Neve 1290 build completed!!
- Thread starter madriaanse
- Start date
Help Support GroupDIY Audio Forum:
hello!
i worked hard on my build, i didn't find what was going wrong i became crazy ???! then…
you know my first problem was i had more level on pin 5 on the output transformer than on pin 8… on all my preamps! (i did 4)
i tryed to change the wiring of the output transformer : i linked 6 and 8 and put the 1,5k + 0,01u between pin 7 and 5 so 7 and 5 become my output..
and now i have the same level on pin 5 and 7!!!!!!! so i think it's good!?
do you think it's possible carnhill did the same error on my 4 VT9049, do you think i could keep it like that?
i worked hard on my build, i didn't find what was going wrong i became crazy ???! then…
you know my first problem was i had more level on pin 5 on the output transformer than on pin 8… on all my preamps! (i did 4)
i tryed to change the wiring of the output transformer : i linked 6 and 8 and put the 1,5k + 0,01u between pin 7 and 5 so 7 and 5 become my output..
and now i have the same level on pin 5 and 7!!!!!!! so i think it's good!?
do you think it's possible carnhill did the same error on my 4 VT9049, do you think i could keep it like that?
Slenderchap
Well-known member
Both 5 and 7 are in phase with each other so you no longer have a balanced output.
You should wire it as normal.... the problem is probably the way you are measuring.
If pins 6 & 7 are connected together as is usually done.... pin5 is the "hot" and pin 8 is the "cold"...... little happy electrons that flow into pin 5 go through the winding and pop out at pin 8.... a "perfect" balanced output....
However, the winding has no connection to any ground so is completely floating..... if you measure the voltage at pin 5 or pin 8 with respect to ground you will get nonsense.... you can only measure the output from pin 8 to pin 5... ie across the winding....
If the transformer were centre tapped then pin 5 and pin 8 would be equal and opposite.... (eg if pin6/7 were grounded)..... but then the balance accuracy depends on winding accuracy.... so it is better left floating.
Colin
www.audiomaintenance.com
You should wire it as normal.... the problem is probably the way you are measuring.
If pins 6 & 7 are connected together as is usually done.... pin5 is the "hot" and pin 8 is the "cold"...... little happy electrons that flow into pin 5 go through the winding and pop out at pin 8.... a "perfect" balanced output....
However, the winding has no connection to any ground so is completely floating..... if you measure the voltage at pin 5 or pin 8 with respect to ground you will get nonsense.... you can only measure the output from pin 8 to pin 5... ie across the winding....
If the transformer were centre tapped then pin 5 and pin 8 would be equal and opposite.... (eg if pin6/7 were grounded)..... but then the balance accuracy depends on winding accuracy.... so it is better left floating.
Colin
www.audiomaintenance.com
madriaanse
Well-known member
adrian said:ok,
i'm so sorry about my mistake! :-X
so in fact everything goes well with my preamps!
now i will know that i can't measure everything, i must think aboud the floatting ground!
thank you !
Hi Adrian,
You should wire it exactly like my assembly guide (and not like your picture); there's a good chance it'll work the first time: http://s3.amazonaws.com/EZ1290/assembly4.pdf
M.
briomusic
Well-known member
Drille said:
the postman will love delivering your carnhill order
madriaanse
Well-known member
Drille said:
Hello, you sound like quite the ambitious builder!
When building multiple channel units I would recommend putting 4 in a 2U box. This seems to be the cleanest way to go. re: boards, email me at: martin_adriaanse (at) yahoo -dot- combest,
M.
3nity
Well-known member
why dont you soldered straight to pcb???
Its a pcb mount switch it dont have solder eyelets!
Think twice.
.02 cents
Its a pcb mount switch it dont have solder eyelets!
Think twice.
.02 cents
madriaanse
Well-known member
herrmann said:
Yes, for several reasons:
1: it will be a a pain, if you HAVE TO go this route, I'd recommend using a 3X12 with solder eyelets
2: it will be a waste of time
3: it's another set of (soldered) connections
Best,
M.
Hey there. I just built a two channel version of this, and one channel seems to be working fine. But when trying to bias the second channel, my output shows up as a fairly complex waveform rather than a sine wave. Also, changing the gain doesn't affect it's level at all. Everything appears to be wired up exactly as the other channel. I am going to go over it carefully and see if I shorted something somewhere, but does anyone have an idea of what this problem could be, so I have a starting point? Thanks! I'm really excited that at least one channel works though!
