Frank's Pultec Support

[lassoharp]

Last I checked - Jul 09, their MEQ coils were 22.38 each.  The PEQ1A is a more expensive coil - 34.33

 

[seavote]

bump a question from last page
i'd like to make 2 channels.  enhanced and mid pultec in one channel. can i connect one passive board directly to the other? 
will one amp section per 2 board channel do or should i amplify befor sending the signal from one board to another? 
thanks for any help. i may have been here for a while but i still have a great deal to learn.

 

[Matthew Jacobs]

bump a question from last page
i'd like to make 2 channels.  enhanced and mid pultec in one channel. can i connect one passive board directly to the other? 
will one amp section per 2 board channel do or should i amplify befor sending the signal from one board to another? 
thanks for any help. i may have been here for a while but i still have a great deal to learn.

Me too, I'd like to know if you can simply connect the two boards together in series to make a "pultec type eq" with mid freq boost and cut?

J

 

[seavote]

advice from "frank" himself at the other (nrg)forum thread:

"I would do it like this. Make two seperate circuits... enhanced and mid pultec and connect the output of the first amp to the input of the second one.

You could also add a switch to seperate the two filters, or use a jack connector so that its possible to insert only one filter to a sidechain maybe.

I think its also easier to make two seperated circuits if you need to find any faults in the circuit."
_________________
his advice makes a great deal of sense. how can you argue with having more options as to how to implement the EQs use.

 

[SIXTYNINER]

i agree

advice from "frank" himself at the other (nrg)forum thread:

"I would do it like this. Make two seperate circuits... enhanced and mid pultec and connect the output of the first amp to the input of the second one.

You could also add a switch to seperate the two filters, or use a jack connector so that its possible to insert only one filter to a sidechain maybe.

I think its also easier to make two seperated circuits if you need to find any faults in the circuit."
_________________
his advice makes a great deal of sense. how can you argue with having more options as to how to implement the EQs use.

 

[mitsos]

Can someone who has these boards please confirm the max lead spacing of the caps?

thanks!

 

[naths101]

I'm just starting to get into the whole DIY scene and learning the ropes but I have a few questions regarding the pultec...

Is there a BOM floating around for this project??
I'm currently sourcing parts on mouser and not sure what caps I'm meant to be getting... I found the MKS4 series but not sure of the voltage rating, lead spacing etc
I want to use franks filter PCBs with gyrafs gainstage and don't even know what parts I need for that... :s

Thanks in advance
nath

 

[briomusic]

hi naths,
there is no BOM as such, especially as you are merging two projects.
the components for frank's filterboard can clearly be seen on this picture:
http://www.nrgrecording.de/temporary/PultecV15.pdf
for the srpp gain stage you should check the gyraf website.

to be very honest, i am not sure if the pultec is a good starter project as it involves very high voltages and might need some fiddling about with the grounding to get hum-free. it also requires some custom/expensive components, like inductors and transformers. For me it's my 6th project after building several SSL9k's, EZ1290's as well as an LA-4 and a forssell optical compressor and a calrec eq and still I am approaching it with a lot of consideration and respect. All I am saying is there might be better documented projects out there to get your feet wet.

whatever you decide to do, good luck!

cheers
brio

 

[mitsos]

I'm just starting to get into the whole DIY scene and learning the ropes but I have a few questions regarding the pultec...

Is there a BOM floating around for this project??
I'm currently sourcing parts on mouser and not sure what caps I'm meant to be getting... I found the MKS4 series but not sure of the voltage rating, lead spacing etc
I want to use franks filter PCBs with gyrafs gainstage and don't even know what parts I need for that... :s

Thanks in advance
nath

Don't know what's best, but I'm planning on using mostly wima MKP4. the lowest voltage rating (usually 50 or 63VDC) should be fine. MKP4 should fit except for the largest values. (I'm still unsure of the lead spacing, I printed and measured off the PDF, and it looks like it should be 10mm, but I am measuring something like 12, so maybe I prented it wrong). CAN SOMEONE CONFIRM THIS OFF A PCB PLEASE? I think FKP sounds even better than MKP (in some non-EQ testing) but most won't fit and are much more expensive.  Also, Wima does not make a 39nF, so you'd have to go with another brand since the PCB doesn't have a spot to put another cap in parallel there.  Give TAW a call and order your wimas from there, they have better prices than mouser, and they'll ship anywhere.  You can go to their site (www.tawelectronics.com) and choose the caps based on lead spacing, type of cap, like at www.wima.com. 

FWIW I've read that some people like polystyrene for the high frequency caps and PIO for the low end, but neither will fit this board too well, so I'd start with Wimas, see how you like it, and experiment with the next one.

