[tamu]

I was just saying thats a good place to start checking. There isnt much visible from the photos.

 

[Olli1324]

Yeah.. I dunno what you lot wanna see in the photos. So feel free to ask for a more detailed photo of something you need to see

 

[bhjazz]

Quote:

Originally Posted by Olli1324 /img/forum/go_quote.gif Yeah.. I dunno what you lot wanna see in the photos. So feel free to ask for a more detailed photo of something you need to see

Actually, just looking for suspicious joints, something that was wired in backwards...that sort of thing. I'll take a look myself tonight.

 

[Olli1324]

I just checked it and I cannot see any diodes/caps put in backwards. The only ones I don't trust are D7. I assume that the end with the solid black ring is supposed to line up with the picture on the silkscreen? Other than that... All fine.

 

[Olli1324]

I just played the sound down my mobile to my dad (lol) and he says it could just be instability.. oscillating.. other long words like that.

 

[adamus]

hmmmm. my first though was oscillation, but this is a pretty stable amp.

If it is oscillating, then it will much more likely do it when nfb is high - is that the case?

 

[Olli1324]

Yes, precisely. It seems fine when NFB is all the way one way (low), but as I increase NFB and volume increases, I reach a point where this very loud hum kicks in.

I am also noticing that music definitely sounds odd. Extremely recessed vocals, very muddled and muddied sound. I am listening to some Megadeth and I know from my speakers (DIY ProAc Response 2.5 Clones) that this album should have very strong vocals, thunderous bass and be very cleanly recorded (well, as far as heavy metal goes

) I get none of this from the Bijou, which confuses me. ANd I listened to Katie Melua's Penguins and Cats; it sounded much different from M3/K701, but there was crazy echo going on which actually made teh song sound even more beautiful

 

[Olli1324]

Double trouble

May as well use this to type something... My dad is suggesting perhaps the 250V is unstable for some reason.. I will check that with a DMM when I get one later this evening.

 

[adamus]

recessed vocals sound to me like you have some wiring wrong somewhere.

Trace all your wiring, NFB and signal and output, sound a bit like you have a singal and ground mixed somewhere which could lead to instability

 

[Olli1324]

I have just checked over all the wiring, and all seems OK.

The only thing I am not sure about is the headphone socket. I never checked whether I had it right; I just looked at the tabs and soldered on R/L/G where I though they logically should go.

In this pic (top down, headphone jack would plug into the bottom of the picture, so to speak), we can see how I have done it. Is it wrong?? I don't think so, but...

 

[Olli1324]

LOL just remembered 'red=ring=right'. There is my first mistake XD! So stupid... I sat there chanting that phrase while wiring it up too!

 

[tamu]

File:Jack plug.png - Wikipedia, the free encyclopedia

 

[adamus]

you only have the left and right wrong though... that wouldnt cause the issue.

Check your nfb pot and input pot.

labelled pics if poss

 

[mugdecoffee]

Quote:

Originally Posted by Olli1324 /img/forum/go_quote.gif Yes, precisely. It seems fine when NFB is all the way one way (low), but as I increase NFB and volume increases, I reach a point where this very loud hum kicks in. I am also noticing that music definitely sounds odd. Extremely recessed vocals, very muddled and muddied sound. I am listening to some Megadeth and I know from my speakers (DIY ProAc Response 2.5 Clones) that this album should have very strong vocals, thunderous bass and be very cleanly recorded (well, as far as heavy metal goes ) I get none of this from the Bijou, which confuses me. ANd I listened to Katie Melua's Penguins and Cats; it sounded much different from M3/K701, but there was crazy echo going on which actually made teh song sound even more beautiful

One channel of my Bijou for the longest time sounded muddier and slightly quieter than the other. Turned out that I ripped a trace when switching caps and one of the interstage coupling caps was shorted to ground. I think this meant that the output stage was pushing but not pulling (or maybe the other way around). At any rate it might be worth checking the voltages across the coupling caps against the voltage diagram on the site.

 

[Olli1324]

Ok, let's talk inputs.

I am using shielded cable; the inner core as signal and the shield as ground. Inner core is blue, the shield is obviously thus the pretty silver one.

That shows the input terminal block. Note that blue is signal, and the silver shield is what I am using for ground.