#124 started

[martin manning]

Sorry, meant to say Mid Boost replacing Deep, obviously both have PAB.

Marcus, Do you now have the mid boost wired correctly, effectively a 2n and 300p in series, with the mid boost switch shorting the 300p? You should hear a significant effect in both Rock and Jazz modes.

[norburybrook]

Sorry, meant to say Mid Boost replacing Deep, obviously both have PAB.

Marcus, Do you now have the mid boost wired correctly, effectively a 2n and 300p in series, with the mid boost switch shorting the 300p? You should hear a significant effect in both Rock and Jazz modes.

I have it wired up as per the layout, need to check the exact value of the treble cap on the board as it should have been 330pf but isn't from the photo.


As I said my #102 has the same switch and values and does nothing really at all. just took it being very subtle so didn't bother taking it any further at the time.

Is the layout correct? I can see the 330p is in series with the board treble cap, is it on all the time? then does it get sent to ground via 4M7 when switched?

M

[martin manning]

Which layout? The post-mod 124 with mid boost has 2n on the board and 300p on the mid boost switch. The Classic has 330p on the board. The function of the mid boost switch is as shown below. 2n and 300p in series is 261p. When you short the 300p you're left with just the 2n (2000p).

[norburybrook]

that makes perfect sense Martin, I'm just having brain ache seeing that through the 6 connections of the DPDT switch.



with the switch up pins 2-3 and 5-6 are on and with it down 1-2 and 4-5 are on. that's counting from top left anti clockwise.

to me it looks like which ever way the switch is the signal always goes through the 300p???


wouldn't a SPST switch be the one in your diagram?
sorry for being thick here.


M

[martin manning]

It's a DPDT switch, but the three pairs of terminals are shorted left to right, making it a SPDT, then the top and middle pairs are shorted together making it SPST. The internal switching vs. toggle position is shown below.

[norburybrook]

ah, the 330p is being shorted to take it out of the circuit, hence me thinking it was always in line. I was thinking of it like a bright switch.

thanks for the basic electronics lesson. I should now do some reading I think, I have a lot of large holes in my knowledge.


so you're saying that the difference in 216pF and 2000pF should be very audible then?

I'm going to open up my #102 now as well as that exhibits the same behaviour in that I can barely hear a difference.


Marcus

[martin manning]

Yes, that's it. Caps in series add like resistors in parallel- the resulting value is always less than the smallest one. A factor of ~8 (261 to 2000) in the treble cap value makes a big difference, drastically reducing the mid scoop.

[norburybrook]

just fired up the old #102 and I can hear the mid boost fine.


I'm going to wait until I get the skyline EQ in before making any more judgements.

If I return it to the classic, should the 330pF be a ceramic?

edit; just looked at the schematic and it does indeed say Ceramic.


Maybe because I've only got a 300pf poly cap in there the difference is too subtle, strange how I can hear it on the jazz setting though, which was the case with the deep switch as well, the effect was a lor more pronounced on the jazz rather than rock.

I've studied that switch again today and can't see any errors in my wiring . I've beep tested all connections and they are as they should be.

should there be a pronounced volume drop in jazz mode?

if not where have I gone wrong?


Marcus

[martin manning]

Either type of cap should have a similar effect, and 300 vs. 330 should if anything make the change more noticable. Switching to Jazz mode does drop the volume, you lose 5-6 dB in the mid range.

[aflynt]

Yes. Jazz mode is quieter and to fairly compare it to rock you need to increase gain elsewhere by turning up the first volume and/or turning up the treble/mid/bass controls. What I do is flip the switch into Jazz mode, hit an open "A" chord and turn up the first volume until I hear it just starting to get louder, then I do the same basic thing with the bass/mid/treble controls: hit an "A" chord and turn them each up to the point where I start hearing them have a big effect on the sound. I generally wind up with the mid control much higher than the bass and treble. Jazz mode is actually pretty awesome once you learn to dial it in.

-Aaron

[norburybrook]

Either type of cap should have a similar effect, and 300 vs. 330 should if anything make the change more noticable. Switching to Jazz mode does drop the volume, you lose 5-6 dB in the mid range.

No I meant at the moment I've got a 330pF treble cap on the board. With the mid switch rather than the deep switch should be 0.002uF (2000Pf) which is a big difference in pF's


M

[norburybrook]

Ok a little update.

updated to the skyliner spec, that changed things quite significantly. less difference between rock and jazz, the boost was also lessened. I'm not 100% sure yet I like it . It does sound very different from my #102.

I've looked at the spec of the bourns pots and looking at the taper graph I can see that they're very different from the alpha pots so I'm going to change them for alphas.

Now ....I've built my first cab...............

Its been an interesting experience bear in mind I have only a drill, a sander and a jig saw and have to work outside.

so, with that in mind here's my cabinet.

The suede fabric was a nightmare for my first attempt. It frays, it has no give and it marks easily with glue!!!!!!! it's a bit of a dog's dinner in places!

also I had no thin ply so made everything front the same 18mm plywood so the back panel was just impossible to cover round the cutouts.
I'm going to re make it with 12mm ply so I can get the curves.

I've made the can slightly taller so I can fit a small form factor Dumbleator in the back

Anyway, here she is....looks OK from a distance

I've got some black vox cloth on order so I can make a new front. I'm quite diggin' the 70's vibe of the brown however


Marcus

[vibratoking]

updated to the skyliner spec, that changed things quite significantly. less difference between rock and jazz, the boost was also lessened. I'm not 100% sure yet I like it . It does sound very different from my #102.

FWIW, I could never like the Skyliner no matter how much I tried. I was motivated to give it a chance for obvious reasons...HAD designed it and many here liked it. In the end, I removed it. I like the classic cleans better and it behaves better with the Strat IMO.

No judgment here on the cabs, covering or any workmanship. Looks good to me.

[Aaron]

Nice work Marcus. I like the the loop in the corner. Might have to borrow that idea from you😉

[dorrisant]

Not a bad looking cabinet... Especially with limited tools.