F-2B + S-F2 or S-F2 + F-2B

[lbpesq]

Jazzy, do you have the jumper in the SF-2 set for no gain?  (I assume you had it set for some gain when you were using it as a preamp).

Bill, tgo

[jazzyvee]

Rob, I was using a series bass, in fact i have tried it with all of them over the weekend trying to come to some kind of consensus but It was still behaving the same regardless of bass. Even if I used the normal jack socket I was still getting the CRACK sound.
I guess there could be an issue with something coming loose inside but I wouldn't expect it on all the basses.

The only thing that has changed in that rack is the replacement of the F-1x with an F-2B and with that setup I never had this issue. Things got funny when I decided to use the F-2B instead.
After posting earlier I put the F-1X back in the rack and put the system back to mono using the SF-2 in the send/return loop and it was perfect. Whatever I did the settings to did not cause the loud Crack sound.

Can I throw this spanner in the works. I got the F-2B new from the Alembic Dealer in Paris and he told the that he had bought it a long time ago and never got round to putting it out for sale. is it possible that there are electrolytic capacitors in there that could possibly have dried out and causing this issue?
Hi Jimmy, Yes I did try the DS-5 direct to the power amp and that sounds really good, though obviously not as loud. I was playing more gingerly with the volume up as I thought the risk of ripping the speakers out on full bore if the crack sound happened. But did put my 21db earplugs in and gave it a bit of a blast and it sounded fine and no unwanted noise.

[jazzyvee]

Hi Bill, that is a different SF-2 in a different rack and whilst I did up the gain for a short while, i put it back as it was cleaner sounding set back to standard setting.  This one I'm using with the F-2B is one i bought new from the UK alembic dealer some years back haven't fiddled with it.

[rv_bass]

Jazzyvee, two more thoughts:

1. Have you tried the F-2B by itself with the power amp to see if there are any issues with it isolated?

2. Do you think it could be the stereo switch on the SF-2?  Maybe try the F-2B and SF-2 configuration in mono on the SF-2 and see if the issue occurs with that configuration. 

[jazzyvee]

Hi Rob, (1) the frustrating thing (perversely) is that using either F-2b or SF-2 on their own in the signal chain to the amp works fine with no issues.
(2) hmm........ well no, i have not tried that option, so that has got to be my next line of attack. Also i probably should try using a different cable just in case something there is misbehaving. While im on that track it might be worthwhile me testing all my leads with my tester too.
Cheers.

[JimmyJ]

OK, reviving this thread to see if we can figure out what's clipping. 

DS-5 >> F-2B >> power amp works great?  Normal kind of amp volume control settings and loud and clear results, right? 

And DS-5 >> SF-2 (rear panel inputs) >> power amp also works fine with normal looking volume settings and no overdrive crack?

What should also work is DS-5 >> F2B >> into the back panel inputs of the SF-2 >> power amp.  And I think that's what you are trying to make work but it continues to give you trouble?

I have not used an SF-2 but was just studying the manual and, if I understand correctly, in stereo mode (using the rear panel inputs) if you have the "Direct Gain" set to 10 and "Filter Gain" at zero, you should be at unity - as if the device was not there.  But when you start adding in the filter gain, particularly super-low frequencies, you are now raising the total output of the device.  At that point you no longer have unity gain but a boosted signal that might be too hot for your power amp's input.  But you should be able to resolve that by lowering both the Direct Gain and Filter Gain until the output approaches a level closer to unity.  The tone should still be there, just at a more normal level.

Can you use the SF-2 with no Filter Gain and have a clean result?  If so, then it's just a matter of reducing the Direct Gain as you boost the Filter Gain until it is relatively the same volume as "unity" or not having the SF-2 in the loop.

Furthermore, you should also be able to do it the other way around - DS-5 >> SF-2 >> F-2B >> power amp.  Same idea here, try to tweak the SF so that it is operating at unity and not boosting the signal level. 

The front panel input of the SF does have an additional preamp and is meant to be used as "the" preamp in the rig.  The rear panel inputs are what you want to stick with.

Then we get into the question I posed on the other thread: what would you like to send to the PA?  Direct sound?  Post SF-2 tone?  Post F-2B?  Mono or stereo?  (Unusual to send stereo bass to the FOH, just sayin'.)

Now I've completely confused you. Ha!

Jimmy J

[jazzyvee]

Thanks again Jimmy, I will try these suggestions again. I have tried all the above except for reducing the gain of the direct signal gain control on the S-F2. Just having the two devices SF-2 and F2-B together in the signal chain causes the crack to appear in my sound. So I will try your suggestions again and reduce the Direct Gain of the SF-2.
The odd thing is that I had previously been using the same setup with my previous amp QSC PLX2402 and my recollection ( which may be flawed) is that I didn't have this but that's old news as that amp has now been sold.
As for what to send to the FOH, I think there have only been a couple of situations where I sent the stereo feed to the FOH and those were when I was gigging with my Jazz Funk band at a local music and arts college gig where our sound guy,(also a bassist), works and he was interested in his students understanding that kind of setup.  Other than those two I expect only to be going to the FOH in mono but I don't rule out occasional experimenting. :-)

Let me try these suggestions today and let you know. In actual fact what I am experiencing may have always been the case but since I don't usually use this setup at home at any significant volume I never hit that spot as usually I have the power amp controls maxed out and control the gains down stream. ( I'm sure I read this on this forum that, maxing the power amp and adjusting the gain of the other devices accordingly gives better head room. Maybe that was only when using a QSC power amp).

