8 Channel, 3U NEVE 1073 completed

Whoops · Dec 21, 2016

Potato Cakes said:
Whoops,

Thanks for info!

I suspected they would be fine, but I'm not knowledgeable to enough with this circuit to figure out if it would.

Thanks!

Paul

In this circuit you can go up for the next capacitor value in case you don't have the exact value.

There's only some caps that you shouldn't increase the voltage too much from stock

From Geoff Tanner also:

"As for other capacitors, move to the next value up like you indicate, 20uF = 22uF, but don't be tempted to raise the voltage rating excessively... keep it reasonably close to the value of the voltages present. EG To de-couple the 24v, 35v is the most you will need... 25v would work. If you used, for instance, a 100v capacitor in a 12v environment it would not correctly bias the electrolyte and you would not gain any reliability advantages over using a 16 volt capacitor in that location."

Potato Cakes · Dec 21, 2016

Copy. I'll make sure my voltage values for these caps aren't significantly higher.

Thanks again!

Paul

XAXAU · Dec 25, 2016

Merry Christmas and sorry for the silly question here but is the Grayhill switch supposed to be the non-shorting kind? I´ve heard of 1290´s popping when switching, anyone of you have this problem?

I´ve seen that pedals use a 1M to ground to eliminate the switching pop!

Whoops · Dec 25, 2016

XAXAU said:
Merry Christmas and sorry for the silly question here but is the Grayhill switch supposed to be the non-shorting kind? I´ve heard of 1290´s popping when switching, anyone of you have this problem?

I´ve seen that pedals use a 1M to ground to eliminate the switching pop!

Hello Merry Christmas to you all.

You're a new member, and it's fine to ask questions, but please always do a search in this forum and also a general google one on the subject you're asking.

this thread answers part of your questions:

https://groupdiy.com/index.php?topic=25244.0

XAXAU · Jan 2, 2017

Whoops said:
Hello Merry Christmas to you all.

You're a new member, as it's fine to ask questions, but please always do a search in this forum and also a general google one on the subject you're asking.

this thread answers part of your questions:

https://groupdiy.com/index.php?topic=25244.0

Thanks man! I´m even more confused now though haha!

Tekay says they should be shorting but Martin suggests using a non-shorting switch. Shorting causes no clicks except where the 3rd gain stage sets in. Non-shorting causes soft clicks. Someone suggested putting 4.7M resistors between every switch step and guitar pedals usually have 1M to eliminate clicks when stomped.

Suggestions? 8)

Whoops · Jan 2, 2017

Both Martin and Tekay are right.

Tekay said that Neve 1073/1048 original modules use shorting switches, he is correct.

Martin suggested the use of non shorting in this 1290 DIY project.

Between 2nd and 3rd amp stage Neve put an OFF switch position. So you could use shorting switchs without pops/clicks

Martin's 1290 project uses a Grayhill switch , and there's no OFF position, so if you use a shorting switch I guess it would be noiseless until the 3rd stage kicks in.
If you use non-shorting you said that there's small clicks, but there's no loud click between 2nd and 3rd gain stage.

Well I used what Martin suggested in all my 1290 builds, so I guess I used Garyhill non-shorting, I don't remember ever having click noise problems, or maybe if theres clicks they are so low in level that I just don't care.
It's not that I keep changing the switch during performances.

I don't know if your clicks are louder than possibly mine. Do the soft clicks present a problem for you?

Maybe someone has had the same problem and wants to chime in and help you out

XAXAU · Jan 3, 2017

Whoops said:
Both Martin and Tekay are right.

Tekay said that Neve 1073/1048 original modules use shorting switches, he is correct.

Martin suggested the use of non shorting in this 1290 DIY project.

Between 2nd and 3rd amp stage Neve put an OFF switch position. So you could use shorting switchs without pops/clicks

Martin's 1290 project uses a Grayhill switch , and there's no OFF position, so if you use a shorting switch I guess it would be noiseless until the 3rd stage kicks in.
If you use non-shorting you said that there's small clicks, but there's no loud click between 2nd and 3rd gain stage.

