Posts Tagged ‘Envelope Filter’

Digitech XSW Synth Wah

Wednesday, January 21st, 2015

Digitech-XSW-SynthWah

What is it?
Digitech XSW Sythn Wah envelope filter from X-series. Made in china around late 00’s

Deeper green on the color than the bass version, the Synth Wah Envelope Filter takes on the battle for autowahs with slight synth features for a guitar. Decent set of features will let you play around for hours. Some of the modes are usable and may even come handy in some situations. Once again, there is nothing close to a schematic available, but once we open the torx screws and check the PCB we notice something that we didn’t want to see. Sea of vias and the auto-routed footprint that is nothing more or less than the same board we’ll see in the bass version.

Digitech-XSW-SynthWah-guts1

This continues when we flip the board over. Yes. It is exactly the same effect as the XBW Bass Synth Wah. Only things that are different are the print on box and some lines of code inside the ROM. I did know to expect this, but it still made me feel stumped. This makes me think that all the X-series boxes have just two different boards inside them. The first are the ones which have a rotary switch as a fourth pot and the second, there are boards with a standard pot in that position. It is just me, but i’m still an analog electronics enthusiast first and thus, not too thrilled about all digital designs such as these.

Digitech-XSW-SynthWah-guts2

I had a conversation over the social media some time ago. One talented guitarist (who uses Boss GT-100 multi effect, by the way) noted that all the effects are just resistors and capacitors, so it doesn’t matter if the design is digital or analog. I just had to correct him. You know, when there is someone wrong on the internet.. No, these two methods are not the same and cannot be compared head to head. Analog designs rely on electronics engineering, while digital designs rely on processing power, code and A/D-D/A signal conversion. Some modern pedals nowadays can easily hold a power of Nintendo64 inside them (some modern multi effects are even more like desktop computers). But the question is like comparing locally hand forged steel gate on your driveway with one that’s been moulded in chinese steel ovens. Yes. These both do the same thing. And yes. To the laymen it doesn’t matter. But for hand forging enthusiast the different is huge. Then comes the question which is “better”. Neither. Or both. Beauty is in the eye of the beholder.

How does it sound?
Not bad. The modes have good and usable wobbles in them. The synth-like sweeps are pretty wild and since there isn’t too many guitar envelope filters with similar modes available, this unit is rather desirable. Whether it is the same effect from electronics design point of view as the Bass Synth Wah is irrelevant. Sure it matters to me, but it doesn’t affect the sound. My personal opinions rarely affect the sounds… Again, the low price point and big user value will make this effect tempting to many. Not to analog enthusiasts, but for everyone else. Not a bad unit. Good and cheap thing to get. Not a bad investment, if you don’t care about the analog/digital aspect.

Digitech XBW Bass Synth Wah

Thursday, January 15th, 2015

Digitech-XBW-SynthBassWah

What is it?
Digitech XBW Bass Synth Wah, Bass envelope filter from X-series. Made in china around mid-00’s.

Ok. I’ve had some of the X-series boxes lying around for quite some time. Just didn’t find it in me to open them up until now. All them sounded and felt reasonable good on initial tests, so i just took the stance of “decent, not great, but decent” and left them be. Now i figured i would finally start checking them through. XBW is a good unit to start with. Good features and there is some notable usability in there. Sure this isn’t meant to compete with Boss SYB-3/SYB-5 with its lower price point and slightly smaller feature set. I haven’t seen schematics for any of the X-series boxes around. Opening the bottom plate gives a clue for why. There are vias like drops in the ocean.

Digitech-XBW-SynthBassWah-guts1

For starters, super dull, auto-routed board design is quite off-putting. Next, the brand is called Digitech. Which made me slightly cautious and suspicious, since the Distortion series is all analog and has roots deep in the old DOD catalogue. Flipping the board over shows what’s really going on. Harman (the mother company of Digitech) branded AudioDNA digital signal processor with crystal oscillator and a ROM. Now this is what the digital effects are made of. Don’t have to see the schematic to tell you that there is analog signal path with buffers ann switching, followed by AD/DA conversion and another set of buffers and switching components. The effect is in the slash between AD/DA.

