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Salas 24th November 2016 09:31 AM


Originally Posted by Siberia (
Bah, now when you said it, I found out, it's out of stock for stereo in my usual go to online store

There is the 10K log Tocos also that's easier to find but I don't know about that releasing too much bandwidth. I would prefer 20K for 1MHZ bandwidth. Maybe getting 10K and 50K (500kHz BW) since they are cheap and decide in your specific system. Keeping the less preferred one for another diy project.

massimo 24th November 2016 09:42 AM

Salas, isn't the input filtered by the 10pF cap? 500kHz is my estimate.

Salas 24th November 2016 09:55 AM

Massimo I had measured -3dB (0.707) sinewave very near to 1MHZ for 20K log pot at half signal volume position with the 3.3K 10pF filter in place. I have 40MHZ sinewave generator and 200MHZ oscilloscope which are very consistent for vertical at few MHZ frequencies. I hope I did not make some mistake but I remember I had checked a few times back when I was developing the circuit.

massimo 24th November 2016 10:11 AM

No doubt it's a wide bandwidth design and your Rigol is (much) better than mine, not to mention the signal generator! :D

Salas 24th November 2016 10:14 AM

Remember at half volume (-6dB) the source impedance seen by the preamplifier is quarter the pot's nominal value. Calculate with that in mind plus R1 3.3K (when assuming very low audio source impedance)

Salas 24th November 2016 10:33 AM

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Just to double check. The simulator finds 800kHz with 20K pot at half and LSK389C which states 25pF Ciss so with the uPA that states 15pF the about 1MHZ test figure should have been right.

ammel68 25th November 2016 05:16 AM

I signed up for the GB for a preamp board and matched transistors.

Any idea when Tea will be sending PayPal invoices and shipping the boards/parts?

Sent him a PM with my PayPal address several days ago, but haven't heard or received anything from him since.

Stixx 25th November 2016 05:38 AM

GB was closed 11/20... did you sign in before?

lykkedk 25th November 2016 06:42 AM

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So i was out trying to find some headphones to try out 😄

But there are not much to try around here unfortunately.
Anyway i tried some pioneer out... They where good
enough; but headphones with bassboost, is not was
i was looking for.


ammel68 25th November 2016 04:49 PM


Originally Posted by Stixx (
GB was closed 11/20... did you sign in before?

Yes, I did.

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