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DIY Stompboxes => Building your own stompbox => Topic started by: Tham on September 26, 2016, 10:36:43 PM

Title: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on September 26, 2016, 10:36:43 PM

I'm no guitarist, but know a little about electronics, and built a
couple of distortion boxes based on projects in electronic magazines
for a guitar friend during the 80s.

Guyatone's PS-021 Guitar Exciter/Compressor, was one of
the most versatile effects of the 80s, and is one that should
definitely be built.

Their range of effects was also made by Nady, presumably under licence.


http://www.qsic.jp/?pid=104385586

http://item.rakuten.co.jp/yasukukaeru/y1989071/


I found the circuit diagram some time ago, but can't locate the
website anymore.


Placing a distortion pedal before it and turning the ''Exciter'' control
to the left gave out even harmonics, essentially that of valve distortion.




Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Mark Hammer on September 27, 2016, 08:45:19 AM
Interesting pedal.  Was not aware of that one.  Thanks for drawing it to our attention.

In some respects, it is a predecessor of later attempts to re-introduce the treble bite that seems to frequently be removed by compression.  I wonder how they did it.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on September 27, 2016, 10:47:22 PM



I made a post about the exciter in this local guitarists' forum
years ago.

It's based on the LM324 quad op amp.

https://forum.lowyat.net/index.php?showtopic=1559773&view=findpost&p=36338118



Revised link of the local supplier.

Very low cost. RM 1.50 = US 35 cents.

http://synacorp.my/v2/en/amplifier-comparator/270-lm324.html



Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on September 28, 2016, 08:39:10 PM
Interesting pedal.  Was not aware of that one.  Thanks for drawing it to our attention.

In some respects, it is a predecessor of later attempts to re-introduce the treble bite that seems to frequently be removed by compression.  I wonder how they did it.




You are welcome.

It doesn't really retain the treble bite.

It radically changes the output waveform.

Turning the ''Exciter'' control to the left generates
even harmonics, simulating a valve amp/distortion,
and turning it to the right generates odd harmonics,
that of a transistor amp and distortion.

No other effect pedal on the market can do that
to this day.

There were other ''exciter'' pedals like Dod's FX-85
Harmonic Enhancer, but they enhance the harmonics
of the original sound, mostly odd ones. giving more
presence.

http://www.americaspedal.net/fx85/


Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on September 28, 2016, 11:28:35 PM







Here's an ''exciter'' circuit using the TL072.

http://www.guitarelectric.eu/schematy/Efekty/Inne/Exciter.gif.html#schemat





Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: StephenGiles on September 29, 2016, 02:56:35 AM
The there is this exciter circuit:

http://groupdiy.com/index.php?topic=889.0


and my goodness - this one!!!

https://www.dropbox.com/s/x66sbryzdt3i7ar/104e_sch.jpg?dl=0
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Mark Hammer on September 29, 2016, 09:44:57 AM
Virtually all exciter circuits require extended bandwidth from both the pickups and amplifier speakers.  People have a tendency to come into music stores, plug a humbucker-equipped guitar into an amp with four twelves (that roll off above 5khz) and ask "Is this thing even on?".  That's one of the reasons why many name-brand attempts (DOD, Boss, Aphex, et al.) at exciter pedals never really took off - because many consumers didn't understand the contexts in which they would be useful or even audible.

This demo video seems to present the PS-021 to good effect:
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on October 17, 2016, 10:59:31 PM


The video doesn't really demonstrate the PS-021's potential,
as he just played it clean.


Way back in 1986, I bought one and let Hillary Ang, one of
the top rock guitarists here at that time, try it. Intially he just
played it clean into his practice Peavey amp and it didn't
sound anything special.

When I met him again a few days later however, he begged
me to let him use it at his performance at this local rock cafe
for the next few weeks, because it was ''really good''.

I then went to the cafe to check him out.

When he soloed, he stepped on both the exciter, connected
after his Boss DS-1, and a DD-2 digital delay after it.

