![]() Now, multiply that by 2 for Stereo (well, only one bias supply). Multiply the potentiometers by 2 for Stereo. Just like so many things, it is a tradeoff.įixed adjustable bias for a pair of push pull tubes: #HEATHKIT SA 2 MANUAL#That means the (fixed adjustable) manual bias robs from the range of the self bias circuit (less auto adjustment effect).Ī self bias resistor that gives all of the bias has a good self adjustment range (no fixed bias circuit).Ī self bias resistor that gives only 1/2 of the bias voltage, only has 1/2 of the self bias auto range (1/2 of the bias in the fixed bias circuit). Global negative feedback can not fix some of the errors in the design and implementation of an amplifier, and this is one of them it can not fix.Ĭombination bias gives both some auto adjustment range, and some (adjustable fixed) manual bias adjustment range of the current.īut the amount of auto adjustment due to the self bias resistor is proportional to the ratio of the resistance of the self bias resistor, versus the impedance of the cathode. It shows the increased distortion at 20Hz and even at 100 Hz, when there is just a small un-balancing of the push and pull quiescent DC currents.Īnd, that graph was taken With the global negative feedback. If you have any doubts about the extra distortion caused by un-balanced DC currents, look up the very last 2 pages of the Heathkit W5 amplifier manual. In regards to power at 20Hz, nothing will ruin the distortion faster than unbalanced DC in the push and pull windings. 1dB less power of 13.69 Watts is so much quieter.ġ dB difference of continuous power will not make any difference, both will burn out 95% of all tweeters. If you need 17.22 Watts at 20kHz going to your Tweeter, then you need to use fixed bias for that pair of EL84 /6BQ5. Each Manual is digitally scanned and all pictures and images are reproduced in the high resolution mode to assure the best quality in document re-production. Serviced Vintage Heathkit SA-2 stereo tube integrated amplifier EL84 6BQ5 The failed small electrolytic capacitors have been replaced by modern high quality. Those large bias voltages do rob lots of B+ voltage when you use self bias, and that robs output power. Heathkit SA-2 Stereo Amplifier Assembly Manual CopyThis Manual was Re-produced using a State of the Art, Sharp Laser Printer with the High Resolution Scanning option. It is not a large Beam Power tube, or a large Pentode, they require 30, 40, or 50V of bias. Thanks for the help with the Antenna's and for all the small things that you have kindly let me have, but especially for the Elecraft K3 that you let me buy off you, I love her lots.First of all, the bias voltage for EL84 / 6BQ5 is only a few volts. Thank you so very much for all that you have done for me in the past with the trips to Germany, and especially for letting me have the Yaesu FT-2000 whilst I was in hospital in a very bad way and the help with the antenna, your kindness is always appreciated. I am selling this beautiful Antenna Tuner as is, as described for the family of a silent key. She will be cherished and well looked after and your kindness will not ever be forgotten. This Heathkit SA-2060A HF tuner covers 1.8-30 MHz with a capacity of 2000 watts peak SSB, 1000 watts CW with impressive specifications. I really am lost for words, for the kindness that you have shown me and the outstanding Yaesu FT-ONE that you have sent me, every time that I look at just how clean she is it blows me away. Thank you so much for all the Drake Equipment, Spare Valves and Various bits of Amateur Radio Equipment, it is going to take me months to go through and sort out what I have, but it will be well taken care of and looked after as best that I can. Those who are Amazing and sent me equipment to Restore or look after: #HEATHKIT SA 2 UPDATE#Thank you so very much for your kindness, it honestly blows me away, and it helps me so much especially on those days when I am not even able to get out of bed, it is really greatly appreciated and it is the least that I can do to thank you here on this site.Īlso I would like to send a BIG thank-you to ' All' those people who have kindly registered on this website, your kindness is helping me keep this site going and allowing me to constantly update it, Thank you so much. Those who Kindly Have Donated to the Site: This amp is the stereo version of the UA-1 or UA-2 mono amps while it also has a preamp and phono section. This is just my Small way of Saying Thank-you to hose that have shown me kindness and Supported the Website by either donating to the upkeep or those that have very kindly sent me kit to restore. ![]()
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