THAT says said:2. Both devices (1606/1646) must be driven from a low- impedance source, preferably directly from opamp outputs, to maintain the specified performance.
useful indeed. Must've missed it. ThanksJohnRoberts said:It is pretty common to put 10dB of gain in a post fader stage. That gain stage could be your low z buffer.
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From the data sheet http://thatcorp.com/datashts/THAT_1606-1646_Datasheet.pdf
I find reading manufacturer data sheets useful.
JR
No. The days when inverting was better than non-inverting are long gone.RSRecords said:Or would it be better as an inverting amp?
I would leave them and put a small (ca. 100pF) cap to ground.also, I don't think the series resistors from the wiper are doing anything positive so disregard.
CurtZHP said:I tried it recently with a THAT 1646, placing a pot right before the input. The result was ugly to say the least.
It depends on the opamp. If you stick to OPA2134, it just doesn't matter. An opamp with significant Input Noise Current may want lower values. FET opamps have negligible INC.RSRecords said:I understand there are a few things to consider regarding that ratio. Any benefit to going lower say 5k, and 8.4k?
I'd put anything between 1k and 4.7k. That's enough to ensure it imposes no restriction on HF response (is 200kHz enough?), whilst protecting the non-inverting input from whatever HF pollution.what would I be looking at for R3? i guess I'm unsure as to what it would be doing.
abbey road d enfer said:No. The days when inverting was better than non-inverting are long gone.
You answered your own question. Opamp designers have dealt with this issue over the last 50 years.user 37518 said:When were those days? And why?, I mean I know that non-inverting can cause common mode distortion if driven with significant source impedance (this is still a problem today), but cant think of why inverting should be considered better at some point in time?
+1 Inverting is easier for multiple reasons.abbey road d enfer said:You answered your own question. Opamp designers have dealt with this issue over the last 50 years.
What happens if you short the wiper to ground (with the pot full CCW)? If there is still spill, I would suspect the grounding arrangement. There could also be capacitive leakage. Measuring would help pinpoint the issue; "ground" spill is linear, capacitive is HF only.RSRecords said:So, finally got around to building this with the above circuit. How can I increase the Kill of the fader? Getting a little bit of signal still when all the way down. I haven't measured yet to give an actual number. The fader is actually a 10k Pot so it doesn't have a switch or a fancy ground scheme like a P&G.
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