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Author Topic: As promised! My ampís tweaks and layout.  (Read 44328 times)
Pickmaster
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« on: October 15, 2008, 05:21:31 AM »

Hello tonelovers,

At last here are my tweaks on the OTS layout.
Those mods work for MY TASTE and not necessarily for other players taste and style.

WORNING !!! PLEASE DO NOT MESS WITH TUBE AMPS  if you donít know how to. You can damage it or worse - IT CAN KILL YOU !!! Better take it to good amp technician !!!

I tried to make OTS bigger, fatter, bit more compressed, even on cleans. Actually get closer to ďBluesmasterĒ mod. Some of this tweaks can apply to HRM model too, especially removing a negative feedback NFB from V1 (just removing 0.05mF cap) which adds fat to the amp. Actually it would be better if one drills a hall near V1 and installs mini toggle switch for switching 0.05uF cap ON (for humbucker guitar) or OF(for strat and tele).
I hope everything is clear on the diagram.
Note that JAZZ/ROCK switch is three position switch and changes DRIVE CHANNEL gain only Ė Hi/Dumb/Plexi. Amp itself is always on ROCK setting.
BRIGHT switch is also 3 position for more flexibility.
As you noticed I removed FET board and there is boost gain pot in the FET input hall.
PAB is disconnected and gain boost happens with simply increasing a CLEAN VOLUME via PAB footswitch. With this you can have regulated (via boost pot) volume (gain) boost on both channels without changing the TONE. It allows to get nice crunch on clean channel and awesome drive boost.
Three way switch near V2 adjusts driveís high cut, so you can go as smooth as you want without affecting clean channel.
Added International power switch (in the ground lift hall) for the travelling musician.

Best wishes to all


« Last Edit: December 14, 2008, 12:15:14 PM by Pickmaster » Logged

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Alpedra
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« Reply #1 on: October 15, 2008, 05:54:03 AM »

Great post.

By the way, the amp name is spelled wrong Cheesy Wink Tongue
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Pickmaster
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« Reply #2 on: October 15, 2008, 06:11:39 AM »

Great post.

By the way, the amp name is spelled wrong Cheesy Wink Tongue

Sorry! Shame on me. Iíll correct it soon. It was there originally BTW, we have to tell Nick.
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erwin_ve
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« Reply #3 on: October 15, 2008, 07:07:59 AM »

Nice work!
That must be a big fat monster on the clean side with 100k slope.  Cheesy
Some things I don't understand:
-Increasing the coupling cap on v2b, doesnt it make your drive channel  muddy?
-What is the effect on decreasing the resistor to 27k (after V2a coupling cap)?
-The size of the snubber on v2B; did you have something to tame here? ; its a huge value for its application.

Grtz Erwin
« Last Edit: October 15, 2008, 07:14:54 AM by erwin_ve » Logged
Pickmaster
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« Reply #4 on: October 15, 2008, 07:33:25 AM »

Nice work!
That must be a big fat monster on the clean side with 100k slope.  Cheesy
Some things I don't understand:
-Increasing the coupling cap on v2b, doesnt it make your drive channel  muddy?
-What is the effect on decreasing the resistor to 27k (after V2a coupling cap)?
-The size of the snubber on v2B; did you have something to tame here? ; its a huge value for its application.

Grtz Erwin

Hi Erwin,

I love sweet mud and dirt Embarrassed Grin, well it does a little bit but 27K (one can put 12K as well) resistor opens up the tone and together it is magic (FOR MY TASTE)!.
Because of the bright 47pF cap on the volume is always ON - Iíve milded drive with 770pF - really Robbenís drive tone.
With experiments I've noticed that better to  keep V2A snabber low and increase V2Bís value Ė better chirp definition and waterier tone.
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hywelg
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« Reply #5 on: October 15, 2008, 08:20:24 AM »

Excellent. Very well explained and documented. Thank you very much indeed.

I really do feel the need for another OTS to try all the mods on!

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hywelg
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« Reply #6 on: October 15, 2008, 08:59:45 AM »

Just a couple of questions about the Rock/Jazz replacement switch. Seems like a good idea to me
as I never use the Jazz setting.

