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Post by imaradiostar on Oct 11, 2012 0:37:55 GMT -7
I read somewhere that this amp uses the same tone circuit. I was curious if it's also ultralinear like the 66. Thoughts?
Maybe it has some sort of negative feedback to promote its "clean" sound for pedal use?
Either way, I think it's an interesting concept. I'm sad to see the KT45 is no longer offered, though I guess it's been a while since it was.
Jamie
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Post by boptometrist on Oct 11, 2012 9:15:58 GMT -7
I don't think Z28 is ultralinear and it shares a similar tone stack. Maybe an expert could tell us about both M12 and Z28 to set the record straight.
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Post by DRZ on Oct 11, 2012 11:06:31 GMT -7
No the M-12 isn't Ultra-Linear. Nor does it use negative feedback. Lower voltage and gain on the EF86, as well as lower voltage on theEL-84's acount for the excessive clean headroom.
DR.Z
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Post by mazmaster on Oct 11, 2012 11:23:02 GMT -7
No the M-12 isn't Ultra-Linear. Nor does it use negative feedback. Lower voltage and gain on the EF86, as well as lower voltage on theEL-84's acount for the excessive clean headroom. DR.Z Thanks, Doc. It seems the LO switch setting takes that concept a notch further than HI mode, correct? I'm really enjoying that mode with OD pedals! What's so unusual about it though is that it feels and responds like a traditional, low gain, single-channel amp that has been cranked up a bit and is getting just the right amount of compression and sustain...i.e., the "sweet spot".
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Post by randalp3000 on Oct 11, 2012 22:08:11 GMT -7
I read somewhere that this amp uses the same tone circuit. I was curious if it's also ultralinear like the 66. Thoughts? Maybe it has some sort of negative feedback to promote its "clean" sound for pedal use? Either way, I think it's an interesting concept. I'm sad to see the KT45 is no longer offered, though I guess it's been a while since it was. Jamie Not sure where you got your info but the KT-45 is still in the current price list.
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Post by diyblues on Oct 12, 2012 5:18:51 GMT -7
No the M-12 isn't Ultra-Linear. Nor does it use negative feedback. Lower voltage and gain on the EF86, as well as lower voltage on theEL-84's acount for the excessive clean headroom. DR.Z This sounds interesting! I have always thought that lower voltages and no negative feedback means more gain/less headroom. Have to look in to this in my next 2xel84 build.. little more headroom would give a bit more versatilety to an 18watt type of amp.
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Post by imaradiostar on Oct 12, 2012 8:41:04 GMT -7
Thanks for the info, Doc. I've always thought that EL84's need so little drive that I'd feared they would overdrive really quickly. I suppose this makes the "high low" mode an important feature.
I, too, was puzzled by the statement that lower voltage leads to more headroom. I wonder how that works? I would have thought less voltage means earlier onset of distortion.
It appears I was mistaken about the KT-45. I feel a bit silly!
jamie
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Post by DRZ on Oct 12, 2012 11:05:25 GMT -7
Well let me embellish a bit for all you curious minds.... The lower voltage is used primarily on the EF-86's plate and screen. As well as a larger cathode resistor to decrease gain. It is a rather unique front end, relying on the tone stack as a high impedance load and the EF-86's ability to drive it .
The Plate voltage on the EL 84's is low by most standards, slightly under 300V which lowers output wattage some and also clipping when driven hard.
I don't want to give all my secrets away, but the Grid Load Resistors which drive that EL 84's are also lower value.
And yes No Negative Feedback increases drive and distortion, but if massaged correctly yields rich harmonic overtones, higher drive levels and little if any added distortion.
DR.Z
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Post by jesslm02 on Oct 12, 2012 11:08:55 GMT -7
Nice Doc, thanks for the breakdown!
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Post by diyblues on Oct 12, 2012 12:25:00 GMT -7
Makes sense. Thanks Doc. That really is quite unique front end... specially for ef86.
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