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In the Forum: Melquiades Amplifier
In the Thread: Planning my DSET

Post Subject: The starting sequence.Posted by Romy the Cat on: 6/11/2015

anthony wrote:
Can you remember what caps you used in the HF filter? They are certainly not standard values and I do have a memory of you trialling air caps.

I presume you ask about the F amplifier channel. I use air caps 530pF and 1591pF. If you do decide to use air caps then be advised that they need to be double shielded in steel and aluminum and they are large and will be located in the location where there is a LOT of noise. I do think that that air caps is an icing over the cake and I am not sure that it is necessary. The caps do not recharge (it is where the air caps shine) in this application and they always operate in one polarity and voltage biased. So, I think a good mica or vintage tantalum or whatever you like caps might be working in this application very well.

anthony wrote:
I spent too much time today trying to figure out if I wanted a power switch for these amps and just how I wanted to switch the unit on and off. In the end I have gone for a regular Schurter IEC inlet with a fuse drawer and switch.

This is not so simple. As you turn the amp you kick on the starting sequence. So, naturally you would need a latching switch, which power your filaments and kicks of the high voltage sequence. In my case I always wanted to have the amp to be able to state and stop by pedal in order do not bend by fat body, So I needed an immediate switching latching switch, it means a short pulse (temp contact, or any other immediate event) turn the sings on and off. You can assemble a little schematic that might do it. I went an alternative way and employed a very good powerful 12A relay that did the job for me. I used Magnecraft 711XBXCL-12D, they are expensive (around $25) but they are very good. I am sure there are alternatives….

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