Help needed with Gyraf Pultec style EQ

[snipsnip]

Hi All,

Ive been looking through what info I can find in the META's and using search, but have a few questions regarding the Gyraf Pultec style EQ.

Firstly, with regards to the inductors, Im a little confused as what values to use. The values on the boards & schematic are clear, but on the Sowter website, it has an 'off the shelf' choke for this project tapped at 269,169,69 &22mH. It says its intended to replace the original values.

Now I understand there is quite a lot of flexibility in the filter values and they can be adjusted to taste, but I am still pretty new to DIY (GSSL, Dual ez1290, Roland Dim D & various effects under my belt to date) and I dont want to complicate matters.

If I go for the off the shelf Sowter choke, will that mean the capacitor values in the filter section will need to be changed? Am I better off just getting a custom choke made with the values shown on the schematic?

Secondly, I couldnt find a BOM for this project. I guess thats because its so simple its easy to create your own. This is what I have done, but was wondering if anyone has any recommendations for cap type and / or a list which shown the required leg spacing? From the board & the few photos I have seen I guess they are all poly... but would be good to double check.

Finally, does anyone know of a good tube to use?  So far my research suggests telefunken or mullard. Are there any good reputable places to hunt these down in the UK (or europe)?

Thanks a lot.
Jake

BTW - Is there a pultec help thread out there that I  cant find?

 

[canidoit]

Drips is coming out with a Pultec EQ soon, if you want to consider that as an option to build a Putec style EQ. www.dripelectronics.com

I have tried his La2a build and its really good. I have compared it with an La2a point to point DIY and the Drips version and I found Drips model to be very quiet regarding hum and noise compared to the other.

His build manual is packed with instructions and information on where to source the parts from. He also has his own forum, though response is a little on the slower side compared to Prodigy, but his direct email response is better especially incase of emergency.

 

[tmuikku]

I believe there is some calculator for passive EQ networks here on this forum, at least some formulas and theory should be there... Did you check META META already?

Edit:
Here is something
http://www.groupdiy.com/index.php?topic=32839.0

 

[hobiesound]

to calculate passive eq's i usually use an electronics simulator program so i can play around with values and add frequencies etc. very easy to do. just redraw the schematic and measure away.

 

[snipsnip]

Thanks for all your help... very interesting points.

I also got this advice on another forum regarding the Sowter choke:

''The inductors on the schmatic are all connected in series - the tapped inductor that Sowter are offering is effectively the same thing in a single package -

22mH = 22mH
22 + 47 = 69mH
22 + 47 + 100 = 169mH
22 + 47 + 100 + 100 = 269mH''

 

[snipsnip]

Also having a few issues finding the bridge rectifiers. The coide on the scematic is B350C1000.

Any tips?

Thanks a lot!
Jake

 

[substitute]

I just finished one of those a few weeks ago.  I used this for the rectifier...

http://mouser.com/Search/ProductDetail.aspx?R=NTE5304virtualkey52600000virtualkey526-NTE5304

I also used separate inductors as opposed to the sowter, it sounds great and was very easy.  I might try a sowter on another channel, seems more pro some how.

regarding caps i used wimas (as a lot of people like them and it narrows down the search) I don't think you can get all the values though.  I had to do a little mismatching. 

 

[snipsnip]

Thanks a lot! That link to the rectifier is a big help!

Cheers
Jake