Preamp Switches....

[v00d00blues79]

Out of the varying combinations of pre-amp switches that are shown in the schematics, which ones do you all find most useful? I'm attempting to scale back my one dumble to a single OD channel amp and am wondering if the pre-amp switches will be useful to me in that venture...

Thanks,

Andy

[Bob-I]

I like the boost, mid boost and bright. I've tried the jazz/rock and deep and wasn't knocked out. The deep is very effective but leaves the tone muddy at anything but lowest volumes, the jazz rock was not a huge difference, nice but too subtle for my taste.

[mlp-mx6]

A non-standard switch that I like is mid-cap select. I have my amp with BOTH a .01 and a .047 mid cap, and a SPDT switch to select. Sort of like a humbucker/single-coil switch. I like it a lot.

[Normster]

On the Bassman, I used bright, deep, rock/jazz, and boost switches. On the Dumble I used the same but no boost switch. I don't use the jazz position at all, but I do use the deep switch a lot to get closer to Carlton tone.

[Darkbluemurder]

It depends on the basic sound of the amp. The bright is indispensable for me to control high end. I usually use a 100pf or 120pf instead of the 270pf or 500pf on the schematics. If the amp does not have enough low end the deep switch is handy (until now I felt that this was not necessary for amps with 2 6L6s as they have sufficient bass even with a .047 mid cap, only for the Deluxe II Reverb).
I like the preamp boost and the treble shift (add a cap in parallel to the treble cap) as well. Have not yet finally decided on that.
The issue I have with many of those switches is that only one mode benefits from them. I do like the bright and deep for the cleans but not for the OD sounds (the deep mode makes it muddy to my ears). Conversely I do like the boosts for the OD sounds but not for the cleans (the preamp boost is fine for slightly distorted sounds but makes the amp very loud). I will certainly not have these problems with my modded Concert where the clean section is independent from the ODS modded lead channel.

[dogears]

Hi DBM,

The .047 and .01 midcaps have much different "Q" frequencies. You can't just say that the amp has enough bass with the .047 It boils down to where is the bass.... And where are the low mids.....

It depends on the basic sound of the amp. The bright is indispensable for me to control high end. I usually use a 100pf or 120pf instead of the 270pf or 500pf on the schematics. If the amp does not have enough low end the deep switch is handy (until now I felt that this was not necessary for amps with 2 6L6s as they have sufficient bass even with a .047 mid cap, only for the Deluxe II Reverb).
I like the preamp boost and the treble shift (add a cap in parallel to the treble cap) as well. Have not yet finally decided on that.
The issue I have with many of those switches is that only one mode benefits from them. I do like the bright and deep for the cleans but not for the OD sounds (the deep mode makes it muddy to my ears). Conversely I do like the boosts for the OD sounds but not for the cleans (the preamp boost is fine for slightly distorted sounds but makes the amp very loud). I will certainly not have these problems with my modded Concert where the clean section is independent from the ODS modded lead channel.

[ayan]

I like the boost, mid boost and bright. I've tried the jazz/rock and deep and wasn't knocked out. The deep is very effective but leaves the tone muddy at anything but lowest volumes, the jazz rock was not a huge difference, nice but too subtle for my taste.

Bob, I'm not sure to what circuit you added the Deep switch, but what you describe is hardly the case in either my amps, or the Dumbles I tried that have the Deep switch. A friend of mine made an observation that's very accurate: when Dumbles were inherently middier and brighter sounding (my favorite circuit, the "1982" one) he put a Deep switch on them to add flexibility and make them fatter if the owner so desired; he later (Skyliner preamp) made the amps bassier sounding and changed that to a Mid switch, as a Deep switch would make no sense in that circuit.

In my most humble opinion after building seven amps, one would be hard-pressed to get a muddy sound out of the 1982 circuit even if the treble control is turned all the way down and the Deep switch on.

Cheers,

Gil

[v00d00blues79]

Just out of curiousity, which schem most accurately reflects the '1982' circuit you are talking about?


Thanks,

Andy

[ayan]

Just out of curiousity, which schem most accurately reflects the '1982' circuit you are talking about?


Thanks,

Andy

The 1982 circuit has been described here by Scott before, although no schematic of it can be found floating around the Internet -- for a reason, and since I don't want to upset anyone, I am being sketchy with details here. I'm sure you can come up with it if you pick out the right values from the choices offered in one of the Steve Ahola Schematics (the guy that put together the "Hybrid A and B" schems). Basically, it doesn't have a post overdrive tone stack and it departs from the 1970s schematic and its 100K plat load resistors and 1.5K cathode resistors, but the architecture of it is the same as that. As much as I have liked some of the other stuff I have tried, I have basically stuck with the 1982 schematic since 1999.

The 1982 schematic is the one that inspired the SLX mode (which used it as a point of departure from he "regular" Fuchs ODS amps circuit) and the one that can be found (with some tweaks, among them using a .01uF midrange cap) in the TR "Sig" amps.

Cheers,

Gil

[v00d00blues79]

Gil,

Thanks for the clarification! I think i know what you are talking about in regards to the tweaks and such. I think i might have to try that in one of my clones...

