Ampeg - Phazzer  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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george giblet
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Post by george giblet »

I tend to use a 4007UBE, as the FETs seem much more robust
Do you leave the power rails (ie. P-channel sources + protection diodes) unconnected or do you connect them to the gates that go to the LFO?

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Post by aion »

Hey Jimi, any progress on the rest of the service manual?

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Post by pinkjimiphoton »

shit, forgot about it completely! let me see if i can find that suckah, i'll try and find and scan it today. sorry old friend!
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Post by pinkjimiphoton »

here ya go!
page one, cover
page one, cover
page 2, manual
page 2, manual
page 3, bom
page 3, bom
page 4, schematic
page 4, schematic
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Post by BMS1971 »

ppluis0 wrote: 22 Oct 2021, 19:01
ppluis0 wrote: 14 Aug 2021, 01:47Had six stage phasers any advantage ? :hmmm:
JiM wrote: 14 Aug 2021, 16:03 It will have three notches in the frequency response, compared to two for 4-stages.
A tiny bit more flange-y, depending on the choice of caps (spacing of the notches).
Image

Hi there,

Found this diagram in the web scanned from a 1976 National Semiconductor audio manual.
In the description of this unit explain that the condenser values of each stage are selected to spacing one octave apart, but in several phaser diagrams I've seen all the condensers in all the stages are of equal value. (Exception are the condensers of Uni Vibe...)

Cheers,
Jose
Interesting for two reasons:
6 stage phaser
2 the possibility to stop phase and select it manually

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Post by edkoppel »

Here's an email i got from the original designer of the Ampeg Phazzer, Donald Tillman after posting about it on the Tone Machines blog:

"This was manufactured by a company called "I W Turner", a very small music electronics company in the town I grew up in, Port Washington, New York. (That's on Long Island, just outside New York City.) This was a basement operation; literally, it was in the basement of a fabric store. It was a side project of the the local high school band director who had an inventor/entrepreneur streak. I was a nerdy kid, and I showed him some of my electronics work and he hired me part time to do some engineering there. The name is made up; the initials stand for the first names of the two partners, the Turner part was a family name that went well with it.

The company sold music electronics to schools. The first product was a metronome. And since synthesizers and electronic music was getting popular then, we made a set of modules to introduce elementary school kids to the rudiments of electronic music; oscillators, filters, etc.

At that time the phase shifter was the cool new guitar effect. (It changes the tone, but not in an obvious way.) We used an MXR Phase 90 as a model, and I reverse engineered it, and tweaked and improved the design a bit:
* replaced the individual FET's with a CD4069 chip, biased off so the internal FET transistors are available, it's cheaper and the FETs are matched
* better LFO circuit, the slow sweeps are smoother
* better mixing of the phased and original signals, better output drive

At the time, Ampeg wanted to get into the stomp box business, so we made a deal to build some number of units for them. (My memory is telling me it was 1000 units, but I'm not sure that's right.) And these were branded for Ampeg (clearly). Ampeg later decided not to get into the stomp box business, and seems to have found them in a warehouse and sold them off at some point."
Tone Machines: vintage effects blog:
http://tonemachines.blogspot.com/

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Post by BMS1971 »

ppluis0 wrote: 22 Oct 2021, 19:01

Found this diagram in the web scanned from a 1976 National Semiconductor audio manual.
In the description of this unit explain that the condenser values of each stage are selected to spacing one octave apart, but in several phaser diagrams I've seen all the condensers in all the stages are of equal value. (Exception are the condensers of Uni Vibe...)

Cheers,
Jose
Yes I have seen it around with the name Cookbook phaser (name of the book I think). I was considering making one. The only change will be to use real FET instead of the impossible to find AM3909CN
Ben

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Post by BMS1971 »

edkoppel wrote: 19 Oct 2022, 02:34 Here's an email i got from the original designer of the Ampeg Phazzer, Donald Tillman after posting about it on the Tone Machines blog:

"This was manufactured by a company called "I W Turner", a very small music electronics company in the town I grew up in, Port Washington, New York. (That's on Long Island, just outside New York City.) This was a basement operation; literally, it was in the basement of a fabric store. It was a side project of the the local high school band director who had an inventor/entrepreneur streak. I was a nerdy kid, and I showed him some of my electronics work and he hired me part time to do some engineering there. The name is made up; the initials stand for the first names of the two partners, the Turner part was a family name that went well with it.

The company sold music electronics to schools. The first product was a metronome. And since synthesizers and electronic music was getting popular then, we made a set of modules to introduce elementary school kids to the rudiments of electronic music; oscillators, filters, etc.

At that time the phase shifter was the cool new guitar effect. (It changes the tone, but not in an obvious way.) We used an MXR Phase 90 as a model, and I reverse engineered it, and tweaked and improved the design a bit:
* replaced the individual FET's with a CD4069 chip, biased off so the internal FET transistors are available, it's cheaper and the FETs are matched
* better LFO circuit, the slow sweeps are smoother
* better mixing of the phased and original signals, better output drive

At the time, Ampeg wanted to get into the stomp box business, so we made a deal to build some number of units for them. (My memory is telling me it was 1000 units, but I'm not sure that's right.) And these were branded for Ampeg (clearly). Ampeg later decided not to get into the stomp box business, and seems to have found them in a warehouse and sold them off at some point."
Thanks for the idea to use CD4069 ! The Am9707CN are impossible to find

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