New at runoffgroove.com: Thunderchief

[petemoore]

To the lab experiment, level playing field approach for recording sound clips: With all the myriads within myriads of possibilities for outside elements to influence the sound of a circuit, it makes perfect sense to have everything outside the cct comparisons to be controlled elements.
 That being said, most of these circuits were designed to have outside elements influence their sound.
 I use tube amps for testing. Cranking the amp even a little brings out tones that are created or influenced by the effect circuit, the amp, guitar, speaker, effect circuit, cables, air [moisture,pressure etc], strings, pickup height....I'm sure there are other things influencing the perception of sound.
 I think most of us here, deep down either use nice tube amp, or pick up enough info to begin wondering how much to want for tubes]..
 Output tube driving speaker:..the most applied [or emulated] guitar effect of all time.
                      "Sounds just like a tube amp"

[petemoore]

Great Job Recording!!!
 I wish I could get such wonderful playback sounds.
 Thunderchief soundclip.. has a great replay value, I load and listen when I need a charge...!!!

[Doug H]

Sound clips are a funny subject because everyone wants something different from a sound clip. Some people like the little 'mini-songs', others want to hear just a clinical run-through of putting a pedal or amp through it's paces with nothing else to distract it. Some people want to hear it through a tube amp, others direct for comparison purposes, others through a clean SS amp. The only thing that is consistent is that you won't be able to please everyone.

In the end, I don't think soundclips really tell you much about how a particular pedal is going to sound through your rig, with your guitar, in your room, at your gig, etc. They just give you kind of a hint or a point of reference to compare with other things.

When I do a soundclip I just try to bring out the best in the pedal, showing it in the best light, whatever it takes except for post-production eq-ing tricks and etc. It's just meant as kind of a snapshot of the pedal's potential.

In general, for my "amp-emulators" I like to use a clean SS amp. Sure, it sounds good with a tube amp, but tends to get colored by the amp sound so much it ends up just being another facet of that particular amp's sound. OTOH, if I can show it making a sterile SS amp sound "tubey" or whatever, than that's really showing something. But, IMO vintage fuzzes and boosters were -made- to drive tube amps, so recording them with anything else just doesn't make any sense. Their purpose in life is to drive a tube amp, AFAIC. To me, it's just a matter of doing things in the proper context.

I mic all the clips, IMO, I don't like the sound of direct and don't use it anyway. Comparing direct recordings doesn't help me since these circuits sound a lot different through a mic'ed amp. I don't mind modulation effects recorded clean and direct, though. That's just my opinion, and I have many.

I like doing little 'mini-songs' because there is an emotional connection I have with music that I can't separate when listening to clips. I love tonefrenzy, great resource and site, but after hearing 2 or 3 "test suites" of overdrives my ears go numb. I just can't concentrate on it anymore. And all the little subtle nuances and differences kind of get lost in the noise anyway, when you consider the variables of guitar, amp, and etc between what I'm using vs. what was used in the clip.

Anyway, that's just my 2 cents, no flames intended. This is a good discussion. I would love to hear Ammscray's clips if they could get hosted somewhere.

Doug

[petemoore]

I;ve built many Runoff Groove Effects based on the soundclips.
 Spent hours just listening to them, I appreciate them very much, also that they are all done with the outside elements [sim and soundcard] stated.
 This puts all the recorded effects on a level playing field, even tho that  may not be the one you or I use, or the one that a particular effect shines best in.
 Once you stray from a given set of variables, the possibilities run wild.
 I like the idea that the soundclips are done in a controlled environment.

[RDV]

Does anyone know where to get the .68uF caps that are in this and number of other projects of late? I would prefer the smaller Panasonic (F) type if possible. It seems Mouser only has the larger higher voltage types, & Smallbear doesn't have them at all..

Regards

RDV

[Eddie]

Let´s concentrate on the thunderchief!

Could someone do me the favor and post the D/G/S Voltages of the third Jfet( third Jfet from input view)?

I have the sound of a misbiased Jfet and I think that the third one is the problem.

See my earlier post in this thread(page 4).

I measurded these voltages(third BF245A):

d 4,5
g 4,4
s 0,4

Yes i checked the orientation. I changed this Jfet too (used a new one).

I got this unit 90 % working and I want to "win" this time! :lol:





THANKS!!!!! :idea:

Eddie

[Jay Doyle]

My voltages on the BF 245 Pinouts, starting with the first, "left" BF 245:

1:
D 4,5 v
g 1,4
s 0,0

2.
d 4,6
g 1,15
s 0,0

3.
d 4,5
g 4,4
s 0,4

4.
d 4,46
g 1,146
s 0,0

Ist the gate voltage of the third BF 245 too high?
Please help me to find the mistake.

Eddie, first off let me start by saying that you are subbing for an essential part of the design. I realize that you may not be able to get J201s but you really have to use the right parts if you expect to replicate the sound of any particular design.

