The Thunderbird Rises...

[Frank_NH]

Well, here it is in all its glory - the new Runoffgroove Thunderbird via the wonderful 1776 Effects PCB!

Just finished this beast tonight, and it took a bit of effort due to the large number of components and some boneheaded mis-soldered parts that required desoldering (grrrr ).  I didn't have enough 10K metal film resistors so I mixed in some carbon film.  My only other comment on components is to watch out for the 470 nF caps - get the smaller box caps that Smallbear sells, otherwise you won't be able to fit them in certain spots on the board.  I really like the 9mm pots and how neatly they mount on the board - should make it easy to box.

One more detail.  I rigged up a stereo jack, as there is a ground connection from the power section which connects to the ring of the stereo jack.  Hence I had to use a modified version of my testing rig to check out the circuit through my amp.  Seemed to work fine.

OK, OK - so how does it SOUND??  I tested this with my trusty Fender 51 Pawn Shop guitar (single coil neck pickup and humbucker at the bridge) into a clean Roland BC-60 1x12 amp.

One word summarizes the sound for me --- WHOA!! 

The Thunderbird is the muscle car of amp sims in my opinion.  The gain on this thing is tremendous!  And I noticed that running at 24 volts provides a very detailed, articulate overdrive sound which is free of flubby, grainy artifacts that I sometimes hear in 9V circuits.  In short, it comes the closest to sounding like a Marshall amp out of all the pedals I've built.  

There are six control pots on the Thunderbird.  The Bass and Treble controls can be adjusted to mix bass and treble, and the "Tone" control allows you to go from the "Normal" to "Bright" modes of the real amp in a continuous fashion.  This is a brilliant option as you can dial in just the right amount overall brightness in the sound (and there is a LOT of treble to be had if you want/need it).  The Gain and Level do what you'd expect, and the gain as I mentioned is huge!  A Marshall on 11!  Finally there is a "Presence" control but it only provides some filtering of the very high end frequencies (you can detect it if you listen closely).  I just keep this full up.

The one caveat that I will mention in my short time testing it is that it is somewhat noisier than your average overdrive.  This may be due to my rigged up input jack and unshielded cables or it could be one of the consequences of operating at 24 v.  I think it can be reduced by boxing the circuit and perhaps using shield cable for the input, but I will explore this more and report back.

By the way, I used 1 LM833 and 2 NE5532 op amps (as these are what I have available in my stash) for the required three dual op amps.  I may experiment with other op amps to see if the noise level is affected.  The original circuit called for 3 LM833s.

So, in summary I'm really excited about using this effect live IF the noise can be tamed a little.  Over the next few days I'll be experimenting with it, and checking the voltages.  I may also examine key points in the circuit with my audio probe to see if the noise is occurring in at a specific location.  We shall see.

Rock on!!   

[Muadzin]

Nice! I do plan to build one myself one day. If you want to tame the noise maybe an onboard noise gate is in order?

Question, regarding the spacing of the pots, what kind of knobs could be fitted? I always use Marshall style knobs for dirt boxes and that would be kinda mandatory I'd think with a Marshall amp sim pedal. But when I look at the spacing of the pots I'm not sure they would fit.

[Heath]

NICE!!!  I'm just waiting for my Tayda order to get in.  Should be in by tomorrow, so this will probably be a weekend build.  I don't keep 9mm pots in stock as they're more than twice the cost of the 16mm, but I wanted to do this one up right.  It also gave me the opportunity to snag some LM833s as I was down to only 1 in my stock.  I built something else a while back that used them, but can't remember what it was.  Anyway, you have me all excited about building this now.

By the way, I LOVE the Fender pawnshop '51.  GREAT guitar.  Is yours stock?  I've found that a Dimarzio Bluesbucker sounds friggin excellent along side the tele-style single coil.

[Frank_NH]

Question, regarding the spacing of the pots, what kind of knobs could be fitted? I always use Marshall style knobs for dirt boxes and that would be kinda mandatory I'd think with a Marshall amp sim pedal. But when I look at the spacing of the pots I'm not sure they would fit.


I've got some of these 1/2" control knobs from eBay.  They're perfect for close-spaced pots as with this build.

