When the auto-complete results are available, use the up and down arrows to review and Enter to select. Cathode-Bias/Fixed-Bias Switching in Tube Power Amps Vintage guitar amps often produce a tone that is described as round or mellow, Bias switching is a.
#Fixed bias guitar amp professional
With tonal qualities as described by Synchro some posts before, the Fixed/Cathode bias SW is much more interesting than the Triode/Pentode mode - all other things equal by the way, and on this amp, of course. Guitar Amp Design Books for Professional Builders. I nearly never used that feature for that reason, the tone in Pentode being better.
#Fixed bias guitar amp pro
The ET Pro One Bias Probe is also available with our custom built 9 pin head.
#Fixed bias guitar amp plus
This allowed a power reduction to one-third, that is to say circa 8W RMS instead of 23W, but the resulting overdrive tone when pushed was dull, poorly responsive to the playing, despite the fact that the loss of power output allowed to max the volume in order to increase drive and sustain. The ET Pro One Bias Probe is calibrated at 180 Milliamps to plus or minus one tenth of one milliamp at 700 volts DC, so unlike other probes on the market the ET Pro One can be used on amps that exceed 1000 plate volts 9 pin probe solutions. It's not what I expect, so I stay with no decoupled cap cathode bias resistor.īefore that - many years ago - I wired the output stage of this amp with a Pentode/Triode connection SW instead of Fixed/Cathode bias SW. get a Digital Multi-Meter (can be a cheap radio shack one) - and buy a weber bias rite head. I'd also re-bias any time you change your power tubes, regardless of what you have read. No noticeable improvement in compression, harmonics or sustain, a little increase in brightness but the crunch smoothness is lost. Fixed bias, dispite what the name implies, is usually adjustable with a trim-pot. Verdict : no great interest, at least for me. I tried 2µ2, 10µ and 27µ to see the difference. The tests that I have made here involved non-decoupled (= non cap-shunted) common cathode resistor. Then there's my Twin with a single 15" and a closed-back cab', which will reverse avalanches.
The breakup characteristics are different than the Cyclone, but I never have occasion to play it that loud, so it stays linear almost always. When an amp is referred to as 'fixed bias', it doesn't mean there's no pot, it means that a fixed negative voltage is applied to the grid as opposed to cathode bias where the bias is more or less self-regulating. Throw the Bright switch and you are instantly transported to Bakersfield, CA. To add adjustable bias to fixed bias amps with no bias pot you simply replace the bias circuits second, larger resistor (connected to ground) with a mini-50k linear pot (or trim pot) and a resistor of about half the value of the original resistor. Your 5E3 is not fixed bias, it is cathode biased.
If John Wayne was a guitar amp, it would be this amp. My other mainstay amp is a Winfield Elizabeth, which is pretty close to a Blackface Pro.
This setup makes for a fairly broad plateau before complete breakup and gives a great vintage sound, perfect for First Wave Surf. I use, and enjoy using a Winfield Cyclone which is a cathode biased, 15 w, EL-84 power amp with an EF-86 in the first preamp stage. I would opine that the onset of breakup is a bit more gradual in the cathode biased mode, perhaps sounding a bit more organic as a result.įor perspective, I tend to play clean most of the time, occasionally getting up into the transitional region where the signal begins to breakup slightly. The fixed bias is a bit more "in your face", but has somewhat clearer articulation, at least to my ear. There's a lot to learn about tube amps.Nice samples. Is there a way to AVOID having to bias my amp if I can't purchase the exact same brand and model of replacement tube? Are there "like" models that can be interchanged?ĮDIT: Thanks for the input, everyone. My available funds are currently limited to a $100 gift card to guitar center (thanks Santa!). I've got cash for a new set of tubes, but not for a tech's fee. I took that tube to the shop and the guy says "you can't just throw a new tube in, you have to have a tech bias the amp". I've determined the problem with the amp is it needs one new power tube, (when I play there's a crackle sound and the tube on the far right dims when I play). 2 Here is a step-by-step procedure to determine the value. Instead, it is a pair of resistors that form a voltage divider to create fixed bias, as defined by the Radiotron Designer's Handbook. This is not a traditional cathode-biased preamp stage with an extra resistor. It's my first tube amp and I'm realizing there are headaches involved with tubes. When the circuit is redrawn, Magnatone's concept becomes clear. Anyway, he gave it to me because I play a lot and am mostly a broke sumbitch. You know the type: hordes gear, but rarely plays. I've been gifted a Peavey 212 ValveKing from a friend who has waaay too much gear.
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