My son mentioned Orange amps to me about 8 years ago and since most guitar amps more or less copy the usual stuff I found it interesting that there were a few different features:
Here is the Orange 120, note the FAC control, and the dual Master volume pot right before the power tubes, interesting that it is inside the feedback loop:
http://www.orangefieldguide.com/OFG_SCHEM/orangeotrschem.gif
The FAC control makes a lot of sense to high pass the signal and protect speakers that cannot handle much bass, or just to reject out of band garbage.
Is overdriving the output stage driver a good thing for distorted tone, it should only provide odd distortion if it is well balanced.
Thoughts?
Here is the Orange 120, note the FAC control, and the dual Master volume pot right before the power tubes, interesting that it is inside the feedback loop:
http://www.orangefieldguide.com/OFG_SCHEM/orangeotrschem.gif
The FAC control makes a lot of sense to high pass the signal and protect speakers that cannot handle much bass, or just to reject out of band garbage.
Is overdriving the output stage driver a good thing for distorted tone, it should only provide odd distortion if it is well balanced.
Thoughts?
Here in the Tiny Terror is another interesting feature, the main input gain is done with a dual pot at the input and output of the second stage:
http://elektrotanya.com/PREVIEWS/63463243/23432455/oldies/egyeb/orange_tiny_terror.pdf_1.png
This is talked about in system design, do you put a volume control at the input, output, or both? If it is at the input you get the best resistance to overload, for a given Master gain setting, but the worst signal to noise ratio since all of the stages noise is wide open to the output.
If the pot is at the output you get the worst overload margin since the amp stage sees all the signal, but the best reduction of noise because turning that volume down also attenuates the noise in that stage.
A better performing option is to put pots at the input and output, if you just crack the volume open, you get lots of dynamic range because of the input attenuation AND low noise because the output pot is attenuating much of the stage noise. This is perfect for a clean channel and if you just crank it full, and turn down the Master volume then it is no different than any other pot arrangement.
You would use a dual linear pot in this situation since the combination approximates an audio taper.
This amp also has Master gain right in front of the power tubes.
Neither has feedback around the power amp.
http://elektrotanya.com/PREVIEWS/63463243/23432455/oldies/egyeb/orange_tiny_terror.pdf_1.png
This is talked about in system design, do you put a volume control at the input, output, or both? If it is at the input you get the best resistance to overload, for a given Master gain setting, but the worst signal to noise ratio since all of the stages noise is wide open to the output.
If the pot is at the output you get the worst overload margin since the amp stage sees all the signal, but the best reduction of noise because turning that volume down also attenuates the noise in that stage.
A better performing option is to put pots at the input and output, if you just crack the volume open, you get lots of dynamic range because of the input attenuation AND low noise because the output pot is attenuating much of the stage noise. This is perfect for a clean channel and if you just crank it full, and turn down the Master volume then it is no different than any other pot arrangement.
You would use a dual linear pot in this situation since the combination approximates an audio taper.
This amp also has Master gain right in front of the power tubes.
Neither has feedback around the power amp.
Last edited:
I seem to remember seeing the odd biasing arrangement shown here in the Soldano SLO-100 in V2b with 100K plate and 39K cathode load:
http://www.4tubes.com/SCHEMATICS/Music-amps/Soldano/SLO 100/slo100_1.gif
That is a very odd value for the cathode resistor, it is a highly imbalanced phase splitter.
I seem to remember seeing those exact values in a Marshall amp but can't find it now.
Anyone know if this provides some good distortion? It is in the dirty channel.
http://www.4tubes.com/SCHEMATICS/Music-amps/Soldano/SLO 100/slo100_1.gif
That is a very odd value for the cathode resistor, it is a highly imbalanced phase splitter.
I seem to remember seeing those exact values in a Marshall amp but can't find it now.
Anyone know if this provides some good distortion? It is in the dirty channel.
Yeah talking about the Post phase inverter Master Volume, been wanting to do it, but need order the dual ganged Pot/resistors. With that said I, heard some amps with them, sounded pretty good while others sounded really weird with it, like all bloated...
