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Hey folks!
It taked more time that expected - specially cause some trouble$$$ happened - but now, I decided to re-start the design of my amp, from the scratch... however, definitely, I'll need some backup here!!!
From the beginning... my intent was to build an british hot rodded amplifier, single channel... the starting point was the ULTIMATE JCM800 (Tone Lizard)... althought the schematic had already been finished, my idea for the amplifier changed a bit in this hiatus... I'm still looking for a more modern and agressive british tone, which keeps the character of the guitar used and clarity of the notes, but will really appreciate if the amp could presents some new features, like:
- a clean (or semi-clean) channel
- a tight and organic british tone channel (maybe with just the traditional approuch: 3 gain stages + CF)
- (maybe) a tube boost in the gain channel, if this one can't go really higain (the idea here is doesn't use a external pedal to boost the drive)
- separate tonestacks for the clean channel and the gain channel
- footswitchable alltube FX loop
- footswitchable solo master
For now, I think that is interesting just talk about the preamp (that is, the place where most of the things happen)...
Initially, the idea was to use the two EL34 for the (standard) poweramp and four 12AX7 (two for the preamp itself, one for the loop, and one for the PI)... now, as I'll need some more gain stages in the preamp for the boost and for the clean, needed to look at the PT specs:
HT Secondary: 0-340Vac/300mA
BIAS Secondary: 0-50Vac/35mA
Heater Secondary: 0-6,3Vac/5A
Switching Secondary: 0-6Vac/1,2A
As the Heater Secondary was developed to hold until 5A, it can be seen that it already have some room to add tubes (0,8A specifically)... so, the ideas are:
- or add until two more 12AX7 (+600mA) and build a bassman clean with three of the stages and using the one that will be left to boost the gain channel;
- or add one 12AX7 (+300mA) for the tweaks in the gain stage and one EF86 (+200mA) for the semi-clean stage...
I have two good references to my "new" gain channel:
- the second channel in the PT-100 (especially in 6:53) - YouTube - Suhr/CAA PT100 amplifier demo
- the Iced Earth tone
If I can reach this kind of drive with the gain boost ON, pretty awesome! It seems that the "stock" gain channel could be more like a heavy crunch, good for rhythm, and will clean a bit with the guitar volume!
Well... I really don't know... I'm still f*cking lost... here is some of the specs that I'm thought about for the gain channel:
1st Stage:
V ~270V
Rgs 1M
Rg 33k (grid stopper)
Rp 100K+(30K//1u)
Rk 2.7K//680n
Co 22n
Rl 200k
500k pot
2nd Stage:
V ~290V
Rg 68k (grid stopper, at the wiper of the first stage load pot - in the case when the boost stage is not engaged)
Rp 100K
RK 10K
Co 22n
Rl 470k
3rd Stage:
V ~290V
Rp 100k
RK 820
Cathode Follower:
Like the usual (V ~290V, Rk 100K), but with the additional components proposed by Merlin, to protect the cathode
Gain Boost Stage (between 1st and 2nd):
V ~270V
Rg 68k (grid stopper, at the wiper of the first stage load pot)
Rp 100K
Rk 2.7K//680n
Co 10n
Rl 470k//220p
500k pot
That's all folks! I think that it'll already extend the preamp's discussion for a while!!
Cheers!
(and sorry for my brazilian's English)
It taked more time that expected - specially cause some trouble$$$ happened - but now, I decided to re-start the design of my amp, from the scratch... however, definitely, I'll need some backup here!!!
From the beginning... my intent was to build an british hot rodded amplifier, single channel... the starting point was the ULTIMATE JCM800 (Tone Lizard)... althought the schematic had already been finished, my idea for the amplifier changed a bit in this hiatus... I'm still looking for a more modern and agressive british tone, which keeps the character of the guitar used and clarity of the notes, but will really appreciate if the amp could presents some new features, like:
- a clean (or semi-clean) channel
- a tight and organic british tone channel (maybe with just the traditional approuch: 3 gain stages + CF)
- (maybe) a tube boost in the gain channel, if this one can't go really higain (the idea here is doesn't use a external pedal to boost the drive)
- separate tonestacks for the clean channel and the gain channel
- footswitchable alltube FX loop
- footswitchable solo master
For now, I think that is interesting just talk about the preamp (that is, the place where most of the things happen)...
Initially, the idea was to use the two EL34 for the (standard) poweramp and four 12AX7 (two for the preamp itself, one for the loop, and one for the PI)... now, as I'll need some more gain stages in the preamp for the boost and for the clean, needed to look at the PT specs:
HT Secondary: 0-340Vac/300mA
BIAS Secondary: 0-50Vac/35mA
Heater Secondary: 0-6,3Vac/5A
Switching Secondary: 0-6Vac/1,2A
As the Heater Secondary was developed to hold until 5A, it can be seen that it already have some room to add tubes (0,8A specifically)... so, the ideas are:
- or add until two more 12AX7 (+600mA) and build a bassman clean with three of the stages and using the one that will be left to boost the gain channel;
- or add one 12AX7 (+300mA) for the tweaks in the gain stage and one EF86 (+200mA) for the semi-clean stage...
I have two good references to my "new" gain channel:
- the second channel in the PT-100 (especially in 6:53) - YouTube - Suhr/CAA PT100 amplifier demo
- the Iced Earth tone
If I can reach this kind of drive with the gain boost ON, pretty awesome! It seems that the "stock" gain channel could be more like a heavy crunch, good for rhythm, and will clean a bit with the guitar volume!
Well... I really don't know... I'm still f*cking lost... here is some of the specs that I'm thought about for the gain channel:
1st Stage:
V ~270V
Rgs 1M
Rg 33k (grid stopper)
Rp 100K+(30K//1u)
Rk 2.7K//680n
Co 22n
Rl 200k
500k pot
2nd Stage:
V ~290V
Rg 68k (grid stopper, at the wiper of the first stage load pot - in the case when the boost stage is not engaged)
Rp 100K
RK 10K
Co 22n
Rl 470k
3rd Stage:
V ~290V
Rp 100k
RK 820
Cathode Follower:
Like the usual (V ~290V, Rk 100K), but with the additional components proposed by Merlin, to protect the cathode
Gain Boost Stage (between 1st and 2nd):
V ~270V
Rg 68k (grid stopper, at the wiper of the first stage load pot)
Rp 100K
Rk 2.7K//680n
Co 10n
Rl 470k//220p
500k pot
That's all folks! I think that it'll already extend the preamp's discussion for a while!!
Cheers!
(and sorry for my brazilian's English)