Sonic T-Amp Rehoused but pulsatin sound. Any advice would be much appreciated, Thanks

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Hi to everyone,
I’ve just completed the rehousing of my Sonic T-Amplifier. I followed the excellent guide at http://www.tnt-audio.com/clinica/t-amp_tweaks_e.html

I found the guide to be very informative and helpful. I’m an absolute beginner and very much learning as I go. I do have some minimal soldering experience, which I didn’t have to much difficulty with this project. I have previously only made up some interconnect leads.

I completed the new rehousing of the T-Amp and followed the instructions carefully and double-checked all of the connections prior to switching on the T-Amp. When I switched the amplifier on I heard nothing at first unfortunately.

I then listened again carefully and all I can hear is a faint pulsating noise. This is the only way I can describe it really. Its not a fast noise probably abit faster than a heart beat. I actually tried connecting the amp using the original DC input on the board and received the same identical results. This was to see if it could have been the new DC input connector I had added.

I’m unsure what could be causing this really. The only thing I did differently to the guide was to carefully desolder the original wires for the phono connectors and I replaced them with some higher quality wire.

I’m also using a fixed 12v power supply as recommended for the little amp. I’m just hoping that somebody maybe able to point in a direction as to why I’m hearing nothing but this pulsating noise. I’m hoping its not over for the amp!

I very much appreciate the time and advice of anyone that can help.


Very best wishes

Jon
 
The things to check for are good solder connections, correct polarity of power supply and polarity of any caps that you may ahve changed.

It's unfortunately very difficult to diagnose the problem without the amp in front of us. Can you take any close up pictures that may give us a clue to the problem? :att'n:
 
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Simple fix

90% of the problems people have with re-housing these amps is mastakenly tieing the negative speaker outputs to ground or each other.

Get a DVM and check for continuity from speaker outputs to chassis or ground. They should both NOT be grounded and be allowed to float.

Also check continuity on negative speaker outputs to each other. Again they should both be totally isolated from ground and each other.

That's my 2 cent guess.
 
H, and thank you for your advice it’s much appreciated. I’ve pasted below the following links to six different images I took today. I hope you can read something from them. Please let me know if you would like to see a more detailed scan or need anymore information.

The different wires are white as I used some better quality wire. I marked the red ones with a red dot (not easily seen in the photos) so I knew which wire went where.

Please copy and paste the links if they don’t show when double clicking them, thanks

http://server5.theimagehosting.com/image.php?img=t1.47.jpg

http://server5.theimagehosting.com/image.php?img=t2.37.jpg

http://server5.theimagehosting.com/image.php?img=t3.24.jpg

http://server5.theimagehosting.com/image.php?img=t4.15.jpg

http://server5.theimagehosting.com/image.php?img=t5.13.jpg


I’ve de-soldered the DC input jack not because there were any loose connections but to re-solder later on an improved joint and neater look.

Here is a scan through the link below of the input jack I purchased from Maplins.

http://server5.theimagehosting.com/image.php?img=t6.13.jpg


Thanks in advance for any help and advice.

Jon
 
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Also, another common problem is the Polarity of power connection. Try changing it around and see if you get music, if the speaker out connections don't do it..

The board is pretty robust, as I got a couple puffs of white smoke, and left it on all night "motorboating" (sound produced when outputs are shorted out to ground) before I corrected it and got it working...still works great.

Can you post a pic of the enclosure? Looks cool. Where did you buy it? Is it a Hammond project box?

Thanks
 
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john65b said:
Looks like you speaker outputs are tied together at the rear chassis panel. Slip in a plastic washer on both sides to float all outputs.

That's exactly it. The outputs should not be connected to anything! Certainly not each other. They way you have the binding posts all outputs are connected to each other! Make sure the binding posts don't make contact with the metal where they go through the chassis either. You could wrap a small strip of electrical tape around the post where it goes through the chassis for electrical insulation.
 
Hi,
I tried placing some electrical insulating tape under the rear phone connectors and unfortunately had the same result. I haven’t as yet though placed any tape or covering through the actual holes where the phono connectors run through. This is probably where the contact is still being made. I will try it later and post back.

A better description is that the noise is similar to a ticking clock. It’s not very loud and can only be heard when near to the amplifier when switched on.

Hi john65b the box is a Hammond enclosure brought from Maplins. It’s similar to the one in the link below but silver on the front and back as well and has a black band at both ends. It’s also narrower than the picture on the first link similar in shape to the picture on the second link below. It’s a perfect fit for T-amp. Its especially easy to work with as the box can be taken apart. The boxes are different sizes the one I have here is 6.7 cm wide and 12 cms in length with a 4.3 cm depth.

http://www.hammondmfg.com/1455R_B.jpg

http://www.hammondmfg.com/1455B.jpg

Thanks very much for your advice. It’s very much appreciated as I really am just learning as I go and it would be impossible without your help.

Thanks

Jon
 
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The tick tick sound is what you will hear if the outputs get shorted or tied to ground. You can hear it from the board, not just the speakers.

It is likely that the output posts are still touching the chassis. You might try some heat shrink on the posts. You may have to drill out the holes a bit.
Or find posts with better thru chassis insulation.
 
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Better yet, pull out all four output binding posts out from chassis (with wire through chassis hole) so there is absolutely no contact, and then see if you get music...then you will definitely know that the output are the cause or not...

Or else, just use a voltmeter or see if you have continuity from the binding posts to the chassis or to the other binding posts (continuity = a short) ...
 
Hi,
Well I managed to totally isolate the phono connectors using black insulation tape and rubber washers. I have no ticking sound anymore through the speakers or from the board itself. Unfortunately when I switched on I have no music either.

There was though a very slight hum through the speakers when I turned the volume control up or touched the toggle switch. I could also feel a very slight current if I left my fingers touching long enough. I didn’t have the board in its box though it was just connected to the front and rear panels. I laid the whole item on top of an anti static bag that once housed a computer part.

I’m really not sure what to do now. I defiantly checked all of the connections and had even resoldered some connections to tidy them up.

I would very much appreciate any advice, thanks.


Jon
 
Hi,
I tried connecting the power to the original input on the board and unfortunately had the same identical results. No sound. I will recheck all the connections but I fear it will be the same. It’s a shame as I followed the tutorial very carefully and checked everything as I went along. I have managed to stop the ticking noise so all of the connections are free of the chassis.

I haven’t seen any smoke or heard any pop so I’m unsure if the board and chip itself is damaged.

Thanks

Jon
 
dnsey said:


That suggests that your amp is working - the induced hum is being amplified enough to drive your speakers.
What happens if you touch the inputs with the volume on max?


Hi, thanks for your reply. I will try that tomorrow evening and post back. I very much appreciate all of the advice I've had, thank you.

This was the guide I followed below - I'm also going to double check everything again tomorrow.

http://www.tnt-audio.com/clinica/t-amp_tweaks_e.html


Thanks

Jon
 
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