Thanks,

Andy

[Darkbluemurder]

Hi DBM,

The .047 and .01 midcaps have much different "Q" frequencies. You can't just say that the amp has enough bass with the .047 It boils down to where is the bass.... And where are the low mids.....

It depends on the basic sound of the amp. The bright is indispensable for me to control high end. I usually use a 100pf or 120pf instead of the 270pf or 500pf on the schematics. If the amp does not have enough low end the deep switch is handy (until now I felt that this was not necessary for amps with 2 6L6s as they have sufficient bass even with a .047 mid cap, only for the Deluxe II Reverb).
I like the preamp boost and the treble shift (add a cap in parallel to the treble cap) as well. Have not yet finally decided on that.
The issue I have with many of those switches is that only one mode benefits from them. I do like the bright and deep for the cleans but not for the OD sounds (the deep mode makes it muddy to my ears). Conversely I do like the boosts for the OD sounds but not for the cleans (the preamp boost is fine for slightly distorted sounds but makes the amp very loud). I will certainly not have these problems with my modded Concert where the clean section is independent from the ODS modded lead channel.

Hi dogears,

I should perhaps have been more specific on that. The lower the mid cap the more low mids which subjectively makes one think that the bass also increased - at least this was my perception.
FWIW I have a .01 mid cap in the Deluxe Reverb II and IMO it needs it to have full enough bass without the Deep switch. My Concert has a .047 mid cap and yet enough bass/low mids for me. I suppose that the power amp in the Concert has way more bass than the one in the Deluxe Reverb II. This is certainly due to the transformers (the one in the Concert is identical to a BF Bassman transformer) and 6L6 vs. 6V6. If I changed the .047 to a .022 or a .01 in the Concert I am sure that the bass and low mids would become overbearing. BTW I read somewhere in this forum that somebody included a mid cap switch to switch between .01 and .047 - good idea.
Cheers
DBM

[Normster]

My .02 on the Deep switch...it doesn't really enhance the bass much at all. I use it primarily with crunchy OD to take some of the rougher edges off the tone. I haven't analyzed what it does to tone, but it sounds like it moves the emphasis from high mids to slightly lower mids as well as smoothing out the gain. (It also seems to reduce the volume and gain a bit.) On my amp it sounds more like a "mellow" switch.

[dogears]

Hi DBM,

All my amps have the midcap switch. In fact, I use a 3 position and have .01, .02, and .047 I also have a 3 postion for treble cap size!

Hi DBM,

The .047 and .01 midcaps have much different "Q" frequencies. You can't just say that the amp has enough bass with the .047 It boils down to where is the bass.... And where are the low mids.....

It depends on the basic sound of the amp. The bright is indispensable for me to control high end. I usually use a 100pf or 120pf instead of the 270pf or 500pf on the schematics. If the amp does not have enough low end the deep switch is handy (until now I felt that this was not necessary for amps with 2 6L6s as they have sufficient bass even with a .047 mid cap, only for the Deluxe II Reverb).
I like the preamp boost and the treble shift (add a cap in parallel to the treble cap) as well. Have not yet finally decided on that.
The issue I have with many of those switches is that only one mode benefits from them. I do like the bright and deep for the cleans but not for the OD sounds (the deep mode makes it muddy to my ears). Conversely I do like the boosts for the OD sounds but not for the cleans (the preamp boost is fine for slightly distorted sounds but makes the amp very loud). I will certainly not have these problems with my modded Concert where the clean section is independent from the ODS modded lead channel.

Hi dogears,

I should perhaps have been more specific on that. The lower the mid cap the more low mids which subjectively makes one think that the bass also increased - at least this was my perception.
FWIW I have a .01 mid cap in the Deluxe Reverb II and IMO it needs it to have full enough bass without the Deep switch. My Concert has a .047 mid cap and yet enough bass/low mids for me. I suppose that the power amp in the Concert has way more bass than the one in the Deluxe Reverb II. This is certainly due to the transformers (the one in the Concert is identical to a BF Bassman transformer) and 6L6 vs. 6V6. If I changed the .047 to a .022 or a .01 in the Concert I am sure that the bass and low mids would become overbearing. BTW I read somewhere in this forum that somebody included a mid cap switch to switch between .01 and .047 - good idea.
Cheers
DBM

[ayan]

My .02 on the Deep switch...it doesn't really enhance the bass much at all. I use it primarily with crunchy OD to take some of the rougher edges off the tone. I haven't analyzed what it does to tone, but it sounds like it moves the emphasis from high mids to slightly lower mids as well as smoothing out the gain. (It also seems to reduce the volume and gain a bit.) On my amp it sounds more like a "mellow" switch.

The effect of the Deep switch is EXTREMELY dependent on the setting of the controls, the preamp volume primarily. I set my preamp volume always between say 10+ and 12 o'clock, and the difference I hear in the low end kind of ressembles that of a closed back VS open back cabinet. The effect is without a doubt subtle, that's why I'm no sure how someone could get a very muddy tone using the Deep switch.

Chers,

Gil