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09-14-2018, 09:01 PM
Hi Kevin,
When I was determining the power level of this amp, and another I built based on a Vox AC100, I was trying to figure out why the RMS power was lower than I expected it to be with both. With the Vox, they claimed 100 watts RMS, but I was only getting about 85 watts RMS going directly in the phase inverter with a sig gen and around the same with the whole amp going and a sig gen going into the input of the amp. I built that out of a Sovtek Mig 100U, but I replaced the output transformer and choke with some clones of an AC100 one from Heyboer. It doesn't make the 100 watts I thought it should but it sounds WAY better than the stock Sovtek did.
With this amp I was figuring that with four 7868's and the voltages that are in the amp (480 B+ b4 power scaling was added) and the output transformer having a 2500 ohms primary impedance that the power should be higher. I was looking for the 88 watts the RCA manual insinuated it might be. I figured it must be the transformer set that was bogging it down, but some others on some forums who have been around a long time and are very experienced said that Bogen didn't often understate their power ratings and that a CHB100 should be 100 watts. The power transformer is smaller than I might expect, but it is also using a full wave voltage doubler setup. I plan to experiment further with this setup as I was able to find another working CHB100 to play with. I might get the transformers analyzed down the road from that one too.
Its not that I want more power out of the amp necessarily. It is loud enough for most of what I might want to do and with the single speaker it works perfectly at local blues jams and what not, getting breakup at just the right volume levels. It would certainly be louder through a 4x12 or something. I was mainly wondering why it wasn't making the power I thought it should and want to make sure I am using the correct methods so that if I design an amp to do something and put out a certain power level that it does so.
If the transformer set can produce the power and the voltages are sufficient then if you input the phase inverter with a sig gen that can supply the current, you should be able to drive the power amp to max power and get the 88 watts or whatever the manual says. Since I'm not getting the power I think it should and I have tried inputting the sig gen directly into the phase inverter, then I would guess it is the transformer set that is causing the lower than expected power level?
Greg
When I was determining the power level of this amp, and another I built based on a Vox AC100, I was trying to figure out why the RMS power was lower than I expected it to be with both. With the Vox, they claimed 100 watts RMS, but I was only getting about 85 watts RMS going directly in the phase inverter with a sig gen and around the same with the whole amp going and a sig gen going into the input of the amp. I built that out of a Sovtek Mig 100U, but I replaced the output transformer and choke with some clones of an AC100 one from Heyboer. It doesn't make the 100 watts I thought it should but it sounds WAY better than the stock Sovtek did.
With this amp I was figuring that with four 7868's and the voltages that are in the amp (480 B+ b4 power scaling was added) and the output transformer having a 2500 ohms primary impedance that the power should be higher. I was looking for the 88 watts the RCA manual insinuated it might be. I figured it must be the transformer set that was bogging it down, but some others on some forums who have been around a long time and are very experienced said that Bogen didn't often understate their power ratings and that a CHB100 should be 100 watts. The power transformer is smaller than I might expect, but it is also using a full wave voltage doubler setup. I plan to experiment further with this setup as I was able to find another working CHB100 to play with. I might get the transformers analyzed down the road from that one too.
Its not that I want more power out of the amp necessarily. It is loud enough for most of what I might want to do and with the single speaker it works perfectly at local blues jams and what not, getting breakup at just the right volume levels. It would certainly be louder through a 4x12 or something. I was mainly wondering why it wasn't making the power I thought it should and want to make sure I am using the correct methods so that if I design an amp to do something and put out a certain power level that it does so.
If the transformer set can produce the power and the voltages are sufficient then if you input the phase inverter with a sig gen that can supply the current, you should be able to drive the power amp to max power and get the 88 watts or whatever the manual says. Since I'm not getting the power I think it should and I have tried inputting the sig gen directly into the phase inverter, then I would guess it is the transformer set that is causing the lower than expected power level?
Greg
