Classic 30 amp sim .. "ROG" style HELP NEEDED

[MartyMart]

Here's the schem ..

http://www.mif.pg.gda.pl/homepages/tom/files/c30.gif

My lady is away, so after some "chores" this morning, I've been trying to construct
a sim of the Peavey Classic 30, using Jfets.
I have all four 12AX7 sections up and running, just like the schem, with just a few subs
because "it's what I have" which are 1k2's for all the 1k5's off the Jfet source's and 500pf's
where the 470pf's are ... the rest is "stock"
I'm at the "eq" stage, at the moment off Q4 I have the 47n/2M2 link to a roll off section using
2 X 15k's and 2n2's to ground.
Perhaps I need a "power tube" stage,  a bit like Prof Tweed ??  ... but it's biased up at 5v and
sounding real nice
Board is large, 12 strips X 36 holes and I've just about run out of space !
I may leave the eq section off, or just use a SWTC at the output.

If anyone has any suggestions .... ? ( clean ones please )

Going well and very possible direct from schem to stripboard/ perf

MM.

[powerplayj]

Any EQ that you provide will be better than the Peavey offering.  I love this amp but the bass frequency isn't low enough and the treble frequency isn't quite high enough, especially in the absence of a presence control.  Looking forward to hearing the clips (if any) when you complete it.

[nelson]

Why dont we do a soldano?

A Sunn bass amp?

A laney?

A sound city?

A hiwatt?

A watkins?

A tremolux?

A Twin?

[MartyMart]

Why dont we do a soldano?
A Sunn bass amp?
A laney?
A sound city?
A hiwatt?
A watkins?
A tremolux?
A Twin?

Yup ... of course, the main reason for this, is that I own a Classic 30, so want to see how "far" from
the tone it is ..... so far, it's getting fairly close  !!
It will take a few weeks of tweaking and comparison, mostly eq/speaker sim adjustments

MM

[tiges_ tendres]

Why dont we do a soldano?

A Sunn bass amp?

A laney?

A sound city?

A hiwatt?

A watkins?

A tremolux?

A Twin?

Add to that ist

ORANGE!!!!


edit: and Selmer!

[wampcat1]

Great idea!! I've been doing this myself, in fact I'm getting ready to release a jtm45 circuit using the jfets. It'll be called the 'plexi-drive' I think.

Anyway, I look forward to hearing your soundclips!! hint!! 
Good question about the power section...is the prof tweed doing this too? ROG, isn't it? I'll have to look at that and see how those fellers are doing that.

Brian

[phaeton]

Why dont we do a soldano?

A Sunn bass amp?

A laney?

A sound city?

A hiwatt?

A watkins?

A tremolux?

A Twin?

Add to that ist

ORANGE!!!!


edit: and Selmer!

A pignose
A Ruby
A 1975 Peavey Pacer
The Quantum Terminator 25R
A Kramer KA22R
The G-Blaster

runs..

[petemoore]

  What about just start with all tube schematics...lol...combine all the values to get a 'standard' value say for the cathode/source resistance/capacitence, of stage one, and do the same for all the stages  .
  A study such as this would be interesting just to see if, on average, these circuits have higher or lower gain setting on the first as compared to latter stages...['more later' would be my guess] or vice versa. Also whether the voicing is 'tighter' [say cutting LF content early in the circuit] at the beginning or the end of the circuits [in general].
  The 'other side' of my little theory here...would be a 'differences comparison'...what are the extremes of Jfet/Tube designs?
  ...Hoping that somewhere in the middle is a high gain TASound Boost/OD/Fuzzbox, I think Yyouu could do it !
  Looking at Jfetube builds this way...
  I love my little 1 transistor and 2 transistor Jfet 'circuits' [boost/od/].
  The 3 and 4 stage Jfet designs have really nice OD tones I like.
  Can't say the Vulcan has massive gain from 3 stages [cause I haven't built it yet]  but it does, 4+ stage jfet circuits for Heavy OD can be very usable...but...to be perfectly honest, I've found Jfets can get noisy and troublesome, could just be my 'stacking' techniques, for some reason, noise, sometimes rediculous noise has 'shortlived' quite a few [all] of my larger Jfet  boards, I've been sticking to fewer stages and employing Mu Technology, which I like the tone of and is quiet for amount of gain IME. YMPV.
  Lazy/frugal...I stick that Brown 2 Jfet 1 Mu Circuit Thang 'O Mine in different chain positions to drive/recover, sticking to smaller Dist circuits is still quite variable/simple . Quite useful for Lead boosts.
  Man I stray [ed] alot...
  Anyway, a 'superoptimized' Jfet 'multicircuit' [either slickly controlling/switched gain levels on X number of stages or cutting stage[s to get Boost/BoostOd/GainyODFuzz] or three usable gain levels from 1 circuit, using 1 battery and 1 box...that'd be the schenatzzz..actually it'd only have to be 2 gain levels, I can just throw the B2J1MCT [minibooster derivitave]...somewhere in the mix.
  Might be a good idea to have some of the harder Fuzz come from the 'middle'...TC after, Boost Before...
  sorry for all the extended theory / sketchy idea / high expectation stuff, I have enough of a time just getting a gain/distortion level exactly how I want it for a specific sound...Joe Gagan did some cool circuits with switche[s for getting from a dialed 'one gain/dist level to the next....about the time I think 'that kinda stuffs' not over my head, I start gasping for air..
   

