Pavel Dudek's (Upupa Epops) LM4780 amp

Jump to Latest
#302
I got one off, then the batteries in my camera died. I'll get some more later.
 

Attachments

  • dscn0503.jpg
    dscn0503.jpg
    96.2 KB · Views: 1,096
#304
The WAGO's are a little hard to find here and I had these handy.

I know it sounds a little nutty but I have read that it's usually better to connect the ground in between the filter caps. I'm sure it makes no difference, but this way, it's permanent and cannot touch anything it shouldn't.

And also, the speaker protection circuit works very well. I had a little heatsink grease get on a few of the chip pins and was getting 27v on one output. It shut it down right away and no harm was done. A little cleaning fixed the problem and everything works well now.



Great job Pavel.
 
#306
Yes, I did see that Pavel. With those connectors that I used, it's just a personal preference. It helps me keep things in the right place too. One amp soldered and working....One more to go!

Thanks again for you and Per-Anders efforts. I hope everyone enjoys this amp and looking forward to hear others opinions.

I like mine!
 
#312
Polypropylene do not exist at values bellow 100 pF. These types are ceramic and you can buy them in every stores... 😎 Still one notice : guys, don't be crazy - at these positions isn't mandatory to use some " exotic " types, like mica or polystyrene, with ceramic ( NPO ) ones is all OK...
 
#313
Big stores like RS Components and Conrad doe not sell the combination 68pF and 500V in Holland. So i have to shop in local stores.

By the way, Conrad has Polypropylene at values bellow 100 pF. Like stocknumber 458660 (68 pF, 630V=, 200V~.
 
#316
Paralleled output resistors

I saw earlier in the thread a mention that all the 1 ohm resistors needed to .6w.....but my BOM did not mention this. I have only .25w devices in mine. I am still building it but need to know, what power rating do all the resistors need to be?

I'd appreciate anyone who could clarify which resistor need to be something other than .25W.

Also what current rating should the mute relay need?

I'm assuming all three relays are 24V coil rated? I have found 16A devices for the outputs, but can only find 3A rated for the mute. Would this be OK?

BTW, that's Pavel and Per....your hard work is much appreciated😀
 
#317
Relay : If this relay have the same pin spacing, the same function configuration and coil voltage 24 V DC, so all will be OK. Type of resistors are recomended 0207, which are metal film resistors, but you can to use also other types. Summary dissipation at output resistors are maximally 1/40 of output power, what is approximatelly near around 2 W, so you can to use 0.25 W types, but probably reliability will be not so high. 0207 are industry standard type of resistors and they are made by most of worldwide manufacturers, so I think that will be not problem to find them...
 
#318
thanks for the quick reply

I am unfamiliar with 0207 as a resistor call out. Perhaps in the US it is differently speced. I did choose metal film 1% from KOA SPEER.

KOA SPEER MF type 1/4W

When you say that my reliability is compromised by my resistor choice, do you mean power dissipation might be a problem or simply my resistor choice is not as reliable as a 0207 mil type resistor?

As long as heat is not a problem, I don't have a problem.

Although I find the paralleled resistors a bit perplexing since having to stuff 10 resistors is work. I would just assume buy a high quality power resistor like the IRC3 or IRC5 or even a Mills 5W.

Do you like parallel resistors for sonic reasons or simply cost of parts?

One thing that might be interesting to try is to parallel bulk capacitors in a large array equaling your larger 15G types. I've heard this sounds better to use many smaller caps rather than one big one.

thx for your hard work!
Tom
 
You must log in or register to reply here.
Top Bottom