Well I used what Martin suggested in all my 1290 builds, so I guess I used Garyhill non-shorting, I don't remember ever having click noise problems, or maybe if theres clicks they are so low in level that I just don't care.
It's not that I keep changing the switch during performances.

I don't know if your clicks are louder than possibly mine. Do the soft clicks present a problem for you?

Maybe someone has had the same problem and wants to chime in and help you out

Thanks Whoops! I haven´t built it yet, I´m just looking to cover every angle before I order the parts!

Whoops · Jan 3, 2017

Well don't try to solve problems you don't have.

It's time to build.
Use what Martin suggests and you're sorted.

That's what I did in all my 1290 builds and never encountered a problem.

XAXAU · Jan 5, 2017

Whoops said:
Well don't try to solve problems you don't have.

It's time to build.
Use what Martin suggests and you're sorted.

That's what I did in all my 1290 builds and never encountered a problem.

Thanks man! Will go through the BOM and my Mouser cart one more time then order!

joakimkarlthomas · Jan 18, 2017

Hi!
Might been asked for before here, but have been looking in the thread for an answer to this simple question with no luck. I'm going to test bias with an oscilloscope and it's the first time I'm going to use this kind of eqipmemt. Would like to know exactly where to connect the signal generator probes (both) and where to put the probes (both) of the oscilloscope. Thanks!

Also, I have tried to test bias with a volt meter. When I measure between 0v and casing/bolts of the 2N3055 I get 1,3vdc which is of course way wrong. When measuring +24v to 2N3055 I get 22.9. What is also strange is that when I try trimming to 5k trim pot nothing happens to the voltage reading on the volt meter.

I haven't built the jlm power supply yet. Im using a 24vdc switch psu (ungrounded). No 48v rail yet.

Whoops · Jan 18, 2017

joakimkarlthomas said:
Hi!
Might been asked for before here, but have been looking in the thread for an answer to this simple question with no luck. I'm going to test bias with an oscilloscope and it's the first time I'm going to use this kind of eqipmemt. Would like to know exactly where to connect the signal generator probes (both) and where to put the probes (both) of the oscilloscope. Thanks!

"set to 1K sine wave into the mic input until clipping is indicated on the oscilloscope. "

It's clear, signal generator connects to Mic Input
Osciloscope Probes the Output

joakimkarlthomas said:
Also, I have tried to test bias with a volt meter. When I measure between 0v and casing/bolts of the 2N3055 I get 1,3vdc which is of course way wrong. When measuring +24v to 2N3055 I get 22.9. What is also strange is that when I try trimming to 5k trim pot nothing happens to the voltage reading on the volt meter.

I haven't built the jlm power supply yet. Im using a 24vdc switch psu (ungrounded). No 48v rail yet.

Or you are not measuring it properly or your unit has build problems.
In the assembly pdf there's a voltage chart for transistors, do a voltage chart of your unit compare with the reference table.
If your voltages are off then Bias is your last concern at the moment

joakimkarlthomas · Jan 18, 2017

Whoops said:
"set to 1K sine wave into the mic input until clipping is indicated on the oscilloscope. "

Yes, I know. I will now try to formulate the kind of describtion Im looking for and maybe someone can tell me if it's right or wrong.

1. Connect the red signal gen probe to pin 2 on the mic input.
2. Connect the black signal gen probe to pin 1 of the mic input
3. Connect the red oscilloscope probe to pin 2 of the output xlr.
4. Connect the black oscilloscope probe to pin 1 of the xlr output.

