MicDaddy

Re: G-PULTEC problems, please help!
« Reply #180 on: June 30, 2011, 06:49:38 PM »
what color to paint this thing? 

My only complaint is the physical buzz from the power transformer.  bzzzzzzzzzzzz   I'll need to play around with how it is seated.

pretty ugly to look at now but it sounds very lovely, studio tests tonight..

First time for metal work, not sure if I'll be doing any more of that.  XLRs weren't too bad, it was cutting the round hole for the VU that drained my will.  2mm steel might have also been a factor, perhaps a more light-weight chassis and aluminum panel would have been a breeze?

Just need to dremel the high cut pot to match the others and get everything painted, and knobs, gotta have knobs.
« Last Edit: June 30, 2011, 06:56:26 PM by MicDaddy »


shabtek

Re: G-PULTEC problems, please help!
« Reply #181 on: June 30, 2011, 09:50:46 PM »
nice mic :P :P
"really fine players do not use stomp boxes or master volume, they match the amp to the room and turn it up to 11.  Stevie Ray, BB King, Albert King, Duane Allman, Dicky Betts, Louis Armstrong"
   -CJ

MicDaddy

Re: G-PULTEC problems, please help!
« Reply #182 on: June 30, 2011, 09:57:39 PM »
nice mic :P :P

it sounds so nice through the eq, wow

idylldon

Re: G-PULTEC problems, please help!
« Reply #183 on: July 14, 2011, 01:21:45 PM »
Can someone tell me what the frequencies are for a Gyraf Pultec using ioaudio's inductor?  I've looked through all the threads and discussions about the math behind it all, but I never saw a final result.  A pic of someone's front panel would be fine as well.  I'm currently working on designing my panel and would like to get it right.

Also, I bought these as unfinished units and they've needed to be completely rewired.  The power transformers included are Triad FS12-1000 and Amveco 62062.  Unfortunately, both of these are rated at 1A @ 12 volts so I'm assuming I need to get some 1.5A 
transformers? 

Thanks,
--
Don

audiophreak

Re: G-PULTEC problems, please help!
« Reply #184 on: July 14, 2011, 05:34:39 PM »
Hi Don,

   Check this link -  http://www.groupdiy.com/index.php?topic=32839.0

  also , if you're doing separate units - check the tube data sheet - but i think the heater draws about 400mA  and B+  is 15-25 mA   - so I think your good for a single channel  ,  a dual unit may be pushing it on the heater side of things. 

also , this forum member has some good info - http://blog.benlindell.com/
« Last Edit: July 14, 2011, 05:40:03 PM by audiophreak »
" Music washes away from the soul, the dust of everyday life "   ... in loving memory of my Father.

Re: G-PULTEC problems, please help!
« Reply #185 on: July 14, 2011, 05:40:09 PM »
Just stick the L and C values here:
http://circuitcalculator.com/lcfilter.htm

or here:
http://www.deephaven.co.uk/lc.html

there are others where you can plug any two of F, L and C and get the third.  Or you can do it the old fashioned way
F= 1 / [2pi * sqrt(LC)]

Also, I think Gyraf.dk has front panel designs for all the DIY projects.  Keep in mind that F doesn't change only because of L, it is also dependent on C.  So you can tweak them both to hit whatever frequencies you want.  I'm terrible at explanations, but it's really pretty simple. 

I don't know the power requirements of the gpultec amp though, sorry.

but hey, maybe you can ask this guy:
http://www.groupdiy.com/index.php?topic=44779.0
 ::)

good luck!

idylldon

Re: G-PULTEC problems, please help!
« Reply #186 on: July 14, 2011, 05:43:35 PM »
Hi Don,

   Check this link -  http://www.groupdiy.com/index.php?topic=32839.0

Thanks!  I looked that over but kind of went cross-eyed.  I'll have another careful look at it.


Quote
also , if you're doing separate units - check the tube data sheet - but i think the heater draws about 400mA  and B+  is 15-25 mA   - so I think your good for a single channel  ,  a dual unit may be pushing it on the heater side of things. 

I'm building two separate units and I thought 1.5 seemed to be overkill for the tube requirements but I thought I'd double check with those who have already got theirs up and running. 

Quote
also , this forum member has some good info - http://blog.benlindell.com/

I will check that out as well.

Thanks!

Cheers,
--
Don

idylldon

Re: G-PULTEC problems, please help!
« Reply #187 on: July 14, 2011, 05:45:01 PM »
Thanks, mitos!  I'll check that calculator out.  Seems like a good way to do it.

Cheers,
--
Don

Majestic12

Re: G-PULTEC problems, please help!
« Reply #188 on: July 14, 2011, 06:31:06 PM »
Does anybody know where I can get the original bypass switch that fits the collective case 3 HE frontpanel ? I'm looking for a while now.

MicDaddy

Re: G-PULTEC problems, please help!
« Reply #189 on: July 15, 2011, 02:02:19 AM »
Just wanted to chime in and thank Chip for the help with some issues I've experienced this build.

