Audio Research LS15 preamp tube positions

[dogscanskate]

https://www.vintageshifi.com/repertoire-pdf/Audio-Research.php

Give the Tungsram time to burn in, that may help.

 

[BillWojo]

Thanks for the schematic. For some reason I always forget to check that site. Looks like they have schematics for just about everything ARC ever built.

BillWojo

 

[reed338]

I hope I'm not hijacking the thread here.... But does anyone know how to tell if a specific LS15 is at the original 12dB gain or had been factory set to a higher gain setting? I understand 12dB was standard but they could be ordered at other, higher, gain settings....

 

[BillWojo]

I think you will need to contact ARC for that info. I just looked at the schematics for any notes pertaining to that and there are none.

BillWojo

 

[reed338]

I think you will need to contact ARC for that info. I just looked at the schematics for any notes pertaining to that and there are none.

BillWojo

I contacted ARC, they provided me the instructions sheet for changing the LS-15 gain from 18dB to 12dB (or vice versa). Anyone curious, see attached.

 

[hrxx]

I contacted ARC, they provided me the instructions sheet for changing the LS-15 gain from 18dB to 12dB (or vice versa). Anyone curious, see attached.

thanks reed338

 

[DeFriend]

I thought V3 and V4 (the back two) in the LS7 were paired and performing the cathode follower function, and that V1 and V2 were paired the gain tubes.
I may have to up my tube-rolling game and start paying attention to V3.
I've definitely found that the right front tube is for the left channel, and vice-versa, and that these positions respond most to my tube-rolling efforts.​