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PostPosted: 02 Aug 2010, 12:45 
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Joined: 27 Jul 2010, 00:57
Posts: 4
Location: Europe
Congrats dgadling !!!
Very nice design and construction.

One question: how did you manage to solve the problem you described in one of you previous post: getting only mono sound and stereo just when disconnecting the ground ?
I have the same problem and now I'm tracing with the scope to see where is the difference between the two signal paths but any suggestion from your own experience solving this problem would be usefful and appreciated.

Congratulations again :)

Alex.


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PostPosted: 02 Aug 2010, 14:07 
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Joined: 20 Apr 2010, 13:29
Posts: 8
iovanalex wrote:
how did you manage to solve the problem you described in one of you previous post: getting only mono sound and stereo just when disconnecting the ground ?

I probed and proded. I used bits of wire to hook up my multi-meter to various parts.
I got really angry.
I probed more, double-checked the schematics.
Then I got angrier.
Then I tore everything off the breadboard and started over, that time it worked.

I really wish I could tell you what the issue was, but I honestly don't know :(


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PostPosted: 02 Aug 2010, 16:45 
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Joined: 14 Oct 2008, 17:35
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Location: Dartmouth, Nova Scotia
This little headphone amp really works great with the MooseFET preamp, I m nearing completion of my all out preamp, I just need to get it to run cooler! :censored:

So the actual preamp has nothing to do with this thread, but I have this headphone amp built into it and it seems to cause over load on the 24 volt power supply, I have not measured the current draw, but I have a 16 VAC winding with two 10A 1500 volt diodes in a voltage doubler arrangement to get 36VDC, then regulated to 24 volts with an LM317T & 2SB950A along side it to help cope with the higher voltage and currents...... And some how this thing gets insanely hot, yes OK the regulator and PNP transistor do, but the 10A diodes!!!! I can't touch them after 10 minutes of use! :hot:

Am I doing something wrong here? Or do I just need to sink the diodes and be done with the problem? The headphone amp sounds great, even with the IRF640, yes highs are a bit short, but it still sounds really good. I have the 50K pot set to 15K and I get about 9 volts before the output cap, isn't this supposed to be at half supply voltage?

I have different variations of the headphone amp circuit mixed together so maybe that is part of my problem, but personally I just want to solve the heat problem or know what is causing it, at the very least I can put heat sinks on the diodes.
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PostPosted: 02 Aug 2010, 18:24 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
dgadling wrote:
Well, I finally finished my build :D

Great work, can see that you added plenty of filtering. Great job!


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PostPosted: 02 Aug 2010, 18:35 
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Location: Denver, Colorado
CrazzyAbtTubes wrote:
And some how this thing gets insanely hot, yes OK the regulator and PNP transistor do, but the 10A diodes!!!! I can't touch them after 10 minutes of use! :hot:

Quick question, what is the VA rating of your power supply?


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PostPosted: 02 Aug 2010, 21:44 
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Location: Dartmouth, Nova Scotia
VA rating? do you mean the power transformer or the actual power supply? I know that the power supply should be able to put out at least a continuous 1.5 Amps at 24 volts, and the power transformer has plenty of juice. The 16 volt winding is capable of 2-3 amps, is VA rating a problem with what I have? :?

If you are wondering, there is a MoosFET preamp running off the 24 volts too, and the 30 volt supply is for the Oatley RIAA phono preamp Kit, so there is not much current really being drawn.

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PostPosted: 02 Aug 2010, 23:40 
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Crazy,

That is what I am thinking, the 16v winding is then rated at 3A or 3000mA, with maybe only 1000mA draw, the voltage may have increased making the regulators work harder? Just a speculation, maybe Gio and them will be able to shed some more light. Even though the headamp only draws about 400mA, the regulator portion must be drawing converting the remaining 2A to radiant heat.

Gonna have to check the currents to find out. You can get a rough estimate by checking voltage drop across the 3.9 ohm resistor what ever it is divided by the 3.9 will give you a current reading into the regulator and through your rectifier diodes.

Rogers


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PostPosted: 03 Aug 2010, 14:07 
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Joined: 22 Jun 2010, 13:30
Posts: 66
robot797 wrote:
i found a tube

the ecc85
but the distrorcion is very heel erg

and my second build doesnt work at all

all is checked and controlled and it does not woerk

i use a irf520



oops a little bit dutch here

the ecc83 works great at full power it distorts
i have made a mono amp
with cd player
and for the looks an em84

i am gonna build a sterio
with my second home etchet circut board

also could all this be modivied to be used as a guitar amp/sound changing box.

and when i have my tubes i will try to use the hidden pentode of a vfd tube

that would be awsome to use a vfd as a dispaly and a amp at the same time


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PostPosted: 03 Aug 2010, 17:57 
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CrazzyAbtTubes, check the current draws and the input voltage to the regulator.

Also, check that you DO NOT have continuity between ground and the metal tabs of the IRF640, LM317 voltage regulators and 2SB950A.

dgadling, fantastic amp build.

Cheers

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PostPosted: 03 Aug 2010, 19:19 
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Joined: 14 Oct 2008, 17:35
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Location: Dartmouth, Nova Scotia
The tabs of the IRF640 and LM317 measure ok and the 2SB950A has an epoxy case so it is isolated. I put a heat sink on the diodes and they are fine now, I'd say over all it is all fine now. :thumbsup:

BTW how hot do your builds get? I'm curiouse because I read some were that with the amplifier running off 12 volts you can run it without heat sinks but the tabs get hot enough to burn your finger tips? If that is the case than I can be sure heat will not be a problem with my amplifier. :hot:

And dgadling, that amplifier looks just amazing indeed, I would love to know where you got that case. :up:

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