Feeler: an "Eee-Zzz" christmas present...ez1073 and ez1073-500

U able to post pics of your iec/power trafo to the board and VRs? Pics can help a lot.

Slenderchap said:

Extremely approximately .....  The circuit takes about 120mA (at 24v).... 

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Do you have the correct slow-blow fuse?

glimmertwins said:

Hey guys - see if you can help me out with something. I got my 1u EZ1073 put together a few months ago.  Everything appears to work correctly with the exception of two things:
  - when I touch the mic gain knob, I get a sudden jump in hum.
  - The mic side has a low hum(kind of sounds like steady wind actually) that I can't seem to figure out where it's coming from.  You have to crank everything to hear it, but it's pretty noticeable with all gains stages maxed out.  The hum does not exist when I switch to Line input.

Any ideas where I can look or how I would go about troubleshooting that?  I admit to being a little green so any bit helps.  Thanks!

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Anyone got some advice to set me on my way here?  Here is what I have done so far:

for #1 - tried to reflow solder points on the mic pot.  Again tested the continuity as I did on original install of all components to make sure I didn't have a cold solder joint somewhere.  No improvement to the original problem though.
for #2 - Read as many posts as I could about sorting grounding issues.  Well the word, "the dark arts" pops up a lot in these types of conversations...  I took another pass at revisiting my grounding scheme to make sure I didn't introduce hum somewhere there (star grounding) and I think my build visually looks the same as everyone else's I have seen.  I had the XLR casings wired together and then to star ground and thought that might be an issue so I removed it with no noticeable detriment to the sound but also no improvement to my original issue.

...I'm kind of stuck here - anyone got some suggestions of how I should approach troubleshooting these two issues.  The mic pre sounds fantastic but in a quiet room you can tell there is obviously a faint hum there when the mic side is engaged and when the gain knob goes up, it gets pretty obvious and of course introducing hum by touching the gain knob is problematic with metal knobs. Thanks for your help teaching me to fish so to speak.

Slenderchap said:

Did you figure out the problem yet ?

Colin
www.audiomaintenance.com

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Have not had the time to check it and now i have to move the studio once again. But once i'm back up and running i'm gonna take a look at it with my dad and see if we can figure it out.

I have read so many great things about this pre and have seemed to miss every time the diy stuff is available ,  well the sky's parted , the angels sang , the banker grumbled , Collin opened the door , Rupert blessed it, I am just ecstatic to build a pair, hope two more follow .

getting there....

Well this is about as far as I can get this time home, I work offshore and gotta leave monday,  did not get my cases yet from collective cases, maybe next time I am home? anyway, some notes on my build.
Hits:
This has to be the most well thought out pcb, I have ever worked with, all caps,  + face the same direction, transistors...ect, even the output wiring ….very cool.
Off board wiring is next to nothing, just b+ and xlrs.
The way the gain stages and op amps are screened on the pcb,
the grayhills switches and all resistors on the pcb, that my friend was truly brilliant. 
misses:
my only  complaint is the pre formed and cut resistors, pre formed is ok, but cut? Turned something I love to do into a huge pain, some leads  were cut too short,  and none of them had enough lead to bend and hold them in place, I tried many things, but it came down to one resistor at a time and took a whole day on just the resistors, cant stress enough Collin, just send uncut leads on resistors...
Wishes:
I wish sw-1, for 600r or unterminated, had holes so one could mount a switch.
In the op amp area, c 23, 23,27 and c39,48, and 50, I wish had wider hole spacing for alliterative cap options.
????
I wonder what the unmarked holes are for around the lo-z switch and input mic transformer were for?
Flux capacitor connection? SSSNC? Super secret sonic nirvana, connector?   
HFE, it is said that the first transistor in gain stages and op amps is selected for an hfe with a gain of 600 or more, testing all the the bc550C I had a range of 450 to 550hfe, “cheep dmm test”, and a lot of 50 bc547c I had 425 to 590, with only one in 50 came in at 650.....
is this critical for low noise ? Am I being stupid ???
geoff tanner has said that the high frequency response with the eq engaged drops about -4db @ 20khz, due to roll off capacitors in the two inverting sections? Is this the op amp sections ? C 23 and c 40?
anyone try this mod, [reducing to 10 pf or removing the cap completely]  even notice it? Is this just cork smelling with an o-scope?