His sound suddenly became much more dynamic, punchy
and fatter with presence.

He used a Fender Strat with a Seymour Duncan jazz neck
humbucker in the bridge, and a single coil in the neck, with
a Marshall JCM 800.

I took a look at the PS-021 on his stage and he had turned
the''Exciter'' control all the way to the left, giving out even
harmonics.

I think the ''Color'' control was at the 9 to 10 o'clock position,
with ''Sustain'' at 2 o'clock.











Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: digi2t on October 19, 2016, 09:12:51 PM
Just found one at a reasonable price. What the heck, I'll pick it up and open it up. Should have it in a couple of weeks.

This intrigues me. :icon_biggrin:

I do have one of these monsters...

(http://files.effectsdatabase.com/gear/pics/exr_projector_003.jpg)

Never used it much, let alone trace it. Probably has nothing in common with the Guyatone, but might be interesting to investigate.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on October 19, 2016, 11:10:02 PM
Just found one at a reasonable price. What the heck, I'll pick it up and open it up. Should have it in a couple of weeks.

You got one at a bargain price ?

Good for you.

It is being sold at some of these Japanese auction sites
at really high prices, some over 12,000 yen.


Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on October 19, 2016, 11:20:30 PM


This guy describes exactly what I was trying to tell you
people about this effect.


'' My friend used one on his setup around 1986, in line after
the distortion unit, such as Boss’s Heavy Metal. You could
get virtually any kind of distortion sound with it, because the
“Color” control, you can vary the harmonics from even to odd.

The “Exciter” adds a brilliance to the sound, similar to the
Aphex Aural Exciter, so it can even be used for vocals. ''

'' With the “Color” turned to the left, around 9 o’clock, you
would get even harmonics, close sounding towards a
tube amp’s distortion.
Placed after the distortion, you
could step on it when you wanted to do a solo, as it would
boost your sound level up as well. This was a
versatile, superb and underrated effect, and none of the
other effects manufacturers made an equivalent unit.
''

'' The closest I could find at that time was Dod’s Harmonic
Enhancer, and this had no “Color” or compressor built in.
Boss had no such effect in their immense armamentarium.
Most guitarists were ignorant of the existence of this effect.
''


http://www.guitarandpedal.com/guyatone-ps-021-compressor-and-exciter-80s-japan/





However, I think he a mistake when he said the ''Color''
control varies the sound from even to odd harmonics. It's
rather the ''Exciter'' control, as you may note from the tiny
waveform symbols at the left and right corners of the knob.

The ''Color'' was more like a tone, brilliance or ''enhancer'' control.


I too ordered Dod's Harmonic Enhancer from the US at that
time, and it was a pale design compared to the Guyatone.



Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: bluebunny on October 20, 2016, 02:45:57 AM
I do have one of these monsters...

(http://files.effectsdatabase.com/gear/pics/exr_projector_003.jpg)

When are you gonna put the wheels back on that pickup truck, Dino?   ;)
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: digi2t on October 20, 2016, 07:12:27 AM

When are you gonna put the wheels back on that pickup truck, Dino?   ;)


Dunno... but I did find a picture of them casting the pedal...

(http://www.emiratesengg.com/images/foundry/aluminium-foundry-2.jpg)

 :icon_mrgreen:
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on October 20, 2016, 10:44:24 PM



Administrators :

The ''Bold'' function in the text window does not work.

And it would be good to include a button to upload files and images.

Virtually all major forums have this facility, including that at
Free Stomp Boxes.










Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: bluebunny on October 21, 2016, 03:40:16 AM
This is really the wrong place to raise this, but anyway...  Aron provides space in the Gallery to upload pictures in case you don't want to host them elsewhere (e.g. imgur.com).  Take a look in the "READ THIS BEFORE..." thread.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: duck_arse on October 21, 2016, 10:48:52 AM
when you say
Quote
The ''Bold'' function in the text window does not work.

are you meaning this (http://www.diystompboxes.com/smfforum/Themes/Prince_of_Darkness_201/images/bbc/bold.gif) button?

when I type "it seems to work", then highlight "it seems to work" and press the B for bold, it seems to work fine.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Ben Lyman on October 21, 2016, 11:10:41 AM
I think it may not work on all computers because it doesn't work on mine either. Not a big deal to me.
I suppose one could find OTHER ways TO ACCENTUATE THEIR TYPE   ;)
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: bluebunny on October 21, 2016, 11:42:08 AM
GOOD IDEA BEN; YOU FORGOT COLOURS   ;)
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: PRR on October 21, 2016, 02:51:55 PM
> upload files and images.

The forum has no funding. Free to use and essentially zero ads. Image space costs real money. There are many fine free hosting services. I like PostImg.org

> The ''Bold'' function in the text window does not work.

Works for some people (browsers), not for others.

Quote
when I type "it seems to work", then highlight "it seems to work" and press the B for bold, it seems to work fine.


I see:
(https://s21.postimg.org/tpuggj9jr/Seems_To_Work.gif)

Page source: (brackets replaced)
{br /}when I type "it seems to work", then highlight "it seems to work" and press the B for bold, {strong}it seems to work{/strong} fine.{/div}

I believe different renderer engines, zooms, and font settings interpret "strong" differently.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: digi2t on October 31, 2016, 06:56:00 PM
Came in today. Here are some pictures;

(http://i214.photobucket.com/albums/cc196/digi2t/Guyatone%20PS-021/DSCF5247_zpsktlqrmu2.jpg) (http://s214.photobucket.com/user/digi2t/media/Guyatone%20PS-021/DSCF5247_zpsktlqrmu2.jpg.html)

(http://i214.photobucket.com/albums/cc196/digi2t/Guyatone%20PS-021/DSCF5246_zpsaxqznwq8.jpg) (http://s214.photobucket.com/user/digi2t/media/Guyatone%20PS-021/DSCF5246_zpsaxqznwq8.jpg.html)

(http://i214.photobucket.com/albums/cc196/digi2t/Guyatone%20PS-021/DSCF5245_zpsx5jqsw9z.jpg) (http://s214.photobucket.com/user/digi2t/media/Guyatone%20PS-021/DSCF5245_zpsx5jqsw9z.jpg.html)

(http://i214.photobucket.com/albums/cc196/digi2t/Guyatone%20PS-021/DSCF5244_zps5f7qvlhc.jpg) (http://s214.photobucket.com/user/digi2t/media/Guyatone%20PS-021/DSCF5244_zps5f7qvlhc.jpg.html)

I had a few minutes tonight to play with it, just guitar in and out to my small practice amp. I'm really rather impressed! It's a really cool tone shaper. There's really no bad settings on this puppy. You can go with settings that brighten up your sound, but not overly so, to settings that help enhance the lower frequencies. For instance, I can kill coil on my bridge humbucker, but that tends to induce a bit of buzziness to plucked open D, B, and E strings. Adjusting the Color and Exciter pots smooth's that right out, resulting in a nice full, buzz free sound, but still retaining that single coil feel. On the neck humbucker, again, Exciter allows you to fill out the lower frequency spectrum, and Color can add some beautiful top end sparkle.

It's a subtle pedal. It makes an immediate impact, yet after a few minutes of playing, my ears believe that my tone was always that great. Then, when I turn it off, my brain goes "WOAH!... what happened?". Tomorrow I'm going to try this with some dirt. Pretty sure it's going to shine.

One of the best buys I've made in a long time. Have to get through the Funk-a-Duck trace right now, but I'll be moving on to this one next. Everybody should have this baby on their board.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Mark Hammer on October 31, 2016, 07:42:47 PM
Interesting.  But what the hell is an LA6324?
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: digi2t on October 31, 2016, 08:27:16 PM
I Googled it. http://www.onsemi.com/pub_link/Collateral/LA6324N-D.PDF (http://www.onsemi.com/pub_link/Collateral/LA6324N-D.PDF)

LM324 equivalent?


Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: PRR on October 31, 2016, 08:44:25 PM
>> what the hell is an LA6324?
> LM324 equivalent?


I think so. Possibly a micron-exact copy of '324, though specs taken and quoted marginally differently. Note 32V max supply; IIRC the '324 can stand more, but not an issue in a 9V/18V world.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Mark Hammer on October 31, 2016, 09:52:58 PM
I Googled it. http://www.onsemi.com/pub_link/Collateral/LA6324N-D.PDF (http://www.onsemi.com/pub_link/Collateral/LA6324N-D.PDF)

LM324 equivalent?
Ha!  The power of subvocal speech and rotated images.  I looked at it rotated and thought "sixty-three twenty-four".  Had it been staring at me in the "right" orientation, I would have thought "Oh, another 324 with a 6 prefix".

The human mind is a perpetual barrel o' laughs.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: digi2t on November 01, 2016, 06:31:07 AM
I Googled it. http://www.onsemi.com/pub_link/Collateral/LA6324N-D.PDF (http://www.onsemi.com/pub_link/Collateral/LA6324N-D.PDF)

LM324 equivalent?
Ha!  The power of subvocal speech and rotated images.  I looked at it rotated and thought "sixty-three twenty-four".  Had it been staring at me in the "right" orientation, I would have thought "Oh, another 324 with a 6 prefix".

The human mind is a perpetual barrel o' laughs.

.siht ekil etirw t'nod I gniht dooG

 :icon_mrgreen:
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Mark Hammer on November 01, 2016, 11:46:21 AM
!erom eerga t'ndluoC   :icon_wink:
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on November 01, 2016, 09:25:39 PM




The LA6324 is a quad op-amp originally made by Sanyo.

The LM324 is the equivalent.

http://www.hkinventory.com/p/d/LA6324.htm



Technically, the low power LM224 and LM2902 can also be used.

http://www.electroschematics.com/7143/lm2902-lm124-lm224-lm324-datasheet/

http://www.ti.com/product/LM224-N


The LM348 is even lower power, but with a minimum supply
voltage of 8 volts.

http://www.ti.com/product/LM348



Part of the design features would come from the LM3080N,
the transconductance amplifier which acts as the envelope shaper.

http://www.hkinventory.com/p/d/LM3080.htm


Equivalent for the LM3080N would be the dual LM13600/13700,
but with more pins.

http://www.hkinventory.com/p/d/LM13600.htm


Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on November 02, 2016, 08:38:32 PM



The TL074. TL084 and TL£2074 are all quad op-amps
and should also be replacements for the LA6324.

http://www.ti.com/product/TL084

http://www.ti.com/product/tle2074/description



Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: PRR on November 02, 2016, 10:14:28 PM
The '324 series has inputs that will go to V- (Gnd). Many other opamps wont.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on November 03, 2016, 11:21:59 PM




A search of the LA6324 replacement  turns up the Renesas (Hitachi) HA17324.

http://www.allxref.com/search.htm?part=LA6324

https://www.digchip.com/datasheets/parts/datasheet/192/HA17324.php


Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on November 05, 2016, 12:08:52 AM

As crossreferenced in the DigChip link above, the NEC μPC324
is also a replacement for the LA6234.

http://pdf.datasheetcatalog.com/datasheet2/1/02e1lrjrqha8tpeu5qr9f3jf23wy.pdf


You can get it from China. It's actually made in Malaysia.



Seems many of their suppliers there are willing to
send a single chip to you by small packet post.

https://www.aliexpress.com/item/UPC324C-UPC324-C324C-DIP-DIP-14-new-original-low-operational-amplifiers/1872256619.html




Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on November 05, 2016, 12:52:57 AM


The LM3080N and replacement, CA3080E, have apparently
been discontinued by NS and Intersil.

