ROG amp-sims and higher voltage

[Mark Hammer]

1) Has anyone used any of these with a higher supply voltage?

2)  If so, how do they sound?  What are the tradeoffs or changes?  More "amp-like"?

3) What sorts of design changes need to be made for this?  e.g., FETs re-biased to V+/2?

4) Worth the effort to do?

[Jason Stout]

I had the flipster running on ~30 volts. I didn't hear or feel any improvements. YMMV

Edit - To do this you need to make sure your electrolytic PS filter caps can handle the voltages you put on them. The drain trim pots may also need to be increased so you can dial in ½V+

[Lonestarjohnny]

I have my TROGG running on 24 V, and compared to the 9V version's i have built the distortion sound's the same but i seem to notice a small amount of more headroom on the clean, as soon as i get my Spectrum analyzer going here i'll verify that
Johnny

[Athin]

haven't tried "in reality" but did a sim of 18 on ltspice. no big difference, the signal has sharper edges (just a bit though). Used 18V instead of 9V. Rebiased Q1,Q3 to 9V, Q2 to 14V. Logical. Look @ picture for freq. response curves. The 100k trims will be more than enough to set the bias.

http://kosi.website.pl/18.zip
sorry 4 the zip, but it wouldn't load gif's, dunno why :x

[puretube]

funny: have just seen this thread right after having posted here:
http://diystompboxes.com/sboxforum/viewtopic.php?t=23875&start=15

long live simulation and modelling!

:lol:

[spongebob]

Raising the supply voltage should be no big deal with all the trimpots on the ROG amp sim boards, unless your trimpots are too small for the required voltage drop, but 18V should be no problem.

About headroom: if you simulate a JFET gain stage in Spice you will see that doubling the supply voltage will also double the voltage gain (a little less actually), so your total headroom should increase only a little bit if at all. However, this was only a simulation, and reality doesn't care much about my simulations :lol: , so I'm not sure if it does behave exactly like this actually.

The Eighteen I built is now running at 15V, not as a stompbox but as a preamp module for my amp, and I'm very happy with it.

BTW, wouldn't a MOSFET output stage be a nice addition to these amp sims? Anyone have experience with these, how do they sound when overdriven?

[Athin]

you know - I'm really glad bout them simultaion thingies - I tried to make the 18 with 2n3819's rather than the j201's and couldn't find out why the critter won't distort. Then I ran a ltspice sim. and found that they actually don't have enough gain/_can_ handle big voltage swings without distortion, so no go. Got mad, put in a gain=10 op-amp before Q2 and duh.. distortion. Real cool stuff, ltspice.

[Ben N]

Would that involve major changes to implement?  I ask only because, hypothetically, it would be interesting to try and graft one of the ROGs into one of a couple of hybrid amps that I have, which have preamp supplies of +/-15 or 30v.

[Peter Snowberg]

40V is the point where you let the blue smoke out of the J201 so as long as the bias trims are large enough, 30V should be just fine.

You could run them from the full 30V if the input is capacitivly coupled, or you could just run from the +15V side, or you could even power the first stage from +15 and Ground and then power the remaining stages from the full 30V if you didn't want to add a capacitor between the guitar and the 1st stage.

[freebird1127]

You guys interested in amp-sims should read into Lateral mosfets, or L-Mosfets... when overdriven they soft-clip the signal (as tubes have a tendancy to do) as opposed to the majority of their hard-clipping solid state brothas.

[Lonestarjohnny]

Veddy Interesting Mr. Freebird, I Checky Checky,
:idea:  :idea:  :idea:  :idea:  :idea:  :idea:
I gotta go check this out, Might be a SolidState version of a Mullard Tube,
Let you know what I find.
Johnny

[Lonestarjohnny]

http://www.anasoft.co.uk/worstcase.html
Check this out
Johnny

[Peter Snowberg]

http://www.tech-diy.com/2sk1058.pdf
http://www.tech-diy.com/2sj162.pdf

[Lonestarjohnny]

Thank's Peter, I'm still reading on the Lateral Mosfet's, there's a lot of info on these thing's, but i'll have to order a few of these and try a building a Emulator with them.
Johnny

[spongebob]

http://www.tech-diy.com/2sk1058.pdf
http://www.tech-diy.com/2sj162.pdf

Nice specs: 160V drain-source, 7 ampere drain current!!!!  :shock:

... but i'll have to order a few of these

Ouch, these things are bloody expensive, would cost me about 15 euro for a pair :cry:

Most designs that I have found on the net (here for example) use push-pull output stages, anyone know of a simple single-ended design? I really don't need 100 watt ouput power...

[Nasse]

Goes more and more off topic, but when it started to go this way I add water to the mill till it ends, dont know where

Anybody heard anything about thingie called FETRON? I was reading some 70´s electronic magazines and there was an article about then new and promising new tecnique to replace elektron tubes with solid state direct replacement. The article claimed that exact replacement of wanted tube type could constructed. And they work without heater current.

But after that mag article I have not seen any info. Just googled "fetron" and this was first on the list talking about same thingie.

http://www.sigtel.com/tel_tech_fetrons.html

When I was looking the mag article describing the construction of fetrons I thought it would not be too difficult to construct a "tube" for some experimenting, it was basically two fets and some other components...

EDIT more informative text info in this http://www.harpamps.com/micKqanda/What-is-a-Fetron.html

[puretube]

Nasse:we seem to love those old mags, don`t we?
Thanx for that info!
No time now, but maybe later, I`ll find s.th. more...

[Nasse]

maybe later, I`ll find s.th. more...

You can never have too many schematics and electronics books and such... At least I don´t have to ask so many beginner questions.

I found my short 70´s Fetron article mag, but only the second page, the first one is under some junk down deep somewhere. But the schem example of 6AK5 equivalent Fetron TS6AK5 is on found page, and I try to post it soon, if anyone interested. The "fetron" part looks like just two jfets connected certain way, no additional components. But the application circuit arrangement is just like what Fetzer valve is adapted from.

Propably not much new benefits in Fetron, but anyway it would be interesting to know why it did not become successful direct replacement for tubes

[aron]

Of course, as long as we have had the Radio Shack 13.5V, 30V power supply we have been testing and running FETs at higher voltages.

The Shaka HV and Jack's earlier amp simulator pedals could all run at higher voltages.

You get more headroom, less distortion and a "stiffer" feel.

All things considered, 9V is still very workable and it is possible to make GREAT pedals with 9V.