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Sunday, August 21, 2011

2011 - Weber Z-Matcher

Weber Z-Matcher 50W version

I've had this red box for a few months now, and have used it exclusively with my Fender Princeton Reverb RI and Epiphone 12" cab, which resided in my isolation cab.

The Princeton is engineered for a nominal load of 8 Ohms, but the Epiphone cab is 16 ohms. Everything I've read about the subject is that the amp down't handle the higher load very well, and that it would be better to run two 8 om speakers in parralell(gets you 4 ohms), rather than an 8 and 16. It's all to do with math and ratio's and running mismatched loads is a no no. Sure it's going to get you a load of 6 ohms or so, but since one speaker has less resistance, most of the power will go through there and will naturally be louder than the other as a matter of course. Also this doesn't fit the ratio that the amp requires.
First I tried using a resistive dummy load to match everything up, but since a speaker doesn't have a fixed resistance (due to the combination of frequency and inductance of the voice coil), the results weren't exactly pleasing.

I'd read all about inductive loads being the way to go, and pretty much the only one that I could find with any reviews, was the one from Weber. The manufacturers of fine speakers for guitar amps.
After a lot of deliberation and indecision, I decided that having a variable inductive load would be the way to go. so I bought the 50w Z-Matcher.

The purchasing process is a little odd, it's all via email and can take some time to get your quote back, but the staff were helpful when arranging the postage. But the transaction itself was done via Paypal and they were happy to send it Via USPS when asked. Weber build all of their stuff to order, so there's a bit of a waiting period, but being in Australia, I've gotten used to waiting for my stuff to arrive. Hey, if I can't get what I want locally (or locally at a competitive rate), then I have to go offshore for the products I want/need.

They estimated up to six weeks for assembly, but it was at my door in less than a month (not bad in my opinion). Anyway, back to the box. It came in a simple postage container wrapped in paper and bubble wrap. It's quite a heavy unit, so I delayed taking it home for a few days.
There's no manual to speak of, but there's no need if you're familiar with the basics of speaker matching (all us amplified guitars and bassists should be!).

Front Panel:
amp in
amp impedance (2-16 ohms)
speaker impedance (2-16 ohms
speaker out

Rear Panel
Line Volume
Line out - Balance
Line out - unbalanced
Parallel Speaker out

It was put to work matching the Epiphone Cab in the isolation box.
The first test I ran it through was the line out. Honestly I wasn't really impressed. Clean guitar was fine, but overdriven just sounded fizzy (pretty much like any amp with line out ever).
But hey, I wasn't exactly expecting a miracle there.

The next test I did was mic (Shure SM57) up the speaker and A/B that with the line out. Guess what? The mic even carelessly placed, sounded a lot nicer than the line out. I left it like this for a few months, and just playing with it when I had a couple of spare hours. After a while I noticed a bit of a weird distortion when using reverb on the Princeton. Especially if I was driving the reverb hard. I figured it was either a dodgy cable or maybe a quirk of the speaker cab inside a fairly small volume of air (there's a lot going on in an iso cab with a large speaker. Standing waves and other funky things can send voltage back to the transformer of the amp if you're unlucky). Also my headphones are a little rattly in some frequencies.

Upon further investigation, it turned out not to be a problem with anything mentioned above, and I haven't got definitive proof yet, but I have a hypothesis which makes sense (need to find an engineer wiling to experiment).

I decided to test the whole rig outside of the cabinet and directly with my ears, reducing the variables where interference could occur(cab, mic, lead, mixer, earphones). First up, I tested the amp by itself on a rubber mat to damp vibrations into the floor. Aside from making the house rattle when it was barely past two on the dial, the amp sounded as it should with the reverb cranked).

