General Music Chat

SlakerG,
you seem to be in this a little deeper than I,
so,
in th e 50 watt spec it indecates 40uF filter caps throughout
but 80 uF were installed. even marshall doesn't go above 50
staying with 32 uF on the 6l6 amps.
any reasoning behind this that you know of?

I think I'll go with 40's and add a choke.

Yes. The more capacitance that you have on your voltage supply the better. (Other than the fact that it could fry you if you come into good contact with anything over 100volts., so be extremely careful)

When you install larger filter caps mfd it cleans up the hum. Another things it does is to keep the maximum voltage to the tube plate voltage higher during hard use. When you are driving the amp hard, the rectified voltage is held by the filter caps. Driving the amp hard causes the voltage on the plate to drop. For instance, if the voltage stored in the caps is 450 volts, when you drive it hard it may drop to 420 volts for a short time. A bigger cap (in capacitance) helps to minimize surge voltage drop. In other words when you hit the same note at the same volume for the same duration, the higher capacitance will help maintain the voltage at 450 volts.

The rectifier in your amplifier takes an AC voltage and changes it into a DC voltage. So the cap is really storing DC pulses. Those pulses can't keep up with the heavier load, but with the larger capacity cap, it will maintain the peak voltage longer. A big enough cap will show hardly any drop in the plate supply at the cap terminals. That also quiets the ripple caused by the pulses, so your amp will be quieter in respect to the AC noise. It does not matter how large the cap is in capacitance in the power supply circuit. I always feel the larger capacitance the better. But that also makes it more dangerous when exposed.

The only problem with raising the voltage considerably as you were speaking of before would be the maximum current limit the windings on the primary side of the plate transformer or how much current those windings could maintain. Raising the voltage would also be harder on the plates of the tubes. At one time beam pentodes were mainly used in TV flyback circuitry. In such circuitry you could get 100 watts of SWITCHING out of them. Tube manuals rated tubes in switching mode. In switching mode a tube or transistor requires far less power than in analog mode because during 1/2 of the cycle the tube is off. But analogue power requirements differ greatly since the tube is drawing power the whole time. Therefore you will get about 1/2 of the power in analogue mode.

That is why a Marshall uses two pair of pentodes and a heavily wound primary on the output transformer. Some amps use dual windings, one for each pair of tubes. Hope that helps.

yes that is a big help,
it may be that in the case of the yb1a
and the mkII esp that they are boosting somehow and thereby picking up more hum than planed for in the original spec, or as you say not maintaining B+ at demand
so they upped the cap value,
wonder why they didn't change the schematic?



http://www.lynx.bc.ca/~jc/740104_YBA1.gif

http://www.lynx.bc.ca/~jc/700912_YBA1_A_Mk2.gif

You mentioned using a choke. I do like chokes in tube circuits. However, chokes cause a voltage drop in the plate supply. I see that it already uses diode rectifiers. If you put a cap at the diode output where the choke would go, and then a cap on the other side of the choke, that will increase the voltage so that adding a choke to the circuit wouldn't make that much of a drop. However, and windings add resistance in the voltage supply and will cut down your plate voltage more than not having a choke in the circuit.

I could not see if your amps are set up that way as I have no way of turning the schematic so that I can see the whole thing at once.

I think you misunderstand the meanings of my posts,
I am not trying to hot rod these amps,
I believe the manufacturer did that already

in the case of the MkII traynor boasted 2x output out of the same el34's
as far as the yb1a I'm really trying to move it back toward the bassman 10 schematic it was obviously copied from.

as you can see from the schematic
these are not tube rectifier amps
they have diode rectified power supplies
I was actually thinking of converting them back to tube recs
for the sag.

Yes. The more capacitance that you have on your voltage supply the better. (Other than the fact that it could fry you if you come into good contact with anything over 100volts., so be extremely careful)

When you install larger filter caps mfd it cleans up the hum. Another things it does is to keep the maximum voltage to the tube plate voltage higher during hard use. When you are driving the amp hard, the rectified voltage is held by the filter caps. Driving the amp hard causes the voltage on the plate to drop. For instance, if the voltage stored in the caps is 450 volts, when you drive it hard it may drop to 420 volts for a short time. A bigger cap (in capacitance) helps to minimize surge voltage drop. In other words when you hit the same note at the same volume for the same duration, the higher capacitance will help maintain the voltage at 450 volts.

