Possibly N(old)AD.

Sweeeeeeet!
What no gut shots?

Gahr, consider the very real issue that the electrolytic power caps in that amp can short and fry the power transformer, and maybe cause a fire.
Old Caps need replacing unless this is to be a collectors museum piece.
 
jtcnj said:
Sweeeeeeet!
What no gut shots?

Gahr, consider the very real issue that the electrolytic power caps in that amp can short and fry the power transformer, and maybe cause a fire.
Old Caps need replacing unless this is to be a collectors museum piece.
Click to expand...
Yes... detailed gut shots. If any electrolytic caps are old or original, these have to be inspected closely and tested for leakage.

@Gahr Congrats on such a classic of an amp. It looks like it's in great condition. Enjoy that little screamer... :cheers:
 
Thanks for the tips! I'll see what I can do about good gut shots; it is a bitch to take apart!

One thing I noticed was weird, though. When I turn the volume on my Derek Trucks down past 9, it suddenly drops quite a lot. This does not happen with any of the other guitars I've tried the amp with. So far I have played it with my LP Junior, SG Faded Special (modern wiring) and SG Future Tribute (50s wiring) in addition to the DT. Any ideas on what ishappening here?
 
Do you notice a difference in the sweep of your controls between guitars regardless of the amp?
I do. I always sweep the knobs once i get plugged in and settled to remind me how the sweep feels.

Could be your taper happens quick on the DT.
 
jtcnj said:
Do you notice a difference in the sweep of your controls between guitars regardless of the amp?
I do. I always sweep the knobs once i get plugged in and settled to remind me how the sweep feels.

Could be your taper happens quick on the DT.
Click to expand...
I can't say I have noticed it on other amps, but I guess I'll have to check.
 
Last edited:
It does: the linear vs. log sweeps are perceived differently by our ears.
Supposedly, the log sweeps sounds more even for volume and the linear for tone but everyone has their preference. The pot resistance value and value of tone caps will shape the way you hear it or where the most responsive part of the sweep is as well., or maybe just the frequency range, again I'm no expert.

Like I said I dont really care I just roll the pots around a bit when I pick up the guitar to get a feel, like where the clutch grabs when you drive some one elses stick shift car.
 
jtcnj said:
It does: the linear vs. log sweeps are perceived differently by our ears.
Supposedly, the log sweeps sounds more even for volume and the linear for tone but everyone has their preference. The pot resistance value and value of tone caps will shape the way you hear it or where the most responsive part of the sweep is as well., or maybe just the frequency range, again I'm no expert.

Like I said I dont really care I just roll the pots around a bit when I pick up the guitar to get a feel, like where the clutch grabs when you drive some one elses stick shift car.
Click to expand...
I wouldn't really care either, but here the drop is so dramatic that the pot almost loses it's function in dialing in a nice tone. It is either full on or really low after it is turned below 8-9. Would that be different if I were to change it to a linear pot?
 
Last edited:
upload_2017-6-20_14-30-9.jpg
That is a quick and not very useful range.
I dont know the specifics, I just know some generalities and aware there are differences.
May be a good spot to start a new thread that will get exposure and attention of the better informed folks here.

From what I remember its Linear volume pots that roll of real fast over a small sweep of the knob and log type pots that seem more of a usable range of the sweep, but ..... not sure.
The chart above seems to confirm what you said and contradict the way I thought I remembered it.
 
Last edited:
Gahr said:
...but the first thing you notice when playing it is that it gives you more power when playing through the mic input instead of the instrument input.
Click to expand...

That's because microphones have a much lower output level than instruments. So, the Instrument input is "padded" with resistors to attenuate the level going to the rest of the circuitry.
 
Last edited:
smitty_p said:
That's because microphones have a much lower output level than instruments. So, the Instrument input to is "padded" with resistors to attenuate the level going to the rest of the circuitry.
Click to expand...
Yep. Playing through the mic input is a lot nicer, actually.
 
Gahr said:
...

IMG_1808_zpsxnllqtsq.jpg

IMG_1809_zpsitoeuhrg.jpg

IMG_1810_zpsv0ld9qoa.jpg

IMG_1811_zpsyhakyybt.jpg

IMG_1812_zps1omhxei9.jpg
Click to expand...

Very, very nice set up. I'm in luv...
 
The finicky volume sweep only happens with your DT SG and the Mic input of the Gibson amp?
How about the Instrument input?
Tone control maxed out?

Usually Log or Audio tapered pots are preferred for the volume control on guitars, because it does have a more even audible response regardless of what is seen on those data charts.
 
syscokid said:
The finicky volume sweep only happens with your DT SG and the Mic input of the Gibson amp?
How about the Instrument input?
Tone control maxed out?

Usually Log or Audio tapered pots are preferred for the volume control on guitars, because it does have a more even audible response regardless of what is seen on those data charts.
Click to expand...
I did a quick test again. The large volume drop happens with the DT (500k audio taper/non-linear pots, 50s style wiring) when the volume is turned down past 9. However, it only happens when the tone controls are not on 10.

With my Faded Special (300k linear volume pots, 500k tone pots, modern wiring) this does not occur. Neither does it happen with my Future Tribute (500k linear pots, 50s wiring).



Am I correct in suspecting that it happens with the DT because of the non-linear volume pots?
 
I'm planning on taking it to a technician tomorrow or Friday. It's got a two-prong power cable (no ground connection), and I would feel more comfortable playing it if I knew someone had checked it to see if everything is ok. Will probably have him fix the treble thing too.
 
Gahr said:
I did a quick test again. The large volume drop happens with the DT (500k audio taper/non-linear pots, 50s style wiring) when the volume is turned down past 9. However, it only happens when the tone controls are not on 10.

With my Faded Special (300k linear volume pots, 500k tone pots, modern wiring) this does not occur. Neither does it happen with my Future Tribute (500k linear pots, 50s wiring).



Am I correct in suspecting that it happens with the DT because of the non-linear volume pots?
Click to expand...
In 50's wiring, when backing off on the tone control, that'll reduce some of the gain to the amp. I have no experience with 50s wiring in combination with linear tapered pots. I wonder if the jumpy volume with the tone control backed down is a normal side effect. I certainly would have noticed this on my guitars, but I will recheck later.

Are sure everything is wired correctly with no sneaky shorts?
 
syscokid said:
In 50's wiring, when backing off on the tone control, that'll reduce some of the gain to the amp. I have no experience with 50s wiring in combination with linear tapered pots. I wonder if the jumpy volume with the tone control backed down is a normal side effect. I certainly would have noticed this on my guitars, but I will recheck later.

Are sure everything is wired correctly with no sneaky shorts?
Click to expand...

I'm pretty sure the wiring is ok. The pots in the DT are non-linear with 50s wiring. With my other guitars I don't have the problem.

syscokid said:
Have you tried your Skylark plugged into a different speaker source?
Click to expand...

The speaker cable is soldered in, so I havent tried a different speaker.

The treble issue is fairly well known with the Skylarks of this period. There is a square Sprague three-in-one thing, containing a capacitor and two resistors (I think) connecting the volume pot to one of the tubes and ground, which gives the amp lots of treble. Replacing it with a cap of some sort will most likely fix it.

If you look at the vid below from around 30-31 min. The guy explains it better than me.

 
You must log in or register to reply here.
Back
Top