The next thing I did was to put the Z-Matcher between the amp and it's stock 10" speaker and set for 8 ohms per side. The distortion came back. Next I plugged in the 16 ohm cab. Again, fine on straight guitar signal, weird distortion with reverb. Last up I placed the speakers in parallel. The 16 ohm cab directly into the amp, and the 8 ohm stock speaker via the Z-Matcher (the amp side of the Z-Matcher was set to 16 ohms in order to present and 8 ohm overall load to the amp). As I'd already had a suspicion that the distortion was happening inside the Z-Matcher, it was no surprise to find that I had the distortion coming through the 10" speaker and not the 12".

The Z-Matcher works flawlessly with any signal presented to it as long as there is no reverb in the mix.
What I think is happening is that there are weird things happening inside the inductors of the Z-Matcher, due to the complex reflections generated by the reverb.

Reverb adds to those complexities and since the coils of the Z-Matcher aren't on the move as they would be with a speaker/magnet combination, there is a bit of a inductive choke effect going on and the result is the distortion that I'm hearing. It's subtle and I don't think that it would matter much in a band setting. The sound does stand out for me now as I'm aware of it. But I don't think it's a deal breaker on the Z-Matcher. It's just a quirk of electromagnetism and I can live with it as the unit serves it's purpose.

Wednesday, August 17, 2011

Reader input

Ok, so I do the update thing whenever I get a new bit of gear or am reminiscing about the good old days, lamenting being a dunderhead or whatever.


But tell me dear reader, what would you like to see on these pages?
Sound files
Videos
More photo's
Tutorials

I've recently passed the 11,000 view mark, but I've only received a handful of comments.
So it seems that I'm either doing something right, or doing something wrong.

Come on kids.
Let me have it!

Monday, August 15, 2011

Repairs: Ibanez FL9 Flanger - Not quite!

Oh man. I went to play with it last night.
The LFO problem is back.

Oddly though, the ability to do a parked flange is pretty nifty.
Kinda like parking your wah, but with a time based effect instead!

Sunday, August 14, 2011

Repairs: Ibanez FL9 Flanger

Since I don't get much time to play guitar these days and when I do, it's generally just guitar and amp. My FX don't get used too often, and the least often used of my FX would have to be my Ibanez FL9 Flanger. Generally I don't havemuch use for flanging effects. It's fun and all, but I prefer to use it sparingly. If I'm going to use a modulated effect, it's more likely that I'll use a phaser. Just personal preference.

Because of this, my FL9 sat in a drawer for the best part of a year. It's an old pedal (over 25 years) and the last time I went to use it, it just passed a clean tone. The pedal wasn't toally broken, the delay chip was still working as there as a bit of a flange sound when twiddling the controls. Upon opening it up, some of the jooints looked cold. So I proceeded to re-solder everything on the board. No go. It took a  while to track down the schematic (didn't end up using it), but I'd read a snippet from one forum about replacing old electrolytic caps, so i figured that i'd give it a try. I went over the board and documented everything electrolytic.

There were two caps near the middle of the board which weren't coloured blue like the rest (they were orange), so I decided to replace them first and give it a test (I'd seen a similar arrangement on a synth I'd built). My hunch was right, they were there to control the LFO rate. The LFO was working again, but the effect was very subtle. Not at all like I remembered.

Fortunately the board has three trim pots for adjusting various biases. Ignore the middle one, it's there to bias a transistor and the factory setting is just right to avoid unwanted and unpleasant clipping. The trim pot closes to the middle controls feedback and the one further away controls depth. With these two trim pots you can get the pedal to self oscillate. Particularly with the first one. It's not a sound I'd want all the time, so I've set it up to kick in at about 70% maximum on the front panel feedback knob. The mod is safe and easy to do. You won't even need to take the board out to do it. While increasing the feedback makes the flanger more prominent, it still falls short of being a true "jet" flanger. Still it is nice to have in the tool kit.

FL9 Service Manual Page 1

FL9 Service Manual Page 2 (Schematic)

FL9 Service Manual Page 3 (Trouble Shooting)

FL9 Service Manual Page 4 (PCB Layout) - LFO Caps Highlighted w/red box.
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