You mention that the switching is Hi/Dumble/Plexi.
Am I correct in assuming that in the Dumble position, ie OFF, the trimmer controls the level of drive?

The two caps connected to the switch via the purple wire seem to be connected to wire X shielding.
Should they be connected to the signal wire of wire X? and what is their purpose since they don't appear to be connected
to anything at the switch?

Many thanks

Hywel Harris
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Pickmaster
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« Reply #7 on: October 15, 2008, 09:53:45 AM »

Just a couple of questions about the Rock/Jazz replacement switch. Seems like a good idea to me
as I never use the Jazz setting.

You mention that the switching is Hi/Dumble/Plexi.
Am I correct in assuming that in the Dumble position, ie OFF, the trimmer controls the level of drive?

The two caps connected to the switch via the purple wire seem to be connected to wire X shielding.
Should they be connected to the signal wire of wire X? and what is their purpose since they don't appear to be connected
to anything at the switch?

Many thanks

Hywel Harris

You are absolutely right Ė in the middle OFF position a trimmer works, for other positions Ė the switch. One can put little trimmers instead of resistors to adjust desired gain settings on Hi gain and Plexi.
Well spotted Hywel, Iíve just corrected it! Caps cut highs Ė when gain increases highs increase too so to compensate!
One can chose caps value according to their taste.
Caps are connected to HOT not to shield (ground).
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hywelg
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« Reply #8 on: October 15, 2008, 12:49:17 PM »

Thanks for the clarification. I think I'm going to do the mods one at a time to get a feel for
what effect they have. First will be Rock/Jazz since that will be of greatest use for me.
The Boost control will also be very useful. PAB has always been a little too much
of a volume step with my TMB settings plus I have never had a use for the FET input.

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erwin_ve
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« Reply #9 on: October 16, 2008, 04:42:43 AM »

Hi Erwin,

I love sweet mud and dirt Embarrassed Grin, well it does a little bit but 27K (one can put 12K as well) resistor opens up the tone and together it is magic (FOR MY TASTE)!.
Because of the bright 47pF cap on the volume is always ON - I’ve milded drive with 770pF - really Robben’s drive tone.
With experiments I've noticed that better to  keep V2A snabber low and increase V2B’s value – better chirp definition and waterier tone.

Hi Ika,

Thanks for explaining!
Interesting thing about the snubbers, I'm gonna try that.

Grtz Erwin
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bluesfendermanblues
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« Reply #10 on: October 16, 2008, 05:44:36 PM »

I've added a 500k trimmer with a 1 nF cap across the overdrive master to reduce the lead highs, which works fine. I use 270p snubbers on V2a + V2b so I need a little extra to trim off some highs.

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mcinku
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« Reply #11 on: October 17, 2008, 12:53:56 AM »

I was really looking forward to this.   Wink


Thanks
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Pickmaster
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« Reply #12 on: October 19, 2008, 10:43:48 AM »

Hello,

This is central scrutiniser again!
Some folks complained that removing the 0.05mF cap from V1ís NFB makes amp TOO FAT!  :Smiley
So here is more flexible solution Ė three way switch with 470pF/OFF/0.05mF.
Drill little hall for the switch near V1  and chose the desired setting.
Iíve added this to the layout. Tongue
Cheers.
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JD0x0
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« Reply #13 on: October 19, 2008, 03:37:35 PM »

Are there caps with variable values that i could use and adjust for the V2 snubber caps? Sortof like the OD trimmers but this adjusts the V2 cap values
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« Reply #14 on: October 19, 2008, 04:07:59 PM »

Hi Pick Master, while the ots is not on my immediate to build list as i am building a couple of other smaller amps at the moment , I may attemp to tackle it in the future. I have quickly glanced over the layouts of both the 100 and 50 watt versions, and forgive me if I am totally wrong as i didn't spend too much time comparing , but they appear similar except for the extra power tubes etc , now your layout shows a 50 watt version . Can your mods also be applied to a 100 watt version , Thanks.
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