Could you expand upon this with regard to unique voicing? I'd love to hear anything you have to say or opine about regarding the early amps.
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Walter Woods Amps History and Development
- Thread starter Uncletoad
- Start date
Could you expand upon this with regard to unique voicing? I'd love to hear anything you have to say or opine about regarding the early amps.
I had two different MI100-8s and a '01 Electracoustic Super (I had that one for 15 years). Each one had their own tonal qualities.
All WW amps had/have Walter's own SMPS; early ones are Class A/B, the Electracoustic is Class D, all of which are solidstate.
- Feb 12, 2006
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There was a unique (at least I've never seen it before in audio) 2 transistor gain stage that was a little bit like an op-amp but with nowhere near the open loop gain. This makes all of the circuitry behave differently even though the circuit may appear similar. This also meant at that the supporting circuit choices will certainly affect the tone and the texture, the distortion levels are quite high (and rise with frequency) compared with a traditional op-amp.
It's a fascinating circuit, but the later models utilized more traditional op-amps because they behave better and are more predictable. They also have a lot more open loop gain so the supporting circuitry becomes more consistent.
The power amp is a very simple topology, the only real enhancement over other early amps is the use of a diff pair at the input, but the VAS and output stage are as simple as it gets.
It's perhaps one of the best examples of "simpler is better", warts and all and in this case the cleverness and straight ahead philosophy of the design is probably the essence of what Walter brought to the market. Of course, this is in addition to the switchmode power supply, which was revolutionary for the time. This goes back to the early to mid 70's... I was still in high school!
WW's gain stage is based on the idea that the current flowing through the JFET is roughly proportional to the voltage difference between the gate and source. So you can apply negative feedback to the source terminal and use it like a crude "op amp" under some conditions.
Where else does this appear? Look at virtually any tube power amp schematic: There's a resistor connecting the speaker output to the cathode of the input triode. It's what provides negative feedback to the amplifier. And look for negative feedback in the midrange circuit of the classic SVT preamp.
Where else does this appear? Look at virtually any tube power amp schematic: There's a resistor connecting the speaker output to the cathode of the input triode. It's what provides negative feedback to the amplifier. And look for negative feedback in the midrange circuit of the classic SVT preamp.
Much "tailoring" can be accomplished by what is done within the feedback loop. It can drastically affect how the poweramp performs.
Indeed, and especially as the output approaches the rails, open loop gain rapidly dwindles.
I don't understanding the tech speak (but love reading about it!)...but I do wish someone would make an amp in a similar vain. The Woods amps really are incredible. I've been using Acoustic Image for E Bass for years and love them, but that's another company that won't be around forever (an aging owner). The Woods just has that something that other light weight amps don't possess (although I haven't tried them all).
Thank you! Much of what you said goes over my head, but I think I understand about distortion levels being the reason I love the tone and texture of the early amp. Also, probably why I couldn't replicate it with the Ultra high power. I can't seem to get close with the Streamliner, D800+, or Bergantino Forte HP either. The Bergantino can get the closest using the drive circuit with the Big Fat tube download. In fairness, I haven't pushed the D800+. I should try that.
Did you have different years, or revisions, of the 100-8, or no idea why they sounded different? Was one better than the other or just different?
I don't recall what date of production they were (that is basically what the serial number provides). One I got in the early/mid '80s, the other in the early '00s. Outwardly they were the same except (IIRC) the later one did not have the channel 1+2 mix switch. Neither was "better" than the other, although the aforementioned mix switch was great for combining the channels when used with one of the two '78 RD Artist guitars I used to have, for a very nice distortion. I have a bunch of recordings I've made with it (guitar, and bass - my old February '67 4005WB).
Can you explain how you did this? Just curious. I've never mixed the channels.
Yep. The Mix setting runs the two preamps (one for each volume control) in cascade mode; Channel 1 feeds into Channel 2, then into the EQ. Never tried it for bass that I recall, but it sounds great with guitar.
Got it! So depending on the preamp volumes, you can get an overdrive sound. Also, in the 2-channel amps like mine, it mixes the EQ's.