Whoops · Jan 18, 2017

joakimkarlthomas said:
1. Connect the red signal gen probe to pin 2 on the mic input.
2. Connect the black signal gen probe to pin 1 of the mic input
3. Connect the red oscilloscope probe to pin 2 of the output xlr.
4. Connect the black oscilloscope probe to pin 1 of the xlr output.

yes,
just short pin3 input to Pin1 in
and pin3 output to pint1 out
you can use aligator clips for that

More important , as I told you previously if you don't have your voltages right, Bias is of no concern at this point

joakimkarlthomas · Jan 18, 2017

Whoops said:
yes,
just short pin3 input to Pin1 in
and pin3 output to pint1 out
you can use aligator clips for that

More important , as I told you previously if you don't have your voltages right, Bias is of no concern at this point

Thanks! I will start to check voltages. Need to learn how to use an oscilloscope first anyway..

joakimkarlthomas · Jan 18, 2017

Btw, as the power supply is ungrounded I get grounding noise in the sound. I tried to connect a croc clip cable between the ground pin of the ac socket and the 0v of the dc jack on the preamp. This makes the noise go away. Can I make a mod to my power supply like this: change the cable between wall ac socket to the power supply to a cable with ground connection/lead. Then connect the ground to the power supply metal enclosure. And lastly also connect the 0v in the power supply to the same enclosure. Would this be a OK?

Will build the jlm power supply when I get time, but would be nice to have this preamp working right away with the psu I already have, if I can.

joakimkarlthomas · Jan 18, 2017

Whoops said:
Or you are not measuring it properly or your unit has build problems.
In the assembly pdf there's a voltage chart for transistors, do a voltage chart of your unit compare with the reference table.
If your voltages are off then Bias is your last concern at the moment

Ok, so now I have checked voltages and on transistor 1-3 I've got problem. 4-6 is exactly the same voltages as in the guide. This is what I got;

1.
C:1.3
B:0.0
E:0.0

2.
C:1.3
B:1.3
E:0,7

3.
C:1.3
B:1.3
E:1,3

4.
C: 3,8
B: 2,4
E: 1,8

5.
C: 12,4
B: 3,8
E: 3,2

6.
C: 20,8
B: 12,4
C: 12,8

Whoops · Jan 18, 2017

joakimkarlthomas said:
Ok, so now I have checked voltages and on transistor 1-3 I've got problem. 4-6 is exactly the same voltages as in the guide. This is what I got;

Yes you have a problem on the output stage part of the amplifier.
You might have a short, a wrong resistor value, you have to troubleshoot that out.

Have you mounted the 2N3055 properly?
case of the transistor it's the collector and the screws and nuts need to actually touch the transistor case and the pcb pads underneath

joakimkarlthomas · Jan 18, 2017

Whoops said:
Yes you have a problem on the output stage part of the amplifier.
You might have a short, a wrong resistor value, you have to troubleshoot that out.

Thanks! I found that the 12ohm resistor was blown on both preamps. Replaced it and now voltages are correct and the preamp sounds great! Except for the ground issue I mentioned earlier..

Whoops · Jan 18, 2017

joakimkarlthomas said:
Btw, as the power supply is ungrounded I get grounding noise in the sound. I tried to connect a croc clip cable between the ground pin of the ac socket and the 0v of the dc jack on the preamp. This makes the noise go away. Can I make a mod to my power supply like this: change the cable between wall ac socket to the power supply to a cable with ground connection/lead. Then connect the ground to the power supply metal enclosure. And lastly also connect the 0v in the power supply to the same enclosure. Would this be a OK?

Will build the jlm power supply when I get time, but would be nice to have this preamp working right away with the psu I already have, if I can.

what power supply are you using at the moment?

take photos of your build and psu and show us, it's easier that way, you use photocuket to host the photos

I really recommend you to build the final PSU now. You don't need JLM psu at all, you can buy something from Europe.

You just need 2 rails, 24v and 48V
you can use the SSL9K psu pcb that you can find easily around this forum, a lot of them were made and sold.

in the white market you have also the APP PSU:
https://groupdiy.com/index.php?topic=33576.0

and Volker PSU's:
https://groupdiy.com/index.php?topic=39570.0

IndietownRecording · Mar 15, 2017

Are there circuit changes between v2.4 and v2.6 boards? I'm wondering if it's worth building new v2.6 channels, or if there are no circuit changes, perhaps just swapping out components?

8 Channel, 3U NEVE 1073 completed

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