Blackheart Little Giant Tube Overdrive "Pedal"

[Hugh Jazz]

I hate hunting for answers across different forums, but I inquired about my project on a tube amp forum a while back and got a mixed bag of answers.  Since what I'm ultimately trying to do is design a really big and heavy tube "FX pedal" circuit, this forum is probably where I should have started.  What I'd like to do is take a 5w tube guitar amp head with a dummy load and a lineout circuit after the output transformer (so the lineout signal is post power amp to get gnarly power tube distortion), run the signal from the head into a pedalboard, and then run the pedalboard signal into a tube amp combo (reamp).     

I know plenty of folks have implemented this idea using a Herzog/Firezog-type lineout circuit like this http://www.charlestongolf.com/lineout/pages/Firezog%20also%20try%2010k%20with%205k%20pot.htm, but I think many would agree that the Herzog-type lineout circuit just doesn't reflect the actual tone and feel of the amp's signal even when reamped and run out a speaker.  To me, the Herzog lineout sounds like a really muffled fuzz pedal.  While that's a cool effect, what I'd like is for the lineout to be more reflective of the sound of an overdriven 5w single-ended amp and not a Big Muff fuzz.  I've also heard horror stories about impedance and/or voltage issues on the Herzog-type lineout damaging pedals when plugged directly into them. 

Here's a sample of the "mixed bag" of answers I got from the tube forum:

1.  A simple resistive dummy load + attenuated output lineout w/ a simple tone filter like this:  https://taweber.powweb.com/store/loadline_schem.jpg
2.  A "reactive" dummy load with resistor & inductor in series + attenuated line out (no tone filters)
3.  A dummy load plus attenuated line out w/ a complex speaker emulator circuit like this http://www.runoffgroove.com/condor.html
4.  Some combination of the above options
5.  Some combo of the above plus a buffered output

I'm getting really long-winded here, but I hate trying to help someone who isn't specific, so here are the 3 things I'd like to accomplish with my lineout circuit:

1.  As natural sounding as possible
2.  Proper FX-level output voltage, impedance, etc for running into a pedalboard (most of these circuits are designed for line-level output)
3.  Capable of running the signal from the Little Giant head in the backline to a pedalboard on the floor (signal then to run to input of combo amp in the backline) without wimping      out (buffered output???)

I'm much more of an amp guy than an FX guy, so I really appreciate the input of this forum.  Any advice, opinions, know circuits, etc are very appreciated--I'm tired of buying too many parts and building too many circuits to find something that works.  Thank you! 

James L. 

[PRR]

There's no good answer.

If there were, it would be $69.99 at Guitar World.

And what is "natural sounding" in electric guitar? The natural sound of a hard steel string isn't very interesting, we must make it "un-natural".

Yes, speaker-load is very important. Small signal emulators do not load the naked pentode the way a speaker does, and I have my doubts about any load other than a working speaker.

As for levels, design your attenuator for a reasonably low output impedance (1K-10K) and adjust the level so that volume does not jump a lot when you bypass it. There are pedals which will NOT be happy with anything other than a gitar pickup source; but the rest only need a reasonable line impedance (more to handle line capacitance and krap then to drive loads) and a voltage which does not blow their minds.

[lowend]

You want to use a full blown amp as an effect unit

[Hugh Jazz]

You want to use a full blown amp as an effect unit

Absolutely!  Crank the bejesus out of the Blackheart so it's giving me power tube overdrive, knock the signal down, run my effects after the power tube overdrive and then reamp.  Best of both worlds--power tubes working hard and FX after the overdrive.  Plus, used Blackhearts are cheaper than many pedals (Valve Juniors are even cheaper). 

[Hugh Jazz]

There's no good answer.

Beginning to look that way, and I've been shocked at the sheer number of options for what I thought would be a simple thing.  I think I may need to bite the bullet and try a few manufactured emulators with load lines and see if it's even worth the trouble.  I know that some designs are proven winners--Palmer, Koch, and some high-end attenuators with line outs, but they're all overkill for a little 5w amp.  They're also ridiculously expensive, so buying one isn't an option.  But, if I find one that I can try out and know will work how I'd like, then I'll see if I can figure out the design topology and work on my own line out based off it. 

In the meantime, further ideas are welcome on this thread.  Thanks for the quick reply PRR.

[bancika]

I'm doing the same thing with my ax84 4-4-0 amp: amp -> resistive/inductive load -> palmer speaker sim -> recorder
You can find info on the dummy load and a bunch of clips here

http://diy-fever.com/misc/dummy-load/

and here

http://diy-fever.com/amps/ax84-4-4-0/

Cheers

[jasperoosthoek]

Nice idea! You can even use the 3W/5W switch as a boost+bright switch. You'd have to replace it with a foot switch thought. But beware there is a pop when you switch it. But it is not affected by the volume control so if you fully crank it you probably can get away with it.

I'm testing my blackheart head next week with a drummer. It'll probably be loud enough for a blues session. I'm not impressed by the closed back speaker cabinet though which has a sharp resonant peak at the lowest B note on a guitar... But you won't have to worry about that.

[DougH]

http://www.charlestongolf.com/lineout/pages/Firezog%20also%20try%2010k%20with%205k%20pot.htm

Boy, I hate it when people copy my sh!t and repost it on their own sites without asking permission...

[DougH]

I have my doubts about any load other than a working speaker.

