[BUILD] GIX-51X tube preamp

[gemini86]

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.

 

[qmp audio]

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?

 

[gemini86]

R31 was specced at 2W for the original G9, but I haven't the slightest clue why. It really only needs to be 1/4W.

 

[bruce0]

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

 

[Toure14]

had my fingers crossed but i got the low whining/hum some have also experienced

 

[Toure14]

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... :-\

 

[gemini86]

Yes, the 'Rodney' cap is required to make the converter run smoothly.

 

[Toure14]

so is that the source of my noise problem? and where do i get the Rodney Cap?

 

[Toure14]

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

 

[Toure14]

Top View

 

[Toure14]

HV board with Cap installed across R503 and R504

 

[Toure14]

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

 

[Toure14]

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]

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

 

[Toure14]

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

 

[gemini86]

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.

 

[Winetree]

K&K Audio, LL1538XL is $300.00 WOW
Doesn't list 5402
Can I find a better deal?

 

[bruce0]

http://www.kandkaudio.com/prices.html

$94?

 

[100WChris]

another one  still waiting for some tubes.
but even with old tubes i had at hand the pre sounds fantastic!!

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

 

[Toure14]

another one  still waiting for some tubes.
but even with old tubes i had at hand the pre sounds fantastic!!

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

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