that appears to no longer be general knowledge. Alas, I lack the wit to re-create it.

 

[Belaji]

Hello,

I was the layout guy for the silicon on the National LM6161, one of the first opamp's to use fast PNPs. I'd like to see you speak about Folded Cascodes in power amplifiers (one of my my current interests).

Thanks for all your good information. I am a big fan.

Bela

 

[DouglasSelf]

Thank you

Many thanks to you all for your replies. Sorry it has taken so long to get back to you, but work has been pressing recently.

I will respond to your suggestions shortly.

 

[DouglasSelf]

Main ones that jump to mind.

1. Improved treatment of double differential IPS. The VAS current indeterminacy is barely mentioned. Lot of stuff in DIYaudio on this

That is going to be dealt with in depth.

2. Better treatment of 2 pole. TPC and TMC. DIYaudio and also Harry Dymond's article and updates.

Same here. Err.. doesn't TPC mean 2-pole compensation?

3. Noise in current mirrors. Samuel Groner has an excellent article that covers this and several other comments on your book.

This too is already planned, with full attribution to Samuel for an article that is indeed truly excellent.

4. Improved Thermal Trak bias spreaders.

This was planned, but it is now uncertain if I will have time to dig into it very deeply.

5. Nested feedback and advanced compensation schemes.

A good deal of content on this is already planned.

I also have a few typos and errors. Do you want them here or in a PM?

PM might be best. You can get my email address from the front page of my website.

Thanks for your help.

 

[DouglasSelf]

Is the topic of switching power amps, e.g. class D, in its various forms, kind of outside the range of what you think is appropriate for the book? I know that 5th edition had a small chapter on this, but I was curious how much expansion you were planning for this chapter.
Akitika GT-101

Well yes, it is really outside. Class-D has almost nothing in common with the rest of the book, except that the final goal is to drive a loudspeaker. It really requires a separate book, but I have no plans to write it. Someone else care to have a go?

 

[DouglasSelf]

I echo Dave Zan's requests.

I would also add

Thermal compensation - especially triples
Stability of EF3's

I would like to add more on these, but time & space are a factor.

Love the avatar.

 

[DouglasSelf]

Doug:
Thanks for asking. I agree with Dave Zan's comments.
I especially would like your analytical rigor applied to alternate topologies.
mlloyd1

You will not be disappointed.

Thanks for your help.