Given this extra information, your multiplexed design makes sense. As long as you keep the Nixies physically distant from the amp input signals and tubes, and give yourself the option of steel shielding if needed, you should be OK with the Tayloredge supply and multiplexing.
David Forbes http://www.cathodecorner.com/ On Jan 4, 2013, at 3:20 PM, Tim <halfpint_ti...@hotmail.com> wrote: > Hi, > > Thank you for your reply David. My reason for multiplexing was due to not > having enough spare pins on the PIC, however having givin this considerable > thought I have the IO pins that were being used to switch the MSD and LSD > anode transistors and a third IO pin which was available to control the > enable pin for the tayloredge SMPS, so by using these three pins allows me to > to have 0 - 7 on the MSD which is great as I wanted 64 steps to indicate the > volume control potentiometer position. > > Sadly there is a but to this (is there not always) I need to be able to blank > the digits which normally involves using all 4 bits of the 74141. Now as I > do not need 7 - 9 I was thinking I could shift all the digits along one > position, so 0 in the nixie is connected to 1 on the 74141 1 to 2 and so on. > This results in being able to blank the nixie by sending 000 to ABC and > having D permanently tied to ground. This digit shift being easy to work > around in the firmware. > > I can position the SMPS in such a way that it will not interfere with the > audio signal path so I would like to try and stick with it for the nixie HT > supply as the valve HT supply has a delayed start to give chance for the soft > started heaters to warm up. I want the volume indication to come on at power > up with a possible count down on it to show the remaining warm up time. > Additionally to this I am trying to keep the analogue and digital power rails > separate from one another. > > This is where my questions begin: Can I leave the cathodes 7 - 9 floating or > do they need to be tied to something? Will floating digits ghost? I would > also like to keep my enable signal to disable the SMPS when the amplifier is > in standby so can I use the now unused 0 output on the 74141 as a logic > signal to drive the enable pin on the SMPS? The only trouble with this is > when blanking the nixie the SMPS will be disabled unless I use extra logic to > look at the LSD bits? (I guess it is quite environmentally friendly to turn > the SMPS off when the digits are blank but if I was worried about this then I > guess I would not be building a power hungry inefficient valve amplifier!) > > Regards, > Tim > > > > On Wednesday, 2 January 2013 22:25:13 UTC, nixiebunny wrote: > On 1/2/13 3:01 PM, Tim wrote: > > I am in the process of building an audio preamp using valves and I am > > using nixie tubes to indicate the volume control position. I am using > > two nixie tubes to indicate the volume and they are being multiplexed > > via a PIC and 74141. > > > > My question to you fine folk is how should I provide power to the nixie > > tubes. I have two options available to me: > > > > > > Regards, > > Tim > > Tim, > > If you can afford the extra four pins on the PIC and another 74141, then > you can run the tubes direct (non-multiplexed) and not worry about it. > > If you will be multiplexing them, then the power supply will not conduct > the noise to any noticeable extent. You will need a high anode resistor > value, so you can insert a simple two-stage RC low-pass filter (10K > series, 0.1uf polyester shunt) between the power supply and the anode > resistors to eliminate noise from the anode power. > > You will want to be careful about mounting the display unit away from > the input stage of the amplifier, to prevent radiated noise from getting > into the input stage where it will be amplified. > > -- > David Forbes, Tucson AZ > > -- > You received this message because you are subscribed to the Google Groups > "neonixie-l" group. > To post to this group, send an email to neonixie-l@googlegroups.com. > To unsubscribe from this group, send email to > neonixie-l+unsubscr...@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msg/neonixie-l/-/wzW1euMoJw0J. > For more options, visit https://groups.google.com/groups/opt_out. > > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
