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Hi Romy,

I am planning my own DSET build.  I have based my speakers on your Macondo and am busy turning MDF horns in my spare time.  Once that is over I will move onto amplifiers.  I plan to build a fullrange Melquiades for a friend and then if that works out the DSET 6 or 7 channel version for myself.

Of course I have read the threads and am reasonably familiar with the evolution of DSET Melquiades in the context of your system but there are still a few questions.  The question at the front of my mind is the following hypothetical: 

“How would you proceed with another DSET build knowing what you know now?” 

If you are willing I would like to work through this in stages.  This is a project that will evolve with time as I build the speakers and move them into the new room.  Initially there will be 5 Channels:

Raal Lazy Ribbon - Direct Tube Drive
S2 into 400Hz tractrix
S2 into 250Hz tractrix
Fane 8M into 115Hz tractrix
Scanspeak 25W/8565-00 towers – 8 drivers each

Then, if the results are satisfactory and the final position of the speakers in the room permits I will experiment with:

K15/40 Midbass Horn
Injection Channel

A very familiar system to you indeed, and I hope you don’t mind me using it as my starting point.  I don’t want to spend a decade or two trying to develop a satisfying horn system from scratch so I am using your documented experiences to make a strong start so that with any luck and a measure of persistence my system is matured within a couple of years and I can let the whole diy thing pass for other endeavours. 

So, to start, I am unsure of a few things regarding the operation of your amps.

• Bias adjustment in the first stages.  Looking at the final 6 Channel circuit diagram the bias for Channels A, B and C are all fixed and non-adjustable.  How do you manage the varying gain of the 6E5P tubes?
• Gain structure.  What is the output from your pre-amp?  Mine is 1.5V RMS and 33 Ohm.  I am trying to get an idea about my required size for the 30K input resistor.
•   ULF through the Scanspeak line array.  My calcs are that at 15W, the SPL at the listening chair would be about 98dB at 20Hz, and much higher at 100Hz.  This is loud enough for sure, but in your experience is the 6C33C/Scanspeak combination good near the amplifiers maximum power?  

Regards,

Anthony

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