Best value T Amp in UK ?

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Puffin said:
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/i239/saxonsex/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
 
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 ?
 
audio1st said:
...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
 
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?
 
Puffin said:
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...........
 
Puffin said:
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/i239/saxonsex/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..
 
audio1st said:



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..

Well spotted Barry, I didn't realise that Puffin hadn't put new caps in there:rolleyes: Must learn NOT to speed read:clown:
Sorry Puffin, you have effectively bypassed the input caps so thats why you're getting DC offset.
 
This will give you some idea of how it should look if wired as a power amp..
 

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Audio1st. Thanks for the pic. I have done the mod and everything is fine now (no suck in on start up) however I cannot put too much signal through it without it momentarily shutting off (overloading ?)
I could not see the values of the resistors on the phono sockets and have assumed 47k. I couldn't really see from the picture how they were connected to the sockets and the leads from the board.

I attach a diagram of how I have connected them up. For binding posts , read phono sockets (it's been a long day !)

http://i73.photobucket.com/albums/i239/saxonsex/Kensington.jpg
 
At the moment I am still "testing" the amp for stability before hooking up to my main system. I do not want another heart attack like when my beloved Fostex Horns were sucked to within an inch of their life !

I am using the headphone out of and old "ghetto blaster" which I have to say does not give the cleanest of signals. In normal circs it distorts a modded S.I at what I would call "reasonably loud". Don't know if that helps ?
 
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