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In the Forum: Melquiades Amplifier
In the Thread: Valve Preamplifier for Macondo/DSET
Post Subject: Not necessarily...Posted by Romy the Cat on: 5/11/2019
 anthony wrote:
Well, probably not up in smoke, but it is just not functional any more.  I was away for a few days and came back to my room to find the Placette refusing to change volume or select a source input, so something is amiss.  Perhaps something has been amiss for some time which may explain why I have not found it as transparent as Romy and others.  
Ok, your Placette did not die. This is “normal” for Placette, I wish it did not have it but it does. The way how Placette is made it need to be plug in all time. If you unplug the Placette for prolog period of time then it need a few days to be powered to have the remote control functionality start operating again, the manual controls still should be working, if you have them. So, let it run for a day or two and your Placette’s control will be back. Another very important thing. The Placette is powered by main 120V power that drive output stage and by flimsy computer-grade low voltage adapter, connected separately. Why Placette was made this way is beyond me but it is what it is. The voltage adapter should be not in operation after the volume was changed so, it should not be a factor in quality. However, over the years I have seen that the low voltage adapter get weaker and impact the remote control functionality. Also, the type of the low voltage adapter I used did have very profound impact to sound, which absolutely makes no sense. I had 4 or 5 of them over the year and the difference was very noticeable. Again there is no explanation for it but it is what it is. Ask Guy to send you a new power adapter, it costs like $20-$30, and you might find that it worth it.
 anthony wrote:
On another point, I have been reading a little about pre-amplification and current output and output impedance.  Up to this point I had not realised that the ability of a preamp to drive capacitive loads has almost nothing to do with low output impedance, but is all to do about current output.  A beast such as the DSET with 6 x triodes and a few inductors and capacitors at the input is likely to be a mighty capacitive load.  This needs to be measured.  If one stage cannot sink enough current into the next (i.e. the current clips) higher frequencies will roll off.  The limiting factors are input capacitance of the DSET, desired frequency response, preamp voltage output and desired headroom.
Yes, it is factor but it is also not. There are very few topologies that can give out a very low, let say sub 10R output. Mostly we are taking about SS DC coupled topologies… It happened that in the realm of a few oHms output any devise will drive a capacitive load.

PS: I need to say that the subject of you post “The Placette has died” make me to cringe. I imagine if my Placette dies then why the hell I would be doing!? In my experience it is VERY hard to find sub 10R pream with proper sound and if my Placette died it would be a disaster for my system

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