Transformers for Car Audio Amplifiers - Page 1
Forum section: electronics / beginners

author: magicmastja
author_rank: Contributor
timestamp: March 28, 2023, 12:00:08 am
content: Hello, so im a good 6 months into my EE self-teaching journey, and I'm really struggling to find good learning resources for the latest and greatest tech in transformer design in general, let alone automotive amplifier applications. I have a few questions that may or may not be obvious answers to the experienced folk in industry.Firstly, why does it seem, at least from the teardowns I've seen, do most car amps use what appear to be just a bare ferrite toroidal transformer cores with an insane number of windings vs one of those cleaner-looking tape wrapped solutions from the likes of TDK, Wurth, etc?Secondly, are there any viable high-frequency high power core implementations (with the use of a custom design)? I know the skin-effect is a big deterrent for high freq, but ive seen spec sheets suggest planar would be able to manage 12V 80A+ inputs at 2mhz in a push-pull or forward converter config? Is it just one of those too-expensive and not-worth engineering headaches of planar being so awkward to deal with just to shrink the solution size by a few centimeters?Its just a neat challenge I want to try to tackle as ive looked over a lot of amplifier guts photos and repair vids I regularly see very copy-pasted designs with older boost controller ICs mixed with older amp chips and it just seems surprising how little effort there appears to be in shrinking the solution size or modernizing the design for noise reduction/efficiency

author: jonpaul
author_rank: Super Contributor
timestamp: March 28, 2023, 03:49:36 am
content: See Class D amplifier design and high frequency magnetics références.Jon

author: coromonadalix
author_rank: Super Contributor
timestamp: March 28, 2023, 01:14:08 pm
content: yep they run at 200khz and more, the standard seems around 250Khz ....I have an sony tv 2x20W amplifier i took off from a dumpster, pretty darn small and works well at 12vdc ....what i have heard so far, you do sometimes have remnants of the switching frequencies in the audio signal ...EDITYou had H class amplifiers too, but better at high power than D class ...

author: magicmastja
author_rank: Contributor
timestamp: March 28, 2023, 11:23:43 pm
content: Thanks, I managed to stumble my way into high freq core materials like PC200 and plan to get a list of all of comparable options and go from there. It just seems like with GaN fets, class D amps, and all of the cool stuff that's been coming out over the last 5-7 years for power management stuff we should be able to pull off some pretty compact high power designs these days. Obviously I know the audiophile crowd is still sometimes not entirely sold on class D over AB but with chips like the TPA3255 idk man its gotten pretty good to my ears.

author: cantata.tech
author_rank: Regular Contributor
timestamp: March 28, 2023, 11:37:27 pm
content: Inevitably, if you want to push the speaker cones harder then you need more voltage.I'm not sure those coils are really working as 'Transformers' per say, they're just increasing the voltage in store as DC in capacitors for the Amplifier stage.The Audio signal itself is a type of AC, but that's the final output.Amplifier efficiency has gone through the roof with Class-D.Other things have also occurred such as DSP and much has changed in speaker design especially related to breathing ports which lower the power needed to produce sound. Old speaker designs often had wave cancelling characteristics which meant they needed a lot more power to drive.You can research the topic more.

author: magicmastja
author_rank: Contributor
timestamp: March 29, 2023, 12:04:53 am
content: Ah thanks for the insight on speakers as well, I hadn't actually factored in the advancements on that side of the equation. Ive spent some time looking over the audio DSP ecosystem and it seems like Analog Devices is the king at the moment with their SHARC+ offerings, I've always enjoyed dialing in the perfect EQ settings so id love the chance to get to see what that's like at the programming level. Granted what little info I've seen about audio programming is that it's extremely challenging but id still like a go at it, will give me more motivation to learn C programming anyway haha.

author: MrAl
author_rank: Super Contributor
timestamp: March 29, 2023, 04:49:00 am
content: Hi,Audio amplifiers and power supplies have a lot in common, especially the synthesized sine converters.Power supplies that output a clean sine wave have to output a switching wave that can be moderately filtered to produce That clean sine wave.Power supplies that put out DC will sometimes have a switcher front end and linear back end, so the switcher can provide higher efficiency while the linear can put out a cleaner DC voltage.If you want to avoid an output transformer you would have to boost the input voltage. That would mean a DC to DC converter front end followed by a switcher back end to generate the AC. That should be able to get up to pretty high power. With this configuration i dont think class H would be of any use because you already have a way to get the efficiency up there with decent output distortion levels. If you still want to go linear back end then you could modulate the DC to DC converter.There have been lots of changes since MOSFET's came into being. Their faster switching times work in a lot of designs.