Valve amps emu:have you built em without problems ?

[Gabriel Simoes]

Hello all ...
This week I found those schematics for emulation of valve amps like dual rectifier or jcm800 ... and I got really happy, so I decided I would buy the j201 transistors, even if I had to get em out of Brazil, since it's damn hard to find em here ... but,
as I've found (using the search) a lot of people is havving or had problems with those projects, using bucksears pcbs ...
Squealing, oscilation, gating, biasing problems (maybe should I call misbiasing problems) ....
So , have someone here built them, without any trouble, and liked the project ? do they really make us remember those amp sounds ?
As in the beggining I've spent all my money buying tools and componentes, and now I have nothing ... and no pedals ... no money, nothing at all hehehe ... so I do not want to spent those last bucks and get disappointed ...
I hope you can help me again in this jorney
thanks
Gabriel

[Gabriel Simoes]

Come on.... no one have built those projects ?
give me a hand hehre =)
Gabriel

[vanhansen]

The issues you mentioned are easily solved using short wire runs and good offboard wiring.  It may take some messing with but they can be dealt with.  I'm not aware of any major issues with the JCM800 circuit, or any issues for that matter.  Higher gain circuits can have more oscillation issues but again, those can be dealt with.

[rodriki1]

Hi gabriel

I live in brazil too.
Here is really hard to find any good stuff about eletronics.

People out there find easily good tubes and fets, so it is easier to make
good amp. Here is really damn hard....

I have been studing the use of fet for amp simulation for good time now.
Fet with proper bias  can sound at computer simulation
(i am using CIRCUITMAKER STUDENT) VERY close in harmonics distortion.

I have problem now with HEADROOM with low voltage source (9v)
to get closer to triode.

I do not know if in real situation, the fet will sound that so close.

I have used 2n3819 (better) or bf245 for test.

If you are really interested in exchanging ideas about this get contact.

rmfidelis@gmail.com

Good lucky

[Gabriel Simoes]

The issues you mentioned are easily solved using short wire runs and good offboard wiring. It may take some messing with but they can be dealt with. I'm not aware of any major issues with the JCM800 circuit, or any issues for that matter. Higher gain circuits can have more oscillation issues but again, those can be dealt with

About the oscilations ... somepeople have just reported that using any pedal with buffered input/output in front of the dual rectifier emul, for example, makes the oscilation go away, so maybe using an internal litle buffer circuit after the emulator output and before the pedal output could sove this issue too, right ?

I will try some emulators those next weeks .... dual rectifier, jcm800, soldano slo, ampeg portaflex (since I dont have the svt project, as I'd like, so I could have a complete eq) ....

About shildered cables .... using them in the input/output wouldn't lead to ground loop ?

Thanks for your attention ,and sorry for the noob doubts .... but who had never been a noob once? =)
Gabriel

[vanhansen]

A buffer wouldn't be a bad idea.  The Simple IC Buffer circuit from General Guitar Gadgets is perfect for that sort of application.  The normal out of the emu circuit would go in to the buffer, then out the buffer to the volume pot and then to the out jack as normal.

You shouldn't get ground loops using shielded cable so long as your ground connections all share the same plane.  Also, when using good shielded cable, you connect one end to the ground and leave the other end unconnected but clipped off.  I hope this makes sense to you.  

[Gabriel Simoes]

Yep ....
I'm now encouraged to buy those transistors, 1m log pots (no really cheap here ...) .... and try the emuls ...
Thanks for your help!
Gabriel

[Connoisseur of Distortion]

my Dr. Boogey STILL oscillates when it's on its own, but i leave it on a loaded pedalboard, so everything works out. the circuit has a ton of gain, so there it goes without saying that noise will leak in.

stopping oscillation is a real PITA, especially when you don't have shielded wire.  :x   buffers will definately help, and maybe an inverter on the output would be beneficial... don't hold me to it...

[TryingToDo613]

I looked in the back posts and I see where bucksear posted links to the layout and pcb, but the site no longer exists. Does anyone have them? I've love to try the dual recto. -ph

[Gabriel Simoes]

I will try to build the dual recto .... and if oscilates ... I will try using a buffer on the output ....
Just as a note, somepeople who used a smaller pot for gain in the dual project have reported no oscilation ... including buck .... when he changed some j201 for mpf102 and the gain pot ...
lets see lets see

[lowstar]

hi gabriel,
i´ve done the portaflex (aka flipster) on perf
and the bsiab2 using stripboard
the bsiab has not made it into a box so far, the flipster is boxed up and lost its squealing problems once it was put into the hammond home. i can´t decide though if i like it or not, i use it more to fatten up the sound (like big bass sound), as a bass overdrive it has got not enough headroom (yes, i could tinker with the fets and put some 5457 or mpf102 in there, no, i didn´t have the urge for that so far, my oc-2 on stripboard project is bothering me more at the moment)

hope this helps,
lowstar

[electrictabs]

Bob N got my permission to host the pcb layout on his server

http://www.dohcfiero.com/drboogey/DrBoogeyPCB.bmp
http://www.dohcfiero.com/drboogey/DrBoogeyPartsLayout.gif

Use shielded cable and a 470k gain pot with all j201.You shouldn't have any problem.

[TryingToDo613]

Thanks very very much.  How do you handle the oddball pots? Just move up to 25k and 250k? -ph

[petemoore]

There seems to be a cieling with high gain circuits, the kind I like, as far as volume/gain/distortion/clarity amounts and squealing.
 It can be raised with attention to wiring runs of the SP, sometimes the easiest way is to turn down the gain knob,.
 Squealing seems also to be proximity or amp/guitar type related, boxing up a project may make things better [or worse, usually better].

[TryingToDo613]

Yea, I tend to always have everything pegged at 11. Might be worth going down instead of up then put series resistance. Seldom is any knob on zero. I think that's what I'm going to do. Thanks for the clarification. -ph