RedB4Black
Well-known member
What pre-amp positions can I put these in my Herbert without causing issues?
mincy
Member
I'm guessing you're asking in relation to the info below. If so, I'd love to know the answer as well. Anyone?
from http://www.petersamplification.com
The Sovtek 12AX7LPS tube can die an untimely death in a lot of guitar amps. You can safely use 12AX7LPS in guitar amplifiers but only if you clearly understand the following information.
The 12AX7LPS has a voltage limitation of which most people are unaware: its cathode-to-heater voltage rating is lower than most other 12AX7 tubes. Since a "regular" preamp stage has very little voltage on the cathode (a couple volts DC if that), this isn't a problem for a "regular" preamp stage. The problem is when using the 12AX7LPS in a "cathode follower" type stage. This type of stage is effective for driving EQs and effects loops. Because of this lots of amps have cathode follower stages, including Peters amps. I could estimate that well over 60% of the tube guitar amps on the market have a stage of this configuration. Higher voltage is usually on the cathode of this stage (150VDC to 180VDC is common), and since the heater voltage is low (around 6V), the voltage between the cathode and heater is too large for the 12AX7LPS to reliably handle. This can and usually does end the tube's life very early. This can cause frustration and confusion due to the amp working improperly; sometimes the problem presents itself as extra noise, instead of "no sound at all", so it can be particularly annoying until the nature of the problem is discovered. Also when the tube fails it can cause damage to the amplifier.
The 12AX7LPS will work fine in amps with cathode follower stages as long as the 12AX7LPS isn't used in those particular stages. The key is to avoid using this tube type in that sort of stage.
from http://www.petersamplification.com
The Sovtek 12AX7LPS tube can die an untimely death in a lot of guitar amps. You can safely use 12AX7LPS in guitar amplifiers but only if you clearly understand the following information.
The 12AX7LPS has a voltage limitation of which most people are unaware: its cathode-to-heater voltage rating is lower than most other 12AX7 tubes. Since a "regular" preamp stage has very little voltage on the cathode (a couple volts DC if that), this isn't a problem for a "regular" preamp stage. The problem is when using the 12AX7LPS in a "cathode follower" type stage. This type of stage is effective for driving EQs and effects loops. Because of this lots of amps have cathode follower stages, including Peters amps. I could estimate that well over 60% of the tube guitar amps on the market have a stage of this configuration. Higher voltage is usually on the cathode of this stage (150VDC to 180VDC is common), and since the heater voltage is low (around 6V), the voltage between the cathode and heater is too large for the 12AX7LPS to reliably handle. This can and usually does end the tube's life very early. This can cause frustration and confusion due to the amp working improperly; sometimes the problem presents itself as extra noise, instead of "no sound at all", so it can be particularly annoying until the nature of the problem is discovered. Also when the tube fails it can cause damage to the amplifier.
The 12AX7LPS will work fine in amps with cathode follower stages as long as the 12AX7LPS isn't used in those particular stages. The key is to avoid using this tube type in that sort of stage.
RedB4Black
Well-known member
^Exactly. I have these tubes in my Bogners and I like them more than any other tube I've tried in them. I'd like to try them in v1 and v2 of the Herbert to see if they'd make a good replacement for the pricey RFTs I have in there now.
So come on Peter/Duesentrieb, out with it
So come on Peter/Duesentrieb, out with it
duesentrieb
Well-known member
Herbert tube layout:
V1 Used by all channels - no prob
V2 Used by channel 3 - no prob
V3 Used by all channels - don't use it here
V4 Mixer & Loop Driver - don' use it here
V5 Return Driver - don't it use here
V6 Phase Inverter - wouldn't use it here
V1 Used by all channels - no prob
V2 Used by channel 3 - no prob
V3 Used by all channels - don't use it here
V4 Mixer & Loop Driver - don' use it here
V5 Return Driver - don't it use here
V6 Phase Inverter - wouldn't use it here
Peter Diezel
Well-known member
Don´t use the LPS. Too less cathode-heater voltage !!!
Bierschinken
New member
Hey Peter,
do you had some probs with them used as cathode followers?
Regards,
Swen
do you had some probs with them used as cathode followers?
Regards,
Swen
duesentrieb
Well-known member
I had probs in preamp - CF positions.
With LPS and 7025 (also Sovcrap).
With LPS and 7025 (also Sovcrap).
Bierschinken
New member
Sovcrap 
mincy
Member
Peter Diezel":1xsez90p said:
Sounds like we have an answer. Good to know. Thanks, Peter!