Plenty of suppliers in China.



https://www.aliexpress.com/item/1PCS-LM3080N-LM3080-DIP8/32470241229.html

https://www.aliexpress.com/item/LM3080N-DIP8/32611758482.html



https://www.aliexpress.com/item/CA3080E-LM3080N-DIP8/32558270503.html

https://www.aliexpress.com/item/CA3080E-CA3080AE-LM3080N-DIP8/32454378401.html

https://www.aliexpress.com/item/NEW-OP-AMP-IC-DIP-8-CA3080E-CA3080EZ-CA3080/32705574595.html




Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on December 06, 2016, 10:15:05 PM


@Digi2t

Oh, looks like you have made a video on your newly acquired exciter.





The sustainer/compressor part of the circuit would be built around the envelope shaper IC, the LM3080 transconductance amplifier.


Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on December 07, 2016, 10:46:27 PM


I let this young Chinese guitarist, Benson, who was then with this local Malay band, Belantara, use the Guyatone exciter when they recorded their album, ''Infiniti'', way back in 1990.


I remember him saying that the PS-021 was used on the
last song on Side 2,  ''Jalan Pulang''.

I think he placed it after a Boss HM-2 Heavy Metal.

He had a vintage Fender with a DiMarzio PAF Pro bridge pickup.

He's the first on the right, white shirt and blue jacket.




The same song in HQ audio.





Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on December 10, 2016, 06:19:36 AM
If I remember correctly, he said during the recording for the
above song, the ''Exciter'' control was at 9 to 10 o'clock, while
''Sustain'' was at 2 o'clock.

I can't remember what his ''Color'' setting was, but I think it
was more on the bassy side, about 10 o'clock, in order to
obtain the fatter, heavier sound in the solo.

His usual settings for the Boss HM-2 was Bass 3 o'clock,
Treble 2 o'clock, Distortion 3 o'clock.






Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on February 15, 2017, 10:09:06 PM

The Guyatone exciter was used and popularized by Tomoyasu Hotei, the lead guitarist of the Japanese pop band, Boowy, in the 1980s.

That is why when you search for the Guyatone PS-021 on the
net, especially in those Japanese auction sites, you will see the
name "Boowy" listed along with the Japanese description of it.









Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: digi2t on February 16, 2017, 09:35:52 AM
Kevin over at Aion has this (and the bass version) on the bench now. It might be out as diy pcb at some point.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Tham on February 16, 2017, 10:12:59 PM
Kevin over at Aion has this (and the bass version) on the bench now. It might be out as diy pcb at some point.

It's good to know that they are making a DIY PCB for it.

The PS-020 Bass Exciter's PCB and components looks virtually identical,
even the position of the preset variable resistor, so initially I thought it
was the same circuit in a different box.

Is the sound much different from that of the PS-021 Guitar Exciter ?

Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: aion on October 30, 2017, 03:51:01 PM
I was finally able to finish the trace on the PS-021.

PNG: https://aionelectronics.com/schem/guyatone_ps-021.png
PDF: https://aionelectronics.com/schem/guyatone_ps-021.pdf

Let me know if anything looks wrong and I can double-check.

The compressor half is nearly part-for-part identical to a Dynacomp, with the exception of the Sustain knob (and yeah, I triple-checked the R10 resistor value: green-blue-yellow... that and the value of the Sustain knob itself are the only components that are different).

The exciter portion looks pretty familiar too:
http://experimentalistsanonymous.com/diy/Schematics/OOP%20Japanese%20Electronics%20Book/phase-exciter.gif

The bass version uses the same PCB, so I assume it's just a matter of swapping out a few capacitors here and there. As digi2t said, I've got the bass version as well, so I'll get that one cracked open before too long and post the changes for that version.

I'm planning on putting together a DIY PCB project for this which will probably be available shortly after the new year. But in the mean time, I thought I'd make the schematic available for anyone who wants to have a stab at putting one together on their own, or just studying it.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Mark Hammer on October 30, 2017, 09:52:14 PM
Putting both a couple of Boowy/Hotei videos and the schematic together, I get the sense that the unit is a kind of alternate approach to a bright compressed sound, different from compressors that include a wet/dry blend, but aiming for the same outcome.

