3/3/2024 0 Comments Bias amp 2 tunerI’m seeing upgrade pricing for BIAS FX 2 Pro/Elite, but I’m not seeing the same upgrade pricing reflected in the bundles. To check if the prices you see are already discounted (based on the licenses you currently own), feel free to log out of our website and go back to the store section to see the original price. I own several product licenses, how do I know the upgrade price for me specifically?Īs long as you're logged in, our website will automatically scan for the license(s) you own, and deduct all the prices accordingly. Upgrade discount is applicable for BIAS FX 2 & BIAS AMP 2 in the same generation, BIAS FX 1 upgrade to BIAS FX 2, and crossgrade between BIAS FX 2 and BIAS AMP 2. On top of our regular promotion, we offer an extra 20% off upgrade discount for users with our software licenses. *Please note this article only applies to our desktop software products. (I specifically do *not* mean to go crazy in the power supply! - this recommendation is for output valve cathode bypass caps only.This guide will explain everything you need to know about desktop software upgrades. Not the case anymore, so optimum designs can be made. Golden age amplifiers used very small electrolytic caps because caps were expensive. Something like 470uF or 1000uF should do. I'd recommend a value large enough to be ignorable, that is, so big that it won't add phase shift within or even near the audio range. WRT the cathode resistors and their bypass caps, there's a big difference between bypassing common cathodes in a push-pull stage (where, at lower levels, almost no signal is expected to appear) and bypassing individual cathodes (where all signal appears all the time). The valves' operation is defined by reference to the cathodes, and if 20% of the primary windings are between cathodes and signal ground, and G2's are at signal ground, then 20% of output signal appears from G2 to cathode. ![]() Surprisingly enough, the Quad II *is* an "ultra-linear" output circuit. I will look up about the cathose bypass capacitor value tonight, but I'm practically certain it's wrong at 47uF per KT66. You need to consider that this design is nearly 75 years old and that thousands of original examples are still going strong with the original valves. I would personally remove these new cathode circuits and restore the original shared 180R||25uF(50V), making sure to use a 5W resistor, mount it well clear of the choke terminals using the full lead length available, and mount the capacitor over to the right (near the GZ32) against the chassis well away from the resistor. This allows you anything between ~58mA and ~86mA. And Quad stated that the distortion specification holds with valve current mismatches of up to 20%. ![]() I don't see where jazbo8 has said anything different, or anybody else, and if they have, they're wrong, by definition. *circuit taken from Keith Snook website with my edits for changes to the bias. So that’s 72mA and 76mA.įirstly, I wonder if I change to 420r that brings it back to 62mA and 65mA which I think is closer the intended Bias value?Īlso, I think this takes the amp out of Ultra Linear mode? Can someone confirm and also maybe offer any pro's & con's which could lead me to understand why it has been changed.Īs I say, go gentle with me, I'm very much at home in low voltage stuff but have very limited experience with beautiful big glowy glass things Resistor is 360r and I have 26.5v and 27.5v on them. My plate voltage is 357v which is a bit high? Think it should be about 330v. Mine have the R & C moved to Pin 8 on the KT66's directly and now live in front of the transformer winding. These are after the transformer winding in the path to gnd in the original. (I know this also can cause the choke to get warm and leak the tar causing choke issues). In the original circuit there is a singe R (known to be underrated) and C which are mounted on the unused choke tags. My main question relates to the relocation of the bias resistor and cap. I've got Russian PIO to go back in place of the orange caps (C2 & C3). I also see that someone has left a signature on the smoother cap body (C4&6)ĭoes anyone recognise the trade mark>? When I opened the amps, I found a few resistors changed (no problem). I was aware that there had been some preventative maint carried out previously when I picked these up. I've done some basic checks before use including the mains selector which required attention and checking the bias. ![]() These latest ones are largely original and came with the Quad 22 and FM tuner too. I've just acquired my 3rd set of Quad II amps (sold my chrome ones about 12 years ago for some god only known reason!).
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