*** The DIY Audio Thread ***

looks to be correct, my amp wont power up witht he bulb in series. Must be a sign of no short though im surprised as i though it was supposed to power up, i dont get a light on the bulb or power to the amp:confused:
 
I'll give it another shot in the morning, I think my multimeter's batteries have died now as well.:(

Thanks for your help.:)
 
Look for shorts were ground pads may come into contact with live pads, check the soldering very closely. ill be back tommorow after sleep and alcahol has worn off to see what i can do!
 
The bulb tester is basically a convenient combination of a safety resistor and indicator. It should light briefly on power up while the magnetic flux is established in the transformer and while the the smoothing capacitors charge. For this moment the power supply is basically a short circuit. The bulb should go out after a second or two and connected to an amp with only quiescent load (ie, not playing into a speaker, which it definately shouldn't be at this stage) the amp should continue to work normally. You can at this stage check voltages and DC offset, oscillation at output etc. Only if all of this is fine should you connect without that bulb! This may not apply for heavily biased or class-A amps but I don't think this one is.

You say you get a good 31V AC from the transformer, is that with the bulb still in circuit? If the bulb lights when you connect the transformer to the amp then it is indeed likely the rectifier has blown and you must replace it before going further. The diodes in the bridge rectifier will usually fail as short circuits btw (can check with multimeter, just need diode test and ohm test). Think I have some like the ones you show there, were 14p Non-ROHS stock from the "fast" store, 8A 400V. Might be able to mail if your in desperate need :)

Please get a bulb holder too, that wiring is scary! Those connections could come free so easily and they carry live mains!
 
gurusan said:
mike that's a beaut...what's the power output on that?
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Well 41Hz say it's good for 100W per chan with 4 ohm drivers. It's 4 channel also, which is nice.

If you look at the datasheet, it's a bit of an optimistic power rating, it's really good for 60W per chan with 0.1% thd, which is plenty for me as I'm using it to drive small satillite speakers which are crossed over at 112Hz. :) One of the main reasons I built it is because I already have a 24V SMPS which is ideal for powering this amp with.

I still havent got around to getting a heatsink on it, I've only just got home from yesterdays all day drinking session on a boat! :eek: :D
 
After looking at the rectifiers with the ohm meter I'm almost certain they're fried. I'm just about to pop out to the trade counter of Far**** who, unbelievably are actually open today. So hopefully I'll be trying the power supply test again this afternoon.:)
 
Quick update: the rectifiers have been replaced and the 5V rail is present and correct.:)

Thanks for the help Damian and Dr EM.
 
Really glad to hear this news, it has brightend my day up no end. Nothing worse than struggling with a project, after a while you wounder if youll ever get it sorted, then faster than the problem appeared its fixed and yur moving again.

Cant wait for your next update!
 
just order parts for the next project.

full valve headphone amp. valve rectified, valve input stage, valve output stage. a nice 260v B+ for me to NOT get wrong.
 
After doing some research I'm pretty set on making a Millitt hybrid MOSFET Maxed linky and pairing it up with an Alien DAC then getting a good set of headphones.

Now I've downloaded the BOM, the main components like the PCB and such can be bought from the web shop affiliated to the site in the US but do you guys buy the "off the shelf" components from the recommended places in the US or from the various component sellers in the UK?
 
I personally buy stuff from the UK - i think its just easier, although i am sure that some components are probably cheaper in the US (in fact, some stuff is cheaper with postage). The large electronic suppliers like RS and Far*** stock almost everything, although the bay and the high street electronics store are good for picking up the odd bits and pieces.
 
Ok cool, thinking about it a little more if I was still in the UK I may have done that but I just looked at a Czech component store I think it may be easier in my case to get them from the US, it's all confusing in Czech and I don't fancy risking frying something based on my dodgy translation :D
 
p4radox said:
Quick update: the rectifiers have been replaced and the 5V rail is present and correct.:)
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Glad you got your PSU part going ok. :) How are you getting on with the main circuit?
Adam W said:
just order parts for the next project.

full valve headphone amp. valve rectified, valve input stage, valve output stage. a nice 260v B+ for me to NOT get wrong.
Click to expand...
:eek: I'll be keeping an eye on this one, valves and high voltages are still too much for me right now!

I finally got my amp9b up and running, i had a small heatsink at first which got to hot.... I was giving it 25v tho, but it would burn my finger! :eek:

I managed to find a huge heatsink with holes in the right places so I bolted it up and tested it all out... Works real nice with the input voltage set to 24v, the heatsink stays nice and cool, but the heatsink is many times larger than the amp! :D

Piccy:
imgp1601pw6.jpg


Next step, get a nice enclosure with room for my SMPS also as it's too ghetto at the moment, even for me... :o :D

Sound wise, I'm really happy with it. It's like an Amp6 but it seems to have nicer bass. This is probably due to my better PSU tho, as my 12v PSU was poor (LCD monitor wall wart which had some 50Hz hum). If any of you guys like the amp6, the amp 9 basic is a great next step.
 
@col - sorry, i didnt look at your location! Certainly the descriptions can be quite confusing (even in english!), and prices are often a lot cheaper in America - i would consider it, but im not sure i could ever wait for the postage!

@Mike - i think it looks cool, but perhaps isnt best suited to the living room... :).
 
col m, I would personally wait a few weeks until the soha II is out of prototype. It offers much better features. and still shouldnt kill you (150v).
 
I get most parts from the speedy shop as i can stomach there postage and lack of high minimum order count, i do use rs a bit though there postage is a bit hard to chew on though the next day delivery is a nice plus.
Havnt used far*** yet though they are very well stocked but the fast shop seems better priced.
I do source harder parts fromt the US though as they are a arm and a tooth over hear, blackgates for instance.#


Just an update on the DAC,

Successfully done the 96khz mod yesterday and got the spdif out wired to an rca panel so i can use my coax lead and the DAC to run off my pc, im really impressed with the differance its made to the sound from my pc and this means i can get it burned in faster. purchased some nice double shielded audio cable today ready to make up all my interconnects. Ive seen these at a reasonable price and im woundering weather to pick a few up as they look pretty snazzy!
52cf_1.jpg

Its just the silver thats putting me off, either these or spend a touch more on some nice ones.
 
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Blackgates arent cheap - i worked out to replace all of the caps on the input stage with blackgates would cost more than buying OS-con caps from rs in (mandatory) multiples of 5....
 
Yeh was going to cost me £38 for two Blackgates over hear, managed to get them for £15 posted from the US, crazy aint it!
 
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