Lab Series L5 preamp in a pedal

[gordo]

Rats, just hit a snag.  In the process of boxing it I noticed that if I installed the compressor LED and it lit, the L5 would sag to half volume and get an almost ring mod sound.  If I switched the comp off it was fine.  Or if I took out the LED the whole pedal was fine (comp works).  Well now I've installed the LED's on the bypass and channel indicators.  LED's work fine but the whole pedal gets the same ring mod sound.  Any idea what's going on?

Voltages look good at -15.04 and +14.98.  I'm using a Line6 adapter.  Is that just not enough to get this thing out of the water, and if so why would it just be the LED's dragging it down?

[aion]

Is the LED driver transistor working/installed correctly? The LED definitely should not draw enough current to cause any PSU issues and the Darlington transistor is there to keep it that way. So, I would suspect the transistor before anything else.

Also, what kind of LED did you use, and what did you use for the CLR?

[gordo]

I'll take a look when I get home.  The LED's were generic 5mm and the build notes listed 100k as the clr's but in the footnotes said to delete them so I didn't use anything.  The LED's are definitely bright.  My first instinct was the transistor (MPSA13 if memory serves) but of course I soldered it in.  I tried replacing both CA3080's are they're good.

[aion]

The CLRs are the big 1/2Ws on the main board, 680R if I remember right. But it does help knowing you left off the 100k resistors - those are highly experimental and it means we can rule those out anyway

[DragonSF]

Rats, just hit a snag.  In the process of boxing it I noticed that if I installed the compressor LED and it lit, the L5 would sag to half volume and get an almost ring mod sound.  If I switched the comp off it was fine.  Or if I took out the LED the whole pedal was fine (comp works).  Well now I've installed the LED's on the bypass and channel indicators.  LED's work fine but the whole pedal gets the same ring mod sound.  Any idea what's going on?

Voltages look good at -15.04 and +14.98.  I'm using a Line6 adapter.  Is that just not enough to get this thing out of the water, and if so why would it just be the LED's dragging it down?

Have you checked the waveform of the -15V line when comp LED kicks in? The oscilloscope showed kind of saw-tooth wave.I had similar problems with the comp LED and and found 9VAC was not enough to drive the LED. I switched to 12VAC and everything's fine now.

[gordo]

I've been following your posts so will keep that in mind. I want to start with clr's because I did notice the LEDs were crazy bright, but that is what it sounds like...half the power supply crapping out.

I do have a voodoo labs AC supply too so might throw it on that to see if it makes a difference. No bench time to nite, which is maddening 😑

[dbp512]

How much current does this draw? I use a one spot daisy chain and don't want to risk tossing an AC wire in the mess as well, so I was thinking this could be a good excuse to finally get an isolated power supply. The Cioks AC Rider/Ciokolate have 800mA, which I assume is more than enough, but I figured I'd ask.

[aion]

How much current does this draw? I use a one spot daisy chain and don't want to risk tossing an AC wire in the mess as well, so I was thinking this could be a good excuse to finally get an isolated power supply. The Cioks AC Rider/Ciokolate have 800mA, which I assume is more than enough, but I figured I'd ask.

Shouldn't be more than 200mA including the LEDs - probably closer to 120mA even.

[aion]

Yes, I am definitely not experiencing that issue with mine! I bet it would go away if you increased the CLR, especially if you thought the LED was too bright. I dug up the specs on the exact LED that was used in the original Lab Series amps and found a modern counterpart that was very close, but the modern waterclear type would probably take a heck of a lot more current with the same CLR - as might some diffused types even, if they didn't have the same specs as the one I'm using.

Another potential solution would be to use a low-dropout (LDO) regulator instead of the traditional 7815/7915s. I'm not sure what "the good ones" are (maybe do a search on DIYSB for LDO regulators and see if there is a favorite), but if the problem is that the regulator is dropping out when the LED turns on, the lower dropout point (~15.5V instead of ~17V) might make the difference.

