TOTALLY BUMMED OUT - used F1X /new 1602PLX combo don't work

[davekoch]

TOTAL BUMMER.  
 
I received my new PLX 1602 and practically new (3-years old, but yes it's used) F1-X. The system doesn't work. With and without (plugging directly into PLX) the F1-X, the volume is VERY weak. It's about half as loud as my 35-watt Peavey Minx - I couldn't gig with this combo.  
 
Lord Valve (who sold me the PLX 1602) says it's a F1-X issue. He says going directly into the power amp will not be loud at all because there's no preamp to boost the signal strong enough so the PLX can utilize it's 1100 watts. Is this true? My bass has an onboard J-Retro preamp and with all Treble/Mids/Bass turned all the way up, it barely makes a difference.  
 
The F1-X seller says the F1-X worked perfectly before he shipped it.  
 
Shouldn't this gear work right out of the box?  
OR  
Does the F1-X and/or PLX 1602 need to tweaked to work with one another?  
 
My gear: Modulus Jazz with an onboard J-Retro preamp - produces a very hot signal!! Eden 4x10/2x10 cabs. I've verfied the cords all work.  
 
Suggestions?  
 
HELP................?  
 
I'm totally frustrated!!
 
(Sorry for the grammatical mistake in the title)
 
(Message edited by davekoch on November 15, 2004)

[adriaan]

I'm no expert on the F1-X, but there are a number of outputs that you can use, and they may not all have the same output level. So which one are you using?
 
Also, what was the seller's set-up? Perhaps the output level was changed.
 
Good luck.

[jagerphan84]

Well, I think the QSC and F-1X combo should work fine.  I thought I remembered something about the two together, and found this when doing a search of this board:  
 
>> I use a PLX1602 and love it. Before I bought it, I actually traded emails with an engineer at QSC that worked on the PLX design team. He bought an F-1X from Alembic to use in the final testing stages to be sure the PLX would be suitable for bass guitar amplification. That sold me.

[davekoch]

I'm no expert on the F1-X, but there are a number of outputs that you can use, and they may not all have the same output level. So which one are you using?  
 
In Bridge mode, out of the F-1X Full Range output jack into QSC PLX Channel 1 and out to Eden 4x10. This results in a very weak volume, which is no louder than if I don't use the F-1X at all, and plug my bass directly into QSC PLX Channel 1 in Bridge mode.
 
In Parallel mode, out of the F-1X Full Range output jack into QSC PLX Channel 1 and then into Eden 4x10; and out of the F-1X High Pass output into QSC PLX Channel 2 and then into Eden 2x10. This results in no sound at all.
 
Could the tube be bad? What symptons indicate a bad tube?

[mica]

Since the F-1X is not new, there may be some corrossion on one of the jacks. Please read this article and do the prescribed procedure, you should be in good working shape after that:
 
The contacts on the jacks may corrode if they are not excercised regularly. For instance, if you leave an effect unit plugged in the F-1X effects loop all the time, it is not excercised. Likewise, if you never use the effects loop, the same is true. Not all jacks are affected.
 
If you hear distortion or experience a loss of signal, try this simple cleaning routine first:  
 
Plug and unplug any 1/4 connector to the jack 20-30 times. This will clean away any corrosion. Spray-on contact cleaners are not effective in this instance.  
 
For the F-1X, excercise the effects return jack on the rear panel.
For the F-2B, excercise the mono output jack on the rear panel.
 
You can decide to excercise regularly, or just wait until you hear the recognizable problem and address it at that time.  
 
 
If you have time for a more elaborate cleaning, here is another method contributed by Dan Brasier:
 
1. Cut a clean business card lengthwise into strips about 5 to 7 mm wide (about 1/4 inch). Keep these clean and handy. White works best as you can see what comes off the contact. (Unplug amp power cable first!)
 
2. Approach the offending switching jack CAREFULLY with the card strip hidden in your hand. Don't let the Jack see it until it is too late and it can't run away. Be careful and avoid psychological trauma by speaking gently to the connector. Use soothing tones and tell it how much better it will feel when it's clean.
 
3. Separate the contacts with a small (non scratching) item like a toothpick. Place the strip of paper between the switch leaves, and keep it well-centered.
 
4. Hold the leaves together with needlenose pliers or fingers, firmly but not too tightly..
 
5. Draw the paper strip out straight and slowly, and see what comes off onto the paper. (check both sides!) If it's dirty, start with a new piece and repeat until it's clean. Continue to keep a calm manner to avoid stressing the connector. Compliment it if necessary. Most like to hear what a low resistance they have.
 
6. Check and adjust the tension and travel on the contact when finished, by inserting a 1/4 male plug in the socket and observing the way the contact slides as it is actuated and deactuated. Too much tension is as bad as too little!

