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Old 24th July 2009, 07:27 AM   #461
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Quote:
Originally posted by Scootxyz
Hi there

(New to the forum...)

The mod that I really want is the noise suppresion one - but is this really something that a total beginner can learn to do?

If I don't do it I'm worried that my speakers are going to pop out one day when turning the thing on...


Also - I am rnning the preamp out from my NAD into the input of the lepai. Is this ok?

Thanks in advance for any advice...

Welcome aboard Scootxyz, I hope you realise which road you have just turned down...

Things seem pretty complicated at the start but you'll soon pick it up.

For starters I used Nick's NE555 circuit (about 3/4 down the page) to supress any start up pops but I was also supressing the startup sound from my modified PS1 so I liked the adjustable timing.
Alternatively you can do it this way for a manual method that cuts out the complicated bit of the one above. It's also shown in the diagram directly above the NE555, so you have two diagrams of the same simple circuit.
You could use the mute opion on the chip and use a selector switch to do pretty much the same thing... it is mentioned several times in this thread and other TA2020 amp threads so have a search.
There are even more options with DC coupling ... but I wont get into that now.
Option 2 is probably the eassiest to do and just as effective as the 1st so start with that and when you get more adventurous...... well, you'll probably start rebuilding the whole amp like everybody else does

Lee
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Old 24th July 2009, 10:57 AM   #462
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Quote:
Originally posted by Scootxyz
Hi there

(New to the forum...)



If I don't do it I'm worried that my speakers are going to pop out one day when turning the thing on...



Thanks in advance for any advice...

Please read the pages #11, when you change the input 2 pcs of input capacitor, the pop up sound is nearly disappeared. I don't know why, just do it.
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Old 24th July 2009, 02:01 PM   #463
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thanks to both for these replies. Never ceases to amaze me how many helpful people are out there on t'internet.

I quite like the look of option 2 as it looks the simplest for anyone without any soldering experience to do... I guess i just remove the wires from the old switch, replace it physically and then solder in the new one?

Is this switch & resistor (?) something that I can buy as a complete unit or do I have to buy the resistor and wire separately?

I had a quick look at the maplin website and couldn't see it there. Is there a good place to buy this sort of thing?

Sorry for all the questions

I take it that the thump that I get will damage the speaker cones if i continue to use it that way?
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Old 24th July 2009, 03:26 PM   #464
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After around 60 years of playing with valve (Iím not going to call them tubes at this stage in my life) circuits I was rather intrigued by the current crop of class D designs.
Started with a Sure TA2024 4 channel board and was not overly impressed. Too much background noise and hiss definitely not Hi-Fi.
Then decided to try the Lepai 2020 and the first thing I did after switch on was to measure the dc offset.
On my version the readings were 10mv on one channel and 120mv on the other
Being used to valve circuitry to me this was quite unacceptable.
I know the specs state that offset could be up to 150mv but to me having a dc voltage of over 100mv across the speaker terminals displacing the voice coil away from its linear operating position is definitely not a good idea.
On a stereo amp having this level of dc on one channel and around 10 times less on the other must have an effect on performance.
In view of this I decided to try the HLLY TA2020 board. This has multi turn pots to null out dc offset
On switch on with this amp I measured less than 1mv per channel and was able to tune this down to zero. Iíve run this for over a month and have just measured .2mv on one channel and zero on the other.
Nice little amp and absolutely no switch on thump.
I did most of the mods to the Lepai promoted on this thread ,op amp change, tone control bi-pass,
Cap changes etc but I would still like to address the dc offset situation.
Surely correcting this on the Lepai would help the switch on thump situation.
From what I can find it seems that 1 50k multi turn pot 1 resistor and a cap on each channel is all that would be needed.
Has any one tried this.
Being unused to SS circuitry I need some guidance on how to implement this type of mod
Stu
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Old 26th July 2009, 01:47 PM   #465
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Hi Stuart, here's the DC trim circuit shown on one channel.
Very simple and easy to impliment 'in the air'
Hope it helps
Attached Images
File Type: gif tripath dc offset circuit.gif (18.6 KB, 1495 views)
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Old 26th July 2009, 02:04 PM   #466
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Many thanks for that.
I'll give it a go as soon as I can.
Stu
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Old 27th July 2009, 09:20 PM   #467
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Default 10uH 3A torodial inductor on Ebay

An easy solution for those wanting to change their inductors:

http://cgi.ebay.com/Choke-coil-for-c...4.c0.m14.l1262

col.
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Old 2nd August 2009, 10:19 AM   #468
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Default djnemesi pop suppressor

Dear djnemesi,

i had make your scheme of pop suppressor, but it doesn't works, i think that i have make a mistake.
The ampli sleep for two-tree second, and after this time the lepai start but with the pop on the speaker.
What do you think that i can try to do?
Thanks
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Old 2nd August 2009, 03:11 PM   #469
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Default Re: djnemesi pop suppressor

Hi to all! I'm a little bit out of work because my ta2020 replacement isn't yet arrived... however

Quote:
Originally posted by totoelettro
Dear djnemesi,

i had make your scheme of pop suppressor, but it doesn't works, i think that i have make a mistake.
The ampli sleep for two-tree second, and after this time the lepai start but with the pop on the speaker.
What do you think that i can try to do?
Thanks
It seems strange, if the ta2020 is correctly powered and the signal on mute pin is correct it should work (have you checked it with a voltmeter?). A thing to check is where the power switch is connected. On some lepay I've seen that it's connected on the mute signal and the pop suppressor can't work; the power switch have to be interrupt the main power.

Anyway a little pop sound is still audible with the pop suppressor but is 1/10 of the original one.

Ciao, Simone!
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Old 3rd August 2009, 03:11 PM   #470
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Default Re: Re: djnemesi pop suppressor

Quote:
Originally posted by djnemesi
It seems strange, if the ta2020 is correctly powered and the signal on mute pin is correct [/B]
I've made a mistake...the the pop suppressor is connected to the SLEEP pin...
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