I am a bit nervous about using 12v AC to power it - this means each regulator is seeing 34 volts DC (12 * 2 * 1.414) and dropping it down to 15, which is a lot to handle without a heat sink (and there isn't enough room for a heat sink). I'd feel much better about a 10V adapter and I think that would provide plenty.

So, I would try the solutions in that order... raise the CLRs first (start at 1.5k or 2.2k), then try LDO regulators, then try a 10V adapter.

[gordo]

Hoping to get a bit of time on the bench tonite. The channel indicators are waterclear but the bypass and compressor are diffuse.  Hodge-podge but looks cool.  Don't know what the spec is on the Line6 supply but I was driving 3 of the big modelers and a variax with the Voodoo and it didn't break a sweat.

I wondered if maybe I have cheezy regulators.  To be honest I don't know the source for them.

[gordo]

Finally got a few minutes with it. Voodoo supply isn't here right now so on a whim plugged in a Yamaha 12vac supply and everything works as it should.  You're right though, the regs get hot. Damn this thing sounds good!

So over the weekend I'll double back and fiddle with clr's and since I'll likely get knobs from small bear I may as well grab a pair of regs as well.

It sounds very much like the real deal. The compressor has a tiny bit of  flutter as it fades out which can be minimized with the trim, as does my amp. My real L5 doesn't have the aggressive boost on ch2 Mid, but I think that's one of the pots I had to substitute and I think it's just bunching up at the end.  Like the original the ch1 bright switch is more subtle than ch2, and the multi-filter is fairly subtle.

[aion]

FYI everyone - I'm now taking names to get a head count for the enclosures. Please go HERE and fill out the form even if you have emailed me or posted in this thread about wanting one. It'll help me to have everything in one place so no one gets missed.

The only difference with these enclosures is that they are matte black instead of the gloss wrinkle, and they have "9VAC ONLY" printed on the back by the power jack.

[gordo]

I've got it back on the bench to sort out the power problems.  I'll let you know what the fix is at this end.  In the meantime it's waiting for SB knobs (aluminum).  It's really hard to get the metalflake to pop for the camera.  It's really more of a blue/green/aqua.

[gordo]

OK, last post, you've heard enough from me.  I put the Voodoo AC supply on the pedal and at 9v still problems but at 12v it's dead quiet and completely amazing.  I'm going to order another set of boards and the case as well and will spend time on that one tweaking 9v issues.  In the meantime this thing sounds so good I don't want to mess with it.  Toss a few low profile heat sinks on the regs and call it a day.

This is going to sound like a used car commercial but you really can't post a true sound sample of this beast, just like the real amplifier.  After spending the day with my real L5 on Sunday and then going home to this beast it's really dead on.  I tweaked out the ripple on the compressor with the trim pot to match the real amp.  You can't really think of the comp as a "compressor" as much as a volume leveler.  It's not squishy, it just puts reins on the output this thing is capable of.  In practical use that means that switching from CH1 to CH2 might mean a massive change in gain structure but with a lot of Comp it attempts to level the two settings.  In the real world it meant that the L5 amp could be used in a small club, or dial back the Comp and open it up to WAY louder levels.

At the tail end of the Mid pot rotation it gets real "boosty" at whatever freq you've chosen.  It's not as dramatic on the real amp and I'm assuming that my choice of pots on the pedal is the difference.

If you want to describe how the amp sounds...think of it this way:  What do Ty Tabor (King's X), Elliot Easton (Cars), and BB King have in common.  Nothing.  That's the magic of a Lab Series.  Clean slate.  In the real world I don't know what Tabor does to get his drive and sustain but the amp is very pedal friendly and this pedal responds in kind.

For my use (progressive Praise band) I use an overdrive for most of my drive sounds and toss in a Klon/Clean booster for my leads and let the Comp take care of levels.

[LedZepp007]

This looks amazing


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