Second Dumble #183 build

[erwin_ve]

Oddvar, the Fet is not necessary, if you leave it out you must add a 150k(2-3W) resistor from B+5 to ground to compensate for the load that the fet circuit has.

[martin manning]

Is the fet amp really necessary for the build? And if it is, why?

It's an option, basically the same as adding a relatively clean boost in front of the amp.

[pompeiisneaks]

a decent amount of people leave it off. It's not mandatory. It was originally designed as an input for acoustic guitar if I heard right. It can give a nice boost to your guitar before it hits the rest of the amp, too, though, but it's definitely optional. Some also have put it on another relay and have it switchable and just use one input. the permutations are unlimited

~Phil

[talbany]

FWIW
I used to just leave the Fet off from my early amps. My latest one was talked into adding it and am glad I did!. I am not a big fan of the preamp boost in clean mode. It's hard to control volume-wise and can also sound a bit thin with the bass pot disconnected. OD w/PAB I use occasionally. However, with the recent addition of the FET on a footswitch and the gain control where the Fet input jack is works great.
I generally set it with around a 3-6dB boost so if I am in the clean channel and want a bit of a boost to push V1a a bit harder it's there. In OD it's also a useful feature if you just want to add a bit more gain there and not alter the character of the overdrive tone to much. So basically what you have is clean and OD channel and 2 different types of boosts to choose from. anyway I recommend adding it as a foot-switchable feature w/ vol on front to dial in the boost you need for that gig

Tony

[norburybrook]

FWIW
I used to just leave the Fet off from my early amps. My latest one was talked into adding it and am glad I did!. I am not a big fan of the preamp boost in clean mode. It's hard to control volume-wise and can also sound a bit thin with the bass pot disconnected. OD w/PAB I use occasionally. However, with the recent addition of the FET on a footswitch and the gain control where the Fet input jack is works great.
I generally set it with around a 3-6dB boost so if I am in the clean channel and want a bit of a boost to push V1a a bit harder it's there. In OD it's also a useful feature if you just want to add a bit more gain there and not alter the character of the overdrive tone to much. So basically what you have is clean and OD channel and 2 different types of boosts to choose from. anyway I recommend adding it as a foot-switchable feature w/ vol on front to dial in the boost you need for that gig

Tony

Tony,

I had exactly the same journey with the FET and agree 100% about it's usefulness when on a footswitch/relay compared to the clean PAB . My second gen and my BM both have switchable FET,



M

[talbany]

FWIW
I used to just leave the Fet off from my early amps. My latest one was talked into adding it and am glad I did!. I am not a big fan of the preamp boost in clean mode. It's hard to control volume-wise and can also sound a bit thin with the bass pot disconnected. OD w/PAB I use occasionally. However, with the recent addition of the FET on a footswitch and the gain control where the Fet input jack is works great.
I generally set it with around a 3-6dB boost so if I am in the clean channel and want a bit of a boost to push V1a a bit harder it's there. In OD it's also a useful feature if you just want to add a bit more gain there and not alter the character of the overdrive tone to much. So basically what you have is clean and OD channel and 2 different types of boosts to choose from. anyway I recommend adding it as a foot-switchable feature w/ vol on front to dial in the boost you need for that gig

Tony

Tony,

I had exactly the same journey with the FET and agree 100% about it's usefulness when on a footswitch/relay compared to the clean PAB . My second gen and my BM both have switchable FET,



M

Yup!! Cool
I am pretty happy with my BM boost. Since those are designed to lift the stack (Mega-boost) in OD
It might be cool to have it on the clean though. I have it on both High plate Skyliner (102) and Low plate sky MM. If I had to choose I prefer it on the high plate 102 amp a bit better. I wonder if there is a way to add an RC network to the FET so you can control both volume/gain and tone of the fet. Hummmm..