Digitech-XBW-SynthBassWah-guts2

This made me worry a little. Could it be that Digitech X-series is as boring designwise as post-2005 Boss pedals? This meaning that the circuitry is exactly the same on all boxes, just with different digital control for each and different code in the ROM chips. Nothing too wrong with that. It’s just that my interest about the X-series boxes just got stomped even deeper in to the ground.

How does it sound?
Like a working “bass synthesizer” pedal. To get a picture, we need to compare it to something we already know. Boss SYB-3 is well more feature packed and wilder in its sounds. Same thing goes for Ibanez SB7. I’d say the synth sweeps here are duller than the competition, but there isn’t that much negative to the sound. More boring than the competition, but still a decent entry level bass synth/autowah unit. For the price and your home recording applications – i’d say this will suffice. Works and sounds pretty good on guitar too. Leaves me baffled, but still trusting.

Ibanez AW7 Autowah

Monday, December 1st, 2014

AW7

What is it?
Ibanez AW7 Autowah from 7/Tonelok series. Made in china, 2005.

Where Ibanez AW5 from soundtank series left me a little on the cold side by its sound and overall feel, the follower for the Tonelok series does things differently. To begin with, all  the control slots on the enclosure are in use. Two slide switches and four pots. Before checking the features, let’s take a quick look under the hood.

AW7-guts1

Board looks like all the rest of designs in this series, so no surprises there. There’s a factory schematic up at Ibanez.com. Which shows us that the design is a hybrid with a 13600 OTA envelope filter and a distortion. Slightly over engineered feel to it, but the board isn’t too packed and still looking pretty pleasing with all through hole construction.

AW7-guts2

Envelope driver and distortion are powered by those three JRC4558Ds.As usual, the pedal is made with five different circuit boards and those boards are connected by wires on clip terminals. The control board and the main board connect with terminal pins directly.

AW7-guts3

Neat, but nothing too exciting. But then, what comes to features.. Board may not be that packed, but the design is. Feature-wise. The envelope has two modes, wah and LPF (low pass filter). Wah mode takes the envelope to wider frequency range than the LPF, which takes some of the brightest highs away from the sweeps. Sensitivity and manual control the envelope. After those we have our drive control and a switch associated with that. On distortion off, the pedal acts as a basic envelope filter/autowah and disables the drive control. Two other modes of the switch activate the distortion. These modes let you choose the distortion to be in front of the wah or after it. This, in addition to wah/LPF switch gives out a lot of options for the tone.

A noticeable amount of features. In many ways the design and features squeezed in are impressive.

How does it sound?
Light years a part from its predecessor, the AW5. The optical envelope used in AW5 has its advantages, but so does the dual OTA based design on this one. The envelope part is decent sounding, but nowhere near the greatness of nine series classic, the AF9. AW7 doesn’t roll out nearly as much lows from the signal as AW5, but still more than AF9. This tri-comparison may feel a bit much, but bear with me. AF9 is a real milestone that is very hard to beat. On this one, i’m thinking the designer has added more features on modernization of AF9, trying to genuinely make it better. As an envelope filter (or autowah) the AW7 still stays light years away from AF9, but it has the firepower to take the AW5 out at any given minute.

Biggest culprit is the the distortion an the tone it has. Which is ok, but not great or not even particularly good. Slightly on the thin side and slightly boring. One can get decent late 80’s and early 90’s lead tones out of this, but it’s all still a special effect that i’d describe as novelty pedal. To sum it up, this sounds way better than AW5, but still not as good AF9.

EHX Doctor Q Nano

Saturday, June 21st, 2014

EHX-DrQ-Nano

What is it?
Electro Harmonix Doctor Q Envelope Follower from Nano series. Made in NYC, USA around late 00’s.

There are a lot of recycled designs in EHX catalog. This is one of those that has been around since 70’s and later made its way to nano series in cost effective and more usable sized enclosure. Of course the board design has been reduced to SMD as well to keep manufacturing cost low. The design on the other hand, remains very close to the original unit.

