** A better engineering solution might be to select one tube that is large enough to do the job. It is my opinion that doubling the feedback-C by using two tubes is only an advantage if one is tryin
** The TS-440S I use for driving a 2, 3-500Z amplifier produces more distortion than the 3-500Zs. I want to increase the amplifier idling current in the 440 to improve linearity. VR1 and VR2 apparent
Amen. Circuit-breakers are not nearly quick enough. One problem is that, during an "oscillation condition" (Eimac/WB Foote) the top layer of gold can be evaporated off of the gold-plated grid before
Jackbooting anyone off of a mailing list is an open invitation for him/her to play the Persecution Card, The best censor is the members of AMPS themselves. This is accomplished by limiting responses
** some people either fail to see the obvious -- or maybe they enjoy hair-pulling and watching WWF wrestling on TV when they ain't postin' on the Internet? cheers, Joe. - Rich..., 805.386.3734, www.
This usually indicates a push-pull oscillation c. 55MHz. There is no big-bang and no destruction like a push-push oscillation. Is the 21MHz bandswitch position making contact with the L ? When a DC
The amp that gets the most compliments from visitors who know little about amplifiers is by far the best. From an educational benefits standpoint, an HF amp design that uses no parasitic suppressor
The net IMD improvement of raising the 440's supplied V to c. 16v (the max allowed), and raising the zero-signal collector current (ZSCC) in the driver to 250mA and final to 400mA -- was not scientif
Your drop-test does not appear to be reasonable. tnx Have you read the amp article in the Jan 1994 QST? The original manuscript is on my Web site. None of 'em are perfect. The best bet is to read up
** Some second thoughts: If a mfg designed an amplifier that did not have some oversights or some marginal components, the service dept. would have virtually no work. - Rich..., 805.386.3734, www.vc
** 60-seconds is enuff. ** Tom Rauch said pretty much the same thing to me at the end of our conversation on the telephone. Apparently, I am not easy to convince that the RF-R of Ni-Cr resistance-wi
yes, but the transient-regulation will be surprisingly poor. I did an experiment with a non-resonated choke ps, and the transient-regulation was worse than +/-40% as seen on a dc 'scope, however, on
In my experiences, parasitics are iffy because not all tubes of the same type have the same vhf-gain. The 2 x 3-500Z amplifier [a friend's factory-stock TL-922] that produced the toasted bandswitch o
** Not quite, Mauri. The 8877 has about 2/3 as much feedback-C as the 3-500Z, but it has about 2x as much gain at 100 - 150MHz. 3-500Zs have a history of vhf parasite problems, so the 8877 should no
8, 500V caps = 4000V. 10, 450V caps = 4500V, so it should have even more headroom. Sounds kinda like a multiplier resistor problem. - Rich..., 805.386.3734, www.vcnet.com/measures.
** Agreed, Ian. However, VHF amplifiers do not have two resonances to deal with in the anode circuit - wherein the tube exhibits substantial gain. HF/MF amplifiers uniquely do -- one at the operatin