DIYstompboxes.com

DIY Stompboxes => Building your own stompbox => Topic started by: ejbasses on May 11, 2004, 01:20:30 PM

Title: To the people at runoffgroove.com....
Post by: ejbasses on May 11, 2004, 01:20:30 PM
first of all, your jfet emulations rock! they sound great. Plus your site is just perfect. easy to follow builds and layouts plus notes.

Im primarily a bass player and i was wondering when are you going to feature a jfet emulation of something bass specific like an SVT or other classic bass amp?

thanks!
Title: To the people at runoffgroove.com....
Post by: Gary on May 11, 2004, 03:49:28 PM
No promises, but we'll look into it.  What amp?  (simpler yields better results)
Title: To the people at runoffgroove.com....
Post by: Paul Marossy on May 11, 2004, 04:22:52 PM
How 'bout a Fender Bassman?
Title: To the people at runoffgroove.com....
Post by: Gary on May 11, 2004, 04:35:46 PM
The Bassman is so similar to the Thunderchief.  It would be fairly easy to convert the TC over to a Bassman.

How about an Ampeg SB-12 Portaflex?  I used to have a '67 or '68.  It could be pretty good for bass or guitar with the tone stack included.  I may give it a shot as soon as we finish wrapping up the ones we are working on now.
Title: To the people at runoffgroove.com....
Post by: Chris Goodson on May 11, 2004, 04:42:39 PM
Thanks for bringing this site to my attention, I don't know why I hadn't come across it before.  Perfboard layouts!  I wish there were more of those around.
Title: Rockets
Post by: petemoore on May 11, 2004, 09:21:07 PM
My first Real Playout' amp. A real Rockin' unit too.
 That thing really sounded great! MXR DIST+ [Ochre] optional.
 I had a master Vol installed, but left it most the way up all the time.
 The Speaker Bluw, I put in a 'not the same as' [Jensen Special Design Concert Speaker]...OUCH...
 That's when I got to start using my Marshall Super Lead 100w by proxy...I heardL "That amps too loud!!!}, 'till I got four 35w celestions at bargain price [just before the store got busted for movin' new stolens][I had nothing to do with that].
 Basically going from a 'little too little' to a "Big too BIG"...DIST+ on the whole time..then this new ROSS Flanger...not bad !!!
 I'm just glad to hear youre getting a kick out of the Rocket, I sure did.
 The lead songstress of our band gave me a great deal on the amp, a much better 'clubber' than what I had going through that clumsy sounding 100w....which could blow your face off, and would, in large places cab facing the wall...lol !!! Stand in the corner..you've been a very, Very bad amp.
Title: To the people at runoffgroove.com....
Post by: bobbletrox on May 11, 2004, 09:35:40 PM
Quote from: Paul MarossyHow 'bout a Fender Bassman?

*drool* yes!
Title: Yipee!!!
Post by: ejbasses on May 12, 2004, 12:16:06 AM
Hey thanks for the replies!

Anything would be great specialy those ampegs. Maybe an SVT perhaps? or those ampeg flip flops?
Title: To the people at runoffgroove.com....
Post by: Alpha579 on May 12, 2004, 12:27:31 AM
Gotta say, god bless that site. Ive learned alot about fets from ol Mr Tremlay and Mr Gary. Thanx alot you guys! Your absolute genius's!
Alex
Title: Re: Yipee!!!
Post by: Gary on May 12, 2004, 09:00:42 AM
Quote from: ejbassesHey thanks for the replies!

Anything would be great specialy those ampegs. Maybe an SVT perhaps? or those ampeg flip flops?

The SB-12 is a fliptop.  It had a killer blue back Jensen in it.  Funky little four conductor XLR type cable that plugged into the speaker cab.  The top of the "head" was perforated steel painted black.  They used two 12AX7s and a pair of 6L6GCs and a 5AR4 rectifier.  You could fry bacon on top of the amp after you had been playing awhile.  I loved that amp.  Too bad I sold it a couple years ago.

The SB-12 is basically a lower powered, simpler old SVT.  The bass and treble controls are very similar.  The only real difference is the lack of all the shift switches and the extra watts.  I think it may work out OK.  We'll see.  I'm sure my wife would love to have something like this to run her Longhorn into.
Title: To the people at runoffgroove.com....
Post by: javacody on May 12, 2004, 01:47:04 PM
Hey Gary, if emulating a 59 bassman, would I model just the 12ay7 and two 12ax7s? Or would it be necessary to model the power tubes as well?
Title: To the people at runoffgroove.com....
Post by: B Tremblay on May 12, 2004, 02:10:57 PM
Like Gary mentioned earlier, working with the Bassman would be similar to the Thunderchief.

We omitted the tonestack and the stage before it, but a visitor to the site requested the schematic of a "full" version shown below.

(http://runoffgroove.com/tc-tone.png)

You should be able to develop a decent emulation by comparing it with the Bassman schematic.
Title: To the people at runoffgroove.com....
Post by: claydavis on May 12, 2004, 02:58:15 PM
check out the preamp at:

http://www.albertkreuzer.com/preamp.htm

it's supposed to sound pretty good, and it looks pretty SVT-ish.

as for the tonestack, according to the schematics i've been looking at, pretty much all of the ampeg bass amps (60's through 70's) use the same circuit, with varying add-on features. i'm working on a bass distortion right now that uses a modified b-15 tonestack, and it's promising. i'll post it on here somewhere once it's finished.
Title: To the people at runoffgroove.com....
Post by: Ben N on May 12, 2004, 03:41:09 PM
For that Bassman emulation, how would it be to add a paralleled input stage with a separate volume control, with one of the stages voiced bright, just to get the complete picture?