That said, ALL of the FETs are misbiased. For a JFET to work properly, the gate voltage has to be BELOW the source voltage. This makes me think that you have the pins mixed up, more specifically the gate and source terminals mixed up. If you look at the schematic there is no way for any of the JFETs, except the third which would still be below the source, to have its gate be anywhere but at ground. Double check the pinout, I think that you will find that you have the gate and source terminals swapped.

Like I say on my schematics: "Experimentation, once you get the circuit up and running as shown, is encouraged."

[Eddie]

Thanks Jay !


I`sorry I mistyped the voltages, G was Source (mixed up by typing..)

So here are my "new" values:
1.
D 4,5 v
S  1,4
G 0,0

2.
d 4,6
S 1,15
G 0,0

3.
d 4,5
S 4,4
G 0,3
4.
d 4,57
S 1,14
G 0,0


It is very hard to get the J201. So I thought I could use the BF245A.The source voltage of the third is a higher value.

Thanks for your help!

Eddie

[Jay Doyle]

OK then. The third JFET is going to have a significantly higher source voltage because it has a higher resistance on it's source. The third one has about 10k of resistance on it's source whereas the second and fourth have 1k and the first has 2k7.

Looking at the BF245A datasheet here you will see that the Vgs(off) value for these JFETs can vary from -0.25V to -8V. This is a huge swing and unfortunately one of the main problems with JFETs. If you have one in that has a Vgs(off) on the lower end, your JFET is biased so that it is always off. You may need to try several different BF245As until you get one that works.

This is a good example of why to use the parts specified. Sorry to beat the horse, but there is a reason the designer's picked the particular parts they did: because they make the circuit work. Subbing for JFETs is a generally bad idea; part variation is bad enough within the same part type, forget trying to make another part work!!!

Good luck.

[Doug H]

I agree with what you are saying about using the right parts, Jay.

But his 3rd stage should bias up okay. The 1M gate shunt resistor is referenced to the bottom of the 470 source resistor. So it should bias up like it has a 470 source resistor.

However, now that I think about it, I had a problem with excessively large "tail" resistors in the "PI" when I designed the Meteor. Hmm...

Doug

[Ansil]

[sings loudly to the tune of when the saints go marchin in]

all those soldering irons,, gettin cold,  all those circuits getting old
im gonna turn off my computer and take my a** back to work


hmm figured if i didnt' do it Tom Would have

[Joep]

Eddie,

I'm pretty sure there was a germany webshop were the sold the J201 and some other US-type transistors. Only I can't remember were, maybe some other forummembers remember??

You can always order some from Small Bear (http://www.smallbearelec.com) They are pretty cheap. Don't formet to oerder a few more for future Runoffgroove projects.....

Bye,

Joep

[Gary]

However, now that I think about it, I had a problem with excessively large "tail" resistors in the "PI" when I designed the Meteor. Hmm...
Doug

I noticed this, too.  There is a point (over 10k?) where the source resistance becomes too large to let the jfet bias correctly.

Eddie,

Here's voltages from the prototype Thunderchief's 3rd stage:
D 4.3  (used a fixed R instead of a trimmer)
S 0.5
G 0

[Jay Doyle]

Here's voltages from the prototype Thunderchief's 3rd stage:
D 4.3  (used a fixed R instead of a trimmer)
S 0.5
G 0

OK, now I am really confused. I didn't think about it but Doug is right, it should be like the source is biased with a 470 ohm resistor. But if Gary's voltages are right, and there is no reason to think that they aren't, then if the gate is at ground, the feedback to the third stage is being shunted to ground.

I'm all kinds of confused on this...

Must be because it is Friday.

[Eddie]

Thanks for posting the voltages.
My Source voltage is over 4 volts. Maybe I have something wrong at the Source resistors (470 , 4k7,4k7, Ground).  

What is more likely, something wrong at the source or the wrong Jfet?
I have found a online shop in Germany  (sells j201)
http://www.banzaieffects.de/parts/transist.htm.


Eddie

[Gary]

But if Gary's voltages are right, and there is no reason to think that they aren't, then if the gate is at ground, the feedback to the third stage is being shunted to ground.

I'm all kinds of confused on this...

Must be because it is Friday.

Sorry, I forgot to go another decimal place.  The gate of the proto is actually at 0.08V.  Not much, but some difference.

I had an earlier build that had these pin voltages.  It works fine and sound similar, if not the same.  (these are voltages from an earlier build, not the one in the clip)

D 4.5
S 2.3
G 1.2

No matter which jfet I stuck in there, when biased at the drain to 4.5V, the source and gate always set around these points.  It doesn't make much sense on the surface, does it?  Anyone want to take a shot at explaining this?

[Joep]

Eddie: That's the one!

[B Tremblay]

The pin voltages for all four FETs have been added to the article: http://runoffgroove.com/thunderchief.html