Hi there,
I've just finished frankensteining this circuit from a couple of others around the t'interwebs, and wanted to check that what I've done will, you know, work...namely, are the XLRs connected up properly, or does there need to be a third connection on the third pin? (I assumed that pin was left disconnected unless I'd added something to the circuit that would be giving out a balanced connection, which I haven't).
Also, will the bypass switch on the highpass actually bypass the high-pass, or have I royally messed that up?
And of course, if there's anything else thats blindingly obvious, please tell me!
Finally, thanks for reading 🙂
I've just finished frankensteining this circuit from a couple of others around the t'interwebs, and wanted to check that what I've done will, you know, work...namely, are the XLRs connected up properly, or does there need to be a third connection on the third pin? (I assumed that pin was left disconnected unless I'd added something to the circuit that would be giving out a balanced connection, which I haven't).
Also, will the bypass switch on the highpass actually bypass the high-pass, or have I royally messed that up?
And of course, if there's anything else thats blindingly obvious, please tell me!
Finally, thanks for reading 🙂
An externally hosted image should be here but it was not working when we last tested it.
Well the connector is labeled "XLR" but the symbol is not that of an XLR connector. Also XLR connectors are mostly used in balanced interconnect systems. This circuit is not balanced.
Hi,
Thanks 🙂
Yeah, I couldn't see an XLR symbol, and didn't intend it (at first) to be looked at by anyone other than myself. Thinking of going with just 1/4" Jack connectors instead, considering the lack of a balanced circuit.
Also - should there be a connection from above R3 to before (to the left of) C1, to give the voltage that it needs to operate, or is that supplied from the conection that goes via R1?
Apologies - ultra-noob here 🙂
*to give the voltage that the transistor needs to operate.
Apologies for the post instead of editing...can't seem to find an edit button.
Apologies for the post instead of editing...can't seem to find an edit button.
'Edit' is only available for a limited time after a post.
This circuit will 'work' as what? High distortion is likely for signals over a few mV.
This circuit will 'work' as what? High distortion is likely for signals over a few mV.
Its meant to be a pre-amp for dynamic microphones on drums, so I would imagine that would exceed the "few mV you mention"...How would I stop it distorting? Is it the transistor I'm using, or resistor values?
No, the circuit. You can't just feed a signal straight into a common emitter stage taken straight from an elementary textbook, unless the signal is very small. Rule of thumb to remember: for a BJT fed a signal of X mV peak at the base the second harmonic distortion will be X %.
Right...After a little bit of research on designing Bipolar Transistor preamps, it looks like I should have a resistor on the base and on the emitter...is that the main problem here? Or are there other things I'm missing - should I have a darlington pair in there to make it more usable (i.e, will there be a decent amount of gain coming from just one transistor, or will I need/will it help a lot if I have the amount of gain given from a darlington)? Can you point me in the direction of an article that discusses how to design a pre that is simple, but works (reasonably) well-ish, or a fairly simple schematic?
But worth every penny. It is the best introduction for serious students of electronics, yet without the maths of a university course. There are cheaper smaller books but they tend to cut corners and create misconceptions. One exception: "Foundations of Wireless and Electronics" - various versions by Sowerby, Scroggie and Amos. Earlier versions on valves, later ones on transistors. Second-hand versions available on ebay etc. Less detail than H&H, but good for beginners. Highly thought of in the UK, not sure how available elsewhere.
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