The compressor portion seems like a ringer for the Dynacomp/Ross, and the output of it goes to a gain-recovery stage, followed by a Big Muff style tone control (Color) and buffered output.  The circuit is a bit simpler if one uses true bypass switching, rather than the FET switching shown.

What differentiates it is the inclusion of an exciter-type circuit to supplement the compressed signal.  IC2C provides 90 degrees of phase shift, beginning around 480hz. IC2D provides a 2-pole highpass filter, to isolate the higher-frequency content of the compressed signal.  IC2A provides a simple gain of just over 3x to make the HF content more evident.  IC3A provides a unity-gain phase-flipping stage, such that when the Exciter control pans between the outputs of IC2A and IC3A, it is either favouring the non-inverted or inverted version of the highpass signal, or allowing them to cancel each other out (middle position).  If a builder finds they would like to have more sizzle to their excitement, simply make R30 larger (e.g., 27k or 33k) or make R29 smaller (e.g., 8k2 or 6k8).

Unlike the Big Muff, whose lowpass and highpass sections form the tone control, with corner frequencies chosen to provide a midscoop, the lowpass (R36/C17) and highpass (C18/R37) sections in the PS-021 overlap, such that there is still a fair amount of treble at the full bass setting and still a fair amount of lower mids at the full treble setting.

What I think is fairly evident from the videos and the circuit diagram, as well as from my experience with exciters in general, is that the guitar itself has to have some HF content, and the amp has to be fairly bright, for what is distinctive about this pedal to stand out.  In other words, dull-sounding HBs or P90s are not going to realize any magic from this pedal.  In the absence of those factors, it becomes simply a Dynacomp with a tone control.  That's certainly not a bad thing - I imagine many a player would love to have a tone control on their Dynacomp/Ross/Keeley/Retrosonic compressor.  But what sets it apart is the ability to add the upper frequency content, to give more articulation.  And if you don't feed it what it needs to do that, you won't hear the difference.  Again, that is true of pretty much ALL exciter pedals; which I feel is largely responsible for them not selling very well, historically, despite enjoying considerable usage in studios.  Bottom line: they need a single-coil-equipped guitar.

In view of the considerable similarity to the Dynacomp, I draw your attention to R19, which sets gain-recovery time.  This is often replaced with a pot in series with a 10k resistor, and labelled "Attack".  Shortening the gain recovery time, combined with the exciter function, should bring one squarely into Nile Rogers territory...which isn't a terrible place to be.

Finally, I will draw a parallel here with the Woody acoustic simulator I whipped up a decade back.  Where the PS-021 uses a 2-pole highpass and boosts that, I used a 3-pole highpass, and boosted/clipped that output before blending back in with the straight signal.  I stole the idea from Jules Ryckebusch's Harmonic Sweetener, that had originally appeared in Electronic Musician.  Jules used 4 poles of highpass and LEDs for clipping, in contrast to my 3 poles and asymmetrical silicon-diode clipping.  He added an inverting unity-gain stage to bring everything into phase prior to blending.  Like the PS-021, I also use a single phase-shift stage, but where the PS-021 shifts phase for a smaller part of the spectrum, and does so ahead of the highpass and boost, I do it after everything (before the mix control), and set max phase-shift for 160hz and up.  No two ways about it, the Woody can be hissy, and could probably benefit from a built-in noise-gate.  BUt the basic principle of blending in addentuated high-end with a straight signal, can be a desirable thing.
(http://www.montagar.com/~patj/harmswtn.gif)
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: albru80 on October 31, 2017, 01:24:22 PM
Thank you for the schematic!
I want to draw a layout but I'm not sure about something:
to completely eliminate the flip flop switching from the schematic would you get rid of Q9, Q10, Q11, R15, R16, R20, R40, R41, R69 and C10?
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: digi2t on October 31, 2017, 03:00:57 PM
Hmmm, I see 3 jfets for the flip-flop bypass. Are two connected to the same side of the flip-flop?

