Rivera Knucklehead Reverb KR 100 T Instrukcja Naprawy Pobierz pdf (Strona 37)

Knucklehead Reverb 1.0 p 37

Recently, Svetlana, JJ/Teslalovac, and Ruby Chinese are in production with decent

6L6GC Tubes. We use mostly Svetlana, and advise you replace your 6L6GC tubes

with this brand. You can use Rivera matched 6L6GC Duets or Quartets, and replace

with the same rating number (found on the label at the base of the tubes) with re-biasing

not required.

Generally speaking, we are quite conservative in our high voltage that we supply to the

output stage. Reliability is quite high as well as tube life is extended. This also bodes

well when selected tube choice is not available, and you must use whatever is on hand.

We are very critical in our testing of our tubes, and throw away many that do not make

our grade. All of our amps are built with matched tubes that are graded as well. When

you need to purchase replacement tubes, if you order the same grade number that are

in your amp originally from the factory (provided that no one has changed the bias set at

the factory), you can change out the tubes without needing the bias to be readjusted. If

you use tubes not from us or of a different grade or value, you will need to have the amp

rebiased. In terms of 12AX7A types, there are only 4 factories that we know of building

this tube type: JJ/Tesla, Sovtek, Yugo/EI, and Ruby Tubes in China. Again, NOS

stocks still exist of RCA, G.E., Mullard, Telefunken, Sylvania, Mazda, and Philips. We

must warn you, there are incredible scams of selling re-branded NOS tubes, and they

are usually not what they are branded. So please be careful and deal with only a

reputable source. Usually the Chinese sound the brightest and have the most gain.

JJ/Tesla seem to have short life and exhibit very strange noise problems (from siren-like

screaming to amazing helicopter-like sounds). Recently the Sovtek 12AX7LP has been

made available and it is improved from it's predecessors, yet has less gain and less

high end than the Chinese. 12AX7Lp’s are also weak for cathode follower circuits, like

position V4 in our Knucklehead Reverb, so we do not advise using this tube in this

position. Marshall users note; The middle tube in the typical 3 12AX7 layout of Marshall

Tops that have a cathode follower circuit (like the 1959 Model), as well as Fender 4-10

Bassman circuits, will have problems with failure using a 12AX7LP in this position.

Sovtek has recently released a 12AX7EH, another good sounding but slightly less gain

tube. RCA, GE, Philips-Holland, Mullard (NOS) are great tubes, but may need to be

selected for microphonics. Sylvania-Philips USA made are usually way too sensitive to

microphonics to be used in positions V1, V2, and V4. We are using mostly Sovtek for

the 12AX7A's. Typical factory fitted layout is: 12AX7WA or WB for positions V1, V2, V4,

with 12AX7LP for V3 and V5. This balances out the tone character as well as gain

levels. If you can obtain selected Chinese 12AX7’s from Ruby, you may use them in all

positions.

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Rivera Knucklehead Reverb KR 100 T Instrukcja Naprawy Strona 37