Recent content by dtbradio
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pop noise during warmup
Wasn't thinking of that, but makes total sense.- dtbradio
- Post #22
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
Ok, thank you! That makes 100 sense. Always learning!- dtbradio
- Post #26
- Forum: Vacuum Tube Audio Forum
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pop noise during warmup
I do understand all of that. However, the tube isn't conducting anything until it warms up, and it doesn't instantly warm up. Where would such a fast transient happen in the tube itself during warm-up that it would cause a sharp pop? Especially curious since the OP's info narrows it down to a...- dtbradio
- Post #13
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
Not trying to argue, but the Baldwin 46C organ that this amp unit came out of was running full voltage from its 5U4-based supply (which I am now using exactly as it was wired in its original configuration) up to the eight original 6BQ5's. The unit was built in the 1950's and the power amp...- dtbradio
- Post #23
- Forum: Vacuum Tube Audio Forum
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pop noise during warmup
Would in-rush cause a sharp pop? Even with solid-state supply, wouldn't the change in current be slow enough that it would sound softer than a pop? To the OP, have you tried different tubes of the type causing the pop?- dtbradio
- Post #11
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
I found a working 5U4 in my random tube box and connected it up. I'm getting 390 volts with just bleeder loading, and with the two 6BQ5's in and biased at about 7 watts each I'm seeing about 369 volts. Bias current is sitting at about 19mA per tube, using separate bias controls for each tube to...- dtbradio
- Post #21
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
Again, thanks for all of the input! The OPT, tubes, PT, etc were all part of the power amp section from a Baldwin 46C organ. It had a 4-tube amplifier driving a 15" Jensen bass speaker, plus a pair of 2-tube amps driving a pair of 12" Jensen full-rangers. The only difference is I'm using solid...- dtbradio
- Post #20
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
The OPT is terminated with a 15-ohm resistor.- dtbradio
- Post #16
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
I will post the circuit once I figure out why my scanner isn't working...- dtbradio
- Post #15
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
Confirmed shorted transformer, tested out of the circuit. Will take it apart if I get time to find the actual short and maybe even attempt a rewind for the learning experience. Good point on the different biasing needing different grid leaks, totally was overlooking that. I went back to fixed...- dtbradio
- Post #10
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
Yup, OPT shorted out. No idea how or why, but luckily I have two more from the same organ amp chassis. They are only 24 watters, though, so going to have to go with just a pair of the BQ's. Darn...- dtbradio
- Post #8
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
So another .1 (or .01) in series with the existing .1 PI input cap? Strange that I've never encountered injector coupling problems with any of my other amp builds, unless they were there and just not recognized. Yes, it is for a bass amp. Are you referring to grid stop in the PA or PI? After...- dtbradio
- Post #5
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
Thank you for your reply! The input cap on the PI blocks DC, making it an AC-coupled circuit. No additional cap needed or desired, as that would affect frequency response.- dtbradio
- Post #3
- Forum: Vacuum Tube Audio Forum
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Strange soft-clipping artifact
I encountered an odd-ball this morning. I'm working on my first attempt at a tube bass amp using the tubes and iron from a Baldwin 46C organ amp chassis. The power amp is a quad of 6BQ5's. I have the power section cathode-biased at roughly 65% for safety, and the PI is a JCM800 circuit but using...- dtbradio
- Thread
- Replies: 25
- Forum: Vacuum Tube Audio Forum
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Power supply sag and load lines
Hi All! I've been looking around Google, etc, trying to find any general rule of thumb with regards to power supply sag when calculating load lines. The measured B+ when the tubes are cold always drops when the tubes begin conducting, barring a regulated HT supply. Maybe I'm over-complicating...- dtbradio
- Thread
- Replies: 1
- Forum: Vacuum Tube Audio Forum
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