Never mind. The schematic of the Boss OD2 just answered my question. :icon_wink:
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: aion on November 05, 2017, 04:30:49 PM
Mark, thank you so much for that analysis! Such a great writeup.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: Mark Hammer on November 05, 2017, 05:08:31 PM
My pleasure.  A whole lot easier to do with a nicely-drawn schematic to work from!
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: gigimarga on December 01, 2017, 05:05:04 PM
Hello all!
Anyone have built it? I've just finished (using this vero: http://tagboardeffects.blogspot.ro/2017/11/guyatone-ps-021-guitar-exciter.html (http://tagboardeffects.blogspot.ro/2017/11/guyatone-ps-021-guitar-exciter.html)) but it didn't work as I heard in demos: it has a low level and distorted output. All the pot seems to work OK.
In the schematic, the 22K trimpot looks strange to me. In all Dynacomp variants, it is only 2K. Maybe this could be a problem?

Thank you!
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: R O Tiree on December 10, 2017, 04:29:07 PM
Hmmm, I see 3 jfets for the flip-flop bypass. Are two connected to the same side of the flip-flop?

Never mind. The schematic of the Boss OD2 just answered my question. :icon_wink:

It's been a while since I did any of this stuff... but I'm not seeing what Q9 does.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: aion on December 22, 2017, 10:37:23 AM
It's been a while since I did any of this stuff... but I'm not seeing what Q9 does.

I think it's just a second turn-off point because it's such a large circuit. They mute the signal in two places in bypass, which happen to correspond to the input of the first half and the input of the second half, although there isn't any way of tapping into just one of the effects.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: R O Tiree on December 22, 2017, 05:03:15 PM
Thanks, aion.

But how cool would it be to have the facility to select "Dynacomp" only (insert compressor circuit to taste), "exciter" only or "both"... ?

A couple of flip-flops + LEDs and associated momentary push-to-make switches, another JFET or 2 (I'd need to work that out), and Robert is one of your parents' siblings.  You could have the comp part of the circuit as a daughter-board, so people could choose from a variety or roll their own.  A standard Orange Squeezer is a very sweet circuit as is and (having built lots of comps) doesn't seem to have anywhere near the noise associated with a CA3080-based topology (never built a 13700-based one, so I don't have a feel for noise on those).  Optos are also nice-sounding... You could have all the components of the switching system on the main board, leaving only V+, GND, Vin and Vout as the only connections needed to the daughter-board.
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: aion on December 23, 2017, 04:23:46 PM
Thanks, aion.

But how cool would it be to have the facility to select "Dynacomp" only (insert compressor circuit to taste), "exciter" only or "both"... ?

A couple of flip-flops + LEDs and associated momentary push-to-make switches, another JFET or 2 (I'd need to work that out), and Robert is one of your parents' siblings.  You could have the comp part of the circuit as a daughter-board, so people could choose from a variety or roll their own.  A standard Orange Squeezer is a very sweet circuit as is and (having built lots of comps) doesn't seem to have anywhere near the noise associated with a CA3080-based topology (never built a 13700-based one, so I don't have a feel for noise on those).  Optos are also nice-sounding... You could have all the components of the switching system on the main board, leaving only V+, GND, Vin and Vout as the only connections needed to the daughter-board.

It would be pretty tricky to retrofit into a real PS-021 with the FET switching and all. But I may end up doing just the exciter portion as its own board (alongside the full PS-021 circuit) depending on how different I feel it sounds from the BBE Sonic Maximizer, which uses some of the same principles but is a lot more flexible (see my Lumin project).
Title: Re: Guyatone's PS-021 Guitar Exciter/Compressor
Post by: digi2t on February 03, 2018, 03:34:19 PM
I went through my unit, and I took the liberty (using Aion's schematic) to fill in the rest of the blanks...

(https://i.imgur.com/b5RqaR5.jpg)

What I find really interesting is the indicator LED circuit. Personally, I find the color representation backwards (red = good, green = bad), but maybe it's a Japanese thing, or they simply inserted the LED backwards on the line.