Technically ripple is from rectified AC. It is strong pulses derived from the mains (60Hz) frequency. Here in the US, full wave rectified, the pulse will be 120Hz (double the 60Hz) but there are some harmonics at multiples of 120Hz. The filter caps and dropping resistors make low pass filters which let all frequencies above around 1Hz, (yes, that is like one wave per second), to ground. The ideal is to have pure DC power with all AC content filtered away.Doesn't introducing AC into a filter cap induce ripple?
I am concerned about the 90mA PT as well. The real test will be how hot the PT is under load. Since there is some good info about a 90mA PT being original to this amp along with the knowledge the Princeton had a PT rated at 70mA... I am optimistic this PT will pass muster. Time will tell.First, because it is worrying me, I've done calculations for the HT current draw
Well the larger bottle is known to be more microphonic.Sonny Reverb has reported an issue with microphonic noise on V2, the pre-and post-reverb intermediate amplification stages
Maybe I'm don't have the electronics smarts to see what the problem is there. The datasheet for the 6SN7 has it rated at 5 W/section, and 7.5 Wcathode for combined for both sections. I've pored over a lot of information about this amp, both factual and anecdotal, and I don't remember folks complaining about it burning out preamp tubes.How does V3A get away with running continuously at 2.6W (service manual volts)?
My hunch is that, like Fender with the Tweed Deluxe and Princeton Reverb, Ampeg was expecting some PT "sag" in voltage as a trade-off to suck more current out of it -- a cost consideration. One of the benefits of having more primary voltage now is that the transformer may well put out the required current at a somewhat higher voltage than it used to with 117 V supply, but as you say, it may get hotter. I'm not the sort of person who's going to overtax an amp, though -- I play on the "polite" side, under "bedroom in a big apartment building" conditions where I pretty much have to be.I am concerned about the 90mA PT as well. The real test will be how hot the PT is under load. Since there is some good info about a 90mA PT being original to this amp along with the knowledge the Princeton had a PT rated at 70mA... I am optimistic this PT will pass muster.
You got me there. A tube will not be microphonic because of reverb.I don't understand how V2 being microphonic is because of the reverb.
Maybe I'm don't have the electronics smarts to see what the problem is there. The datasheet for the 6SN7 has it rated at 5 W/section, and 7.5 Wcathode for combined for both sections. I've pored over a lot of information about this amp, both factual and anecdotal, and I don't remember folks complaining about it burning out preamp tubes.
Well the larger bottle is known to be more microphonic.
I realize the 6SN7 has far less gain than a 12AX7, but it is reverb driver. Think of it as single ended amplifier. Instead of driving a speaker this transducer wiggles springs. In the Princeton it is like diming one of Rob's micro amplifiers 100% of the time. Lead dress and maybe even backing off some gain is likely very important just like in a Princeton Reverb.
Just how hard is that tube being pushed? Something to think about.
Isn't microphony a result of uncontrolled oscillation?
OK, so snubbers don't have anything to do with microphonic tubes. And microphonic behavior has only to do with physical exposure to sound waves or other vibration? So the only fix is to isolate tubes that tend to be microphonic is physical isolation from such vibrations?
Are snubber caps intended (according to something found by googling) "to reduce the impedance rise at high frequencies due to the parasitic inductance of the main electrolytic capacitors"?
I also read something about them helping to reduce the current load on the plate resistor and plate due to higher frequencies.
I agree it has been misused, and I am guilty of misusing the word. I think it is more correct to use the word *snubber* to describe a cap across a switch.Not sure I even know the official meaning of “snubber”.
Yes, you're correct.
Based on what I've learned about 'em, this is a very early Reverberocket. Another clue is on on the tube chart (the handwritten "R" after the model), because they did make R-12 Rockets before they made Reverberockets. They used a Rocket label in this one and wrote an R there. This info I got from Ken Fischer (RIP), who worked at Ampeg when these were being built.
Being that the Reverberocket was the first amplifier built with onboard reverb, it makes this particular amp pretty kewl.
I'll take a peek under her skirts tomorrow when I get some time, and record some voltages.
Here are pics of the PT and OT. It does have a PT-106 installed.
'926' on the PT is the EIA code for the manufacturer--Todd Electric Company of Yonkers, NY. '129' is the production date: 1961, week 29.
'682' on the OT is the EIA code for Electrical Windings Incorporated of Chicago, IL. '112' means the 12th week of 1961.
More info as I get time... Cheers!