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Yesterday, 11:22 AM
Hi Strelok
You seem to be talking about three different things
Splitting the guitar signal using active circuitry requires as a minimum a buffer for the guitar signal. The signal can fan out from that point but the loads may interact with each other. The next point of evolution here is to use separate buffers for each output with all being fed by the single guitar input.
Remember that the inherent characteristic of a "buffer" is that it has high input impedance and low output impedance. The former allows several buffer inputs to be tied together without loading down the signal source (guitar). The separate signal paths keep the loads from interacting with each other. In this regard, this active split is far better than using a multiple-secondary transformer for splitting as the loads interact via the transformer.
Each buffered outpuy can have its own transformer for ground isolation.
Whether you need gain or not, or gain for only one output, or independent gain for each is a secondary matter. In the first form of this, the guitar would feed a single gain stage. There would be multiple buffers driven from the gain stage output, and from there it is as described for using buffers alone.
You can expand the single gain stage into parallel gain stages driving their own buffers. now each path can have its own amount of gain, which could be switched at preset levels, or be variable, depending on the specific circuits used.
For either of the split-with-gain options above, it is assumed that the guitar input is high-impedance, like a tube grid or jfet input.
The BFX mixing effects loop using tubes and to the Sigma mixer project from TUT5 both seem to be the opposite of a splitter; both have multiple inputs mixed to a single output. The mixing stage of BFX input impedance is set by the weighting resistors that are in series with the signal. Yes, these can be set quite high but then there is a noise penalty and overall there is no point to use a virtual-earth input stage for a splitter.
The Tweed mixer has high-impedance inputs, but again the goal is to mix multiple inputs into one output. The basic method of gain control here is useful in the splitter. To achieve the splitting function, you would tie the multiple inputs together but separate the anodes so each is independent.
How high an input signal can be for any of the above depends on specific circuit details. Basic buffers may be clipped by line level signals, with the easy fix of elevating the input and output voltage of the buffer and using capacitive coupling for signals. This applies to the splitter with gain, as well.
BFX as a kit is simplified compared to the Best All-tube Effects Loop in TUT to keep things simple and to cater to what the most common uses are.
You seem to be talking about three different things
Splitting the guitar signal using active circuitry requires as a minimum a buffer for the guitar signal. The signal can fan out from that point but the loads may interact with each other. The next point of evolution here is to use separate buffers for each output with all being fed by the single guitar input.
Remember that the inherent characteristic of a "buffer" is that it has high input impedance and low output impedance. The former allows several buffer inputs to be tied together without loading down the signal source (guitar). The separate signal paths keep the loads from interacting with each other. In this regard, this active split is far better than using a multiple-secondary transformer for splitting as the loads interact via the transformer.
Each buffered outpuy can have its own transformer for ground isolation.
Whether you need gain or not, or gain for only one output, or independent gain for each is a secondary matter. In the first form of this, the guitar would feed a single gain stage. There would be multiple buffers driven from the gain stage output, and from there it is as described for using buffers alone.
You can expand the single gain stage into parallel gain stages driving their own buffers. now each path can have its own amount of gain, which could be switched at preset levels, or be variable, depending on the specific circuits used.
For either of the split-with-gain options above, it is assumed that the guitar input is high-impedance, like a tube grid or jfet input.
The BFX mixing effects loop using tubes and to the Sigma mixer project from TUT5 both seem to be the opposite of a splitter; both have multiple inputs mixed to a single output. The mixing stage of BFX input impedance is set by the weighting resistors that are in series with the signal. Yes, these can be set quite high but then there is a noise penalty and overall there is no point to use a virtual-earth input stage for a splitter.
The Tweed mixer has high-impedance inputs, but again the goal is to mix multiple inputs into one output. The basic method of gain control here is useful in the splitter. To achieve the splitting function, you would tie the multiple inputs together but separate the anodes so each is independent.
How high an input signal can be for any of the above depends on specific circuit details. Basic buffers may be clipped by line level signals, with the easy fix of elevating the input and output voltage of the buffer and using capacitive coupling for signals. This applies to the splitter with gain, as well.
BFX as a kit is simplified compared to the Best All-tube Effects Loop in TUT to keep things simple and to cater to what the most common uses are.