[davekoch]

The seller only used the Full Range output jack. He said he gigged using the Full Range output jack and it worked fine (30 days before I received the F-1X). But perhaps there is corrosion on the High Pass output jack. But then why wouldn't I get any sound at all when I use two cabinets in Parallel mode?
 
Also, what was the seller's set-up? Perhaps the output level was changed.
 
What kind of adjustments (output, or any other kind) can be made on the F-1X and a power amp?  

[cntrabssn]

Dave,  
 
I would try using the QSC in stereo mode, and use the F1-X full range output into each channel of the OSC one at a time, i.e. try channel 1 first, then channel 2. This might help narrow things down a bit. If you're still getting the weak output, you can work from there to determine where the trouble is. Remember, you can try this with each of the F-1X outputs.
 
By the way, you are not using the parallel mode of the OSC correctly. In parallel mode, the channel 1 input is internally connected to the channel 2 input as well. This allows a sort of 2-channel mono mode of operation. This is just like using a y-cable to connect one output to the channel 1 & 2 inputs simultaneously. If you want to use the QSC channels in a bi-amp mode of operation, you have to run it in stereo mode.
 
A bad tube can result in weak output, but try the simplest connection set-up first before trying anything else.  
 
I forgot to mention the corroded jack issue, but as usual, Mica has that well under control.
 
Good luck,  
- nate  
 
 
 
(Message edited by cntrabssn on November 15, 2004)

[mica]

That's exactly why the effects return jack has corroded - it's never been used in the three years.  
 
Trust me on this, I know it sound silly to excercise your jacks but it solves 98% of any problems reported with F-1Xs. Please try the plugging/unplugging procedure, it really works and it takes almost no time.  
 
Checking QSC's website, the input sensitivty is less than other amps I've seen, but certainly the F-1X has worked in systems with even less. I do not think you are facing a compatability issue here, it's just a small bit of maintenance needed.

[bassman10096]

Hope you can get functional soon.  (I really did enjoy the instructions for the more elaborate cleaning...)  As for compatability:  I use an F1-X both full range and hi/lo through a PLX 2402.  I believe some other Club members use the same set up.  I've had good results.  
Bill TBO
 
(Message edited by bassman10096 on November 15, 2004)

[davekoch]

Nate,
 
Weak output occurs when in Bridge mode and in Stereo mode out of the Full Range jack.  
 
By the way, you are not using the parallel mode of the OSC correctly.
 
Here's the response from QSC on whether to use Stereo or Parallel mode when using 2 cabinets:  
 
If you want both loudspeakers on both channels of the amplifier to receive the same signal yet have independent gain control, then use parallel mode and not bridge mono mode. The power ratings and sound of the amplifier in parallel mode is identical to that in stereo mode. The only difference is that in parallel mode the inputs are tied together internally so that a Y-cable is not needed.
 
Could I run Stereo mode and come out of the F-1X Full Range jack into PLX Channel 1 and into the Eden 4x10; and then come out of the F-1X High Pass jack into PLX Channel 2 and into the Eden 2x10? This would retain independent gain control for each channel/cabinet, right? Is this what you mean?  
 
Thanks so much Nate,
Dave

[cntrabssn]

Dave,
 
You're correct, that's exactly what I mean.
 
One other thing; the full range output and the crossover outputs are not in phase with each other.   To get the outputs in phase, you'll need to reverse the speaker connections on one of the QSC's channels. Some other club members may wish to chime in on this one or you can search the board for other posts on this subject.  
 
- nate.

[jagerphan84]

If anyone has the ambition to post a thorough, step-by-step procedure for making this change to the power amp, it would be much appreciated.  (My PLX 3402 was shipped out this morning, I'm gonna have to do this change once it arrives.)
 

[cntrabssn]

Jagerphan84,  
 
There is no internal modification required for the power amp or pre amp. You perform the polarity reversal at the speaker terminals for one of the channels only. If you're using the spade lug terminals, you just reverse the connection. If you use the speakon connector, you will have to modify a cable to reverse the polarity.  
 
Remember, you don't run into this issue if you use the crossover outputs only.  
 
One of the threads discussing the the phase of the outputs is:
 
http://club.alembic.com/Images/393/7147.html
 
- nate.
 
(Message edited by cntrabssn on November 15, 2004)

[lembic76450]

Mica,
    Just a suggestion from a guy who often has to clean low voltage contacts, such as millivolt contacts; instead of a busniess card, try a strip of a dollar bill. It is just abrasive enough without damaging the contacts, and much thinner than a card.
    Kenn R.

[Manfred]

I'm not completely sure, but I do remember there are some output dip switches inside the F-1x.
 
Manfred