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Old 8th July 2007, 11:00 AM   #21
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Quote:
Originally posted by Puffin
Lostcause. DC on left channel is -0.06 and Right +0.05. I attach a copy of your phot with details of where I connected to.

http://i73.photobucket.com/albums/i2...nsex/S2000.jpg
Hi Puffin, that photo is Barry's but with such small DC offset you should not be getting the 'sucking-in' on your speakers.
Is it only when you switch on, and then it settles down?
PS do the test on some old drivers.
I'll have a look at Barry's photo but he usually gets it right

EDIT: OK just had a look and those connections should be OK. Have you connected it up as a power amp or put another pot in there?
As far as the feedback resistors are concerned Barry just bypassed them to change the values/gain. I will probably replace them with 20K's and put nice 20K input resistors from the caps.
Maybe a DC null circuit as well........

Lee
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Old 8th July 2007, 01:16 PM   #22
Puffin is offline Puffin  United Kingdom
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Lostcause. The cones stay in until you power off. However the sound through them is not distorted, but clearly something is not right. There is a large thump on switch on.

I am using it as a power amp.

I attached the ground for the phono sockets to the ground underneath the jack socket. Will that be o.k ?
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Old 8th July 2007, 10:30 PM   #23
cpemma is offline cpemma  United Kingdom
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Quote:
Originally posted by audio1st
...it is not as loud because of the input and feedback resistors give it different gain... I attached 47k resistors in parallel with the 33k input resistors to give about 20k input and 20k feedback, but still not as loud.
The question here is, does it give as much low-distortion volume as the SI? I seem to remember distortion rising sharply above about 5W on the Sonic T, and my own is rarely used with the knob past noon.

Panomaniac measurements
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Old 9th July 2007, 07:53 AM   #24
Puffin is offline Puffin  United Kingdom
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Lostcause. It has occurred to me that I may have the wrong connection for the phono grounds. I attach a diagraqm of the bottom of the 3.5mm jack socket and where I connected the ground.
Attached Files
File Type: pdf jack socket_1.pdf (12.4 KB, 66 views)
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Old 9th July 2007, 10:15 AM   #25
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Puffin, I think some photos might be a good idea @ this stage, I'll open one up tonight.
Still can't understand how the cone can be moving without significant DC on it though? Maybe someone else can comment on the 'oscillation' question? Can this do the same thing without obvious distortion to the sound?

Edit: Shouldn't the feedback resistors be at least the input value and bigger for more gain? The F/B resistors on this thing are significantly smaller than the inputs...... Doesn't this lead to instability?
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Old 9th July 2007, 10:28 AM   #26
Puffin is offline Puffin  United Kingdom
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Lostcause. Presumably you connected to the 2.2uf's where I did ? and your ground was connected Where ?

I assume yours works o.k. My digital camera is with a friend on holiday until the weekend !
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Old 9th July 2007, 10:55 AM   #27
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Quote:
Originally posted by Puffin
Lostcause. Presumably you connected to the 2.2uf's where I did ? and your ground was connected Where ?

I assume yours works o.k. My digital camera is with a friend on holiday until the weekend !
I think you're getting me mixed up with Audio1st (Barry), he's the one who discovered and modded this one Puffin.
I have purchased a couple but as yet have not even opened one up.
I'm still wondering about that input circuit set-up though. I'm pretty sure that the inputs should be 20/22K and the feedbacks should be the same or greater...........
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Old 9th July 2007, 11:02 AM   #28
Puffin is offline Puffin  United Kingdom
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Lostcause. Sorry, I seem to be mixing you up.

Audio1st. Are you able to assist in this matter ?
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Old 9th July 2007, 11:04 AM   #29
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Quote:
Originally posted by Puffin
Lostcause. DC on left channel is -0.06 and Right +0.05. I attach a copy of your phot with details of where I connected to.

http://i73.photobucket.com/albums/i2...nsex/S2000.jpg

Hello Puffin, I 'm sorry that I didn't make it clear that you must remove the on-board 2.2uf caps and connect to the points you marked in the picture with your new input caps. You then connect the other end of your new caps to your new input terminals and add a 47k resistor to ground for each channel..
Hope this makes sense, Barry..
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Old 9th July 2007, 11:31 AM   #30
Puffin is offline Puffin  United Kingdom
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Audio1st. Thanks I'll give that a try.
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