[jazzyvee]

Hi Jimmy, i've been experimenting since yesterday so here are my results using my 4 string series I shorty.
Today I have wired my rig up as follows.
Neck Pickup
In-2 Front A output ->>  F-2B channel 1 front,  F-2B Rear out A ->> SF-2 A rear input, SF-2 Rear out ->> IN-2  Rear A "From PRE AMP To Lo-Z Output", then IN-2 Rear A Output ->> Power amp input 1.
Bridge pickup
In-2 Front B output ->>  F-2B channel 2 front,  F-2B Rear out B ->> SF-2 B rear input, SF-2 Rear out ->> IN-2  Rear B "From PRE AMP To Lo-Z Output", then
IN-2 Rear B Output ->> Power amp input 2

Did that and plugged in and the cracking started. I then turned the input gain of both channels of my F-2B to between 2 and 3 and the power amp on both channels to 50% as I know the crack usually sounds at that setting.

Then I turned my bass volumes on full and then turned the trim pots on the back of the bass down bit by bit until there was no cracking no matter how hard I played the bass.  Then I turned the SF-2's channels up independently until the cracking started and again backed off the bass trim pots until the cracking  stopped.

So where I am now is that I can turn the bass up full and the SF-2 direct and channel gain on full and any setting on the power amp and get a clean signal sound out of my cabs.

I am not sure if this is scientific or methodical in the right way but I guess now it seems to be OK though I guess the real check is when I next have a rehearsal with one of my bands at volume to hear how it will be before I find out on stage.
If you think that should be OK I will then adjust my the trim pots on my 5 string basses to find the level they need to be to work with this arrangement.

[JimmyJ]

Hey Jazzyvee,

You are doing a fine job of tracking down the problem and may have already nailed it.  It sounds like the output of your bass may have simply been too hot for the downstream gear.  I will mention that your master volume (or individual pickup volumes) do the exact same thing as the trimpots so it's very easy to quickly adjust the output while doing these experiments.  Then if you find a "sweet spot" with the master, but prefer to run that pot wide open (remember it makes no difference in the tone), then you can adjust the trimpots to set the output level accordingly.  Make sense?

Your description of the chain reminded me of a cool feature of the IN-2.  That is, when you plug into the "Lo-Z Input" on the rear panel, the other rear panel output jacks become the DI's "thru" jack and work in parallel.  That interrupts the direct signal from the front panel.  So the way you routed it is the ONLY way it could all work.  And you have your tone from the F-2B and SF-2 feeding the transformers for the front panel DI outputs.  Pretty neat.  Now, if you find you need to use rear panel outputs, then back in and through, there are simple ways to modify it.  It's a very flexible piece of kit!

Let us know how it works out when you get in a full band situation.  And remember, if it starts complaining when you start to play hard just trim the MV and turn up the amp a bit more.

Cheers,
Jimmy J

[jazzyvee]

I was experimenting with my rig again early this morning and using my two barefaced cabs 1x18 and 1x12 this setup allowes me to use my F-2B with two cabs and a mono non series bass and still keep the heft in the 1x18 dubster and the mids and higher stuff in the 1x12.
Not sure if this is an appropriate way to connect the two channels but it seems to work fine. Not something I would do regularly but some dep reggae gigs I've done the band have a vocal PA so it's good to keep the heft in the 18" speaker and have the 1x12 on the top and control the EQ and volume so i can use it more as my monitor.

[JimmyJ]

Jazzeyvee,

I don't think there's a "wrong" way to do these things and linking the F-2B channels like that should be fine. 

The first thing the two 1/4" inputs on an F-2B channel see is a resistor - one for each jack.  This kind of isolates the two inputs from each other so that (if I understand correctly) you could plug two guitars into channel 1 and they would not load each other down.  Or, both A+B outputs from a DS-5 running in stereo, and the signals would be properly summed to mono. 

Here you're kind of using that isolation as a "pass-through" and looping into channel 2.  Channel 2 may see a slightly reduced level because of the resistor arrangement, but there should still be plenty to drive your power amp and 18" cab.

I bet that sounds mighty good!

Please continue your good work at Jazzyvee's Experimental Alembic Sound Laboratories and keep us informed.

Jimmy J

[lbpesq]

I’ve been doing just that with my F-2B for years.  It’s an old Fender trick, known as “jumpering”.   Sort of turns mono into stereo.

Bill, tgo

[edwin]

I’ve been doing just that with my F-2B for years.  It’s an old Fender trick, known as “jumpering”.   Sort of turns mono into stereo.

Bill, tgo

You have to be careful jumpering because the signal can meet back up at the phase inverter out of polarity with each other in some Fenders.

[jazzyvee]

My Experimental Sound Laboratory has been back at work. I have had a few gigs recently and couple using the In-2 rack that includes the F-2B. I am almost convinced the cracking sound is something to do with the cab tweeter as the new 12" speaker unit i got sent from barefaced didn’t solve the cracking sound which seems to be more evident even at low volumes whilst the tweeter control is open.
I have also swapped the F2b in the rack for two F1x preamps and put SF-2 in each preamp send and return loop. So sometime this week i will find time to test it again. Let me see if i can find my old white lab coat too. 😂😹🤔🤨🤞🏾