M Fowler wrote: ......But I will see if I can tame the hum altoghter and how much (uf) I have to go to get there without resorting to a choke.
A choke is not always the solution.
A tech school instructor I had summed up a discussion of calculating power factors where inductive and capacitive phase angles were concerned. "Capacitors suck where inductors blow. They suck and they blow, what else do you need to know?"..... xPPPp..........
OK good - I was struggling to grasp that myself. The prof that taught electronics at the local University used a more traditional vernacular. In the rare cases where we talked about analog circuits the only discussion of anything blowing usually involved a fuse.
I do recall discussions about phase angles, inductors, and capacitors but had sorta forgotten about of that... maybe someone can help tie all that together with "reduced hum" as the end goal?
I think it was commentary on how far away real world components in practical application fall from theoretical calculations, rather than a useful tip ;>.....
[quote="lzzrdgrrl]A tech school instructor I had summed up a discussion of calculating power factors where inductive and capacitive phase angles were concerned. "Capacitors suck where inductors blow. They suck and they blow, what else do you need to know?"..... xPPPp..........[/quote]
A quite interesting way of describing current phase lead and lag for capacitors vs inductors.....
The fact that current and voltage is out of phase in reactive components, is exactly what enables us to use them as filter components, and phase wise extremely important in RF resonant circuits....
Hello from Santa Rosa, California. I've been on this list for about a year and have been so impressed with the amount of knowledge, thought and assistance offered here on TAG. Please pardon me if this is too detailed for my first real post, but I thought it would be nice to share my experience with building this amp.
I've been into electronics as an amateur for 45 years, and have been repairing some of my own amps for a couple of years (currently have an Acoustic 160 I bought 35 years ago, a THD Bivalve, Marsh 18 watt Marshall clone, and Dana's Lil' Devil. While I've learned a great deal each time I've worked on one, I'm no professional, and have so much to learn.
The Eagle Premium seemed like a good way to complete my first build without taking on a larger project than I have time for at the moment. The great idea RJ had to involve everyone in the design, along with the terrific quality of chassis, parts and service offered by RJ made it a really attractive project.
Tonight I finished the amp, after about 10 hours of build time. It would have taken me about 7, but I made two mistakes; reversed the polarity of C3, and did not see in the layout (and therefore connect) the wire from C6 to R4 and R6, so did not have any B+ to the input section. That took me awhile to figure out, but as this was intended as a learning tool, I took advantage of that opportunity and the chance to talk about the problem with my long-retired engineer father who gave me a laundry list of tests to conduct to find the problem. Got it all corrected, and fired it up tonight (until my wife politely asked me to please shut the hell up).
So, here are my impressions, and two photos. First, the chassis was quite impressive; thick, well formed, and very tidy. The components are all excellent quality (love that blue paint and excellent fit and finish of the Edcor transformers), and RJ's packaging and shipping were top-rate. Though he missed packing the resistors and diodes, he shipped them out the day after I let him know, along with a very kind email.
The schematic is clear, and although the polarity of most capacitors is not actually denoted on the schematic, I think it's reasonable that someone building an amplifier understand ahead of time how to orient the caps. Had I been paying better attention, I wouldn't have reversed C3, but again, it was a useful learning experience.
The amp is actually very quiet! I paid particular attention to lead dress, and elevated the heater wires above the other wires, and tried to use as little wire as possible but minimize crossing too many wires over each other (don't know if that is good or bad?), so I'm very pleased in that regard.
Because RJ was out of the Russian output tubes, I used an NOS 6V6GT, and when I was trying to figure out my lack of input stage, I swapped the heater wiring so I could use a known good NOS 12AX7, so that is the current configuration.
Having played a Champ only once about 40 years ago, I wasn't sure what to expect, but find that the tone is rather chimey and clear until the volume knob on my PRS was turned full up, and then the amp started really roaring at full volume. At half volume, the town is a little "quacky" or "honky", but that might be typical for a circuit like this, I'm guessing.
Next step in the learning process is to try a little voicing - I'd like to add a capacitor to the volume pot, but don't know what values I should start with. I might also like to put in a liftable tone circuit like the Eagle Supre. I am sure much voicing can be accomplished with different tubes and speakers, but this is about learning how component changes affect tone. Since the Edcor PT has 5V windings, I am even considering a tube rectifier, though I did read many posts from those who thought it would make little difference to tone.
I welcome any comments about the build quality, changes I should try, and ideas for voicing you may want to share.
Thank you RJ for putting this project together, and for taking time to provide such great service to me.
I hope to contribute something of actual value to this list in the future.
Cheers,
Greg Tatarian
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