[MartyMart]

Thanks for your comments guy's .... however I need some help here ..

As Pete suggested, comparing the values provides an alarmingly "close" set of
numbers, ... 33k/47k/68k input  1k5/22uf off source   1M gain pots and 22n to 47n
values off drain to next section and the tonestack arrangement.... these all seem to repeat within several designs ..!!

I have a problem "biasing" Q4 and I'm not sure that I understand what's going on here
There's a 250k pot as feedback, returning before Q4 along with a 2M2 gate/source link
Also Q3's drain connection via a 1M resistor then 22n/10k connection to the 10k pot ( says 12 volt relay on schem ? )
not sure of that function ...
Tried 100k trim and 250k trim, but Q4 is either 2.3v or suddenly 8.4v ! there's around .5mm area where
you can get the "full" tone and bias, but its short lived !
Perhaps someone could suggest "why" this happens ... mistakes/components are ruled out, I'm just wondering
if that 10k pot is just to feed the reverb section and what that Q3/Q4 stuff is all about  ??

Thanks,

Marty.

[Ge_Whiz]

"Why don't we do a..."

Yes, why don't you? All the necessary design principles are out there, thanks to ROG and others - all you need is the original schematic, and a bit of time and effort.

[MartyMart]

EUREKA !!

I'm getting somewhere now ... OK so the 250k pot is "blending in" clean signal, and when used
alone it's quite a reasonable "clean" tone.
1M pot is the "gain" side .. I removed the little 10k pot off Q3 and reduced the roll off 15n cap
to a 3n3 ... we have some top end now
Best off all, now after ditching the 10k, I have a biased Q4  !!  ( all at around 4.5v drain )
I've increased the 150k resistor to Q4's gate to a 680k and have more level ... whats wierd
is that output volume is not very high ( above unity ) but using an aligator clip lead, if I short
the 1M from Q3 direct to the 680k I get a much louder, but slightly "splatty" signal ... gain
and tone are quite good, as I also increased the Q2 drain cap from a 1n ( ?? ) to a 15n ..
the 1n seems awful small to me !
Any way, I'm ranting, but have an 80% working version now, which is better than yesterday !!

Still could use some help ... stm ... pete ... RG ... Mark   

MM

[MartyMart]

OK last one for now, scrap the 680k ... that was just " B S "  !
No resistor needed here, direct from the roll off section from Q3 to gate works GREAT !
( with a slight re-bias too )
I've full level now, using about 25% of the "clean volume" and 75% of the "gain" control
I have way .. way above unity and a nice "hard" spanky overdrive too    ... oh happy me !

It's still has some of the C30's personality, but some more top end is needed, it's quite mid boosty
in tone, but there's enough low end there ( like the original there's not tones of it )
So a bit of "eq" tweaking and I'll post an update in a few day's

MM.

[hairyandy]

I can't wait to hear/see the outcome of this.  I've always loved those amps, ever since I worked for a Peavey dealer and they were the only amps they made at the time that were worth a shit...

[Dragonfly]

nice job so far marty....

ive done several of these style circuits...orange 120, bogner, hiwatt, vox ac4, etc....

one thing i think several people forget....though ROG certainly "popularized" this style of emulation (as well as refined it), people like doug hammond were integral in developing the technique in the first place....i dont want to take anything away from the ROG guys, who are absolutely amazing, but it'd be nice to see people like doug getting proper credit too

AC

[nelson]

"Why don't we do a..."

Yes, why don't you? All the necessary design principles are out there, thanks to ROG and others - all you need is the original schematic, and a bit of time and effort.

Add to that ist

ORANGE!!!!


edit: and Selmer!

I look forward to an apology.

http://www.elixant.com/~stompbox/smfforum/index.php?topic=40353.0

[Ge_Whiz]

Apology? From whom?

And did you ever build the Citrus? The link doesn't make it clear... 

[nelson]

No I havent built it. I was just making it clear I contribute.

Your post was very accusing, like I was expecting everyone else to do the work.

[tiges_ tendres]

so there is already an orange one, cool. 

I'll see if I can dig up some selmer amp schematics.  Those tiny little amps are my favourites, with all the push buttons.  Should be a snap for anyone else to do, might take me a couple of weeks, but I'm up for a challenge!

[hank reynolds 3rd]

I've done a hand drawn layout for the Citrus/Orange Mkii (plus a few other things)....
I don't have access to a scanner at the moment, but if your patient I'll see if I can get it up sometime this week( busy working week..hhmpphh)

Sam

[Ge_Whiz]

Sigh.