2004 Bogner Uberschall (Blue)

Bogner amps was started in the early 1990’s by Reinhold Bogner who was born in the German town of Ulm and was the son of a Telefunken Tube Factory worker. In the 1980’s he moved to L.A. and became well known for making hot-rodded Marshall JCM 800’s and Fender Showman circuits. He sold these early mod-heavy circuits to the likes of Eddie Van Halen, Allan Holdsworth, and Steve Stevens. The Uberschall was created to supply player demand for a super High-Gain amp that was dialed in for down-tuned bass heavy music like the emerging Nu-Metal, Alt-Metal, Death Metal, and Grunge genres.

This amp came in to my shop in original condition. It had leaking filter caps, heat damaged power resistors, the OD channel was fuzzy, and the FX Loop was having volume issues. This one needed a full restoration including a full electrolytic cap job, new power/misc. resistors, new tubes, and cleaning.

This was not an easy job due to the to way the amp was constructed, in fact as far as restorations go this is one of the most difficult amps I have had to take apart and put new parts in. Engl and Diezel brand amps from the same era are also like this. The PCB’s are so tight in the chassis, and the snap-in radial caps are physically so close to other easily damageable parts that it’s almost impossible to get tools in there. Then the amount of hard-wired ribbon cables tying the boards together make this amp a nightmare to do this level of work to. But it can be done and a lot of these types of amps from this era are now in need of full restorations. I guess I get to look forward to a lot more of this!

The amp was given a full restoration. All of the radial leaded electrolytic capacitors in the power filter supply were replaced with new high-quality Nichicon and Rubycon brand units. All the axial leaded electrolytic capacitors in the power filter supply were replaced with upgraded temperature rated MOD brand units. The multi-section electrolytic cap cans were replaced with new German made F&T 50/50uf 500v type units. The under-rated 1/2 Watt 100 Ohm resistors in the low voltage supply and artificial center tap for the heater lines were upgraded to 2 Watt Reduced Mass Metal Film type units. This was done due to the original parts being burned and also for reliability and preventative maintenance. A brand new correctly sized 3AG 250V fuse was installed as the one previously in place was the wrong value (Mains Fuse).


The amp was completely re-tubed with the following compliment: V1/V6 = EHX 12AX7, V2 = JJ 5751, V3/V4/V5 = JJ 12AX7S, V7-V10 = JJ E34L Matched Quad. I picked out this lineup specifically for this amp to give the best balance of tone, reliability, and low noise. The adjustable Fixed Bias was set to Factory Spec of Approx. 35mv per each E34L tube. All pots, switches, and tube sockets were cleaned with De-Oxit and all hardware was tightened. Amp now works correctly, all symptoms were resolved.