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In the Forum: Melquiades Amplifier
In the Thread: Single-stage Melquiades vs. DHT amps
Post Subject: Some clarifications.Posted by Romy the Cat on: 4/19/2009
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Ok, I have figured out why I have so extended bandwidth over 73kHz for my tweeter. I forgot that when I measured it I had the LPAD wide opened and in this configuration the parallel resistor is 20K and series is shorted. So, in that case I had just one 12K bias resistor against the grid and the full HF bandwidth of the original not restricted Milq. That explains the mystery part and my concerns with HF.
Now is the explanation of the idiocy part. I consulted with a friend of mine and dumped to him my dilemma with limited up to 23KHz bandwidth of MF and the ugly square wave. He listed me carefully and then asked: “So, what is the problem?”
According to him the HF limitation of my MF is perfectly reasonable and the square wave is very much what shall be expected. He explained that order to write the correct square wave via an amp the amp shell have at least 10 times extra bandwidth. If I have 5kHz square and try to do it with 20kHz bandwidth and at full amp neat clipping power then he would not expect anything different then what I got. I do not completely agree with him but his explanation certainly removed me from an alarmist position that something is wrong with my MF channel.
The greatest result after his explanation was that I might not blame the topology and HF restriction in the some minor subjective dissatisfaction from the Sound I am getting listing my new DH MF channel. It is not that I have dissatisfaction but I would like to have more “brisk”. Well, it suddenly come to me: perhaps I need to stop to make my assessment listening FM? Anyhow, here what I think. I need to finish the amp with not temporarily hook up wire, not the temporarily prototype grounds and not to connecting the amp with 25” Radio Shake-bought interconnects and speaker cables. I mean I need to finish the DH channel as is with the same precision and accuracy as my single-stage MF channel is made on another amp and then to compare the results. If after then I’ll feel that I might stress my S2 driver more then I would go do for 25:1 coil for my output transformer. According to my measurements with 20:1 output transformer I need 3,5:1 innerstage transformer. If I go 25:1 or even insulting 30:1 then I will still have spare ration in my innerstage to release.
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