Keep in mind the high voltages of the valve circuit as briomusic said. They can kill. You might want to build this using Frank's solidstate gainstage first, then when you have some experience and everything is working, start experimenting with the valve circuit.
good luck

 

[Apache5]

Hi, on mine enhanched pultec filter pcbs (v 1.4) the lead spacing are 10mm maximum (with 5mm and 7.5mm option too)

Arnau

 

[mitsos]

Cool, thanks, I must have printed the PDF wrong. Good to know.. 

 

[naths101]

Thanks for the replies brio, mitsos and arnau.

I'm currently working on the Gssl, drip LA2A and drip V72. One of my mates has built a few tube kits before and he's helping me out when i need it.
Also planning on building a few 1176s before the pultecs.

As well as the frank filters + gyraf gainstage I'm going to make the gyraf filters + frank gainstage since I have the boards. I won't be building these kits until I've finished the other ones though, so it could be a few months... Just wanted to find all the bits to add up how much everything will cost.

And thanks for your replies regarding the voltage rating and lead spacing.

cheers,
nath

 

[seavote]

will be making my own inductors.  is there a special glue (epoxy?) i should use to glue the cores together?  should it be conductive?

 

[nrgrecording]

will be making my own inductors.  is there a special glue (epoxy?) i should use to glue the cores together?  should it be conductive?

I tried cores which needs to be glued together and I didn't liked them. Its hard to adjust the inductor value with glue  :-\
Try to buy the cores from "epcos".

bobbin 1422721 (farnell)
clip 443750 (you'll need two clips for one core)
core 1422720  (thats the 3300nH... i use 1600nH but I can't find it in the farnell online store)

The epcos cores are very good. No glue needed. You can get the cores in different sizes. For the pultec you'll need "RM8". For Neve/API up to 2Henry you'll need "RM10".
I use 0,1mm enameled copper wire. You can build your own winding machine with a cordless screwdriver from the building center. For the counter you can use an old
calculator and a fork light barrier... type 1+1 into the calculator and connect the "=" button with the fork light barrier and you will have a nice counter. 
This will cost less than 50€ and works fine.

Frank.

 

[seavote]

all ready purchased these:
                              http://www.conrad-international.com/websale7/?shopid=conrad-int&act=product&prod_number=516619
after some experimenting the author of this page:

http://www.diygallery.de/DIYsites/inductor.html

found these cores to sound "sweet".
had nothing to go on so i put my trust there.
any glue suggestions?
if conductivity is not an  issue im thinking some type of cyanoacrylate glue 

 

[nrgrecording]

I tried these inductors in the beginning. I used 2-component glue. Cyanalcrylat may work.
I always have the LC meter connected to the inductor to see/adjust the inductor value. (space/gap between the cores)

Frank.

 

[flintan]

the lead spacing are 10mm maximum..

I used polystyrene for all except the lowest frequencies where i took what i had at hand of polypropylene or polyester. Polystyrene caps are ridiculously large and i had to use up to four caps for some positions. But i got it all within ~1% tolerance. They are 63V.

It would have been easier to build on perfboard but well..  :

 

[nrgrecording]

They are 63V.
It would have been easier to build on perfboard but well..  :

I measured a voltage/audio signal lower than 64V at the filterboard.  I just used capacitors which fit to the pcb.

The Manley and Langevin circuit does use small capacitors, too:
http://img10.imageshack.us/img10/1357/56211232548504.jpg

 

[flintan]

Hehe, i just used what i had in my drawers. The bigger the better, isn't it?  From the size of mine you could think they are couple of 100V's..

 

[briomusic]

crossposting this from franks forum in case anyone here can be of help:

i am having troubles getting my enhanced tube pultec to work. I think my gainstages are fine, as they work as amplifiers and I can get them to unity gain with a simple voltage divider in place of the filterboard.
however, with the filterboard connected, I just get a ca 20dB amplifier with a tiiiiiinnny bit of hi boost working. all the other frequency bands have no effect whatsoever 
it is a little difficult to troubleshoot this project as there is no schematic, so I tried to trace one myself from the pcb, and if I am not mistaken, there are some significant differences to the layout of the gyraf version (additional frequencies aside):

This is obviously an extremely simplified version with just one fixed frequency for each band. I found that apart from the 10k and 1k resistors missing on franks board, the caps for hi cut and lo boost are connected differently. Is this correct? or did I make a mistake tracing the pcb?
As I am having the same problem on both boards, I don't think that this is due to a solder bridge or similar. Any help appreciated!
Briomusic