8 Channel, 3U NEVE 1073 completed

[Dazazone]

ok it seems one of my 3055 legs was touching the heatsink! The heatsink measured 23.5V, nasty.  Fixed and now the 50Hz hum is gone! woo!  :-*

 

[deuc224]

I wanna know about the EA-1166 trannys in the 1290 also.

 

[desol]

It's probably fine...the Carnhill is fine too.

 

[Dazazone]

J0e M@lone was telling me that the original 1166 is different in the way it is wound which affects the capacitance, and that is where the Carnhills fall short.  I cant remember exactly but one of the windings requires flipping the transformer and winding the opposite direction.  Tom M won't let this design happen anymore apparently.  Hey Tom I did yr coarse 10 years ago and it sucked!  :-X

 

[desol]

Well, there's been alot of talk concerning this subject. It's been going on forever.
As far as i know, no one has succeeded in cloning the original.
CJ would know a hell of alot more on this subject than I. I speculate when I disuss this matter...
as there's always someone out there that knows more, or has seen something else.
I'm assuming Carnhill has a transformer that does match the Neve spec. Whether it's the
same transformer people buy or not, i do not know. Nor do i care really..

I don't know very much about Ed's transformer...or Telefunken's attempt.

 

[Dazazone]

Yo Ed, are you gettin about? 

 

[Jazzboms]

Hi

Just put together 2 ez1290, and I got the same problem on both.

With both transformers connected I get nothing. Removing input transformer, and put signal right into the pcb, sound flowing through the preamp, but checking the signal with my probe at pin 5 on output transformer, the sound is not nice. Checking the sound at pin 1, the sound is good.  So with transformers = no sound. Only output = bad sound. No transformers = sound ok.
Edit: After some more checking i found it kind of passes signal with transformers, only it is very distorted and low. More like sound variations in the noise(Ground issues???)

Im hoping to also use the transformers in the amp

My transistor measurings are:
TR.1: C 3.66 / B 0.91 / E 0.34
TR.2: C 22.4 / B 3.65 / E 3.09
TR.3: c 22.4 / B 3.1 / E 2.5
TR.4: C 3.76 / B 2.37 / E 1.81
TR.5: C 12.23 / B 3.76 / E 3.14
TR.6: C 20.4 / B 12.24/ E 11.61
Seems to be inside.

Also measured the transformers
Output
Pin 1: 22.4
Pin 2/3: 22.8
Pin 4: 23.1
Rest 0

Input:
all 0V

Double checked resistor value, and caps direction.

Im using a SSL9K psu, with 23,9V measuring. Transformer is a toroidal 25V/60VA.

Hope that anybody can direct me towards ending this beautiful preamps.

Thanks for reading and helping.

Best

 

[Jazzboms]

Hi again

Done some more checks, and now the output transformer is ok when bypassing the input transformer. It is actually very nice without input trans.
But I really dont know what is wrong with the input. I have tried with some of the other input trannies i ordered(4 of them), with the same result.
Shouldnt it be signal on pin 7 on the input transformer?

Thanks

LAST UPDATE: Finally got it working right. Puh. I rewired the input tranny, and it worked. So now Im putting together 2 more, and make a 4 unit box!
Thanks for making this great project.

 

[desol]

Everything is listed on Martin's assembly guide.

 

[Slenderchap]

This is what your problem sounds like to me....

In this application the transformer output is fully floating and has no groung reference..... so if you try to probe the output (pin 5) you will get nothing (or something poor) unless the ground of the probe is attached to the other side of the transformer winding (pin 8)....

.... in other words you must "listen" across the transformer winding..... probing either pin 5 or pin 8 will yield no signal because the other end of the winding will just "flap about in the wind"...

Alternatively just attach the transformer output to the input of a piece of balanced gear (pin 5 to hot, pin 8 to cold.... no ground required) and see what you get.

Colin
www.audiomaintenance.com

 

[scottlangendyk]

Awesome project, are PCB's still available?

EDIT: E-Mailed Martin and was informed that they are available 

Had a few questions though for fellow builders.

With regards to the power supply, is there any reason to use the transformer listed in the BOM, or will any transformer work as long as it's outputting 24 volts? I'm not quite sure how the 0 volts would be wired up that way though. I read somewhere that toroidal transformers  are better for line noise in audio applications, but does it really make a difference especially when the power supply is in a separate enclosure all together? Also Any particular reason why 4 pin XLR was chosen for connecting the power supply?