I did too until I built an Airbrake. I think the key to making resistive attenuation work is to get the load impedance right, which is not the same as the impedance rating of the reactive speaker.  It works great as a speaker attenuator, have not tried implementing it with a line-out.

That said, re. the original post- You need three things:

1. Load for the amp.
2. Line out.
3. Filter to emulate the freq response of the speaker.

If you *just* want to reamp through a guitar speaker, you don't need to worry about 3. I've played with resistive and reactive loads and in all honesty, I don't hear enough difference to be worth agonizing over- *if* you get the impedance right with the resistive load. Look at some speaker impedance curves and aim for a value that is an average of impedances in the freq range you are interested in. It will be quite higher than the "impedance rating" of a speaker.

I've also played with re-amping and it sounds very good. Probably the best method for doing the "quiet cranked tone" thing with a speaker. Does it sound exactly like the original amp? Absolutely not. *None* of the attenuation methods including VVR etc will give you the exact same sound as the original amp. They will all color it somewhat in at least subtle ways. If you want the exact sound of your amp cranked up- get a good pair of earplugs and find a place where you can rehearse without disturbing others and just crank it up. You have to accept the fact that everything affects everything- there's no way to get a facsimile of your loud amp sound at a low volume. But you can get a very good sound that is very usable. Focus on that instead, and this gets a lot easier.

[jasperoosthoek]

It seems like a lot of people only look at the coil of the speaker when they build a reactive load. That's like having a speaker that is not able to move. Imagine fixing the coil with epoxy. Obviously a real speaker does move and works like a microphone. It stores energy as a moving mass and as a spring. Part of the energy is sent back to the amp as it picks up its own movement as a microphone. IMHO the most accurate speaker simulation without sound is a real speaker where the cone is replaced by a spring and a damper (like in a car suspension). I've never seen that, I also don't know if it really would be that much different but at least it has a similar mathematical description.

You could play around with a cheap model car suspension that you get off ebay. Or keep it simple and just use a simple LR reactive load and accept that it won't be exactly the same.

[DougH]

You could play around with a cheap model car suspension that you get off ebay. Or keep it simple and just use a simple LR reactive load and accept that it won't be exactly the same.

Or keep it even simpler with a some carefully chosen power resistors and call it a day...

[jasperoosthoek]

Absolutely. My point is just that adding an inductor doesn't even get you halfway.

[dan5150]

This might add complexity (and cost) to the rig, what what about running the blackheart into an ISO cab? You would need to probably insert a mic pre to it would properly drive the pedalboard. But wouldn't that get you closer to where you want to be tone wise? At least you wouldn't be "simulating" a speaker.

I have never tried that, just thinking and typing out loud here...

[Hugh Jazz]

I'm doing the same thing with my ax84 4-4-0 amp: amp -> resistive/inductive load -> palmer speaker sim -> recorder
You can find info on the dummy load and a bunch of clips here

Cheers

Thank you!  You MAY have convinced me to just save and get a Palmer.  It seems silly that a passive item with such few components is so expensive, but they work and Palmer owners seem to swear by them.  Don't know if there's some magic in their inductors or something else that nobody's quite figured out???  That's the most natural sound I've heard yet.  Love the 4-4-0 too

[Hugh Jazz]

This might add complexity (and cost) to the rig, what what about running the blackheart into an ISO cab? You would need to probably insert a mic pre to it would properly drive the pedalboard. But wouldn't that get you closer to where you want to be tone wise? At least you wouldn't be "simulating" a speaker.

I have never tried that, just thinking and typing out loud here...

That's the best way to go, but I really don't want to lug one around to every gig.  Definitely a good option for a home studio though

[Hugh Jazz]

Boy, I hate it when people copy my sh!t and repost it on their own sites without asking permission...

Sorry Doug--didn't know he posted it to his site w/o your permission. 

[jasperoosthoek]

You could also just mic it with a smaller cabinet. Or buy an even smaller 1/2 watt amp and do the same. If it's for a live gig than your 'master' amp will be much louder anyway. You could even direct the speaker to the back of the stage.

[petemoore]

  There's always a 'simpler' solution, but getting it going isn't so simple.
  For now it's all about accoustic impedance and getting the signal you want, that of a tube output and speaker and their interactions, probably some accoustic damping [enclosure or enclosure +speaker suspension], of course still transformer coupled.
  Necessarily large, heavy, and requires 2 amplifiers or a way to [open or adjust the accoustic blocking] to get anything usable except a source signal.
  The 'other side' [of the amp/cab/speaker for tone] could be approached with the same prehensions as recording, a whole nuther new ball of sound to unwind, much like getting an amp to sound nice was.
 

[Derringer]

Never seen or heard of this being practiced but what if .....

You mic up the small amp the way you like it, then run the mic into a variable booster/buffer and then run that signal through all of your time based and modulation effects, buffered out to another amp's or mixer's input?

[jasperoosthoek]

I've seen Dweezil Zappa last year in a medium size venue. His and the other guitar players amp were directed to the back of the stage. The miced signal was sent to the PA and to their monitors.

Not the same as running it through a chain of effects and another amp though. But at least the amps were directed the wrong way . You would get twice the influence of the speaker unless the second cabinet is more like a hifi speaker (monitor). I kinda like the idea of using a cheap tube amp as an effect but I think I would go for a simple resistor/inductor circuit. And as Doug said call it a day.