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~misfit~[_3_] ~misfit~[_3_] is offline
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Default Attenuate highest highs?

On 19/02/2020 3:45 am, Peter Wieck wrote:
Please note the interpolations.


so there might be relevant info there. I'm using a very basic pre-amp with no tone controls and a certain Dynaco ST120 power amp. There is a pass-through crossover between the two taking everything below 70Hz to a 10" subwoofer as described in another post.


I see that. And you mentioned that the Sub amp has a level-control. Have you tried boosting that just a bit?


Yes. I've tried boosting and dropping it. In fact I adjust it depending on source material. With
older source material it sounds better with a slight boost, with more recently recorded stuff I
drop the bass level a bit as it can become overpowering.

Were I to run the system "flat", I would have exactly the problem you describe. The 3x has a 'loudness' switch that boosts the bass relative to the treble, just a bit. That allows a more balanced perceived sound at the low levels I use. That capability went out of style more-or-less in the 1980s. The other option would be an outboard equalizer - overkill certainly, but an option.


I've been watching auctions for good quality EQs but unfortunately anything other than used
gimmicky plastic 90s things (that people seem to ask new prices for) are well beyond my price range.


The SE-10 I mentioned came my way for $0, as it was perceived as totally dead from the BIN (Buy-it-Now) pile at Kutztown. You will notice that the fuse is inside... and missing in the example I found. As I have my original example purchased as a kit, I do not need two. So, to you it would be cost-of-shipping, not inconsiderable.


Thanks for the kind offer.

The 'disrupter' method, while cute, may require you to try many sorts of materials before you are satisfied and/or may require different materials based on the signal at hand. It does *work* however.


Getting back to your sub-amp. I am assuming that it is strapped for a single output at 300 watts into 4 ohms.


320 watts into 4 ohms and 200 watts into 8.

For the record, driving 2N3773s in that configuration to 300 watts is wildly optimistic. Much as one *can* operate a Ford Focus engine at 6,000 RPM - just not for very long.


It uses three pairs of 2SK1058 / 2SJ162 TO-3P power MOSFETs.

All that aside, I also understand that particular amp sometimes has a problem amplifying mains current hum? When I looked it up, I saw no associated power-supply (or, to be fair, no transformer) or diode/capacitor block. Just a "suggested power supply" http://home.alphalink.com.au/~cambie/PM300/PM300.htm I would also 'fix' the bias (replace the pots) for stability, once you are sure of the proper value(s). A number of US manufacturers used pots back in the day - and as the pots went open, all that magic smoke escaped. And given that device was designed c. 1980, that may be a consideration.


That's a different amplifier. Unfortunately it seems they recycled the name. The unit I'm using was
described in Electronics Australia 1995-04 and 1995-05 issues and was sold as a kitset through
Jaycar Electronis and Dick Smith Electronics in Australia and New Zealand.

The power supply uses a 300 VA toroidial transformer and has 20,000uF of capacitance on each
channel. The active crossover was previously released as a stand-alone kit (1994-09) but integrated
into the same case as the power amp in this version.

I have pdfs of the magazines but can't find them hosted on-line anywhere.

Cutting to the chase, try playing around with the bass output levels, and keep in mind that pretty much anything below 500 HZ is non-directional in any case - such that distance between the treble source and bass source (and you) are the governing factors, not direction. Leading to having the bass source, ideally, the same physical distance from your ears as the treble source. Do also verify phasing - speakers out-of-phase give all sorts of unhappy effects.


Thanks. The sub is directly below the left channel (bookshelf) speaker, facing the same way. I've
tried swapping the phase and it sounds best in-phase. The output from the subwoofer is more than
enough (and I like good clean bass) so that the level control is rarely above ~85% - and that high
only with material recorded in the 70s and early 80s (such as Rickie Lee Jones' eponymous album on CD).

I rarely have the issue of half-heard fatiguing highs on older material. It's mainly on stuff
recorded after 2000 or so.

Some "stuff" on that: https://us.kef.com/blog/how-to-get-t...nd-positioning

Some further experimentation with placement may be in order.


I'm a bit limited within the space in which I use them but have experimented with toe-in and
subwoofer placement and the current set up seems optimal - except for that annoying half-heard high
frequency stuff. Maybe it's just that my age, the condition of my hearing and these otherwise
excellent speakers aren't suited together?

That would be a shame as they are by far the most revealing and best imaging speakers that I own.

Cheers,
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy little classification
in the DSM"
David Melville

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