I haven't dug deep on this one so I apologize if it's been covered. Is the Hot Tubes a beefed up version of the TSF or is the TSF a stripped down version of the Hot Tubes? Thanks.
First Anderton TSF (with an op-amp front end) was in the Jim Messina cover issue of GP around late 76 or early 77 (though autumn 76 seems about right). EPFM came somewhat later. I can't find anymention of the Hot Tubes prior to 1978, but that's not a guarantee of anything.
I don't know that I've ever seen the schematic for a TSF with an opamp front end, I'll have to dig. Thanks.
Yes. Most people equate the TSF with the one in EPFM that uses two invertors and nothing more. This also formed the basis of the Way Huge Red Llama. The first version, with the op-amp front end, is actually a closer relative to the Hot Tubes. Here's an archived post from the old days (I was "META" at that time) about that very topic: http://www.harmony-central.com/Guitar/Faqs/faq/faq.tubeSoundFuzz.txt
After some poking around, I noted that....well duh!...Jack Orman had the original posted here: http://www.muzique.com/schem/tubesnd.gif he dates it as Jan 1977, so I wasn't that far off.
After building that back in 19-whatever, and finding it still a little unsatisfying, I came up with this thing.: http://www.geofex.com/FX_images/mhtsf.gif This schem has been on RG's site for many a year. I made it for a guy in Victoria, BC. The 2-pole lowpass filter was interesting in many ways, but a little overkill, so I eventually dropped it. The basic 2-invertors-plus-an-opamp has enough output that I simply replaced the active filter with a simple passive RC+RC 2-pole filter that I could bypass for "bite/round" tone. Since the filtering loses amplitude, the "bypass" mode inserted a resistor in series with the output level pot to provide approximately equal output level across tone modes.
The brightness cap across the Drive pot was a nice addition and could yield some Rickenbacker-like midrange bite under low drive conditions. Certainly one of the reasons why I opted for the non-inverting front end rather than the inverting version that Anderton started out with, was because it provided more options for tone shaping of the signal pushing the invertors. Having recently A/B'd it with Doug Hammond excellent Highway 89, it nails many of the same tones. The Highway 89 pulls out ahead, though, in the sorts of cleaner-oriented tones it can yield. This thing never seems to get completely clean. Great for that Tom Petty vibe, though.
Here is a more recent version that is simpler in some ways, more complicated in others. The same principle of op-amp gain followed by modest invertor gain still applies: http://gaussmarkov.net/wordpress/circuits/forty-niner/
The intermediate stage of the Anderton Frequency booster is not essential. Since it lets you find something useful to do with the other half of a 4558/TL072/NE5532, and can be easily bypassed, it does little harm to include it. The specific boost frequencies are entirely up to you.
Thanks for the info!
1973: (http://www.fairchildsemi.com/an/AN/AN-88.pdf)
Quote from: A.S.P. on April 28, 2008, 06:40:28 PM
1973: (http://www.fairchildsemi.com/an/AN/AN-88.pdf)
Which R Penfold must have picked up on: I have some old 70s project books (1975/6) by him that outline the use of CMOS inverters as amps. No distortion circuits...but it was only a matter of time! :icon_lol: