New at runoffgroove.com: Thor

[WGTP]

Being the sick gain pig that I am, I'm thinking you might as well use a dual op amp and add a Tube Reamer or Blue Clipper type circuit to the front end, the way you would a real amp.   

[lovric]

Hey RoG, not only that i like the amps that inspire you but your cover text is great and informative, not to mention pleasant and civilized. Somehow i very much enjoy the fact that your share is so popular.

[petemoore]

  Doing up a 16 pin 'perma-tweek-perfboard' build...
  Looking at Q1C w/the 5k trimpot...is that an error? 
  Also I couldn't remember cap conversions so I brought up this Nf/Pf/Mf chart:
  http://www.radio-electronics.com/info/data/capacitor/capacitor_conversion_chart.php
  and the cap on Q1 output is shown as 1n [1 nanofarad converts to .001uf...small...is that what is intended for SLP/THOR?

[stm]

Pete, the trimpot values are optimised for the JFETs specified for each stage.  A 2N5457 requires a drain resistor around 1.6k when fed from 9V, thus a 5k pot is a good choice of value, as oppossed to the overly large 100k trimpot traditonally employed.  In a similar manner, the J201 requires a drain resistor around 10k, thus a 20k or 25k trimpot is perfect.

The 1n series capacitor just after the first stage is small on purpose, and it produces a low frequency rolloff that has its -3dB point at 160 Hz. There is nothing to be afraid of, since the original valve stage uses a 2k7 cathode resistor in parallel with 0.68uF, which also produces less amplification for the bass frequencies.  All in all, the 1n cap value was chosen so as to match the original amp soundwise (based on listening tests), however you may experiment with its value if you like as this is certainly an important component for tweaking.

Cheers.

[petemoore]

The 1n series capacitor just after the first stage is small on purpose, and it produces a low frequency rolloff that has its -3dB point at 160 Hz. There is nothing to be afraid of, since the original valve stage uses a 2k7 cathode resistor in parallel with 0.68uF, which also produces less amplification for the bass frequencies.  All in all, the 1n cap value was chosen so as to match the original amp soundwise (based on listening tests), however you may experiment with its value if you like as this is certainly an important component for tweaking.
  Cool thanks for the verification/explanation STM! That particular cap, being the first Seriesed in the SP, closest thing to an input cap on THOR, got 4 pins of a socket !
  I got this mostly done on 2 x 16 pin IC sockets, The first socket is for Q1/Q2 and the coupling caps, second socket for the Mu and OA stages..I've tried this kind of layout a few times before, I like both sides of a full IC socket, the wiper lug type are accomodating of slightly larger leads/two small leads per lug...I prefer solidly mounting [two 'sides'] them, just use the whole thing...RS is dwindling down, no more 8pin IC sockets...

[Rafa]

Thanks a lot guys
Cheers
Rafa

[koulis]

Exactly what i was looking for
                                                             
                                                                                   Many thanks...

[Peter Snowberg]

Once again, my hat is off to 'The Groove. 

You guys are fantastic.

[billings]

The writeup mentions the fixed bias mu amp stage as being suitable for emulating the breakup of the LTP moreso than a JFET stage.  Is it a fact that the *JFET* SRPP/mu amp is so strong in the odd orders?  I've messed around with both a minibooster and a tube SRPP on a similar layout, and to my ears the FET minibooster sounded substantially sweeter, although admittedly the two were in completely different places in the signal chain so that evaluation means very little.

[stm]

The writeup mentions the fixed bias mu amp stage as being suitable for emulating the breakup of the LTP moreso than a JFET stage.  Is it a fact that the *JFET* SRPP/mu amp is so strong in the odd orders?  I've messed around with both a minibooster and a tube SRPP on a similar layout, and to my ears the FET minibooster sounded substantially sweeter, although admittedly the two were in completely different places in the signal chain so that evaluation means very little.

The main reason to use 2N5457's over the J201 for the last stage is softer clipping.  In fact, as the Vp parameter of the JFET increases, the clipping is less hard and "rounder".  The MPF102 / 2N5458 / 2N5459 should have even rounder clipping.  In addition, the inclusion of the 390 resistors with the sources help tame the excess of gain and make clipping less harsh.

[petemoore]

  This isn't a Fuzz!
  You've done a Fine Job, the Friends at ROG!!!
  Thank You!
  It's going pretty good and sounds Great!!
  This pedal is making my amp emit smooth sweet sounds ! Quite responsive with amount of OD to attack/input amount, leads in particular are ringing with a Com-Plexi-Ness which reminds me of the plexi sound I could never get enough time on [loud enough to DO that] to get used to, very rarely would an opportunity come up to crank it to that level...I never really figured it out...lol...this Reminds me of it, but doesn't have the 'dont touch hard here' caveats which the amp I had exhibited..I had to be very careful with bass note loudness to avoid 'overwhomping'...
  So the pedal has some of the characteristics, lacks some of the caveats...sounds about as real plexi as I've gotten close to with a real plexi, generally easier to play >IME. I have excellent feedback/sustain on lead notes, even at moderate volumes...haven't had the TS out lately, none of my other pedals really even try to do the smooth 'settling into a sustain pitch' like this...
  I'm Happy !
  The Thunderchief I built...well that's quite a different circuit, I think the Mu Amp in there is a great choice, I like Mu's anyway, this pedal has a very nicely voiced distortion tone IMO.
   

