[BUILD] GIX-51X tube preamp

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Toure, some people are lucky enough/brave enough to just plug it in and start running signal through it. I recommend powering the 24v rail alone and measuring the hv output to make sure it's working properly.
 
are there any wattage specs for the resitors?  i have all 1/4w resisters.  r31 on the pcb is bigger... is 1/4w ok here?
 
I had the same question , a short in the tube or the ht psu would stress that resistor while it drained the reservoir and smoothing caps but i don't know how to calculate what is appropriate
 
Yeah so I tried again this morning and there is noticeable hum seems to die out a little bit with the filter set to 150Hz but it's still there. So do I need that rodney cap or is it the tubes? I ordered my tubes brand new as a matched pair with noise check. So the only thing they couldn't do was burn in. I don't know what burn in noise would sound like so I'm left to assume something is off.

Looking at the schematic am I correct to assume I check the HV Out at the molex connector closest to the tube?

My tubes heat up and nothing is smoking or burnt so kinda drifting at this point... :-\
 
Just thought Id post pictures of my build so I can get some help with this annoying low but present hum. Don't know how to put all the pictures in 1 post so I will take up a few post
 

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HV board with Cap installed across R503 and R504
 

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I added small spacers so my board wouldn't be grounded to the metal plate
 

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I also can verify that the cart that is accurate although I added WIMA caps where ever I could so Mouser may not have all the WIMAs but TAW Electronics does
 
100WChris said:
HV board with Cap installed across R503 and R504

put the cap across R503 and R502 as shown in pictures by bruce on side 3 of this thread, reply 45.
Might solve your hum-problem.

Cheers
Chris

This solved it...I think I miss read the instructions...Both Pre's are working now..The Lundahls sound amazing with the RCA tubes I have installed in them. While the OeP sounds good with the Raytheon tubes there is simply not enough gain compared to my other pre's but it has a bunch of character to it. I think I am going to swap the OEP input for an EA2622 from CAPI. should get better results

My WHITE Face and My BLACK Face
 

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I love seeing these finished pics... I like to think that someday, maybe one of these preamps will be used to record a hit in a small independent studio and launch some musician or band into stardom and in some why I will have played a small part in all that.
 
another one  :) still waiting for some tubes.
but even with old tubes i had at hand the pre sounds fantastic!!
GIX_1.jpg

GIX_2.jpg

frequency-plot with old tubes i had lying around (made with fuzzmeasure).
I was surprised to see a clear bass rolloff, even with filters off

GIX_plot.png


 
100WChris said:
another one  :) still waiting for some tubes.
but even with old tubes i had at hand the pre sounds fantastic!!
GIX_1.jpg

GIX_2.jpg

frequency-plot with old tubes i had lying around (made with fuzzmeasure).
I was surprised to see a clear bass rolloff, even with filters off

GIX_plot.png

How are you able to attach multiple pictures in one post?
 

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