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

[ding]

Are the ez1073 kits gone forever??? :'( I looked at the site and the page is gone, 404!!! I was hoping to get a kit within the next few months. Forget Christmas, I need a spring solstice present.

http://www.audiomaintenance.com/acatalog/aml-17-020_extended_info.html

 

[saxmonster]

There are no kits anymore unless you find someone selling one on here that they never built.  You best bet it to purchase one from Jeff as they are commercial products now.

http://classicapi.com/catalog/product_info.php?cPath=66_114_68&products_id=239

 

[ding]

I am not a 500 series guy. Are the 1U kits gone too?

 

[stribor1]

Seems like they are out of stock, Maybe Collin can chime in.

I just received my second kit yesterday, ordered it last week so it's something recent.

 

[Slenderchap]

We have run out of GR-03-003 switches... so a bunch of kits are affected. I believe that we should have more switches soon as they were ordered on 1st November.... then they will be available again.

Colin
www.audiomaintenance.com

 

[dribro]

Hi Colin

Me and a friend are in need of one your ez1073 kits. Can you estimate when will it be online?
regards, Adriano

 

[Slenderchap]

For the moment it is available again.

Colin
www.audiomaintenance.com

 

[haystack]

How many do you have in stock and will you stock them in 2/3 weeks time do you think?

Thanks

 

[ding]

I used polystyrene in all the gain stages and opamps... As well as tantalum capacitors.

I image you replaced all the wima caps in all 3 stages and both opamps with poly's but which caps did you replace with tantalums?

Thanks.

 

[ding]

So from what I can gather the tantalums would be...

Stage 1,2,3
------------------------
C45, C68, C54, C8, C37, C64, C42

Opamps
------------------------
C26, C18, C46, C36

The poly's I'm going to do are...

C43,C53,C49,C55,C58,C60,C10,C21,C35,C19,C29

Does that sound about right? I was also reading that to prevent a common high frequency rolloff when the EQ is engaged that C23 and C40 should be lowered to 10pF but I imagine since this was not done that this is a non-issue.

 

[ding]

After reading a bit more I think I am going to skip on the tantalums as the might make the preamp "too clean sounding" and stick some audio grade electrolytics. I'm probably going to put in the poly's in the audio path since I think that will not change the sound too drastically and it is closer to the original specs.

 

[ding]

1073's are inherrantly noisy and distorted anyway so it does not really matter what you put in there..... avoid capacitors sold as "audio" caps.... you will pay a lot of money for them because they have low distortion .... which is not what you want.

Colin
www.audiomaintenance.com

Maybe not.

 

[SKJGProject]

unfortunately my ez1073 raised it's noisefloor over night and it is not a steady noise...i recorded one
minute of it while playing with the controls...sometimes the noise goes away instantly when i switch from mic to line
for several times which you can notice at around 50 seconds.

i have no clue what could be causing this but maybe someone can help me?

https://dl.dropboxusercontent.com/u/499952/ez1073_noise.mp3

 

[deveng]

I've got 2 EZ1073's that I had completely stuffed and mounted but just not wired up in the chassis yet.  Yesterday I finally I got one of them completed for a mic comparison I was doing for a couple of friends/musicians.  I used my API's for the mic comparison since I have multiples and needed a similar mic pre so we could focus on the mic differences.  Well, the mic comparison was a success but the icing on the cake was the EZ1073!  I am impressed with the sound of this thing and all I can say is it sounds damn good.  I threw it in when recording a Tyler Telecaster-->1955 Fender Deluxe.  There were 2 inexpensive AKG mics (my friends gear) and Telefunken 251 clone at about 2' out from the Jensen speaker, all into API's.  Just because I had the 1073 done, I slapped a SM57 in a "normal" 3-4" distance just off the voice coil, into the EZ1073, 60dB of gain, the trim all the way back, no eq.    The EZ1073 sounded very, very good.  It was a bit compressed due to the high gain and trimmed output but it sounded wonderful.  Now I can't wait to get the other one wired up!  Based on what I heard in this comparison I'm really interested in a vocal with the Tele251 and the EZ1073.

As for the mic test, nothing surprising to me.  As expected they all sounded a bit different.  It was really a LDC comparison to see how cheap mics stood up to a custom 251 style mic.  In my view, the 251 sounded the best of the LDCs on both snare and guitar.  More open with no hyped frequencies.  It also was better at capturing the attack of the stick on the snare head.  Not my usual use of this style of mic though.  The SM57 through the EZ1073 was the best on the guitar amp even though it was not supposed to be in the comparison! 

Colin, great job on the EZ1073!  As I've said before I'm not a purist.  I don't have an authentic 1073 to compare to, but in my opinion this piece really does sound great.  Its another tool in the arsenal.

Btw: the cheap mics were AKG 420, AKG 120.  Not my cup of tea on either one.  Maybe I should have put them through the 1073!

Also, absolutely no problems with the EZ1073 build.  Wired up the power, adjusted the 48v supply and bias....use it!

regards,
Jeff

 

[haystack]

Finishing up the ez1073 build and awaiting case to arrive. Hopefully everything will go ok on power up.

Just 1 (probably daft) question:
Which way to solder the LED on the extreme right of the pcb (as you look from the front)?Does the longer lead go in the right or left
hole?

Thank you to anyone who can help.

Hay

 

[Slenderchap]

Looking from the front, the long lead is to the right (i.e., closest to the edge of the PCB).

Colin
www.audiomaintenance.com

 

[haystack]

Crikey that was quick! Thank you Colin.

 

[deveng]

Got both of my EZ1073's running now.  Measured both with RMA and found 60hz (and harmonics) at about -99.2dB.  Rest of noise is at -129dB.  May have to spin the toroid or move it back off the pcb and away from the board.  Anyone else see this with the transformers mounted?

Regards,
Jeff

 

[deveng]

I pulled the entire circuit board out of the chassis (to disconnect all ground connections), and removed the power transformer from the pcb.  Level of 60hz changed a bit but the rest of the harmonics were there at -99.8dB.  Disconnected the grounds from all the in/outs just leaving the balanced signal wires.  Still the same.  Disconnected the chassis ground connection on the pcb with no change.  Both units behave exactly the same.  I have a set of custom 512 style mic pre's and they run clean with the using same AC outlets.  Since the level of 60Hz is so low its difficult to debug!  They are definitely usable as is but I sure like to get it down.    Here's the actual RMA test.  60Hz and all its harmonics are visible during the noise test and are peaking at about -100dB.  The rest of the noise is down below that at about -129dB and consistent across the frequency range.  White is loop back.

Colin,  have you ever run into this?  Never mind, found Post#579 regarding 60hz.  Will try external supply.

 

[deveng]

Hi Again,

Ok I've done some measurements.  I've just realized that the RME digicheck software has a convenient noise measuring function. So not as bad as I thought.
So the figures I get are into the line in set at +4 mic level +15 (input not shorted, no mic connected) output trim on full level. When the EQ is engaged all switches are off and gains set to zero.
EQ out  =  -99.7db  (RMS +3  20hz -20khz)
EQ in  =  -92.6    (RMS +3  20hz -20khz)

so about 7.1 db more noise. It sounds like mostly hum.

cheers  Greg

Greg,
I've measured the exact same thing (although I didn't measure with EQ in).  Did you try using an external supply?  I've moved the transformer and it doesn't change anything.  This thing sounds great and I'd love to get rid of the 60Hz.  Did your results show the harmonics as well?

I'm going to experiment and try running from a bench supply.  If that works I'll just build an single external supply with enough juice for 2 units. 

regards,
Jeff