G-PULTEC problems, please help!

[kazper]

Getting a Bom together for my 2x single Gpultecs.
Just want to make sure these power traffo's will be ok.

http://www.mouser.com/Search/ProductDetail.aspx?R=VPT24-1040virtualkey55310000virtualkey553-VPT24-1040

24.0V CT @ 1.04A 12V @ 2.08A Parallel
Power Rating: 25 VA
Primary Voltage Rating: 115 V to 230 V
Secondary Voltage Rating: 12 V to 24 V

On the Gyraf PDF it calls for 12v 1.5A.
Thanks

I used Antek transformers (www.antekinc.com)
AN-0512 (50VA) + AN-0212 (25VA)

The 50VA is the first transformer that feeds the heater, and the 25VA is used on the step up.

So your $24 per unit in transformers this route.

You may also look at there new AS-0512 as a alternative for $3.50 more.

The units I built are surprisingly dead quite with the IEC grounded to the chassis.

Kaz

 

[EHOFFA007]

Thanks for the info. The beefier traffo1 makes sense.
Beefier is better  ;D

 

[kazper]

The regular one is probably more than enough.

 

[audiophreak]

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 - https://goo.gl/photos/dDLHy9yr2zdCZAUH7

  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.


 

 

[creal]

wow very nice eq audiophreak. i like your frontpanel.
very good post about the gainstage here. i think, i'll start my dual gpultect soon.

 

[audiophreak]

Thanks Creal !
           
        Not really sure how I got it to not have grounding problems... maybe Newbee luck  ;D

But even Jakob stated that a number of people have tried a dual G-Pultec and have had problems. Thats why I posted the link with detailed pix of what I did. That Hammond PT only has 115v primary mains, I see your from France, so that PT would not be an option for you, I don't even know if that is the reason it worked for me or not, but good luck with it, and I'll help as much as I can.

  Snipsnip ...  you there ?  - maybe this could help with yours ?

  Thanks again,
                      Chip

 

[snipsnip]

Hi Chip,

Good work, looking really nice.

Im also in europe so need the 230 primary. Im currently waiting for grandmasteraudio to get better so I can order some front panels and rebuild mine as 2 separate units. Glad yours is working though, everyone needs a bit of good luck from time to time

Im with you on the sound, the bottom end on this thing is wild, but never gets flabby. I also tend to pass mine through my ez1290 pres (with a pad) and this gives massive 3D tight lows.

I have smallish sinks on my voltage regs like you, and they overloaded from time to time when mine was up and running. If you do see any strange behaviour in future, take a look at those.

Congratulations, and enjoy!

 

[sonicwarrior]

Finally got some pix of my Dual G-Pultec !!!   

Nice idea to secure the power switch. 

 

[audiophreak]

Thanks sonicwarrior  !
    I've always installed the handles on the cases because I'd like to think they would protect the knobs and switches. This is my first panel layout, and I got a little too close the the left side, made adjusting the low boost and cut knobs a little difficult, so I removed the handles and put studs in with the acorn nuts. The knobs are pretty beefy, but left the switch exposed    had a couple of those switch guards left over from another build.

  Thanks snipsnip !
      The ez1290s are on my list  ;D  .. for the heat sinks, the PT I used has a 6.3v secondary, although I could just use a dropping resistor, I went with a TL1086, its a low voltage drop out regulator, so its regulating from about 8vdc or so, so it doesn't get very warm.

 

[snipsnip]

oh yeah! Should have read your post in more detail.

 

[muffy1975]

Hey guys,

can anyone detail how to bypass the ouptut ( yes output ) transformer on this build? Where do you connect the output xlr/jack and are there any parts that need to be added?

Many thanks in advance

Michael

ps, I've already built one unit with the OEP trannie output! Not a bad sound at all but would like to build a second without the transformer

 

[JW]

Bumping this one to ask about inductor shielding

I have a ringing going on with my G Pultec. I usually don't hear it but it occasionally comes on.
I have switches that terminate the outputs with 600 ohm resistors. Those don't make a difference so I don't think it's transformer ringing. (I have 600:600 Tamura/Yamaha PM1K transformers on the input, and the recommended Edcor on the output)

If I had to guess I'd say the ringing was up around 16K or so. Pretty high.