[petemoore]

States "Dig In" !...push on it to get out the great stuff !
  This put a new angle on picking and style after a while. At first I wasn't quite sure and didn't know what I have...
  Being the 'sick gain pig' that I am, I'm thinking you might as well use a dual op amp and add a Tube Reamer or Blue Clipper type circuit to the front end, the way you would a real amp.
  Yeap, it's tasty treat , gain ... and it's hard to tell it': "I've had enough"..'No More for Me'...'Very Good but if I add Anymore I may appear a bit shaggy from the side'...shaggy is cool, but I'm trying to cut back !
  That OA could be a single, but why, dual is more space effecient..if I were to build this with the 'other OA used for something Distortey, I'd put it on a Bypass.
  Getting used to the dynamics / response of the circuit...I began to re-develop a dig in style of picking..very fun sound to 'lean on hard/tread lightly/play medium, let the sustain work for me.
  Reminded me of my 'amps of type' I had..at first plug in, quandried by the tone/unsatisfied preconcieved notions [I bought a Plex/4x12 thinking Bad Co. AC/DC..greeted by something very different [great, but 'dull' compared to expectations] upon first amp test. Thor is quite similar, took a minute or three of playing before I actually dialed in the dynamics/response thing, besides dialing in the gain/vol/amp vol.
  It wasn't/isn't 'till I began digging in, acclimating myself to the response, altering picking style etc. before I understood what could be released by whomping on JB Good rythms, letting single/double note leads sustain etc. a 'workingmans' sound, it doesn't play itself like a Fuzztone...you have to lean on it!
  Then I added somethings and had my longtime P.C.Expectations satisfied.
  Very pleasing, usable high gain tones, dynamics, sustain.
  After hours of adulated playing on this one, it's a great 'base tone' circuit. Stick a Fuzz or Dirtbox before it or my Starved MuBoost after it...WOW is that fun.
  Preliminary summation:
  Great sounding circuit !
  Does the 6' amp in a 5'' box thing really well.
  Responds to dynamics, very fun to play.
  Responds to being Fuzzed or driving Dirt/boost boxes really really nicely.
  A1 Jfet amp sound!...does the 'ampinbox' thing convincingly, in some ways better than the real thing! [doesn't require shaking the rafters in the house next door]...easier to work with than: a way too big tube amp trying to sound big when dialed to miniscule settings, requiring a dirtbox to come close to sounding anything like itself cranked. Surely this would make a plexi turned down sound more like a plexi turned up.
   I can solidly recommend this distortion circuit to anyone trying to get a 'plexi sound' out of a plexi at low volume, actually any volume...unless you have a plexi and are already getting 'that'..I rarely to never did...I always had to put a dirtbox on it anyway.
  Nicely voiced balance of great stuff: Sustain 'pitch finding', dynamics/compression/distortion...but it isn't, and doesn't do 'fuzzbox', without a fuzzbox.
  Turn the gain knob down a bit for thick 'dirtboost' tones.
  A highs adjust knob would be a useful addition, I have this two knobber in a 3knob Box!...maybe a few switchable mods, lifting a bit of the LP filtering near input...lotsa places you could mess with it.
  Superb sounding circuit gets finishing touches and pedalboard status [right after the RM/Dist+ box, before everything else in chain.

[Xavier]

I have added a perf layout for it. Hope it's correct, at least it looks so.
http://aronnelson.com/gallery/albums/Layouts/Thor.gif

[gaussmarkov]

sweet.  thanks very much! 

The active filter idea is a good one- Coincidentally, I came up with a very similar idea for a design I've been working on for a few weeks.

yeah, i've been interested in this, too.  seems like the passive tone stack approach has been a default.   

[phil]

I have added a perf layout for it. Hope it's correct, at least it looks so.
http://aronnelson.com/gallery/albums/Layouts/Thor.gif

Thanks for the Layout Xavier - This will be my first build for 2007!

[Xavier]

I have added a perf layout for it. Hope it's correct, at least it looks so.
http://aronnelson.com/gallery/albums/Layouts/Thor.gif

Thanks for the Layout Xavier - This will be my first build for 2007!

Please let us know how it works for you. Also let us know if you find any error in the layout

[phil]

Please let us know how it works for you. Also let us know if you find any error in the layout

Will do - I just ordered the parts so when I get them I'll start the build and update this thread with the results and any necessary modifications to your layout if any. Thanks again for the layout - even if it's not 100% it's a really big help as I just don't have the hang of creating decent layouts from schematics yet ...

[petemoore]

  Count the number of connections at each node of the schematic, count where the traces go on the layout, printed versions makes this easier I think.
  Also at each node, note how many parts connected there have 'orientation, and what they are.

[MikeH]

Does anyone have any soundclips of the thor yet?  I want to hear it; I'm guessing it sounds like the Thunderchief only more badass...

[gaussmarkov]

thanks again to xavier for the layout.

i think i found one error.  first, note that the labels on Q3 and Q4 have been switched relative to the rog schem.  that's not an error, but you'll need to know this in order to check this error:  i think that C9 is incorrectly wired to C6 at e16 and e17.  instead connect e17 to e14 by running a trace or wire under C6.

if i'm confused, apologies in advance! 

all the best, gm