EHX-DrQ-Nano-guts1

There are a few schematics available. The first one looks like original factory schematic, but the scan quality isn’t too great. I’d prefer to read the redrawn one. As the design has been rather popular in DIY crowd, there are number of additions available. Some of those add very good features and address the shortcomings of the original (like J. Orman’s Dr. Quack or Nurse Quacky that includes M. Hammer’s mods). In essence, the original design has input impedance on rather low level, resulting in possible pickup loading. That is, unless you have a buffered pedal placed before the Dr. Q. Other improvements are for stability of the trigger and for the effective range of the filter part. Original works fine, but for those building their copy, i’d suggest reading about the improvements before doing anything rash.

For the basic functionality, the incoming signal is splitted in two. The other part rushes to the filter for being modulated and the the other is sent for the trigger. Output is taken from the filter.

EHX-DrQ-Nano-guts2

The board is standard and modern EHX design. Nothing to write home about, but it works. The range trimmer is rather sensitive. To get it perfectly in tune with your chosen instrument (bass, guitar, organ, whatever), you’ll need to spend some time screwing with it. You can tune it throught the board, so there’s no real need to detach the board from the enclosure. The main differences between this Nano unit and the vintage ones are the added power filtering and parallel polarity protection.

How does it sound?
Usable, but pretty squishy. The design contributes to some noise, which will be present at all the times when filter sweep activates. Squishy noises do, however, leave us with sort of an vintage feel to the sound. So we could argue that this is not a “studio quality” effect, but it’ll serve well for vintage vibes on stage. Sure. There are other envelope filters that you might want to consider over this, but if the effect isn’t used that much.. Then the price range and quality should be right on que. Yes. That’s an idiotic pun.

DOD FX25B Envelope Filter

Sunday, June 8th, 2014

DOD-FX25B-EnvelopeFilter

What is it?
DOD FX25B Envelope Filter in “final” US DOD enclosure. Made is USA in the late 90’s.

Grabbed this one off from eBay as the price was correct. I was totally expecting a V-serial unit for the price and once this thing arrived and i opened the box – no type plate sticker. Damn. But there wasn’t a “made in china” stamp under the DOD logo on the rubber mat either. I still wasn’t convinced. So i headed over to America’s Pedal site and checked the info for the FX25B. What do you know. All the components are exactly as depicted in the AP’s article. Check here to compare. But then again.. From the article, i get the impression that the FX25B was never issued as a chinese VFX unit. And furthermore, there are apparently only three Final Series designs that never went on to VFX, namely FX91, FX84 and FX25B. Funny how you learn something new every day.

DOD-FX25B-EnvelopeFilter-guts

The design is evolved FX25 with added blend control. This control was probably added so the effect would work better on bass. On the board design point of view it is the usual, dull modern DOD design with nothing special in there. There is a schematic up at FIS. Should be worth noting that the filter is created with LM13600 OTA. Trigger driver is JRC4560. TL072 takes care of the mixing and blend control. I can’t recall any other OTA-based envelope filter right of the bat. I’m sure there are some though.

Well. I’d like deconstruct the working idea behind all envelope filters. First of all, we’ll need to split the incoming signal in two. First splitted signal needs to be sent to filter and the other to trigger.  Trigger needs to have some sort of threshold so it knows when to trigger the sweep. When the incoming signal for the trigger is strong enough, it will pass voltage to LM13600 control pin in a sweeping manner. From that signal the OTA knows to modulate the frequencies of the signal passing the filter. Filters come in many forms, shapes and sizesall of them have components to determine frequency and gain of that frequency. OTA-based filters are usually used due to their capability of offering tight frequency ranges with reasonable amount of components around it. All methods can do the same thing, but different methods result in different tones while the working idea remains.

How does it sound?
Nice. Not squishy or mushy. Straight up clean filter sweeps all the way. As basic analog envelope filters come, this takes its place in top 5 with ease. The frequency ranges this circuit can sweep are good for most instruments. Haven’t tried this with a synth, so i can’t be sure if it will stay unchoked when driven with line level signals, but it is very well working and good sounding envelope filter for guitar and bass. Low noise floor and even lower noise on the sweep make this very attractive effect. Recommended as top shelf quality sounding effect.