Want to build my first amp

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#161
Thanks Jens,

I've got a question about the Toroid trannie I bought. On the side of it there is a lable that says this;

I/P: 0V-------------115V-------------------230V
----BLK------------RED--------------------YEL
O/P:0V-------40V--------0V-----------------40V
----BLU-------BLU--------GRN---------------GRN
----0V--------15V--------0V-----------------15V
----WHI------WHI--------ORG---------------ORG


Does it matter which blue and which green wire I hook up to the rectifier? If not, is there a way to tell which one/s to hook up ?

Nuther question, What is the 15V output normally used for, if anything?

Thanks, Terry
 
#162
Hi Terry,

you've marked it as if the dotted line goes all the way across the label.

Please check that blue and green are not connected to each other, and that white and orange are not connected.
If they are not connected with each other in pairs, hook the two blue wires to the AC side of the first rectfier bridge, and the two green wires to the AC side of the second bridge rectifier.

If you plan to use only one rectifier, connect a blue and a green wire together as your center tab. if you're measuring around 80V AC across the "loose ends" (a blue and a green), the secondaries are in phase. If you measure a voltage close to zero, the secondaries are not in phase, and you need to switch the blue wire of the center tab with the free one. You should then have around 80V ac between the free leads. (blue-green), and 40V AC between your center and each loose wire.

The 15V is often used for accessory power, such as relay switching, pre-amp power, or similar. On many transformers, there is a current or wattage rating for each secondary. Often the low voltage secondaries (15V) is not able to deliver a lot of current, but when used for control circuits of a couple of op-amps, this is not needed.

Jennice
 
#164
Terry,

IF you're using the ESP suggested power supply with 1 bridge rectifier, ive done a drawing to show what Jennice has said for a 1 rectifier setup, showing where to measure, Also changed colors on the power transformer to match yours (yes i was rather bored at work) 😛

http://www.users.on.net/~majord/untitled-terrytran.JPG


I dont know why they dont use multiple colours on the tranny, mine are induvidual so you can tell what phase is what without measuring
 
#166
Hey, thanks guys!

That's exactly what I needed to know. I can see where the low voltage might be handy in an integrated amp to power the preamp side. Guess I'll just safety off the ends of those wires.

I should get my heatsinks this week and will begin putting things together. I'm sure I will have some more questions when I'm ready to start heating things up.

Thanks again, Terry
 
#169
Hmm... Isn't this an interesting coincidence?

Out of nowhere pops a guy with the describing handle "bvp9223", who has just registered on Dec 12th, 2004. We're having a thread on a first DIY amp, and interestingly enough this guy shows up with a link to his site, which includes a power amp.
Is it just me, or does something smell funny here????? :xeye:

Jennice
 
#170
hahaha "diyAudio.com , proudly sponsered by Delta Audio" 😉



(just kidding)





just remembered i took some pics of my 'for all intents and purposes' finished amp ,


http://www.users.on.net/~majord/amp/top-ang.jpg

http://www.users.on.net/~majord/amp/sidetop.jpg


http://www.users.on.net/~majord/amp/frontside.JPG

Terry the heatsinks so far are holding up well (0.7c/watt) , with moderate (but not full or 3/4pwer ) they only get warm to touch, ill need to hook up a dummy load of some sort to do any long term testing, 100watts is way to loud in this room/house to run for any time thru my speakers , id be killed by the family.
 
#171
mAJORD,

We certainly wouldn't want to loose a forum member due to family violence, provoked by high sound levels . :whazzat: It might be wise to find a nice dummy load.

Personally I haven't found high power dummy loads I'd wanted to invest in, so I've used a couple of wire-wound 7W resistors in parallel, which I put into a glass of water. I think I have invented the most expensive, true-sine-curve powered water boiler. :clown:
(Only problem is that the resistors start to smell funny when all the water has evaporated! 😀 )

Jennice
 
#173
I received a some of the heatsinks that I had ordered on ebay. You guys have me worried right now about having enough heatsink. The large one I ordered with the intention of cutting it in half is not going to work since two PCBs will not fit side by side on it. I also bought some that resemble the sinks that mAJORD is using.

See them here.

They are nicely made but I fear they are a little too thin to do the job. Too bad because they look very nice and will make nice sides to an amp.

I may have to go with the Conrads after all. He still hasn't contacted me though. That not a good sign in my book.

So, I guess I'm still on hold for the time being. The large sinks I bought would work I'm sure if I didn't mind the amp being 10" tall, but I do. 😀

Guess I'll try and contact Conrad again. 🙁

Blessings, Terry
 
#174
Hi Terry,

Don't worry about your heat sinks. Try to have a look at: www.conrad.com . When choosing language at the bottom, they have a map symbol between the flags, stating "international".
They have a lot of heat sinks to choose from. Their main location is in Germany, Europe, so I don't know what shipping would cot, but I suppose you could email them about it.

As for the heat sinks you already have (nice ones on the pic, by the way!), I'm sure you'll find use for them. By the time you have completed your first DIY amp project successfully, the DIY'er within you will probably think of something else to build some day. 🙂
This kind of purchases are what give DIY'ers their priceless stock of stuff, which their spouses usually shake their head at. 😀

Once again, remember the BIAS adjustment of your amp before powering it up for the first time. Otherwise you'll just let out the magic smoke that makes things work....

Jennice
 
#175
OK, I ordered two of the MF35-100 heatsinks from Conradheatsinks.com .

I can't believe how much I'm spending on this amp. Like they say though, "You have to pay to learn."

And You're right, I will make use of the extra stuff eventually. I'm already thinking about what I want to build next. 😀

Not to worry, I'm not putting juice to anything without checking with you guys again.

I want to keep all that magic smoke inside the parts where it can do some good.:angel:

Blessings, Terry
 
#176
Yesterday evening I got my first PCB set up with a couple of spare darlington transistors for test. It amplifies, allright! 😀
WAY too much, that is.. It could seem like the feedback path doesn't work correctly, but I haven't had time to go error-checking yet. Hope to do that today. Then again, the output signal does actually look very much like the input (except that it's amplified a LOT), but fortunately I have a 2channel scope around, and will use it to trace the signal backwards, from the output transistors to the long-tail-pair at the input stage. Strange thing is that signal reproduction looks all-right in shape, but the feedback resistors look like having the correct values!?

Good thing: No secret smoke, and no hot components. (Then again, it's a 500mA regulated PSU, so fatal (for the circuit) currents are not likely to happen.
Oh, well... time will tell.

Ahh.. and I got my front plates for the enclosure today, too. They'll need polishing, but the cutting/drilling is all done by a friend & colleague 😎

Jennice
 
#180
mAJORD,

:djinn: I just found out how to make the magic correction! :happy1:

*doing the happy dance for office chairs*

You were correct. It was simple... annoyingly simple. I rechecked the wires, and during my fiddeling around yesterday, I must have moved the small switch on my oscilloscope probe from x1 to x10 . Thus, the 10:1 divider on the input monitor channel was active, which explains why I thought I amplified a very small signal to a huge signal. In reality I didn't amplify a very small signal. It just LOOKED like a small signal!

Right now it's playing a test tone (sine) into a little speaker 🙂
 
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