Hi zei,
LJM LM3875 chipamp kit ?
This one :
DIY Board Kit GAINCLONE 3875 LM3875 50W+50W 8ohm Amplifier Board + Speaker Protection(IC3875 Not Included) $15.36 Free Shipping @GoodLuckBuy.com
Phil.
LJM LM3875 chipamp kit ?
This one :
DIY Board Kit GAINCLONE 3875 LM3875 50W+50W 8ohm Amplifier Board + Speaker Protection(IC3875 Not Included) $15.36 Free Shipping @GoodLuckBuy.com
Phil.
I have same, works well, very smooth..
Phil.
An externally hosted image should be here but it was not working when we last tested it.
Phil.
Measured 26VAC (why extrapolate "harmonised voltage", "possible local mains variations", etc. when we have a measurement? ... unloaded to boot) will make some 36V rails, unloaded, so in practice they will be slightly lower.
And the second the amp starts pulling current, rail voltage will drop, as much as 20% at full power.
By the way, "transformer regulation" refers to VAC, resistive load; with the fast narrow capacitor charging pulses plus apparition of ripple, which can only go down,never up, the 35V suggested max. voltage barrier gets crossed downwards.
Of course, keep load at nominal 8 ohms, do not even try 6 or lower.
Problem is not chip destruction but avoiding activation of SPIKE protection, which sounds worse than horrible.
And the second the amp starts pulling current, rail voltage will drop, as much as 20% at full power.
By the way, "transformer regulation" refers to VAC, resistive load; with the fast narrow capacitor charging pulses plus apparition of ripple, which can only go down,never up, the 35V suggested max. voltage barrier gets crossed downwards.
Of course, keep load at nominal 8 ohms, do not even try 6 or lower.
Problem is not chip destruction but avoiding activation of SPIKE protection, which sounds worse than horrible.
Hi,
Yes and no, I use this kit with 4 Ohm fullrange driver in BR, and it's works well.
Impedance curve, (notch filter at 1300 hz) :
Yes and no, I use this kit with 4 Ohm fullrange driver in BR, and it's works well.
Impedance curve, (notch filter at 1300 hz) :
Attachments
Transformer regulation is the amount the output voltage rises as load current is reduced.
A 230:26Vac 100VA 7% regulation transformer will give an output of 26Vac when fed with 230Vac to the primary and a secondary current of 3.846Aac into a 6r76 dummy load.
As the dummy load resistance is increased the secondary voltage increases. Ultimately when the dummy load is infinite, the secondary output voltage is 26*1.07 = 27.82Vac.
Increase the mains voltage by 5% and the output voltage will rise by 5%.
Increase to 253Vac and the maximum output voltage will increase to 30.6Vac
The guidance given earlier still applies
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So..
I powered the amp with the 26v trafo and it worked.. and of course that is always a nice feeling, even when just soldering a "kit"..
Very silent background and smooth overall sound..
I used my iphone as source, old pioneer speakers and youtube playing some random songs..
Phil, what are you using as source with this?
Thanx
JZ
/JZ
I powered the amp with the 26v trafo and it worked.. and of course that is always a nice feeling, even when just soldering a "kit"..
Very silent background and smooth overall sound..
I used my iphone as source, old pioneer speakers and youtube playing some random songs..
Phil, what are you using as source with this?
Thanx
JZ
/JZ
ah ok.. Wonder how much the iphones headphone jack is giving.... With my "test" speakers it wont get very loud.. Proberly low sensivity on those old pioneers..
My subjective impression is that it does,nt sound any way near as good as my supersymmetric chipamp.. but for the money still good
No pictures yet.. I,ll upload some pictures when the casing is done etc
Best regards
JZ
My subjective impression is that it does,nt sound any way near as good as my supersymmetric chipamp.. but for the money still good
No pictures yet.. I,ll upload some pictures when the casing is done etc
Best regards
JZ
100VA will allow good to adequate performance from amplifiers with a total maximum power output of 50W to 100W.
i.e. two channels of 25+25W will work well and two channels of 35+35W will work well.
two channels of 50+50W will work adequately.
There is a further point worth considering.
A 100VA transformer will have a higher regulation.
You MUST check the worst case maximum voltage being fed to your smoothing capacitors and to your amplifiers.
EI generally have a higher regulation than toroids and as a result over-voltage in worst case conditions is a higher risk for EI transformers.
i.e. two channels of 25+25W will work well and two channels of 35+35W will work well.
two channels of 50+50W will work adequately.
There is a further point worth considering.
A 100VA transformer will have a higher regulation.
You MUST check the worst case maximum voltage being fed to your smoothing capacitors and to your amplifiers.
EI generally have a higher regulation than toroids and as a result over-voltage in worst case conditions is a higher risk for EI transformers.
Don't know how to do what?
I did not ask you to do anything other than sum the total maximum power !
I don't know how to do the check.
Maybe a bigger toroid is a good idea, but this one fit in my case.
You need to measure both the AC input voltage (mains voltage) and the output voltage. Then work out the worst case output voltage. I'd assume ±10 % mains variation.
Too much voltage on an electrolytic cap will cause it to explode. You really don't want that. The electrolyte is very corrosive and will wreak havoc on any circuitry nearby if not cleaned up completely. It's a filthy mess.
~Tom
Too much voltage on an electrolytic cap will cause it to explode. You really don't want that. The electrolyte is very corrosive and will wreak havoc on any circuitry nearby if not cleaned up completely. It's a filthy mess.
~Tom
How do you know what I want
It's like you don't know me at all
Also I still don't get it.
You know I'm slowly coming to the conclusion I really shouldn't be building amps.
Especially, considering people that know way way way more than me think it's too complicated for them to do.
It's a 19-0-19 volt toroidal transformer. I figured it would put out 19 VDC.
I don't know how to set it up so I can tests it's limitations
"It's a 19-0-19 volt toroidal transformer. I figured it would put out 19 VDC."
this tells me that your electronics knowledge is at a very early stage, i.e. less than a Beginner.
And confirms that you should be doing a lot of safe learning before
"You know I'm slowly coming to the conclusion I really shouldn't be building amps."
I recommend you do this learning in small and safe steps.
Be careful, it's not just the hardware that can get damaged by mistakes.
Try these two sites.
ESP
Decibell Dungeon.
http://sound.westhost.com/projects.htm
http://www.decdun.me.uk/
this tells me that your electronics knowledge is at a very early stage, i.e. less than a Beginner.
And confirms that you should be doing a lot of safe learning before
"You know I'm slowly coming to the conclusion I really shouldn't be building amps."
I recommend you do this learning in small and safe steps.
Be careful, it's not just the hardware that can get damaged by mistakes.
Try these two sites.
ESP
Decibell Dungeon.
http://sound.westhost.com/projects.htm
http://www.decdun.me.uk/
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Yes, you're right.
I need dual secondaries I think.
I was hoping that maybe this was like 1.5 secondaries or something
Maybe dual secondaries but with one ground
Okay I will find a proper transformer
I actually did build a LM3875 amp before from a Brian GT kit and it sounded very good, I thought.
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