8 Channel, 3U NEVE 1073 completed

[useme2305]

so, what are the (dis)advantages of biasing too hot or hotter than necessary?

 

[MRecords]

I just set it to what madriaanse recomended when you don´t have a scope. Sounds good t me Haven´t tried any other setting.

Any news for the new cases?

atticmike: my starground is on the 5pin XLR where i connect m power supply. thanks

 

[useme2305]

the thing about setting it to the voltages according to madriaanse's voltage chart is that it seems to be way off from what i get with biasing it with a scope.
when biasing it with a scope to just get a symmetrically clipping waveform i get 16V at the collector of the 2N3055 (TR3 on the chart) as opposed to 22.6V while some if the other transistor's voltages not even 0.5V off from the voltages in the chart.

here's m. adriaanse's voltage table again:
ez1290 transistor voltages

EDIT:

about the cases. i'm still waiting for the funds to buy some proper cases from modushop for the pres. i can't wait.
until then i'm stuck with this.

some ideas for front panels:

 

[MRecords]

Now that´s a nice one useme.

Haven´t noticed that there´s such a difference in biasing. I´m not a specialist when it comes to electronic but wondering what´s the difference soundwise. Is it just like more third harmonics when it comes to clipping becuse it´s asymmetrical? Maybe a little bit more headroom?

And one real noob question . Is my star ground on my 5 pin XLR? The only ground connections are the two 0V on the pcb and the LED one..

 

[atticmike]

Now that´s a nice one useme.

Haven´t noticed that there´s such a difference in biasing. I´m not a specialist when it comes to electronic but wondering what´s the difference soundwise. Is it just like more third harmonics when it comes to clipping becuse it´s asymmetrical? Maybe a little bit more headroom?

And one real noob question . Is my star ground on my 5 pin XLR? The only ground connections are the two 0V on the pcb and the LED one..

your star ground is a dedicated point in your chassis where you gather all the grounding to one point separately at best. 

 

[Le Roux]

I have original output transformers I'm going to use.

Any benefit to using the original cap and resisitor? Or will this just cause noise?

Thanks
Neil

 

[Mr.GrinchSD]

AHHH I am having serious problems with my ez1290. Signal is passing through but Barely I have to turn the output knob just a little over half way to hear anything and if I turn it up to much is sounds like one of the transformers is whistling. NOT GOOD lats night It smelled like something was burning!!!!!! I turned it off right away. Also I noticed a couple of the resistor measure different they they should. Could this be because they are mounted to the board and things around them are affecting them or is something wrong. (HELP IS MUCH APPRICATED)

Also if using an external power supply should I just run a ground to somewhere on the power supply or ground the power supply and run the signal up to the case and ground the case to???


HERE IS A PIC the Vintage 1272 is working fine just not the ez1290.

 

[useme2305]

first of all, don't bother trying to measure resistor values in a built circuit. are you building one channel or do you have two channels with the problem happening in both channels?

 

[Mr.GrinchSD]

2 one a vintage 1272 and the other a EZ1290 the 1272 sounds fine just not the ez1290 I poasted a pic. Also if I touch the case like the front panel some of the noise stops.

 

[useme2305]

the first thing you should do is remove the trimmer pot and don't forget to place the resistor replacing it on the board.

also, try moving the input and output transformers of the 1290 apart...maybe begin with turning them 180 degrees in all possible configurations using the already drilled holes before you drill new holes.

make sure that audio grounding goes to chassis grounding at only one terminal...make that terminal a 10R resistor.

 

[Mr.GrinchSD]

ok so dont ground the power supply just run the ground up from the JLM AC/DC to the actual preamp case and ground that

 

[desol]

For my unit which has an external power supply....i ran the ground from the power supply case(from wall ground) to the preamp case like normal. A 10ohm resistor is built into the ACDC. Simply don't connect your Ov @ the preamps to ground. So, when you measure from your preamp 0v to case ground, you should get 10 ohms.

 

[Mr.GrinchSD]

ok so I did what you guys told me and now for 0v to case I get a 10 ohm resistor reading. !!!!!!but now no audio is passing at all the second I plug anything in to that channel Just a REALLY BAD LOUD NOISE COMES THROUGH What is my next step???

 

[desol]

Double, triple check your wiring....input, output, audio ground(0v), case ground, etc. Sounds like you were having some strange issues before. I'm assuming just the ez1290 is making this noise. Go through and check the various voltages at components using Madriansse's voltage reference chart....you may have burnt something by accident from the sound of your previous post. Check voltages in/around the output section. Be sure to double, triple check things and blow off the pcb before any power up(small pieces of wire/metal). You should also have a fuse connected at the power supply just in case there's any mistaken shorts.

 

[Mr.GrinchSD]

ok ya I think Im grounding it right now. I appreciate the response Is there any way for me to check if the transformers are still working. I know something burned cause for about 15 seconds or so it smelt like something burning. Also I have since removed the output knob and the transformer not longer makes a funny sound. But now no signal is passing. AHAHAHA Just a really loud noise comes out. I will check the transistors when I get home today.

 

[useme2305]

when you removed the trimmer knob you didn't foget to place the 10k resistor and the jumper on the board right?

 

[Mr.GrinchSD]

Hey thanks fo the reply. No I made sure that I put those in place. Man it can be frustruating right. This has put my studio on hold. I cant wait till it works. TRIAL AND ERROR TRIAL AND ERROR!!! HAHA


ALSO I JUST noticed I for got to connect 2 points on the output transformer 6 to 7 I completely missed it!!!!!!

 

[Mr.GrinchSD]

AHHH been working on it for about 3 hours no luck at all the second I plug in the out put xlr the signal starts peaking even if its not turned on

 

[Mr.GrinchSD]

ok  I got signal to pass but there is a horrible horrible HUM

 

[Mr.GrinchSD]

HAHAHAHAH ;D ITS WORKING!!!!!