Does this sound like a possible symptom of the Torroids getting into the inductor? Or would that manifest itself generally at a lower frequency?

 

[gyraf]

..probably a unhappy tube - have you limited supply voltage to ca. 250V? That is relatively important.

Try changing tube...

Jakob E.

 

[JW]

Okay,

Looks like about an 8.5K resistor instead of the 3.3K 2 watt will get the high voltage down to 250V. I had it up around 267V.
Also, the 125V was down around 98V or so. I did some testing with a pot, and it looks like about 470R instead of the 1K resistor beside the 4.7uF cap should get it close to 125V.

As for the heater, I'm getting 6.03V. How important is it to get it all the way up to 6.3V?

 

[EHOFFA007]

Just finishing up a pair of these bad boys
first test seems as if the HF board is not acting properly.
I used these bournes inductors from mouser. Are these acceptable?

http://www.mouser.com/Search/ProductDetail.aspx?R=RL622-104K-RCvirtualkey65210000virtualkey652-RL622-104K-RC

LF board working fine.
polarity of I/O is correct
I have tied the filter boards together.
Took a chance with these inductors. Newbie so may have missed something in the specs

 

[kazper]

Just finishing up a pair of these bad boys
first test seems as if the HF board is not acting properly.
I used these bournes inductors from mouser. Are these acceptable?

http://www.mouser.com/Search/ProductDetail.aspx?R=RL622-104K-RCvirtualkey65210000virtualkey652-RL622-104K-RC

LF board working fine.
polarity of I/O is correct
I have tied the filter boards together.
Took a chance with these inductors. Newbie so may have missed something in the specs

Those look ok..

 

[EHOFFA007]

Just finishing up a pair of these bad boys
first test seems as if the HF board is not acting properly.
I used these bournes inductors from mouser. Are these acceptable?

http://www.mouser.com/Search/ProductDetail.aspx?R=RL622-104K-RCvirtualkey65210000virtualkey652-RL622-104K-RC

LF board working fine.
polarity of I/O is correct
Took a chance with these inductors. Newbie so may have missed something in the specs
I have tied the filter boards together.

Those look ok..

Thanks for the reply man
I didn't see any polarity markings on the inductors. My first time dealing with these. There aren't +/- poles, correct?
I'll have to look deeper.
Reading a lot of threads about input signal and loading properly. I'm using the recommended lundhal Tx's. I'm pushing it with a balanced out on a PS audio DAC for testing.
would this keep the HF section from not responding at all?
Flipped the boards and tested continuity against the schematics and all the inter-pcb jumps are good.

Any other insight would be great.

 

[EHOFFA007]

Just finishing up a pair of these bad boys
first test seems as if the HF board is not acting properly.
I used these bournes inductors from mouser. Are these acceptable?

http://www.mouser.com/Search/ProductDetail.aspx?R=RL622-104K-RCvirtualkey65210000virtualkey652-RL622-104K-RC

LF board working fine.
polarity of I/O is correct
Took a chance with these inductors. Newbie so may have missed something in the specs
I have tied the filter boards together.

Those look ok..

Thanks for the reply man
I didn't see any polarity markings on the inductors. My first time dealing with these. There aren't +/- poles, correct?
I'll have to look deeper.
Reading a lot of threads about input signal and loading properly. I'm using the recommended lundhal Tx's. I'm pushing it with a balanced out on a PS audio DAC for testing.
would this keep the HF section from not responding at all?
Flipped the boards and tested continuity against the schematics and all the inter-pcb jumps are good.

Any other insight would be great.

I had the High Cut and High Q pots mixed up!
I'm Finding on my first couple of builds not to trust myself too much
Sounds great! Thanks for this great project!

 

[JW]

Okay,
Voltages now are:
222V at the HT
120V at the 4.7uF poly cap,
and 6.31 at the heater.

Seem good?

 

[gyraf]

yes..