Difference between clean and lead channels

psyx

Hey guys!

So I have been wondering about this for a while... In a regular 2 channel amp (tubes of course), the clean and overdrive channels have distinct tonal differences of which obviously gain and volume are the most noticeable differences.

So my question is, what happens inside the amp when you switch the channel from clean to overdrive?
playing the amp at high volume and the gain set as low as possible on OD,sounds very different to playing the clean channel at the same volume... Why?

For instance, using a big muff on my HK 25th edt tube amp's clean channel with a high volume sounds more awesome than doing the same in overdrive mode... Now I also understand that the preamp tubes are responsible for the overdrive channel's increased gain, but what is physically different?

Thanks!

Nicholas-L

Clean channel usually runs on the two halves of V1 into the phase inverter. The one thing that is in common to both channels is usually the first half of V1.
The Lead channel will run on first half of V1 + the two halves of V2 into the phase inverter. Now the difference is that V2's two halves are usually biased a certain way with their gain structures and the second half of V1 is usually biased a different way with its gain structure. In the end the amount of gain stages + the way it is biased makes quite a difference to how the channels sound.

Hope this makes some sense.

bottledtone

Your clean channel could be voiced more neutral, or with a slight mid cut and treble boost, which your pedal is better suited too. The drive/lead/od channels often are voiced to clip in a certain manner. There will be filters to cut out or focus properties that won't suited to a clean tone. Cold biased sections, or diode bounding circuits etc. Lots of possible gain, requires a circuit to have smoothing components to kill/tame overtones produced.

psyx

Thanks guys!

Also, do more preamp tubes (more or less) mean more gain?
Like the Orange Dark terror having 3xECC83's and the Tiny Terror only having 2XECC83's and both offering the same 7/15 Watts. But the Dark terror offering more gain than the Tiny terror?

bottledtone

Not always, as some sections of the valve can be used as a cathode followers (valve buffer which has less than unity gain ±0.9) to drive FX loops and tone controls. So won't be part of the 'distortion' (Gain is not distortion/overdrive as its commonly referred too, but rather its amplification factor)
4 gain stages can provide as much distortion as anyone needs if voiced to do so. But as an example, a JCM800 as 3 gain stages in preamp, but so does a twin reverb on its vibrato channel, yet they will not both achieve the same distortion levels, because of the different attenuation components between stages.

The Dark terror has a valve FX loop hasn't it? And chances the recovery stage after the loop, so in theory should have the extra gain.

psyx

bottledtone wrote: Not always, as some sections of the valve can be used as a cathode followers (valve buffer which has less than unity gain ±0.9) to drive FX loops and tone controls. So won't be part of the 'distortion' (Gain is not distortion/overdrive as its commonly referred too, but rather its amplification factor)
4 gain stages can provide as much distortion as anyone needs if voiced to do so. But as an example, a JCM800 as 3 gain stages in preamp, but so does a twin reverb on its vibrato channel, yet they will not both achieve the same distortion levels, because of the different attenuation components between stages.

The Dark terror has a valve FX loop hasn't it? And chances the recovery stage after the loop, so in theory should have the extra gain.

I see... Far more factors weighing in on it than I thought!