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Old 2nd October 2010, 12:49 AM   #1
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KenCalgary's Avatar
Join Date: Nov 2009
Cool What am I experiencing?

I have just completed my first tube preamp using John Broskie's Aikido line and Tetra phono PCBs. It replaces a solid state preamp but still plugs into my solid state amplifier. It has very little (perhaps 3 hours) burn in time. The line stage (e.g., when using the CD player) is quiet, clear and delightful. All the tubes are NOS organ tubes.

The phono stage produces a lot more detail than did the SS preamp. So much so that groove noise (and/or recording tape hiss on older classical LPs) is very obvious. It isn't a problem on newer well pressed reissues. There also seems to be an emphasis on high frequencies; for example sibilance comes through on several LPs.

The strange thing is that much of this white noise (if that is what it is?) recedes or goes away after an hour or so of listening.

Since I have no experience with tube equipment I was wondering if:
1) Tube equipment needs to warm up before sounding proper?
2) The tubes/wires/etc. need some burning in time?
3) There is a wiring/soldering/other construction problem that is causing this?
4) Something else?
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Old 2nd October 2010, 04:52 PM   #2
Arnulf is offline Arnulf  Europe
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Join Date: Feb 2009
Originally Posted by KenCalgary View Post
1) Tube equipment needs to warm up before sounding proper?
Yup, give it a minute or a couple of minutes to warm up to the working temperature. This is very much unlike solid-state.

2) The tubes/wires/etc. need some burning in time?

3) There is a wiring/soldering/other construction problem that is causing this?
Mostlikely: no.

4) Something else?
Mostlikely: yes. I have never met a tube amplifier that didn't hiss on its own. A simple test to perform is to short the input (use a piece of uncoated wire, a leg piched off a resistor or something like that). UIf it still hisses, it's your preamp. If it doesn't, it's someting ahead of your preamp (either the recording itself or the reading mechanism).
mod verb, transitive /mod/ to state that one is utterly clueless about the operation of device to be "modded" and into "fixing" things that are not broken; "My new amplifier sounds great so I want to mod it."
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Old 2nd October 2010, 07:34 PM   #3
DF96 is offline DF96  England
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Join Date: May 2007
Double-check the components in the RIAA network(s) - it is possible that the HF cut is wrong, perhaps by a factor of 10 (7.5us instead of 75us). After a while listening to it you will get used to it and so not notice it so much. If possible, both re-check the component markings/colour codes and measure them with a DVM.
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