1/2" knobs from eBay

By the way, I LOVE the Fender pawnshop '51.  GREAT guitar.  Is yours stock?  I've found that a Dimarzio Bluesbucker sounds friggin excellent along side the tele-style single coil.


I modded mine with a better bridge and changed the rotary switch to a Les Paul three-way switch.  And I'm using an old Tele neck that had from another home-made guitar.  The pickups are stock and sound great to me.  I like to use it for testing as I can get both single coil and humbucker sounds from one guitar.

By the way, I played the Thunderbird again this morning and there is definitely an issue with the ambient hum/noise at higher gains.  I'm going to check out the circuit more thoroughly over the next few days to make sure I didn't mess anything up.  Despite that, the sound is phenomenal!

[Frank_NH]

Here are some pic of the completed build.  It was a tight fit in a 1590BB!  However, there is a lot less noise when this thing is boxed and grounded properly.

By the way, you don't need to use Q1 or a stereo input jack if you're not going to use a battery.  There is some info on this at the Madbean pedals forum, but let me know if anyone wants more details.

[rocket88]

Totally awesome. How does it sound all boxed up?

[Frank_NH]

rocket88 wrote

Totally awesome. How does it sound all boxed up?

It is definitely much quieter in the box.  I used proper star grounding at the input jack sleeve.  What I have noticed, however, with this circuit is if you turn up the treble and the Level, you can hear some white noise / hiss, similar to a tube amp.  So I guess if you're trying to emulate a tube amp like a Marshall Super Lead, you may as well emulate the hiss!    Having said that, the Level doesn't need to go much above 12:00 to get well above unity gain, and then combined with the Gain control, you can easily get that saturated, massive, crunchy Marshall sound, and the hiss is not a problem.  There is a lot of treble to had, but it can easily be dialed back.  The Tone control, for example, provides a continuous variation from the Normal to Bright channel on the Marshall amp, so you can set the Treble and Bass controls to taste, then dial in more upper mids and treble using the Tone control.  In think they should have eliminated the Presence as I find it doesn't do much (maybe you can hear a little sheen in the higher frequencies > 3 Khz).

All in all, a great design from the ROG folks, who have done so much for the DIY community over the years.  I think this puts them in a unique position where one of their designs (in my opinion) has gone well beyond the current crop of boutique Marshall-style overdrive/distortion boxes.  It will be interesting to see if they release some updated designs for Britannia, Umble, and Azabache.

[Muadzin]

If you ask me, the biggest advantage this beast has over other Marshalls in a box is..... no JFET's. Don't get me wrong, pedals like the Pinnacle or DLS sound awesome, but sourcing and matching JFET's is a pain in the ass. Opamps are so much less of a hassle.

[Travis]

Definitely easier to build with op amps than JFETs, but Frank here is the JFET king!

Your build looks excellent Frank! Glad to hear the noise is more under control after boxing

[Frank_NH]

Well, maybe the JFET queen but not the king...

Seriously, jfets are fine if you want to take the time to measure them and then modify the source and drain resistors so they are optimally biased.  I agree that using op amps permits getting more uniform results from a given circuit.  And, as has been stated by others, jfets aren't perfect substitutions for tubes, so there's never any guarantee that an "amp-like" circuit will sound like the amp it's based on.  That has more to do with tweaking the pre and post gain filters and tone stack, among other things.

For now I'll see if it's feasible to use the T-bird live for some crunchy Marshall tones using my Gretsch 6120 DSW.  Right now my effects chain is guitar-->Klon(e) set as a preamp -->overdrives-->chorus+delay-->clean amp.  I have been using an RP1000 but am moving towards an all analog rig which, to my ears, sounds and responds much better than a digital multi-effects system.

[alltrax74]

I finally finished building mine yesterday
This is a little monster, a ton of output level and gain (no problem for metal with drop tunings), all controls (except presence) are very reactive.
Can't wait to play it at band level tomorrow

[Silver Blues]

Nice build, I love the color of that box.

[Sensei Tim]

nice work, guys!

how does this circuit compare to the jfet based JCM800 preamp sim that's on the blog?