Another interesting feature is that they chose the cathodyne PI. They usually use this type for lower powered amps where the power tubes don't need as large a signal to drive them, like EL84 amps
The cathodyne tends to produce different signals from the outputs since one almost is like a cathode follower and one is like a normal gain stage. This will give the power tube pairs different drive signals and produce more even order harmonics with the tubes operating at different drive conditions. I think they did that by design. This way, they can get pleasant overdrive without blowing out your eardrums and then if you want over the top sounds, then dime the volume. Also, it is interesting that they didn't use a grid stopper on the cathodyne input.
I rebuild old Hammond organ amps and this is the same place they use to inject the feedback, although it doesn't come stock with any contols, so I can choose what I want for them. I add changeable FB values for different sounds.
One question, aren't almost all post PI MVs inside the FB loop? You say it is interesting that it is there.
Last edited:
Well, yes if there is feedback and there is a post PI MV then it would be inside but do you know of any other amps that do this?
Triode Elecrtonics,Ceriatone, MetroAmp and Trinity all offer an add on mod or sell it with their kit. I don't have the time to pour over the thousands of older schematics to see who did this. Not sure why it is important. But it seems as though most of the older amps used the pre PI MV. Much less work and don't have to use a double-gang pot. When it comes down to saving production costs, many decisions are made by the bean counters, especially 1965-1985, the CBS years at Fender and the Rose-Morris years at Marshall. Cliff Cooper and the rest at Orange didn't have these constraints.
Last edited:
Phase splitter....? I'd say an ordinary common cathode gain stage.
...But it's biased much closer to cutoff than the standard 1K5/100K circuit setup. In essence, plate voltage will be significantly closer to B+, which effectively limits positive signal swings at very early point and in practice clips the signal very asymmetrically: Positive half wave clips first, and continues to clip harder and harder before negative half wave even begins to clip at all.
Clipping to cutoff will be "hard" and will thus generate plenty of high order harmonics (essential for high gain tones), asymmetric clipping will generate dominantly even order harmonics but likely more important is that subsequent DC bias shifts (crated by signal asymmetry) will dynamically shape the harmonic pattern of the next stage that clips the signal. This proves more livelier tone and more touch effectiveness.
As for tonal characteristics... Excluding all tone shaping by filtering (crucial) and analysing the particular gain stage as is, it probably sounds extremely hideous when overdriven. As a part of an entire system (the entire preamp and all associated signal processing) it will achieve goals the designer wished to achieve. Yes, these "cold cathode" stages are employed in many hi-gain amps exactly due to their overdrive characteristics; but isolated from everything else the resulting tone is probably just typical distorted buzzing.
...Oh, voltage gain of the aforementioned stage is very, very low so it needs plenty of drive signal for clipping.
Interesting about the .068 uF coupling caps, but there is the FAC control to tailor the bass just right.
You know I'm a 6l6 guy though, cant help it xD, getting closer to more slo like.
https://www.youtube.com/watch?v=k1vhyDcdVfQ
https://www.youtube.com/watch?v=k1vhyDcdVfQ
Last edited:
I found I could get quite a good valve sound by using a soft limiter circuit I found in 1980's Wireless World magazine.
An externally hosted image should be here but it was not working when we last tested it.
Intresting, removing plate/cathode bypass on on V1B...whatever Dumble like that is?....grid resistance is bit too low though, need to adjust that, removing silicon clippers etc really does help its a lot clearer
NE5532 being used as well,. its interesting how it sounds. added more of those PP Film&foil to the humbuckers this time too. yeah slam it hard with a booster
why wish had some V30s types it would go insane with those/harmonic's
NE5532 being used as well,. its interesting how it sounds. added more of those PP Film&foil to the humbuckers this time too. yeah slam it hard with a booster
why wish had some V30s types it would go insane with those/harmonic's
Last edited:
- Status
- Not open for further replies.