Ben
Title: To the people at runoffgroove.com....
Post by: Peter Snowberg on May 13, 2004, 12:31:12 AM
Quote from: Ben NFor that Bassman emulation, how would it be to add a paralleled input stage with a separate volume control, with one of the stages voiced bright, just to get the complete picture?

Ben
Something that blends tones like this? :D

(http://64.7.66.217/circuits/tc-tone-dual.png)

If you used a cap in series with a resistor tied to the junction of the 470k/470p series filters, you could use a 3 position toggle to switch the bright cap to the CW lug of either pot. The center would turn bright off for both channels.

Note to ROG: Sorry if I shouldn't have posted the above schematic.

Take care,
0Peter
Title: Re: Yipee!!!
Post by: Basonsubatomia on May 13, 2004, 03:12:34 AM
Quote from: GaryI'm sure my wife would love to have something like this to run her Longhorn into.

Shouldn't you be the one running your Longhorn... aww, nevermind.
Title: To the people at runoffgroove.com....
Post by: B Tremblay on May 13, 2004, 07:08:15 AM
Quote from: Ben NFor that Bassman emulation, how would it be to add a paralleled input stage with a separate volume control, with one of the stages voiced bright, just to get the complete picture?

You could do that, though I'd add it as a separate input rather than Peter's version.  Also, it seems that the only difference (at least in the 5F6-A circuit version) between the Bright and Normal channels is the 100pF cap on the Bright's volume.  Simply adding in that cap and a SPST would provide the same results as a separate input, with less parts.
Title: To the people at runoffgroove.com....
Post by: Arno van der Heijden on May 13, 2004, 07:57:28 AM
I was looking at these fet emulations myself and I was wondering whether the absence of the 470k mixer resistor of the second channel has influence on the sound of a single channel version.
Maybe you guys can enlighten me?
Title: To the people at runoffgroove.com....
Post by: Arno van der Heijden on May 13, 2004, 05:41:05 PM
bump
Title: To the people at runoffgroove.com....
Post by: B Tremblay on May 13, 2004, 06:56:35 PM
Which circuit are you referring to?
Title: To the people at runoffgroove.com....
Post by: Arno van der Heijden on May 13, 2004, 06:59:45 PM
marshall plexi/thunderchief
Title: To the people at runoffgroove.com....
Post by: B Tremblay on May 13, 2004, 09:15:27 PM
I'm not sure.  We didn't include it at any point of our development or testing.  I'd guess that it would knock back the gain a bit.
Title: To the people at runoffgroove.com....
Post by: Fernando Aguirre on May 14, 2004, 12:30:58 AM
What about an emulation of a Soldano SLO, a Bogner ecstasy or a mesa mark II ?

Your work is amazing
Title: To the people at runoffgroove.com....
Post by: Peter Snowberg on May 14, 2004, 12:47:51 AM
Another natural would be a Dumble.

Take care,
-Peter
Title: To the people at runoffgroove.com....
Post by: Arno van der Heijden on May 14, 2004, 05:55:14 AM
QuoteI'm not sure. We didn't include it at any point of our development or testing. I'd guess that it would knock back the gain a bit.

I was also wondering if the gain control of the second channel influences the first channel (and vice versa). I don't know if this is true for the actual amp, never having played one.
Title: To the people at runoffgroove.com....
Post by: Gary on May 14, 2004, 08:52:17 AM
Quote from: Arno van der Heijden
I was also wondering if the gain control of the second channel influences the first channel (and vice versa). I don't know if this is true for the actual amp, never having played one.

Yes, it does affect the sound with the amp.  Since we went for as simple as we could with the Thunderchief, we did include this.  You could very simply.  You should notice subtle differences in the sound as you play with the second volume.  You could also "jump the channels" like many people did with the amp.  Ofcourse, you'd need atleast three input jacks and all the associated resistors feeding into the first fet.  Also, you'd need to add another input fet to simulate the bass channel.  Both of those fets would tie together via the resistor you mentioned.

You can see why we left this off the Thunderchief.  Far too complicated for a stompbox, IMO.

But please let us know what you find if you do try this.
Title: To the people at runoffgroove.com....
Post by: Doug H on May 14, 2004, 09:46:31 AM
Quote from: GaryYou could also "jump the channels" like many people did with the amp.  Ofcourse, you'd need atleast three input jacks and all the associated resistors feeding into the first fet.  Also, you'd need to add another input fet to simulate the bass channel.  Both of those fets would tie together via the resistor you mentioned.

You can see why we left this off the Thunderchief.  Far too complicated for a stompbox, IMO.

But please let us know what you find if you do try this.

You can also do internal plexi-style jumpering. You can split the input signal into 2 parallel channels, one voiced bright, one voiced dark, ea with it's own vol control. Using the plexi example, dark ch would have series 470k, bright ch would have series 470k/470p on the respective vol pot wiper and would both tie into the next ch input. (These are commonly referred to as "mixer" resistors.) Then you dial in the bright/dark mixture with the volume controls. See the "november lite" schem at ax84.com for reference.

I've experimented with this sort of thing and it works pretty well. This will save you the real-estate of extra jacks and screwing around with jumpers.

Doug