Transformer input TDA8932 mono amp

Jump to Latest
#81
Richard is the only thing precluding the use of 4ohm loads on the amp the current through U4? What would the current demands be worst case with a 4ohm speaker?
I built mine with LD1084 which is a 5A device, although I assume it will need some more heatsinking .?
 
#82
You can use a 4ohm load without any change, you'll forfeit about half the max output power. Upgrading U4 to a 5A type means the current limit stops being the regulator and becomes the TDA chip itself as that's spec'd at 4A. Theoretically 5A is the peak current for a 4ohm load. That 4A figure for the chip is the worst case so it might be able to put out more. I doubt you'll need more heatsinking unless either your input voltage is above 24V or your music is heavily compressed and you listen loud.
 
#84
To be fair X the current small heatsink barely gets warm when powering my XRK Ref monitors 🙂! So probably a switch to a lower impedance speaker shouldn't prove too much a problem heat wise. I look forgot hearing your opinions on this amp!
 
#87
Hi Abraxalito,
Is this the correct schematic that goes with the kit you sent me?
Thanks,
X
1662386692214.jpeg
 
#89
My populated boards are almost here. I just need to pay a whopping (>30%) customs duties and tax on this side first.

Just something I am wondering about - running these boards straight from a cheap smps, would there be benefits to filter the power with a CRC or CLC? What would you recommend?
 
Last edited:
#90
I haven't tried but there might be an improvement from using a CLC (or CLCLC) filter. I have a schematic for one if you like, or you could take a look at Mark Johnson's SMPSU filter which is available at the DIYA store. My design is quite a lot more bulky than Mark's but on paper the HF rejection is better. Before building a filter, have a listen to how they sound without - the signal regulator for the TDA8932 already has an LC filter built-in.
 
  • Like
Reactions: twocents
#91
I was looking for alternatives to my hot running Class A amp for daily duty. I decided to venture into cool running Class D territory. In my searching I discovered Abraxalito's TDA8932 mono kit boards and they seemed the perfect choice. The positive feedback and reviews from other members on this thread also helped. And I can confirm – this is really a great sounding amp. A keeper for me.

Got them boxed up running and I am really very impressed and satisfied with the beautiful sound. They are driving my (not so efficient) full range speakers in a 2.1 bi-amped system. Using the Pass H2 V2 as a preamp. The 9dB gain of the pre matches perfectly with the TDA8932 amps. I feed them from a 24V smps with CLC filters (because I had them). Other psu options to be tried later. The amp is as quiet as a dead church mouse – absolutely no background noise. The sound is very musical, very detailed, and without any harshness. The bass is also very very good. Soundstage is wide and open. I am amazed how well the amp sounds, even at low volume.

The two mono boards are boxed up in a simple mdf enclosure of my own design, for a modular build approach. I am trying to get everything into similar sized boxes in order to stack them on top of each other. Like a hifi tower. Not much for the eye, but very cheap and practical. Currently the H2 preamp and TDA8932 amps are in similar sized boxes. Next will be the DAC and subwoofer amp.

Thank you Richard for a stunning amp at a very low price point. And thank you for your support and helping me to get this amp running. I am a VERY satisfied customer and a believer in Class D now.
 

Attachments

  • TDA8932 mono amps.jpg
    TDA8932 mono amps.jpg
    430.6 KB · Views: 203
  • Like
Reactions: Rossautomatic, xrk971, abraxalito and 3 others
#92
abraxalito said:
You can use a 4ohm load without any change, you'll forfeit about half the max output power.
Click to expand...
I’ve been running these amp boards for a month now and can report that I am more than happy. No heat, no heavy psu, no turn on, or turn off thump, no background noise – just beautiful effortless music. They drive my 8-ohm full range speakers beautifully.

I was about to ask how the amp will perform with a 4-ohm load, then I saw this post. Thanks.
 
  • Like
Reactions: abraxalito
#98
abraxalito said:
For those as yet unfamiliar with ferrite cored magnetics, here are the component parts of the EE25 transformer. The material is 10k ferrite - a high permeability blend so as to get the highest shunt inductance. Its downside is a lower peak flux (~0.25T) compared to the more common forms of ferrite.

Turns on the primary are 1200 and 1200 using 0.07mm wire. I've laid this down in two individual windings to see if I can create selectable gain. Secondary is 144+144 (CT) with 0.19mm. There are about 4 layers of transformer tape between pri and sec.
Click to expand...
Are the primary & secondary windings interleaved (sectionalized) to reduce leakage inductance? If the xfmr is wound like a power type is (one entire coil wound over the other), then HF response may suffer.
 
#99
No, the secondary is wound underneath the primary in the production trafos. The leakage inductance does lead to some peaking which is compensated for by an RC 'zobel' network and RC low pass filtering on the secondary side. HF response looked fine when I measured it as part of the design process.
 
#100
abraxalito said:
"While we're on the subject of transformers there's another caveat - they don't like DC at all, not even a few mV. So AC coupling is a requirement to the input of this amp, I usually use an electrolytic. If you choose an overly small valued cap there's the chance of introducing some bass-boost, which may (or may not) be desirable. I will run some sims to give an indication of the values of coupling cap which might be gainfully employed."
Click to expand...

Hi Richard, just to be clear about the above statement, are you stating that if our preamp/DAC doesn't have at least a 10uF film cap DC blocker on its output that we should add one to the signal input of these amp boards or are you suggesting a higher value electrolytic cap be added before the signal input to the amp anyway?

Thanks,

Pete
 
You must log in or register to reply here.
Top Bottom