Bogner Ubershall Twin Jet and MK2-KT88 Retube Kits

The Bogner Ubershall Twin Jet and MK2-KT88. The kits we offer here are the most distinctive in tonal character, forged from many years of research. Every kit is configured to provide a specific sound/experience.

These amps are adjustable bias and you can use the factory test points and a Multimeter or you can use a bias probe with a Multimeter which is more accurate, or you can use our All-in-one “Pro One” bias probe which reads the plate voltage and the plate current simultaneously.

The default power tubes for all the Bogner Ubershall Twin Jet and MK2-KT88 kits are the JJ KT88’s. This tube is a replacement for all standard KT88 and most 6550 applications. These are a higher power tube with lots of headroom, thunderous lows and thick/aggressive mids.

You can also use the JJ 6550’s. The JJ 6550’s. This tube is a replacement for all standard 6550 applications and most KT88 amps as well. The JJ 6550 is a high power tube with more headroom than your standard EL34 or 6L6 variant. Compared to the KT88, it breaks up a little earlier and has very raw and open overdriven sound.

The Standard Retube Kit is as close to OEM as possible. Maintaining the amps stock level of headroom and gain while providing a warm but even handed overall sound. The kit includes one matched quad of JJ KT88’s by default, one Balanced JJ ECC83S for the phase inverter (V6, closest to the power tubes in the back row), and seven Standard JJ ECC83S’s for V1 – V2 – V3 – V4 – V5.

The Gold Pin Retube Kit uses the JJ ECC83S Gold Pin variants to provide a smoother, creamier, and more singing overall sound. This option is less aggressive and has less “teeth” when driven hard. If you like a classic raunchy gritty overdriven tone, we recommend looking to the Standard or High Gain option. If sweet, open, and more refined is what you’re after this kit will do it. The kit includes one matched quad of JJ KT88’s by default, one Balanced JJ ECC83S Gold Pin for the phase inverter (V6, closest to the power tubes in the back row), and four Standard JJ Gold Pin ECC83S’s for V1 – V2 – V3 – V4 – V5.

The High Gain Retube Kit uses our hand picked high gain selected JJ ECC83S’s. If you’re looking for maximum crunch and grind this is where you want to be. Sonically this setup is very similar to our Standard Retube Kit but with a little extra gain on tap. The kit includes one matched quad of JJ KT88’s by default, one Balanced High Gain JJ ECC83S for the phase inverter (V6, closest to the power tubes in the back row), a Standard ECC83S for V5 and four Handpicked High Gain JJ ECC83S’s for V1 – V2 – V3 – V4.