help with lo frequency rise: problem solved : actually not

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kambo

Well-known member
Joined
Apr 24, 2009
Messages
1,975
Location
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i replaced my Lundahl LL1538XL with Jensen JT-115K
now i have this on low end!


edit: it was bad cable... wrrraaaaghhhhhh!
 
That's not "lo freq rise". It is a total LACK of any useful signal. -140dB is "nothing" (assuming any normal "0dB" reference". The "rise" is an analysis window artifact.
 
actually it wasnt the input trx.   
i replaced LL5402 2:1 trx with a spare 10k:600 output transformer to test my SRPP output...

that graph at first picture is actually accurate... i recorded some drums, and bass became huge!
with RMA spectrum looks flat, but in noise graph, its there,

so, my guess is i shouldnt be using 10k:600 where i should be using 2k4:600
( i cant use 10:600 in my system, i am running out of gain anyway, just curiosity)

 
Agree with PRR.  That graph is -110dB and lower.  That's what noise floors look like in tube gear on analyzers.  Most of that is under 20Hz too. 

You may have a resonant frequency with the transformer in that circuit, which would appear in the noise floor somewhat too. 
 
emrr said:
You may have a resonant frequency with the transformer in that circuit, which would appear in the noise floor somewhat too.

i think that what it is...
any tip for reducing resonant frequency in this case.
10k:600 is connected to SRPP output.

(i loaded trx with 600r, helped a little, but not cured, also made me run out of needed gain)

same SRPP with LL5402 wired 2:1...
 

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