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Chip Amps Amplifiers based on integrated circuits

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Old 21st July 2009, 02:56 PM   #821
troystg is offline troystg  United States
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Quote:
Originally posted by mhconley
OK - I have it wired correctly. Thanks Jericoh & Troy.

Should the 15 watt bulb in my dim bulb tester be glowing when only the transformers are hooked up? (Power leads are not plugged into the boards.) It is lit very dimly.

Martin

I use a variac and volt meters so I can't answer...

However I think Andrew is doing a WONDERFUL job advocating safety through the dim bulb tester. Saving more people to be able to participate in DIY.

Thank you Andrew..
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Old 21st July 2009, 06:33 PM   #822
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Quote:
Originally posted by troystg
However I think Andrew is doing a WONDERFUL job advocating safety through the dim bulb tester. Saving more people to be able to participate in DIY.

Thank you Andrew..

I agree - thanks, Andrew.

Here is a picture of the dim bulb tester I built in less than 15 minutes for just over $20:

Martin
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Old 23rd July 2009, 01:47 AM   #823
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I received the heatsinks today. Thanks, Troy!

I mounted them using the supplied shoulder bushing, insulator and some artic silver and tested each board separately.

Both boards seem to be working. The relays click and the LED lights. I measured these output voltages with the input shorted:

Board 1: 0.1 mVAC / 0.4 mVDC
Board 2: 0.1 mVAC / 0.2 mVDC

In the next couple of days I plan to mount them in the beginnings of my chassis, hook up the "DACT type" pot I picked up on eBay, fire up my trusty SCPH-1001 PS1 CD player and play them through a pair of speakers.

Martin
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Old 26th July 2009, 02:09 PM   #824
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Thumbs up Yup - They're Grrrrreat!

Hi All,

Click the image to open in full size.

I finally finised two channels of MyRefC and tested them. All seemed OK, and not misbehaving on a spare speaker, so I put them into the main system. As Uriah said to me, the Lightspeed has no trouble driving these amps. My AYA DAC sounded brilliant and the bass from the IPL S3TLM Transmission Line speakers was room-shaking on some tracks. Overall, they are a superb amp, and suit my system well. I socketed the relevant caps, but haven't rolled any yet. The heatsinks barely get warm, even after prolonged high volume playing.

I get a bit of hum, but that's not surprising given they're not cased etc. One think I did find on one amp is that the DC Offset was wandering up and down when I measured it. One of my amps has since reduced it's output and I suspect an misbehaving LM318. I'll build my other two channels and have a look at them all on the 'Scope - the op amps are socketed, so it'll be an easy swap with a new part.

Overall, I'm delighted!! Many thanks to Mauro, Peter and Uriah for all their hard work in making this great amp available to us!

Cheers

Jon
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Old 26th July 2009, 02:26 PM   #825
udailey is offline udailey  United States
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Jon,
Nice job man! Dont forget you can remove the DC blocking caps if your DC offset is low. I did some more reading on that and found that less than 100mV is fine but that above 50mV starts to effect quality of sound. How much I have no clue.
So where did you get those beautiful toroids?
Really nice toroids.
Uriah
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Old 26th July 2009, 02:43 PM   #826
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They are super, aren't they??

225VA, encapsulated and best of all, cheaper than Farnell by a long shot!!

http://uk.rs-online.com/web/search/s...uct&R=223-8831

Build quality is superb and they are very, very quiet!

I'll be getting a couple more when funds allow, so each of my 4 channels is truly monobloc!!

Cheers

Jon
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Old 26th July 2009, 04:21 PM   #827
udailey is offline udailey  United States
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Cant get the encapsulated kind in 120V Would have to get double the secondary voltage and double the amperage on primary and secondary for the encapsulated.
Uriah
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Old 26th July 2009, 08:52 PM   #828
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Folks,

What is the acceptable DC offset on these amps? What is the typical offset?
Last I checked, I was getting roughly 4mV on each channel.
How do I tweak them to reduce the offset?

TIA
Prasad
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Old 26th July 2009, 09:12 PM   #829
udailey is offline udailey  United States
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4mV is exceptional. You could only get 4mV lower.
Uriah
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Old 27th July 2009, 11:01 AM   #830
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Lightbulb DC Offset

Speaking of which, I measured my amps at the output, but with the input unshorted (or connected to source). I recall shorting input to ground being mentioned. A Google search wasn't that helpful as I found advice exactly as I did.

Clarification gratefully sought, please!!

Cheers

Jon
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