projectx102 wrote:Would it be giving away a huge secret to tell what the filtering is in the SL68? All I want to know is what the pre-amp cap is
Flames1950 wrote:250-330uF like Marshall used is way too much cap for the application. A simple 25uF like Fenders use should give a gain boost to all frequencies relevant to guitar or bass.
To lower the bass response you could use a smaller cap in place of the 250uF to focus the gain boost away from the bass frequencies. A 3 to 5uF cap would focus that boost on some nice hot midrange and high frequencies.
projectx102 wrote:As far as filtering goes looks like the two positives of the screens caps are tied together. So it's possibly a total of 32uF on screens.
Something I noticed in the gut shot John Suhr provided. Also, a few mentioned the specs; in particular the mixer and tone stack capacitors. I believe, 470-470/470pF mixer and 500pF (or 560pF) tone stack caps is incorrect. Looking at the picture carefully, I noticed a few things regarding the mixer cap and tone stack caps; the caps are longer than the resistors around them. And, I'm sure we can agree that John is using 1/2 watt resistors (they look to be Xicon).
So, what is my point? Glad you asked I've provided a picture that compares a 1/2 watt Xicon resistor to the CDE mica caps that are used in John's amp. The top cap has a value of 200pF (1000v) and the bottom two caps are 500pF and 560pF (1000v). All three caps are of the same type. I have (obviously) the 200pF, 500pF and 560pF CDE's. So, I think, the mixer and tone stack caps are closer to 200pF than 500 to 560pF.
John has also mention that every SL68 amp he builds, is put on a piece of lab equipment (he did say, but I forgot the name. It's an analyzer of sorts) and the EQ is swept to match the "Holy grail amp". In Pete Thorn's demo video, it's my opinion, that the amp almost nails the EQ part of Ed's sound, however a bit too much gain and clutter to my ears. EVH's amp, to me, sounds less distorted and more open and articulate. However, since the EQ (or voicing) of the amp is nailed, we get the impression that everything "falls together".
So, this is my contribution, opinion and detective work to this topic, for what it's worth. Check out the pic and let me know what you think.
P.S I do believe that, as someone mentioned here, that the power tranny is switched from it's input. For example, two sets of leads that tap different points of the primary of the power transformer.
Tone Slinger wrote:You are a lucky man to be able to do that (dime your plexi, with no attenuation).I sure wish I lived somewhere that could handle the volume,or have a soundproofed studio.
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