Tony

[ayan]

FWIW
I used to just leave the Fet off from my early amps. My latest one was talked into adding it and am glad I did!. I am not a big fan of the preamp boost in clean mode. It's hard to control volume-wise and can also sound a bit thin with the bass pot disconnected. OD w/PAB I use occasionally. However, with the recent addition of the FET on a footswitch and the gain control where the Fet input jack is works great.
I generally set it with around a 3-6dB boost so if I am in the clean channel and want a bit of a boost to push V1a a bit harder it's there. In OD it's also a useful feature if you just want to add a bit more gain there and not alter the character of the overdrive tone to much. So basically what you have is clean and OD channel and 2 different types of boosts to choose from. anyway I recommend adding it as a foot-switchable feature w/ vol on front to dial in the boost you need for that gig

Tony

Tony,

I had exactly the same journey with the FET and agree 100% about it's usefulness when on a footswitch/relay compared to the clean PAB . My second gen and my BM both have switchable FET,



M

Yup!! Cool
I am pretty happy with my BM boost. Since those are designed to lift the stack (Mega-boost) in OD
It might be cool to have it on the clean though. I have it on both High plate Skyliner (102) and Low plate sky MM. If I had to choose I prefer it on the high plate 102 amp a bit better. I wonder if there is a way to add an RC network to the FET so you can control both volume/gain and tone of the fet. Hummmm..

Tony

I’m not sure if you guys have tweaked the FET boost design or not. All my amps have had it, and I’ve never used it. For a footswitchable boost, with volume, bass, treble, and dirt control... maybe a used RC Boost for $70?

[martin manning]

Not so much tweaked, but biasing and setting the Vdd has been more-or-less standardized, and making it foot-switchable with the gain control on the front panel allows adjusting boost without opening the amp, and switching it in and out on the fly. Same basic circuit with more consistent results and better usability. Cost is low compared to a separate boost pedal too.

[norburybrook]

the quality of the clean boost from the on board FET is amazing, really high quality.

Using a pedal means , more cables, power supply etc etc . The switchable FET on the front panel is a perfect clean boost in front of the amp

I Posted a sound clip of my second gen using the FET boost on the OD on the build thread. The second gen has a lower gain than later models and a lower gain P.I. so the FET works great on the OD too.



M

[ayan]

the quality of the clean boost from the on board FET is amazing, really high quality.

Using a pedal means , more cables, power supply etc etc . The switchable FET on the front panel is a perfect clean boost in front of the amp

I Posted a sound clip of my second gen using the FET boost on the OD on the build thread. The second gen has a lower gain than later models and a lower gain P.I. so the FET works great on the OD too.

M

I can totally understand that if one doesn’t have/use a pedalboard. Personally, I’ve always used one, and it isn’t precisely small. A must for gigs that provide (and sometimes mandate) a back line, plus, I ditched my rack and have time based effects on the floor now. I use the RC with the dirt pedals like I use the PAB with the amp’s OD.

[norburybrook]

Do you use a dumbleator for your delay, verb etc?

M

[ayan]

Do you use a dumbleator for your delay, verb etc?

M

Absolutely— when I use the amp’s OD. Doing that was what allowed me to hear how dramatic the loss of highs can be because of the Dumbleator 250K send pot. I now set it at about 25K to ground. As I turn that up, because of the 18 ft cable to the FX in on the board, the loss of highs is immense. Was not a problem when I used the rack and the cable to the FX was about 4 ft. That was the reason I started a thread about that thing about a month or so ago.

[talbany]

Before I installed the foot-switchable boost in the amp I also used the RC on my board. It worked great and as I said I miss the ability to control the tone of my boost with the RC. My lator and EFX are in a small rack and now have the option of not using the pedalboard and use the OD in the amp (which I've always preferred) I also have a Wha pedal I'll throw down and stick a battery in that.
OPTION B
Bring the pedalboard and leave the rack at home and use the pedals for my OD sound and use just the clean side of the amp no loop.
This way everything stays modular and I have 2 rigs to choose from depending on which OD sound I need for that gig. I end up having to carry either the rack or the board but never both
Option C
My Bluesmaster and 2nd gens have both built-in D-Lators. I I used to just throw my HOF pedal on the amp and run that with my pedalboard and have the option of either OD in the amp or OD on the floor. The problem I had with this setup was all the buffers I had on the pedalboard altered the amps input impedance whereby the overdrive in the amp became too compressed and squashed I prefer the sound of all my ODS amps guitar plugged straight in ala Robben Ford. So I am slowly getting away from that setup and getting back to plugging straight in with as little cable as possible which is the main reason why I added the foot-switchable boost inside the amp. It's not always perfect and hopefully, over time I'll get used to no pedals on the floor and having a more organic sound This way I can go ahead and set up my pedalboard to work with all the other amps I've built that don't have built-in overdrive like my JTM 45 and old Tweed Fenders and not having to constantly be re-configuring my pedalboard for each rig.. My new slogan KIMS. Keep it modular stupid.
Tony