To the people at runoffgroove.com....

[ejbasses]

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!

[Gary]

No promises, but we'll look into it.  What amp?  (simpler yields better results)

[Paul Marossy]

How 'bout a Fender Bassman?

[Gary]

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.

[Chris Goodson]

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.

[petemoore]

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.

[bobbletrox]

How 'bout a Fender Bassman?

*drool* yes!

[ejbasses]

Hey thanks for the replies!

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

[Alpha579]

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

[Gary]

Hey 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.

[javacody]

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?

[B Tremblay]

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.



You should be able to develop a decent emulation by comparing it with the Bassman schematic.

[claydavis]

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.

[Ben N]

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

[Peter Snowberg]

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

Something that blends tones like this?



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

[Basonsubatomia]

I'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.

[B Tremblay]

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?

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.

[Arno van der Heijden]

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?

[Arno van der Heijden]

bump

[B Tremblay]

Which circuit are you referring to?