Ross Phazer - completed with Mark Hammers mods

[lightningfingers]

--Those mods are, a vibrato switch, and a switch which switches between allpass and lowpass filter for the last 2 stages. What can I say, it sounds great. In stock mode the phaser is quite prominent...the prominence increasing with regeneration......in the phase-filter mode, it becomes a little subtler, kind of rounder/more wah-like. In the vibrato mode it all gets very swampy, not much vibrato to be heard....its an incredibly strange sound, not something i've ever heard anything quite like. Thank you once again mr hammer -- I salute you sir    

Martin

[MartyMart]

Sounds cool !  any pictures ?

Marty.

[puretube]

not the same, but very related:
http://www.moosapotamus.com/frankenstone/frankenstone.htm

[lightningfingers]

yeah i saw that page, i wanted to do that stereo outputs thing, so i could have wet signal going to one amp, dry to another amp, but i forgot to buy 3 jacks :roll: .
Marty: its really nothing to look at. Its in a lunchbox i bought for £0.59 from the local supermarket. I will post pictures if (when) it gets a better enclosure. :oops:

[Kleber AG]

hello Martin
Seems to be a nice circuit.
How could you describe the stock phase sound of this circuit, compared to the others (phase90/small-stone) Distortion headroom???

Please tell me more about the phase tone, I'm about to start building it

Thank you so much!
Kleber AG

[hair force one]

Is the ross phaser the next big thing from vibeland (after Univibes, MXRs, and Smallstones)?

[Mark Hammer]

The Ross Phaser, and especially with Francisco Pena's sublimely compact and convenient layout, is an exceptional value for time and money invested.  Seriously.  Once you find a source for LM13600/NJM13600 chips, the rest is a piece of cake.  The board is compact and fits a variety of enclosures.  It's extremely mod-able.  The sound is great.  I can confirm that it makes an excellent Univibe type effect when the cap values are switched, and the phasefilter option delivers somethng you've never heard before and can probably think of lots of uses for.

I've never A/B'd them but I should be able to in the next few weeks.  From memory, though, it is not dramatically different than the Small Stone, which is no big surprise since there is not a huge difference in their design.

[petemoore]

Where does one find the correct Chip ?

[Mark Hammer]

LM13600's are not THAT exotic a chip (well, assuming you look beyond Radio Shack), and are carried by plenty of distributors.  I'm certain Small Bear has them, in addition to the usual suspects (Mouser, Digikey, Jameco, etc.).

There are some applications where an LM13600 and LM13700 can be used interchangeably, but I don't think this is one of them.  The 13700 has some advantages over the 13600, but their relationship is NOT like that of, say, an NE570 and NE571, where you can pop one out and the other in for a slight hike in noise performance.

[puretube]

for me, the interchangeability worked, IIRC from 2 yrs. ago...

National sez:
"The output buffers of the LM13700 differ from those of the LM13600 in that their input bias currents (and hence their output DC levels) are independant of  I ABC.
This may result in performance superior to that of the LM13600 in audio applications."

they are pin to pin compatible, layoutwise...

[lightningfingers]

My clone was built with the LM13700, I have experienced no problems...

How could you describe the stock phase sound of this circuit, compared to the others (phase90/small-stone) Distortion headroom???  

I assume you've heard a small stone? The Ross phaser is VERY similar, but without the noise while not playing/oscillations.

[Mark Hammer]

Thanks gentlemen.  These are both useful pieces of information.

[puretube]

btw.: has anybody ever thought of staggering the IABC series resistors to "univibe" that thingy? (instead of the caps, i.e.)

(talking `bout the versions with rather large individual V-to-I resistors, here...)
:wink:

[Kleber AG]

Thank you guys!  
Yes I've heard a SS Martin, thanks.
Have to build it next.

btw.: has anybody ever thought of staggering the IABC series resistors to "univibe" that thingy? (instead of the caps, i.e.)

(talking `bout the versions with rather large individual V-to-I resistors, here...)

err.. sorry, what do you mean by "staggering the IABC resistors"?

Thanks
Kleber AG

[gez]

btw.: has anybody ever thought of staggering the IABC series resistors to "univibe" that thingy? (instead of the caps, i.e.)

I like the way you think Ton!    Could use pots to tune range?

[Mark Hammer]

The OTA-based allpass stages also set the sweep range by means of a cap, just like the FET/LDR-based ones do.  Since the Univibe thing is achieved via the staggering and more even distribution of where phase shift occurs, one way to do it is by altering cap values.  Another way to do it is by electronically staggering the allpass stages so that they start their sweep from different points (which is really all that staggered cap values does).  The Iabc resistor sets the amount of control current going to the OTA, functionally equivalent to changing the start and stop resistances with an LDR or FET.

[puretube]

btw.: has anybody ever thought of staggering the IABC series resistors to "univibe" that thingy? (instead of the caps, i.e.)

Could use pots to tune range?

sure;
but the main idea behind it (...and of course I tied it!), is avoiding "plops" when switching caps (which again can be overcome with pulldowns...);

so just use pots to find the "sweet spots", and then replacing with fixed values; (or read Dome once more, and find his deductions... err, was it s.th. like 5.4 to one, or 7.1 to one - I forgot...).

although this reduces the overall amount of maximum sweepability IABC -wise,
with a million to one ratio in the LM13700, you can go a long way...
(which in that case may call for a full-rail-swing LFO beforehand).

To be honest: I haven`t done any A/B comparisons, since I`m more of a filterguy than a vibe-ist, and therefore prefer equally tuned stages,
but the electrical/musical end-effect got to be exactly the same
(the OTA allpass transfer characteristic being defined by C and the equivalent resistance (or rather gM), set by IABC).