SLO tube positions?

  • Thread starter Thread starter reverymike
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reverymike

reverymike

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Okay, in a SLO, when you are looking at the amp from the front, is preamp position V1 on the far left or right? I thought it would be the first tube on the left, so it'd be V1, V2, V3, V4, V5 (phase inverter). But, then I came across this directly from Mike Soldano himself. It seems to indicate that the phase inverter would be the first preamp slot on the left when looking at the front of the amp???

"The 12AX7LP and LPS sound the same, with the LPS being slightly less noisy. The only thing I must warn you about is that the 12AX7LPS can not handle very high cathode voltages, such as that which exists in the phase inverter, and tone and effects loop drivers, of the SLO - so you must use the 12AX7LP in those positions. I recommend that you use a 12AX7LPS only in the "first" position (the tube closest to the input jack) and the 12AX7LP in the others. That's what the tube line up is in all new SLO 100s, and it sounds great!"


The reason I'm asking, is that if this is the case, I may have the wrong tube in the phase inverter position.
 
reverymike":p6z7t4t8 said:
Okay, in a SLO, when you are looking at the amp from the front, is preamp position V1 on the far left or right? I thought it would be the first tube on the left, so it'd be V1, V2, V3, V4, V5 (phase inverter). But, then I came across this directly from Mike Soldano himself. It seems to indicate that the phase inverter would be the first preamp slot on the left when looking at the front of the amp???

"The 12AX7LP and LPS sound the same, with the LPS being slightly less noisy. The only thing I must warn you about is that the 12AX7LPS can not handle very high cathode voltages, such as that which exists in the phase inverter, and tone and effects loop drivers, of the SLO - so you must use the 12AX7LP in those positions. I recommend that you use a 12AX7LPS only in the "first" position (the tube closest to the input jack) and the 12AX7LP in the others. That's what the tube line up is in all new SLO 100s, and it sounds great!"


The reason I'm asking, is that if this is the case, I may have the wrong tube in the phase inverter position.
Click to expand...

Looking at the front of the amp, from left to right, the first 2 tubes should be the 12AX7LPS as per Mike's instructions and the next 3 positions V3, V4 and V5 should be the 12AX7LP
V1= OD/CL
V2= OD
V3= Cathode Follower for FX Send
V4= Cathode Follower for FX Return
V5= PI

Above is for the stock SLOs.
Cheers,
Mike
 
Thanks Mike. I was under the impression that the phase inverter tube was the one that needed to be different from the others. Specifically, when I bought the amp from the seller he said that he was advised to use a 'balanced' tube in the phase inverter, so he had that marked as being the PI tube when the amp arrived. I honestly didn't check to see what the other tubes were.

What's a balanced tube? According to the seller, all the tubes were the same (jj12ax7s), other than the one that goes in V5. This sounds like it's not the correct advice. Sounds like I might need some other tubes in there?

I'll check it out when I get home.
 
reverymike":vsf0fs18 said:
Thanks Mike. I was under the impression that the phase inverter tube was the one that needed to be different from the others. Specifically, when I bought the amp from the seller he said that he was advised to use a 'balanced' tube in the phase inverter, so he had that marked as being the PI tube when the amp arrived. I honestly didn't check to see what the other tubes were.

What's a balanced tube? According to the seller, all the tubes were the same (jj12ax7s), other than the one that goes in V5. This sounds like it's not the correct advice. Sounds like I might need some other tubes in there?

I'll check it out when I get home.
Click to expand...

The PI and both CF position need to be different because of the lower heater to cathode voltage rating that is common to the New Sensor manufactured preamps tubes. If they are all jj12ax7s, those don't have the hk issue so no worries about them. Also V5 does not need to be a "balanced" or matched preamp.
Cheers,
Mike
 
So, jj12ax7s would be fine across the board, in all positions?
 
Mine has Sovtek LPS across the board... 1-5. Not sure that's "right," but that's what's in it.
 
drewiv":26bgexho said:
Mine has Sovtek LPS across the board... 1-5. Not sure that's "right," but that's what's in it.
Click to expand...

If you ever have an issue with the amp going 1/2 volume on you, volume fluctuations or simply no sound with power on and no HT fuse blown....look at the LPS in positions V3-V5.

Cheers,
Mike
 
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