How specific are the capacitor selections in the BOM? I noticed that some of them are axial mounted as opposed to radial mounted, and I'm wondering if that was a design thing specific to the PCB, or just a random selection at the time?

Thanks guys.

Scott

 

[scottlangendyk]

Bump

 

[desol]

Awesome project, are PCB's still available?

EDIT: E-Mailed Martin and was informed that they are available  

Had a few questions though for fellow builders.

With regards to the power supply, is there any reason to use the transformer listed in the BOM, or will any transformer work as long as it's outputting 24 volts?

It depends on how many channels you are building...how many amps you need. Two channels can use a smaller transformer than 8 channels. It also depends on which power supply your using. If your using the JLM stuff, you'll need 24vac.

 

[scottlangendyk]

It depends on how many channels you are building...how many amps you need. Two channels can use a smaller transformer than 8 channels. It also depends on which power supply your using. If your using the JLM stuff, you'll need 24vac.

Only looking at building 2 channels at the moment, depending how that goes might look at building two more in the future, but would want to run those off the same PSU.

I'm looking in to using the JLM stuff, as it's well praised around here (unless I can find a 24 and 48 volt power supplies). However assuming I go the JLM route, the power transformer is where I'm a little stumped. I have a 24V 12VA transformer from somewhere (same as http://www.plccenter.com/buy/ATC-FROST/CA1225), for which I'm wondering if I can just use this over spending 60 bucks on a toroidal transformer. I'm concerned the 12VA may not be enough, as I was reading somewhere that each channel can use upwards of 500mA, but I've also got two 24 V wall transformers rated for 20VA and 40VA respectively.

Thanks again.

 

[desol]

Well, you can only fit 2 channels in a 1u rack, so unless your planning to put them vertically into a 3u, you may as well just focus on doing a two channel. If your planning on doing 2-1u racks...2 channels each...you would want to pre-plan your powersupply(amperage/wiring) for 2-1u racks.

For a single 1u rack with two channels, i'd probably go with Y236102 from Avel Lindberg transformers(30VA/24v)...and the JLM acdc. For the 4 channel powersupply, i'd step up to the 50VA toroid with the acdc. Either way, the acdc needs to be assembled to provide full rectification to just the + rail. Simple mod..

Welcome to the forum BTW.

 

[scottlangendyk]

Most likely the second pair would be in a separate enclosure all together, so don't even worry about that, I just want to plan ahead as best as I can. For now I'm just focusing on the two channels in a single 1U or 2U case. I'm still in the stage of doing as much research as I can before I actually set my foot down and start purchasing all the parts.

That avel transformer is dual 12vac, and the amveco from the BOM is dual 22vac. The diagram in the assembly shows the dual 22vac being wired up in series, which from my understanding would double the output to 44 vac? Which one should I be looking for?

 

[desol]

I don't know why Martin spec'd the 44vac transformer. If your using the ACDC, it runs off of 24vac input.

 

[statzern]

No, desol - the one you want is a 22-0-22 transformer.

If you get the 24 VAC one, you will not be able to get your +48 up to 48. And probably will have issues with your +24 too. I had this issue, and I am 100% sure that you NEED to have more than 24 vac.

 

[mitsos]

JLM specifically states that their PSUs will generate 3-5 rails (depending on model) off of one or two 24-30 VAC windings. So you could get one 24VAC or 24-0-24 or 24-0,24-0, and each can be made to work. You generally don't want to use a lower AC voltage winding than the DC you need in your circuit, although in many cases it will work just fine.

 

[desol]

No, desol - the one you want is a 22-0-22 transformer.

If you get the 24 VAC one, you will not be able to get your +48 up to 48. And probably will have issues with your +24 too. I had this issue, and I am 100% sure that you NEED to have more than 24 vac.

Have a look at JLM's site. All you need is one 24vac winding ( 12+12 in series)...
You don't need a larger transformer than the 30VA 12+12...for two channels.
Plus, your only using the + rail, so the powersupply needs to be modded for full rectification
using both windings on the the transformer (12+12 series) at 1.25 amps single rail only(negative rail disabled; parts left off). Then the pump charge is set to tripler to get the 48v rail. Your not using the negative rail...so, no sense in powering it with half of a larger transformer. Consult Joe at JLM. Have a look at my post on page 30 here...

I wish someone would make a definitive post about this at JLM's forum. It confused me too for a while until Joe helped me with the basic idea. It began when i realized i didn't want to use a larger transformer than necessary and/or the neg rail.