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In the Forum: Melquiades Amplifier
In the Thread: Valve Preamplifier for Macondo/DSET
Post Subject: OopsPosted by anthony on: 6/29/2022
Hi Jarek,

Apologies for missing your post.

To answer your questions:

(1) Yes and no.  I've bundled the preamp into its new chassis (that I made from scratch) and it does not sound as good as before.  There is a grounding problem with the new installation that I need time to track down and I am only getting volume from even numbered volume settings on the attenuator, not the odd settings, which is weird, but related to my grounding issue.  The preamp has sat there for some time waiting for work to calm down a little to give me weekends to myself so that I can do this last little bit of work to get the preamp back into use.

(2) I have been using Ales operating point.  However, I have a new source that puts out almost 4V and it will drive the preamp input to audible distortion so I will have to bias the 801a/10y deeper, probably around -10V.  Once the grounding issue is sorted I will pull out the audio analyser and figure out just where to bias the valve to suit that high input source.

(3) No decoupling with a new cap...although there is already the series cap at the output of the hybrid mu-follower that rids DC from the output.

(4)  Initially just sic filament bias.  I do have other options here to try once the preamp is operating correctly.  Reading descriptions of sound from other builders I think the sic diodes will probably suit Macondo/Melquiades most appropriately but only time will tell.


However, and this is a big however, I personally need this preamp, or something like it, because I have high input amps (4Vrms) and low output sources (1Vrms) and I like to listen loud which Macondo/Melq does unlike anything else I have heard.  If you do not need the gain in your system, there are likely to be better preamps about or even a more conventional DHT preamp using a good output transformer and a suitable tube (not the 10 family:  perhaps 71a if you can tame the microphonics).  

Entire system gain structure is much more important to good sound than any particular qualities of the preamp.  If I didn't need the x8 gain from my preamp I would be using a different pre with just the right amount of gain, no more.  The 10y/801a is the right tool for my job, but it may not be so for yours.  

Listening to the Placette active linestage with my new high output dac is very nice indeed and I do appreciate what Romy values in this setup, and if my sources all put out 4Vrms then I would have no need for the 10y preamp in its current guise, or the 10y tube at all.   
Anthony

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