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Has anyone tried changing the tube types on the VTL 5.5?This preamp calls for:
2 - 12AXT
4 - 12AT7Will other types like 12AU7 work in place of the 12AX7?
I have been having fun with trying different brands the past couple days (Mullard, GE, Sovtek, and Phillips). I would like to find a way to lower the gain.I am new at this, and I do not want to blow up my equipment.
Thanks,
Follow Ups:
FYI-
I tried a 5751 tube in place of the 12AX7. This lowered the gain, but seems to have sacrificed some speed and response in sound.
will it blow up? No. Is it optimal, probably not. Certainly I would NOT change the tube types in the phono section, as that will probably screw up the RIAA equalization. In the line section, if it uses feedback, then the 12AU7 may not even lower the gain because that will be set by the feedback rather than the tube gain. Also, the resistor values are chosen to optimize the operating conditions of the 12AT7/12AX7 (whichever tubes are used there) and are likely to be suboptimal for the 12AU7.If you get ahold of the old VTL book by David Manley he has some choice words to say about people who substitute tube types (as opposed to substituting alternate brands of the SAME tube type) will nilly.
on Tweaks, page 36, "The replacing (or rather displacing) of tubes with others that happen to have similar sizes or number of pins is another deplorable practise.....The tweeker wouldn't know a tube-manual from "Pravda" - or even that such things exist.... One thing tweekers do really proficiently is the voiding of manufacturer's warrantees. Be warned."
Thank you JimL.
The standard disclaimer: best to follow the recommendations of your equipment manufacturer; risk of damage or voiding the warranty.You can substitute 12AU7 for 12AX7 because the AU is a lower gain tube. I've actually done the above. I think the AT is in between the AU and the AX. There are other tubes that could sub too. DO a search on something like '12AU7 AND 12AX7' and you should be able to find many old posts about subbing tubes.
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