Deep Switch - Wiring Discrepancy?

[jam-mill]

Hi All,

I'm new to the lore of the Dumble amp and have been studying (some would say 'lurking') these forums for about 10 months now. The wealth of information is astounding and I am truly grateful for all of the expert advice shared here.

Current research is for a 'scratch' build comprised of a #124 low-plate, classic tone stack front-end and a 6V6-based power amp with a 5AR4/GZ34 tube rectifier. The hope is that this new build will be a nice practice/small gig amp that will provide the needed warmth in tone for a single-coil stratocaster.

Getting to the point...

While looking at several different schematics and layouts, a 'discrepancy' in the wiring of the 'deep' switch has become apparent. Some documents show one of the 270K resistors (the 'input' side of the filter?) connected to the wiper of the 'bass' pot, others show it connected to the 'input' leg of the 'bass' pot.

Which connection is correct? Or, if both are valid, what are the advantages/disadvantages of one over the other?

Thank-You in advance for your help.

-jack

[aflynt]

Hi All,

I'm new to the lore of the Dumble amp and have been studying (some would say 'lurking') these forums for about 10 months now. The wealth of information is astounding and I am truly grateful for all of the expert advice shared here.

Current research is for a 'scratch' build comprised of a #124 low-plate, classic tone stack front-end and a 6V6-based power amp with a 5AR4/GZ34 tube rectifier. The hope is that this new build will be a nice practice/small gig amp that will provide the needed warmth in tone for a single-coil stratocaster.

Getting to the point...

While looking at several different schematics and layouts, a 'discrepancy' in the wiring of the 'deep' switch has become apparent. Some documents show one of the 270K resistors (the 'output' side of the filter?) connected to the wiper of the 'bass' pot, others show it connected to the 'input' leg of the 'bass' pot.

Which connection is correct? Or, if both are valid, what are the advantages/disadvantages of one over the other?

Thank-You in advance for your help.

-jack

I put it on the common lug of the Rock/Jazz switch in my layout for 102 Lowplate Classic.

http://ampgarage.com/forum/files/102_lo ... _2_123.pdf

I decided that was the most likely wiring based on pictures of 133 that were floating around a few months ago. I can't comment on the sonic differences, though.

-Aaron

[jam-mill]

Aaron - Thank-You for sharing the layout.

The Early 80's Grail Tone schematic ([url]http://ampgarage.com/forum/download/file.php?id=3415[/url]) seems to indicate a different connection; unless I am misreading it.

Seems that some experimentation may be in order...

[ic-racer]

I put a deep switch on my Fender Super Twin conversion. I connected to the Bass pot wiper. Sounds good, but I did not try it the other way.

http://ampgarage.com/forum/viewtopic.php?t=5396

[jam-mill]

ic-racer,

Thank-You for responding.

Got my mods finished yesterday and have the deep switch connected per the pictures from #133 that Aaron mentioned.

The most profound effect, for me, is on the Strat neck pickup. When engaged with the overdrive on, it seems to mitigate some of the excessive bass (or 'flubby' sound); making the neck pickup more usable in overdrive and boosted modes.

When the amp gets opened up again, to install the treble bleed mod, I'll try connecting the deep switch to the bass pot wiper and give that a go.

-jack

[ic-racer]

ic-racer,

Thank-You for responding.

Got my mods finished yesterday and have the deep switch connected per the pictures from #133 that Aaron mentioned.

The most profound effect, for me, is on the Strat neck pickup. When engaged with the overdrive on, it seems to mitigate some of the excessive bass (or 'flubby' sound); making the neck pickup more usable in overdrive and boosted modes.

When the amp gets opened up again, to install the treble bleed mod, I'll try connecting the deep switch to the bass pot wiper and give that a go.

-jack

If asked to describe my implementation, I call it a "Blackface" or "Skyliner" switch. It seems to accentuate base and lessen midrange giveing a 'deep' and somewhat hollow sound. Sounds great with a strat, but is too much bass when used with OD. I think it is most useful in amps without a Skyliner tone stack.

[jam-mill]

Not to be contentious, but isn't the 'deep' switch essentially a hi-pass filter with a -3dB point of about 60Hz and falling off from there as frequency increases; having the opposite effect of 'accentuat[ing] bas[s]...'? And, without the parallel 1M resistor more of the other frequencies would get dumped to ground as well. There is a subtle lessening of the mids, but certainly not as drastic as the reduction in the bass response.

So, with that said, it seems that when the 'deep' switch is engaged it would decrease the overall bass response. Thus, making the Stratocaster neck more usable even with the OD on (as empirical analysis and a circuit simulation demonstrate).