Harsh Sounding Pre Amp(slo100 clone)

[DA-Drummer]

Hi guys this is my first post here.

I have a questioin for you guys.
I've made myself a pre amp of the Soldano SLO100. kind of used the schematic of the GTFO Pedal(link below) but only used power section, and used the real SLO100 Value's for the pre amp section.
I plugged that thing in into my VOX AD50VT-Xl and it sounded very very good. But i am building my own 100W guitar AMP. So i thought let's hook it up to my 100w power amp.

But the sound was not very satisfeiing. It sounded very treblly, like a recording a guitar with a cab simulator that's doing only the half of the job.

I wondered how that's possible and what i can do about it.

GTFO : http://www.diystompboxes.com/smfforum/index.php?topic=93936.0
(sorry for my bad english)

[J0K3RX]

what kind of 100w power amp? You may need a buffer between the preamp and power amp

something along these lines...
http://www.blueguitar.org/new/schem/misc_mod/crate_v18_clean_channel_conversion-preamp_schematic.jpg

[DA-Drummer]

I am using This power amp: http://sound.westhost.com/project27.htm
And this is the pre amp i've used: http://i1320.photobucket.com/albums/u530/DA-Drummer/SLO100_zps60160e69.jpg

Q1 Serves as a buffer.

[J0K3RX]

No tone controls?

[DA-Drummer]

Tone control is after te buffer, same as the Dual Rectifier, but (yet) without prescence control.
And from master control directly in the power amp

[FiveseveN]

What speakers were you using? Try plugging it into Vox's speakers.

[DA-Drummer]

I am using the same speakers as the vox. Disconnected the speaker cables form the vox ad50vt-xl and connected my own speaker cables

[ggedamed]

When you tried it in AD50VT XL, it was in the preamp input or in the Return input?

[DA-Drummer]

Pre Amp input

[DA-Drummer]

There isn't even a fx loop in the Vox.

But seriously, there's is no one who could help me?. The sound is very sharp. and sounds like there is a square wave signal coming out of my speakers, nothing is rounded off the signal by the speakers/power amp/ etc.

Isnt there a small filter or something else i could place behing the Pre Amp that makes te sound more round/natural?

[ggedamed]

Pre Amp input

My bad, I looked at AD100VT-XL.

The reason I asked this is that if you look in AD50VT-XL manual at page 5 (Signal Path), you'll see that the ouput signal of your SLO clone goes through a lot of procesing before reaching the speakers. On the other hand, when you put it through your solid-state power amp, you get exactly what you put into it. If you mike the Project 27 project and feed it through the Vox, you'll probably get the same thing as the SLO going through Vox. There's no way to compare the two amps as they're as different as it gets.
This is because while both have solid-state power amps, in the Vox the signal is heavily processed to simulate the post-preamp stages in a tube combo. So I'll gues an amp simulator between the SLO clone and the Project 27 amp would get you much nearer what you get out ot the Vox amp.

[anchovie]

sounds like there is a square wave signal coming out of my speakers

At all preamp volume levels? You're sure you aren't feeding in a signal way over the sensitivity of the power amp input?

Also, did you build the power amp just for this project or have you tried it with a straight clean guitar signal to confirm that it works correctly?

[DA-Drummer]

At all preamp volume levels? You're sure you aren't feeding in a signal way over the sensitivity of the power amp input?

Also, did you build the power amp just for this project or have you tried it with a straight clean guitar signal to confirm that it works correctly?

I have a volume knob that/s almost closed. Because the signal out of the preamp is around 4V amplitude. and i simulated the power amp and its maximal amplitude wihout power amp clipping is 3.5V. So with the master volume almost closed it's should not be the power amp thats clipping.

And i tried it with an Boss Metal Zone 2 and the sound was just fine.

So I'll gues an amp simulator between the SLO clone and the Project 27 amp would get you much nearer what you get out ot the Vox amp.

What kind of "amp simulator" do i have to look for?

[slacker]

I have a volume knob that/s almost closed. Because the signal out of the preamp is around 4V amplitude.

Rod's article says the power amp takes about 750mV for maximum volume, so your preamp is capable of distorting the crap out of it, maybe even damaging it. Like you said with the volume turned down enough this shouldn't be a problem but I'd look at reducing the maximum output of your preamp somehow.
You might not need to add anything extra just tweak your preamp a bit to change the tonal response maybe reduce the top end to warm it up a bit. You've gone from running it in front of a guitar preamp in the Vox to running it into a HiFi power amp, it's never going to sound the same.

[DA-Drummer]

Lowering the pre amp output is on my list.
But what i ask myself is on the orignal amp there's is tube pre amp, and a tube power amp. I already have the tube pre amp. but does the tube power amp makes such a difference?
And why would the pre amp in front of the vox sound good(on clean channel) and sounds very sharp directrly in the power amp?
I know that in the vox the sound gets processed but it was on clean.

Tomorrow i will test the preamp on a other amplifier. and do some tests with the power amp. but i dont expect that there will be any huge difference

[ggedamed]

Now I think I was over the top with the "amp simulator". At that point I was thinking another pedal like the "English Channel" Vox AC-30 on www.runoffgroove.com.
But an EQ could be all you need. Of course, you have to match the level with the pedals.

[DA-Drummer]

I already have an EQ

[anchovie]

As in a graphic EQ? If so, set up preamp -> graphic EQ -> poweramp and see if you can get a decent sound from cutting the high frequency bands. Might be a simple case of working out a filter to be placed after the preamp out.

[DA-Drummer]

Preamp- bass/mid/treble - poweramp
But i don't think the problem is the eq, because i dialed the treble down to zero and the sound is still very sharp.

[ggedamed]

You didn't say what kind of EQ is what you tried. A Baxandall filter can be pretty shallow. A Marshall tone-stack with the mid and treble knobs on minimum should kill all the treble. The usual graphic EQ pedal will allow cutting down to -15dB (if my memory serves), so not much improvement over the Marshall tone-stack. For more you can breadboard a second or third order low-pass filter. If you put a dual pot on a second order LPF, it becomes adjustable.

If you still have too much treble content after the EQ, two possible causes come to my mind: either the EQ is not doing its job or the "square wave" is generated in the Project 27 amp, after the EQ. Did you do "some tests with the power amp"? Did you try the SLO preamp in a Return input?

It would be easier if we could hear what you hear.