The rectifier in your amplifier takes an AC voltage and changes it into a DC voltage. So the cap is really storing DC pulses. Those pulses can't keep up with the heavier load, but with the larger capacity cap, it will maintain the peak voltage longer. A big enough cap will show hardly any drop in the plate supply at the cap terminals. That also quiets the ripple caused by the pulses, so your amp will be quieter in respect to the AC noise. It does not matter how large the cap is in capacitance in the power supply circuit. I always feel the larger capacitance the better. But that also makes it more dangerous when exposed.

The only problem with raising the voltage considerably as you were speaking of before would be the maximum current limit the windings on the primary side of the plate transformer or how much current those windings could maintain. Raising the voltage would also be harder on the plates of the tubes. At one time beam pentodes were mainly used in TV flyback circuitry. In such circuitry you could get 100 watts of SWITCHING out of them. Tube manuals rated tubes in switching mode. In switching mode a tube or transistor requires far less power than in analog mode because during 1/2 of the cycle the tube is off. But analogue power requirements differ greatly since the tube is drawing power the whole time. Therefore you will get about 1/2 of the power in analogue mode.

That is why a Marshall uses two pair of pentodes and a heavily wound primary on the output transformer. Some amps use dual windings, one for each pair of tubes. Hope that helps.

are you saying an electrolytic capacitor can fry you? I believe that unless it has a bleeder ressitor draining it off when power shuts down? maybe.

hey JCP I see a schematic at
http://www.lynx.bc.ca/~jc/YBA1Schems.pdf

Yes. The more capacitance that you have on your voltage supply the better. (Other than the fact that it could fry you if you come into good contact with anything over 100volts., so be extremely careful)

When you install larger filter caps mfd it cleans up the hum. Another things it does is to keep the maximum voltage to the tube plate voltage higher during hard use. When you are driving the amp hard, the rectified voltage is held by the filter caps. Driving the amp hard causes the voltage on the plate to drop. For instance, if the voltage stored in the caps is 450 volts, when you drive it hard it may drop to 420 volts for a short time. A bigger cap (in capacitance) helps to minimize surge voltage drop. In other words when you hit the same note at the same volume for the same duration, the higher capacitance will help maintain the voltage at 450 volts.

The rectifier in your amplifier takes an AC voltage and changes it into a DC voltage. So the cap is really storing DC pulses. Those pulses can't keep up with the heavier load, but with the larger capacity cap, it will maintain the peak voltage longer. A big enough cap will show hardly any drop in the plate supply at the cap terminals. That also quiets the ripple caused by the pulses, so your amp will be quieter in respect to the AC noise. It does not matter how large the cap is in capacitance in the power supply circuit. I always feel the larger capacitance the better. But that also makes it more dangerous when exposed.

The only problem with raising the voltage considerably as you were speaking of before would be the maximum current limit the windings on the primary side of the plate transformer or how much current those windings could maintain. Raising the voltage would also be harder on the plates of the tubes. At one time beam pentodes were mainly used in TV flyback circuitry. In such circuitry you could get 100 watts of SWITCHING out of them. Tube manuals rated tubes in switching mode. In switching mode a tube or transistor requires far less power than in analog mode because during 1/2 of the cycle the tube is off. But analogue power requirements differ greatly since the tube is drawing power the whole time. Therefore you will get about 1/2 of the power in analogue mode.

That is why a Marshall uses two pair of pentodes and a heavily wound primary on the output transformer. Some amps use dual windings, one for each pair of tubes. Hope that helps.

are you saying an electrolytic capacitor can fry you? I believe that unless it has a bleeder ressitor draining it off when power shuts down? maybe.

if you do not know what a filter cap or a start run cap can do to you,
you should not open a amp cabinet

dude, JCP I know an electrolytic capacitor can kill a person..I was not joking around.. I learned that at my TV repair class back in 1977..

a flyback transformer can kill ttooo

hey JCP I see a schematic at
http://www.lynx.bc.ca/~jc/YBA1Schems.pdf

yes that's where these came from,
well the ones I am using are glued to top of the chassis cover.
but hey are pretty much the same.

I was referring to the fact that the larger capacitance that they are the more current they store.

Voltage without current is harmless, such as walking across the dry carpet during the winter and nearing something and having a several thousand volt static charge fly from your finger tip. Put a some current behind that and it would be like grabbing the high tension wire on a power line. You would be charcoaled crispy.

Some older amps don't have resistors to bleed the caps.

dane are you drinking?

you thought process seems very erratic.

dane are you drinking?

you thought process seems very erratic.

no, I am insane.. to a certain degree