ROG Eighteen finished: low gain?

[Bucksears]

I finished the ROG Eighteen last night and was a little disappointed. It is very low-gain, although that's what I was expecting, but not to this extent. It doesn't have a lot of 'cut through' to it, seems a little flabby at higher gain settings. I added in a 300pF cap on the volume (gain) to brighten it up a little, but it didn't do much.
Anybody have any mods for the Eighteen that you are happy with?

Thanks,
- Buck

[markm]

I got the same result from Prof. Tweed.
Didn't really do much other than produce sound if ya know what I mean.
I haven't completely abandoned it but, It was dissapointing.

[petemoore]

  It is supposed to sound like a small-ish tube amp, or at least somewhat like. I've had little tube amps, and one of the first things on the agenda is 'where's the Stompbox?..I thought it would sound MorE...uh...Distorted'.
  You can diddle with the gain, I'd check voltages first, bias can be a little tricky on those, then you can add to that LOTSA Gain if you want, either diddling with that circuit topology, or that topology with more of itself added to itself, or add some other type active component or...use it for bait.
  One thing I liked about the smaller amp sims is the amp-like qualities, not all but enough of them to keep things interesting for [you got one, you know the sounds of it], and the ability to distort cool with 'pre' [something w/active], distortion or boost or amp sim. one thing I didn't like is noise, bias trubbles...oh wait, that's two.

[Bucksears]

It's ok. I pretty much made it out of spare parts (case, jacks, pots) and there isn't that much to the board itself, so I'm not looking at it as a loss of anything other than time.
I'm still really stoked about the ROG May Queen and Big Muff that I just finished, so if the Eighteen gets dismantled, so be it. The BSIAB II and JCM800 cover a lot of the Marshall-y territory on my board and I'll probably look at the Thunderchief again, this time the Ver 2.0 with the tone stack.

Thanks again,
- Buck

[burnt fingers]

I don't know if you ever heard a Marshall 18 watter but they were not a high gain, or even medium gain amp.  It doesn't surprise me to hear that the ROG 18 doesn't have much gain.   I think your on the right track with the BSIAB or JCM for the higher gain stuff.

Scott

[markm]

I don't know if you ever heard a Marshall 18 watter but they were not a high gain, or even medium gain amp.  It doesn't surprise me to hear that the ROG 18 doesn't have much gain.   I think your on the right track with the BSIAB or JCM for the higher gain stuff.

Scott

I wasn't looking for high gain with the tweed,
however I could barely get unity out of it.
I suspect I need to change some of the J201's to find some
that work better in that circuit.
For now it's on the shelf and I'll get back to it at some point.

[tiges_ tendres]

I don't know if you ever heard a Marshall 18 watter but they were not a high gain, or even medium gain amp.  It doesn't surprise me to hear that the ROG 18 doesn't have much gain.   I think your on the right track with the BSIAB or JCM for the higher gain stuff.

Scott

I wasn't looking for high gain with the tweed,
however I could barely get unity out of it.
I suspect I need to change some of the J201's to find some
that work better in that circuit.
For now it's on the shelf and I'll get back to it at some point.

I must have done something wrong with my tweed because it gets really over driven, almost no clean sound!

Sounds like we should compare notes!

[markm]

I built mine using an etched board and the layout on ROG.
No changes but, I wonder if I could have screwed up on my Nano conversions to uF??

[dano12]

Did you use J201s for your build? You can tame things down a bit by trying MPF108s or other jfets.

[markm]

I used J201's and can't quite get unity gain out of it! 

[plucky]

I built mine with 2sk30A jfets and got the same result, the overdrive is really low... and the output volume too.
You should try to change your fets and maybe use a buffers stomp after it.

[markm]

After all of thes ROG posts, I decided to really get P Tweed straightened out tonight.
I did a search about Professor Tweed here and found info about the Cap in the
feedback loop being an issue.
I changed it from the 1uF that is shown in the schem and the layout to a .01 and
there was the problem......now I have Gain.
Then I went down to a .001 and now I have enough Gain to blow the roof of the house!
Just thought I would try to help you guys out with this info.

[chemman]

18 sounds great. More like an overdrive than distortion but makes my modded blues junior sound different in a good way. Easy build and biased easy with J201. Very low noise on mine (not enclosed I got no hum or hiss with high gain settings). I used all metal and film components and no treble bleed cap. Not much gain at all with a strat. Add boost to get it flying! amz Mosfet boost is golden.

-matt

[MartyMart]

You have to remember that with these "amp emu's" we are after the tone/gain of the
original.
My 'Eighteen' is quite accurate and is NOT a high gain amp ... never was !
The English Channel has more gain to it, but it's an AC30 topboost emu, NOT a trainwreck
Use an OD/Dist/Boost in front of these and they can quickly COME ALIVE .... or turn to mush
if pushed too far  :-(

Marty.

[grolschie]

18 sounds great. More like an overdrive than distortion but makes my modded blues junior sound different in a good way. Easy build and biased easy with J201. Very low noise on mine (not enclosed I got no hum or hiss with high gain settings). I used all metal and film components and no treble bleed cap. Not much gain at all with a strat.

Funny, I get quite a bit of gain from the Eighteen with my strat. Not metal distortion like the Thunderchief though, but it fattens up nicely. As much as expected from a cranked tube amp of the 70s. My build was an OLC kit with J201s.

[Uma Floresta]

After all of thes ROG posts, I decided to really get P Tweed straightened out tonight.
I did a search about Professor Tweed here and found info about the Cap in the
feedback loop being an issue.
I changed it from the 1uF that is shown in the schem and the layout to a .01 and
there was the problem......now I have Gain.
Then I went down to a .001 and now I have enough Gain to blow the roof of the house!
Just thought I would try to help you guys out with this info.

Interesting. I'll give this a try. It might be worth putting on a toggle switch.