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In the Forum: Melquiades Amplifier
In the Thread: Output transformer for bass-channel of Super Melquiades.
Post Subject: Output transformer for bass-channel of Super Melquiades.Posted by Romy the Cat on: 8/17/2007

Further looking at where I would like to take the new 6-chennal version of the Super Milq I am contemplating a new revision of my bass channel output transformer. Currently I have Jack Elliano’s made 450mA, large, single section LF transformer that begin to roll somewhere around 800Hz. The transformer ha s a lot of core mass and at full Melquiades’ LF power (~20W) it begins to clip around 7.5Hz. The transformer loads the full 6C33C surprisingly hard, somewhere around 250Ohm, but I do this strange load not because power considerations but the very freaky response of my LF drivers to higher load – they juts sound  more properly this way. (Though they very finicky – a change of load for .25R immediately troughs sound to junk). This somehow ridicules configuration in terms of loading. However, it does look like very appropriate what I measure it: the full 6C33C tube at 225V/210mA and being load as is clips simultaneous at voltage and current. Also, sonically I hear no problems with this operation (do not forgers that I use 6db filter on bass and any excessive harmonics that uselessly come with hard loading would not be welcome).

During the last could weeks I talks to deferent people and it looks like I will underwrite the project that I have been drooling for over a year – to make the same dedicated LF 7.5Hz transformer as I have only with amorphous core. I really have no problems with bass as now but I would like to take advantage of the amorphous core’s articulation, transients and dynamics. Go figure how it will work on bass….

It will take for a while to my transformer people to figure out how to make the LF optimized amorphous core transformer and I think the result might be interesting to observe. While doing this new transformer I would like to switch my woofers from 3 parallel sections of series connected 8R pairs to all parallel connected. The 6 of my beloved 25W/8565-00 woofers connected all in parallel would make 1.3R load. Also, I will be dropping the voltage on the 6C33C from 225 to 200V.

Since the 25W/8565-00 drivers are so fastidious I would need some kind of playground to experiment how I would need to load the bass plate… I have an extra 8:1 Electraprint LF transformer and I could take off the turns from secondary but it would model/predict the sound with M6 core not the amorphous core. Dima proposed to wind the amorphous transformer with bifilar or tryfilar in order to have multiple connection options but this solution will give too large loading gap. I do not what to have taps on that transformer as well… I do not know what to do at this point…

Frankly, I do not see a good solution yet.  I see a lot of system management problems with any variability of my LF transformer load. The LF in Melquiades, since it is the less sensitive channel, it sets the reference much I need to attenuate the input signal on my channels that drive horns. Since the voltage divides in the Super Milq input are not juts simple attenuators that feed of the driver tube’s grid but also they set the 6E5P’s bias and act as part of the input filters then I would have great difficulties to match faxably the attention of the horn channels to any change of the LF gain. Not to mention that in the single stage channels I would like to have adjustable plate current 6E5P…

Still thinking….
Romy the Cat

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