This reduced grid pulse creates negative feedback, so the output triode can offer more than just its rp in opposition to the pulse, as the voltage difference in grid-to-cathode voltage prompts a larger change in current conduction by the output tube. A stronger CRC filter would r educe the ripple further, but at the price of increased peak charging currents which we find are a worse problem. But wouldn’t sourcing a power transformer with two high-voltage secondaries be a pain? VHT amps use CF after the phase splitter to drive the power tubes. The input triode o the left gets the floating power supply.
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cathode-follower output stage design part-3
Once the grid becomes positive relative to the cathode, the grid and cathode define a forward-biased diode and goes from not conducting to conducting heavily.
What if we didn’t use a cathode-resistor bypass capacitor? Since this capacitor must usually be a large value, electrolytic types are almost universally used in spite of their poor sonic reputation. So, I moved on with the 6. Click image to see closeup The frontend is a modified Aikido gain stage, which uses two 12DW7 tubes.
By comparison the simple follower reaches the numerical generator levels by about the 6th. I certainly sounded powerful, very powerful. In fact, we might try an Aikido version of this topology.
Amp Chokes, Cathode Followers, and other Maplifier Questions
As with the indirectly heated DC power, the residual ripple is reduced substantially but not completely; we feel the other advantages of this arrangement are more important sonically than just getting the very best ripple measurements. Attenuator between common cathode stage and cathode follower. The output signal present at the bottom of the output transformer primary is in inverted phase relative to the input signal, just as we would expect from a grounded-cathode amplifier. Looking forward to building the Aikido, will send some comments when I’m done!
I was just wondering whether the choke has to be sized for all frequencies or whether hz upwards would do.
If you know well your load Z you can do things to support the output current demands and unload the CF fo,lower any other output which always helps, and is dollower much faster than “Stasis” style topologies like the WF.
The following schematic makes this point. Transformers are positioned and oriented for minimal magnetic pickup as well. A Patch For Live Messenger.
For instance, in phono preamps, you often see a CF between the last voltage gain stage and the volume potentiometer. They had a White Cathode follower with a choke between both triodes. This solution makes a lot of sense, as the cathode follower offers a gain close to unity and a low output impedance.
In this configuration, the cathode-follower output stage could get the huge input voltage swings that it requires, without having to withstand V on its plate. Then the following schematic and formula is needed. What I meant with the WCF is just keeping the plate voltage folloder, versus sampling the upper plate current with a resistor and coupling from there to the lower tube grid.
Simple Tube Math & White Cathode Follower Power Buffers
If the PNP transistor’s collector had attached to the bottom triode’s grid, the phase would be off, as an increase in the MJE’s conduction must result in a decrease in the bottom triode’s conduction. Two big advantages obtain here: In other words, by forgoing a phase splitter, we have made the output stage needlessly complicated.
With an coke load, however, the bottom output xathode, the MJE, draws a varying current, while the top transistor, the MJE, draws a fixed current.
In contrast, the follower option yields a very linear transfer curve, low distortion, large headroom and very low output impedance.
Many readers have admitted to me that they are something of a fpllower klutz, a math lummox, a math blunderer, someone who is incapable of using Ohm’s law. Now, let’s get a bit more creative. Actually, we could use an inverting amplifier feedback loop that would connect to the driver tube’s grid, rather than its cathode.
The second question is the output tube working as a cathode follower or a grounded-cathode amplifier? It offers a low output impedance and low distortion but no voltage gain; in fact, it suffers a small insertion loss.
Wed Jul 13, 9: The two secondaries bridge the two outputs into a single output.
In fact, it can be used to calculate passive crossovers for use with acthode by entering 8 ohms as the terminating resistance. Building such an amplifier will require three heater windings: