The hard part of the biasing process in finding your tubes maximum power dissipation rating...."the tubes power output in watts to anybody that doesn't know"....and this is hardly top secret....practically all the online shops that sell tubes give this rating in the information about a particular tube if not in the title line of said tube....
I started off with my Evil Robot....a self biasing amp....?....over 3 days checked both the plate voltage and the cathode current with the BiasPro VI and each time got the same ratings....spot on....this told me two things....1. that the Evil Robot is rock steady and 2. that the BiasPro is also rock steady....any wavering in these ratings and something is not worth the money....
Onto the Egnater Renagade....This amp has biasing probe points on the back panel with a section in the manual on how to bias the amp yourself using any number of tubes...I had always thought that my Renagade sounded sweet....Channel 1 has 6V6's to give me a very retro tone and with a Tele gives a very passable Keef Tone and has Twang aplenty....Channel 2 has EL34's to give a very Egnater modern rock tone....tons of fun....can be a bit much....but dialed in with the 6V6's is just about a perfect do anything amp....the 6V6's taking the edge off the 80s metal tone....
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| "ignore the multimeter in the photos....its not needed....it's plugged into the Renegades test points" |
Using the AsharpFretworks BiasPro VI is simplicity itself....all you need to know is your tubes power rating....then with the probes installed under the tubes in your amp the BiasPro gives you the two other values needed to bias your amp perfectly....One of the probes cables has a little box with a toggle switch on it and the switch gives you either the Plate Voltage or the Cathode Current and that's it....Different amps will have different PV's and not knowing your amps PV is going to make any bias setting a wild stab in the dark....you only need to be a little out and your risking bad tone at best and a tube letting go at worst....The CC is your amps bias setting....
Maximum Power Dissipation Rating
JJ 6V6 S = 14watts
JJ E34L = 25watts
JJ 6L6 GC = 30watts
Tung-Sol 5881 = 23watts
TAD 6L6WGC-STR = 30watts
You then divide your amps Plate Voltage by your tubes power rating....this gives you the tubes maximum bias current....then you need to set your amp to 70% of this maximum current....
JJ E34L 25w/440 Plate Voltage = 56.8 maximum bias current
56.8 x 70 and hit the % button on a calculator gives you 39.7
39.7 being the magic number....it really is as easy as that....
"if you can not see this video in the email Blogger version....click HERE"
The BiasPro VI is designed and built in the US by Ken Koga of AsharpFretworks....they look like they are built to last....not at all like something your mate made for you....the cables that make up the probes are as good as anything I've bought over the years not cheep and flimsy looking...it comes with two probes but if you need or want 4 you can buy two more....The probes are the big eight pin versions....you can also get nine pin versions for EL84's....two more probes would have been best for my Marshalls....it will just take me longer to bias my JCM900 but I can live with that....The BiasPro will also show you how well matched your tubes are....but best of all....it works and works very well....is stupidly simple to use and for the money I think every guitarist with a tube amp needs one....My Egnater is an even better amp that I thought it was with a perfect biasing....now on to my other amps....cheers Ken your a star....this thing ROCKS....k.j.
Asharp Fretworks....
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