Swapped out a faulty power transformer and this thing is very quiet now.  I was prepared to live with the hum, but this thing is 100x better, sounds so nice.  Played around with it just talk testing through a dynamic mic, for literally over an hour.  Can get tones from speakerphone all the way to voice of God with the gpultec.  I couldn't be more happy with it.

Also thanks to Jakob for helping with getting the VU set up properly.  This specific meter had no internal diodes or other circuitry.  I added one diode on the + side and now the meter works great.  The change in tone with/without meter is negligible.  What happens if I replace the diode with an LED and mount it in a hole to be drilled in the VU faceplate?   Would it light up as signal passes through it?
« Last Edit: July 15, 2011, 11:07:19 AM by MicDaddy »


Majestic12

Re: G-PULTEC problems, please help!
« Reply #190 on: July 20, 2011, 06:05:56 PM »
Do I have to change anything in the power supply when using the Don Audio transformer with 9V output ?

who

Re: G-PULTEC problems, please help!
« Reply #191 on: July 21, 2011, 09:20:39 AM »
Do I have to change anything in the power supply when using the Don Audio transformer with 9V output ?

nothing to change. just put both cables to the destined connectors.

Inductors, Power Trafos, Knobs, Trafo shielding sheets, Frontpanels
http://don-audio.com
https://www.facebook.com/DonAudioShop
Visit us :)

Majestic12

Re: G-PULTEC problems, please help!
« Reply #192 on: August 03, 2011, 09:07:54 AM »
I fired up one of my two builds today and realized that the 250V anode voltage was only 50 V. After tracing the voltage, I noticed that the mains transformer only provides 50V instead of 220V (I'm using the don audio transformer with 9V/5V/220V secondaries). 6,3V and 5V are both correct, so I guess that I have a faulty transformer.
I'm changing it for my second one I have, let's see if it works.


EDIT: The second transformer works as it should. 220V on the secondary side. But the anode voltage is 320V after the 3K3 2W resistor.. What am I doing wrong ?


EDIT2: Changed the 3K3 to 15K, but it's not enough. Will try to use a 30K to get the voltage down to 250V. Don't know why the voltage is that high.
« Last Edit: August 03, 2011, 12:15:48 PM by Majestic12 »

Majestic12

Re: G-PULTEC problems, please help!
« Reply #193 on: August 03, 2011, 03:53:03 PM »
Even when it doesn't work properly yet, it already looks beautiful :)


Majestic12

Re: G-PULTEC problems, please help!
« Reply #194 on: August 04, 2011, 08:15:54 AM »
Changed the 3K3 resistor to a 100K resistor and still having 300V HT voltage. What the heck is wrong? Can't seem to get the voltage down to around 250V. Could it be the tube?


MicDaddy

Re: G-PULTEC problems, please help!
« Reply #195 on: August 04, 2011, 11:00:45 AM »
FWIW I used a 33K, and my secondary was showing 289VAC before rectification.

What AC voltage is your secondary showing before rectification, and after rectification?  What kind of tube are you using?

Your front panel is a lot prettier than mine  :'(
« Last Edit: August 04, 2011, 11:12:19 AM by MicDaddy »

Majestic12

Re: G-PULTEC problems, please help!
« Reply #196 on: August 04, 2011, 02:33:26 PM »
I'm voltages (after 5 minutes warm-up)

AC Inputs rectifier:     240V (slightly high....transformer has 220V written on it)
AC Input to ground     125V

DC after rectifier:       330V
DC after resistor (now at 100K):  275V     
Heater Voltage:           6,03V

Voltage on 4u7 dc coupling cap:    101V

I'm using the don audio transformer and a JJ 12AX7 (ECC 83S) tube.

MicDaddy

Re: G-PULTEC problems, please help!
« Reply #197 on: August 04, 2011, 04:24:56 PM »
I'm not familiar with the ECC 83S, I used ECC88  Could be the tube causing you problems??
Isn't that a 12AX7??   :o

I believe anode current is quite different on the ECC83?

I'm no tube guy, so I'm gonna sit this one out and let somebody else step up.
« Last Edit: August 04, 2011, 04:35:29 PM by MicDaddy »

PeteC

Re: G-PULTEC problems, please help!
« Reply #198 on: August 04, 2011, 05:03:06 PM »
No expert here - but if your not getting voltage drop with bigger power supply resistor then it sounds to me like there is not enough/no current being drawn by your tube stage - if there was then you would get the corresponding V=IR drop across this resistor.  Sounds like a problem with your tube or the cathode circuit maybe ?

measure round your tube circuit and report back - someone more experienced will step in ...

I am yet to build mine so cant measure typical voltages and calculate current draws.

Rgds
Pete




PeteC

Re: G-PULTEC problems, please help!
« Reply #199 on: August 04, 2011, 05:17:00 PM »
just noticed you're using an Ecc83 - not 88 - a very different tube.

you need 6Dj8/Ecc88/E88CC/CV2943

Rgds
Pete




 

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