SB4000 Support Thread

[walkz187]

HI All

I'm looking to take on this project, curious about the quad VCA upgrade before i place my order. i cannot find much chatter on the Quad VCAs, well atleast in the first 31 pages i have read. from what i read on serphant.com is the normal PCB/build has a noise floor of 90db. am i right in assuming this is already low? is there much benefit in the upgrade?

this is my second DIY project and didnt want to complicate things too much if can be avoided.

Thanks,

 

[Quantum J Audio]

this is my second DIY project and didn't want to complicate things too much if can be avoided.

Thanks,

It shouldn't add more complication to the actual build.  From memory the board is quite clear on what you stuff for each configuration.  There is also the BOM for the 202 build, which should make things clear.  Setting the THD doesn't look very complicated, but will add more time to the build. 

The hardest thing is sourcing the 202's at a reasonable price.  You can get them on ebay, but when importing to the UK the cost is a lot and I was not convinced there would be a discernible difference. 

I have 2 of the SB4000 with the THAT VCA, I also have a GSSL.  I've never had a problem with the noise floor, I normally slam one pretty hard on the drum buss and put another over the mix buss.

 

[EmptyMusicBox1]

hello
I have a question about the 0db THRESHOLD

When i use a 1Khz 0db signal on the input of the SB4000 the GR meter and audio out work at -4db  it's Normal ?

 

[daveg62]

Does anyone know if Serpent Audio is still selling the boards and faceplates? I'd like to be sure before I start ordering components for a build. I emailed them a few days ago and didn't get a reply yet.

 

[gabygab]

Yes! I bought a pcb, faceplate, and component kit from him a little over a month ago. Great service!

 

[gabygab]

Hello,

First of all thanks to everyone who has contributed to this project and this thread!

So I'm still populating the board.  The bridge rectifier I received from the kit is a W08G. The BOM and board both say it requires a W04G. Can I still use the W08G without everything blowing up in my face?

Thanks!

Regards,

Gab

 

[Harpo]

The bridge rectifier I received from the kit is a W08G. The BOM and board both say it requires a W04G. Can I still use the W08G without everything blowing up in my face?

Yepp. Have a look at the parts datasheet to confirm the not needed, but even more increased parts voltage rating. (a W01G would have done as well. At these quantities parts cost are probably the same).

 

[gabygab]

Great! I figured as much, I just wanted to make sure. Thank you very much Harpo!

 

[Harpo]

welcome, only bored answering the same question over and over again.
Stereo. In short, left and right side audio signal gets filtered/shaped and rectified. The higher of both sides (not the sum of L+R, that would be Aarhus/GSSL mode) get timed and controlls both L and R audio-VCAs (this is a stereo compressor) for the listenable response.

 

[robertoray]

I'm trying to understand what i need the send channel.
For ext. sidechain i use only the return channel, or not?

 

[Harpo]

Welcome,
send and return is most often used for inserting a maybe parametric EQ for different/individual shaping of control signal.
Inserting another compresser for smoother responses might be worth a try.
Inserting a delay for always too late compressing is probably not that useful, but might allow for rythmic patterns when playing with the delays feedback, ...

 

[mrkrawn]

Hi
i want to wire correctly the sb 4000 sidechain
i read in the post it's an unbalanced sidechain, i also look the shematic  so i draw a pic if someone can tell me if i'm correct for the return thanks

 

[sullivan]

Hi,

I look the schematic SB4000 Rev 4 and I don't see value for C12, C14,C15,C16 ... and R16,R17,R18,R19,R20 ...

What's TBD value (To be determinate right now?) ?

why these components haven't value?

For the phase inversion , where I can change that ? in an another place that input de-balancing ?

Cheers!

 

[robertoray]

Welcome,
send and return is most often used for inserting a maybe parametric EQ for different/individual shaping of control signal.
Inserting another compresser for smoother responses might be worth a try.
Inserting a delay for always too late compressing is probably not that useful, but might allow for rythmic patterns when playing with the delays feedback, ...

Thank you, Harpo
now it's clear

 

[Barton]

I am in the process of getting everything together to start my SB4000 build and have a quick question.  I noticed that on the BOM, the transformer is listed as the VPT36-1390 with the specs, 25VA, 36V CT @ .69A, [email protected] Parellel.  However, when I looked up the specs on the VPT36-1390, they are listed as:

Electrical Specifications (@25C)
1. Maximum Power: 50VA
2. Input Voltage: Parallel: 115VAC, 50/60Hz 3.
    Output Voltage: Series: 36VAC CT @ 1.39A Parallel: 18.0VAC @ 2.78A

Is the transformer listed on the BOM incorrect, or are the specs listed on the BOM incorrect?  I did note that the specs for the VPT36-690 match the specs on the BOM.

 

[walkz187]

Photos would be very useful however ;-)

Here are some photos of my transformer + mounting kit - I think it's pretty standard.

As I said, my main concern is whether it will be a problem if the top of the mounting washer touches the top of the chassis.

A Nylon bolt was mentioned which seems sensible - do you think this will be strong enough to hold the transformer in place?

Many thanks for your help!

mine is definitely hitting the top of par metal chassis. I am about to start wiring. I'll let you know if the bolt hitting the chassis is an issue.

You don't want a conducting bolt touch the top of a conducting case. This will make a (unfortunately shorted) single turns secondary winding and fry the primary winding of your toroidal transformer that cannot deliver the current demand of this shorted secondary winding. With a little luck your mains fuse will blow faster.
Just cut the bolt to the min.required length. Maybe glue some insulating material to the top of your case to play safer.

I all I'm up to mounting my transformer. Is there a need to screw the bolt from the outside of the chassis? What other mounting options are there?
I'm concerned that with the bolt protruding thru the bottom. This will cause scratches on other gear sitting in my rack and may not even fit.
I'm using a 19in case 1 ru.  Any help or ideas would be great.

Thanks

 

[druu]

Simply cut it shorter. The top of the mounting plate is designed so that the nut can be sunken into the top of the toroid (given your toroid is designed to fit into a 1RU case).

 

[EmptyMusicBox1]

My Sb4000 Finish !!!!

Thank You !

 

[sullivan]

How did you do the ''gravings'' on the panel?

My Sb4000 Finish !!!!

Thank You !

 

[EmptyMusicBox1]

It's a professional  screen printing (serigraphie) if somebody are interested i can make for $$  

How did you do the ''gravings'' on the panel?

My Sb4000 Finish !!!!

Thank You !