G-PULTEC problems, please help!

[TillM]

Thanks !
I will check this !

 

[ratty_7]

If anyone wants the panel graphic, I have it in Illustrator , just email me.

Hi All,
Finally got some pix of my Dual G-Pultec !!!

I used the Hammond 261G6 power trans, it has a 250V C.T. @ 130 ma secondary 6.3V @ 2A secondary. I replaced the 3k3 2w resistor with a 33k 5w resistor to bring the rectified 380vdc down to 240vdc. I replaced the LM317 with a TL1086, its a low voltage drop out regulator and a drop in replacement, although Kingston mentioned that just a dropping resistor could be used as after rectification its about 7.8vdc.
The front panel was done at Prodigy Engineering, I think I may have crowded the left side as I wanted to keep as much room as possible between filter boards and power switch. Collin at AML now carries all the pots for this all in 1/4 inch shafts.
I haven't done extensive testing yet, but so far it sounds Fantastic ! - clean, fat, big bottom end ... and Smoooooooth ;D
no hum or buzz or grounding issues - I only have IEC ground to chassis, I have a ground wire in place to connect to pin1 XLR inputs, but haven't tried it yet

Here is a link to some pix - Dual G-Pultec

If anyone wants the panel graphic, I have it in Illustrator , just email me.

All questions / comments welcome

Big THANKS to Jakob E. / Gyraf , Kingston , snipsnip , benlindell , and to this great forum.

Hi Mate

Mike from Melbourne. Australia.
An amazing build you have done there. Love the pics, and the Hammond power tranny...!!!
I am starting my build soon and love your 2U layout.
Am very interested in your panel graphic, if it's possible.
Once again great dual stereo build...!!!

Cheers
Mike

 

[audiophreak]

Hi Mate

Mike from Melbourne. Australia.
An amazing build you have done there. Love the pics, and the Hammond power tranny...!!!
I am starting my build soon and love your 2U layout.
Am very interested in your panel graphic, if it's possible.
Once again great dual stereo build...!!!

Cheers
Mike

Hi Mike !
No problem on the file ( I just have to find the the drive I stored them on ) LOL Thanks for the kind words , although the pics came out nice , in use they are a little thin , the laser engraving didn’t have a lot of contrast ( dark grey on light grey ) so you might want to change the font to something a little bolder if you are laser engraving. Just PM me an email address to send it to.

please post of your progress and pics when done !

Cheers,
Chip

 

[ratty_7]

Hi Mike !
No problem on the file ( I just have to find the the drive I stored them on ) LOL Thanks for the kind words , although the pics came out nice , in use they are a little thin , the laser engraving didn’t have a lot of contrast ( dark grey on light grey ) so you might want to change the font to something a little bolder if you are laser engraving. Just PM me an email address to send it to.

please post of your progress and pics when done !

Cheers,
Chip

Hi Chip,
Thanks for your quick reply.
Yes, I will post my build and pics. I have a problem getting the Fastron 100MH Inductors from Mouser (out of stock). We are a bit staved for suppliers down here, but the sun is still shining Just waiting on the boards from Analog Classics. Will pm my email address.

Cheers
Mike

 

[timtom]

@frazzman
here is a diagram how to wire this trafo:


You can also wire it parallel for use in 110v countries.


I used a LED lamp with a 3k9 resistor. If you want to use the original fender 5v lamp bulbs you need no resistor.



all the best
"who"

How do I dim those 5v lamp bulbs?

 

[gyraf]

put a resistor in series, perhaps?

 

[timtom]

I tried this already with some resistors in the 100-1000ohm area but then there was no light anymore. Perhaps I need to get some smaller resistors.

 

[gyraf]

yes

and if in doubt, trust ohm's law

/Jakob E.

 

[ratty_7]

Hey guys,

Had to do something during Covid lock down, so I started my G-Putec Stereo build. Starting with the boards from Analogue classics, have taken some advice and put in a 2k variable for the LM317 just in case, as some had problems with overheating. (see pic). Also for the inductors am using Festrons, and thanks to MR Audiophreak from the good ole US of A who sent me the 100mh as "Oz" Mouser only had them on back order.

Also, if anybody is interested for the future, I found these DakaWare knobs and a whole lot more from China, so much cheaper than D Audio (see pic) talk to Nana. Here is the link. http://www.omter-tyxn.com

Am using a "matched pair" of E88CC and did read some stuff on that topic but am not convinced of the matching criteria, Seems there's a whole heap of debate on the subject. Still, am having to use E88CC as the ECC88 are impossible to source in Oz. Although on Ebay they are going for any where between $60 and $100 AUD including shipping from Europe and even more from the US.

However, as Jacob said, am paying particular attention to the 10k Lin pot for low boost. Have gone to our local store and measured a heap of them....!!!
Finally here is pdf of my front panel, with the spaces for the Dakaware. Again thanks Mr Audiophreak for the inspiration
Well that's it for the moment. Any feed back would be most welcome. Would like to thank all the great work from all who have gone B4 me, as it making my life so much easier... More pics will come as I get more parts from Europe ect... cheers Mike

 

[LinusGrane]

Hello i have almost finish the build of my dual G-pultec. It works great except for some hum... sounds like classic grounding fault hum.
I have read that dual G-pultecs can have that problem.

If i just plug on side of the pultec to the mixer the hum is gone/lower but if i use both on main insert the hum is coming back. I think the hum has reversed phase but are not 100% shure..

i Have tried to connect all the pin1 direct to the ground on the power socket (made it worse) and also flipped the ac cabels en the left board. Cant tell if its the same hum or maby worse .

The power trafo was rated to be used to 2-4 Mono G-pultec power boards.

I have only output transformers and uses trs-in/out puts.

Any suggestions?

 

[gyraf]

..first of all, you'll want to have the power transformer as far away from audio transformers as at all possible.

Then try rotating the power trafo, to see if it nulls at some position

then check grounds - hint: on transformer balanced outputs you do not need a ground

/Jakob E.

(ps: it is very much on purpose that it was not originally intended as a dual unit, it gets too complex quickly)

 

[LinusGrane]

Ok im going to try that

i read something about using only one DC power supply. is it just to remove the AC cables and connect the 250v DC and 6.3v DC to the "slave card"?

 

[gyraf]

yes, and ground. At one and only one point.

 

[LinusGrane]

Is it correct to takte the 250v and 6.3v on the tube-socket to the other and ground? Should i remove anything else or just the ac wires?

 

[LinusGrane]

Grounded the boards directly to the IEC-ground and now the unit is hum-free ✌ think i can hear som noise if i turn my monitors to the max .

 

[JerryPbury]

Anybody have a current source for a pair of boards?

Thanks,

Jerry

 

[innercityman]

Sure... Analog Classics

https://analogclassics.com/product/gyraf-pultec-pcb-set/

 

[Gustav]

Ok im going to try that

i read something about using only one DC power supply. is it just to remove the AC cables and connect the 250v DC and 6.3v DC to the "slave card"?

go to www.pcbgrinder.com - there is a schematic for the PQ2 in the google drive folder linked.'
'
You can see how I did the PSU for a "double"- and it works perfectly.

Gustav

 

[JerryPbury]

Sure... Analog Classics

https://analogclassics.com/product/gyraf-pultec-pcb-set/

Thank you! That didn’t show up on my web search.

 

[Blissy]

Hey All,

Just finished my own G Pultec Build and everything seems to working expect the the 100k "Low Cut" seems to acting as an full spectrum attenuator of the entire signal. everything looks good on the board valves and joints and tips on where to start looking?
Thanks
J