aleph X monoblocks

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quan

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Joined 2007
#1
Hi guys , my first post on this section of diy. I have never build an amp before. I bought off a diy fellow aleph X monoblocks few years ago but got sidetrack until now . The problem i have with it is that it won't work with the pre-amps that i have at home which includes heron VTSP3 and Parasound HP850. But if i take the output from my headphone amp then it would work but the relays from protection circuit constantly kicking in. My speaker is typical bookshelf 6-8ohm load. I am not sure where to start to trouble shoot a problem. I suspect it could be impedance mismatching? . Please advise where should i start . I have been having problem with posting attachments for pictures.😕😕
Quan
 
#4
Did you measure the dc offset (absolute and relative)?
Click to expand...

That's the very first thing to check!

Different impedances at the inputs do cause dc-offset variations, but typically not something to worry about. However, if the protection kicks in, that usually means at least 1V offset.

Hannes
 
#5
aleph x monoblocks

Hi guys, i measured the monoblocks and get zero DC output at speakers terminals. I measured it by turning the amp on with no speaker load and waiting for about 10mins. The heatsink does get really hot but i gather it is class A thus putting out a lot of heat. The protection circuit from what i can see is a DC offset protection circuit board designed bu Daniel Purvis. What should i do next ?
Quan
 
#7
Hi,

normally the heatsink can´t get really hot after 10minutes unless something is wrong or it is way too small.
Zero DC output? Normally you should measure some mV of DC offset (absolute) and a lot more (relative). Are you sure the relay switched through?

William
 
#8
wuffwaff said:
Hi,

normally the heatsink can´t get really hot after 10minutes unless something is wrong or it is way too small.
Zero DC output? Normally you should measure some mV of DC offset (absolute) and a lot more (relative). Are you sure the relay switched through?

William
Click to expand...
Sorry , do i have to play some signal thru the amp before i measure the dc offset? I find before that the relays keep on kicking in when playing the music .
 
#12
some pictures
 

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#16
Hi , have checked there is no contact between the back to back transistors.
Everytime i turn the amp on the relay kicked in thus unable to measure any meaningful DC offset. Where should i start measuring the voltages to work out where the problem is ? Should i start removing the dc offset protection circuit?
Quan
 
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#17
1. X have balanced out , your protection circ is unlikely made for that

2. amp needs initial setting ,, and dc offset is certainly above trigger level of protection circ ; ignore output relays and measure ditto from amp's pcb output nodes .

3.considering that you made it with Lego approach , it's really clever to find someone locally who have enough knowledge to address both #1 and #2 , bfore you make some damage to amp
 
#18
Zen Mod said:
1. X have balanced out , your protection circ is unlikely made for that

2. amp needs initial setting ,, and dc offset is certainly above trigger level of protection circ ; ignore output relays and measure ditto from amp's pcb output nodes .

3.considering that you made it with Lego approach , it's really clever to find someone locally who have enough knowledge to address both #1 and #2 , bfore you make some damage to amp
Click to expand...
Thank you Zen Mod, i definitely would avoid messing the amp up for sure. Any Sydney diyers out there can help?
I suppose just to start from begining and measure the different voltages at different stages to work out where the problem is. There are so much info on the site and it is hard to cram the info with my basic electronics understanding but hey that's the spirit of diy.
Quan😀😀
 
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