I have kind of copied  ruperts ideas here in  caps where I could,in the signal path  transposing from neve schematic to the ez1073  has been fun and a learning experience.

Sorry for the long rant, kinda of excited …
HYS

It is easier to fit the pre-bent components.... either use an assembly frame (cost about 150 USD).... or just put the resistors in... lay some sponge over them... lay a sheet of wood over the sponge and flip it all over (that is basically all you are doing with an assembly frame anyway).... bending the legs is not a good idea ....

Fair point about the SW1 switch.... but you could just wire your switch to the phase switch and resistor.....

The unmarked holes are vias not connection holes.

1073's are noisy and distorted anyway.... I wouldn't get too worried about HFE values.... we don't select and no-one ever has an issue with noise floor.


Colin
www.audiomaintenance.com

Cases are now available from Dan Deurloo at www.collectivecases.com ... they are not shown on the website but they are available so just email him.

Colin
www.audiomaintenance.com

Hi all,

Long time lurker, first time poster...

I know that it's already been said, but these units are stellar! Thanks Colin - my two units have added more to my studio than I could possibly have imagined...

If , like I was, you're contemplating the ez1073 as your first major build, I'd say go for it! It's a very rewarding experience, and Colin's colourbook makes building a doddle - Almost like a grown up Lego! (technics of course...)

Seriously, you won't regret it... The EQ is incredible, which took me by surprise, as I initially just fancied a couple of neveish preamps. My drum bus now pops with life and character, and acoustic guitars reach out of the speakers with incredible depth and tone; I'm a very happy man  ;D

Cheers,
Richard

there done, and just sound, uhh fatter than a redneck at a country buffet?  muhahaha
first one fired right up, and voltages were exactly where collin said they would be, brought bias up to 130ma from 82ma, plugged i into the computer and the worst noise,
I had my  rme interface  pre's running at 60db, yikes, turned that off and all is good, and didn't fry my rme pre, 
second unit, all voltages as before, bias however was at 400ma and change, it was a bad  moto 2n3055, swapped that out and it biased right up...
so 2 more ez1073's are a running in this world....
I did add the unterminated and 600 olm switch to the rear of the panel,  cases are collective, knobs by cathedral pipes....
few 312s up next

thank you collin

HYS

They should sound like the 500 series version:

http://www.youtube.com/user/Audiomaintenance

Colin
www.audiomaintenance.com

they do sound great, the line in is a ton of fun to pump tracks through .... eq is very musical...
and truly the best pcb layout I have ever seen...
just love it, thanks again collin

Finally gotten the chance to build my 1073, I just have 2 questions, does the Voltage Regulator and 2N3055 require any thermal paste or any insulation of any sort? Or is it safe to just clip it on with the clip fastener and place the 2N3055 on the board freely touching?

I used themal paste , and the clips , everything is running fine.

chipss36 said:

I used themal paste , and the clips , everything is running fine.

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on the Voltage Regulator and the 2N3055?

I did use it on both, the heatsink on my 2n3055 is on top, not the one that goes
under, I would not use paste on that type.

I also used A smaller size bolt on the 2n3055, after reading this thread a few times ,
Did not want to short that area to ground ,  no insulators were used , 

Everything works great,  left em pluged in for 3 days and no issues .

chipss36 said:

I did use it on both, the heatsink on my 2n3055 is on top, not the one that goes
under, I would not use paste on that type.

I also used A smaller size bolt on the 2n3055, after reading this thread a few times ,
Did not want to short that area to ground ,  no insulators were used , 

Everything works great,  left em pluged in for 3 days and no issues .

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Ok never mind the voltage regulator - I know that needs paste now.

the 2N3055 - did you use any thermal paste or insulator between the PCB and underneath of the component? - From what I understand you are saying that you also used thermal paste on the between the PCB and the 2N3055?

No nothing between the pcb and 2n3055 , pull up a data sheet, and its pretty clear why you would not do that. Look at the pin out. Not trying to be smart , but I would not short all pins and expect the thing to work, just work off Collins color book, it works perfact.
My heat sink sits on top, paste is between transistor and heatsink.

Thanks for your reply, I understand now. I have my case now and every thing soldered I just need to wire the unit up, do I need to use shielded cable for the Xlr to pcb connection or can I use standard hookup wire, what gauge wire, does it need to be twisted, I also see a few units linking each connection to the earth, do I need to do this too? A bit confused in this area

use shielded wire.