TCE Integrated Pre vero build.

[digi2t]

Hey everybody,

For some reason, this little beastie captured my attention. Maybe because I drive a lot of cable, and even though my Klon buffer is doing an admirable job of handling that, I guess I'm always on the lookout for a better mouse trap. Although a vero already existed, I wasn't too keen on the layout, so I redrew it. Came out to the same size as the other one, but it meets with my criteria of keeping resistor leads short, and having mounting holes too.

Here's the schematic;



And my verified vero;



Couple of shots of the board;





I made a video to demo the circuit. I have it running at 18vdc, and as I point out about half way through, I'm using a TL071 in place of the spec'd LM741. The LM is still MIA (more like MIM, Missing In Mail), probably due to that Christmas thing going down.  Anywho, the 071 seems to work just fine in here, so, take it with a Jimi Photon sized grain o'salt. On with the shoo;

[pinkjimiphoton]

dino, please pm me your addie...

i have some of the old can type 741's for ya.

[digi2t]

dino, please pm me your addie...

i have some of the old can type 741's for ya.

PM on it's way. That's what I bought as well, going to the trouble of sourcing them from a supplier in Miami. I figured, if I keep it on this side of the ocean, I would get it quicker.

WRONG!

So far, I have stuff that I ordered from Singapore around the same time come in already. Curses!

Thanks bro!

[Kipper4]

Dino
Is this you in a former life?


http://www.youtube.com/watch?v=CXFs9DvPGO8

[digi2t]

Dino
Is this you in a former life?


http://www.youtube.com/watch?v=CXFs9DvPGO8

That, my friend, is a slow day for me.

[Gus]

Looking at the schematic and this thread
http://www.diystompboxes.com/smfforum/index.php?topic=89712.0
the other schematic in the link shows input power switching and the one posted in this thread output jack power switching

input left to right sleeve, ring, tip
output tip, ring, sleeve

Q1 is a constant current circuit fragment.  The current is the (two diode voltage drops - the Vbe drop of the transistor) divided by R7.  R1 and R5 supply current to the base of Q1 and when a tip, sleeve jack is installed the base is connected to ground by R5.  I don't see a DC path for Q1.  This looks to be an antipop circuit when inserting or removing the input jack.

The IC with Q2 is interesting notice R10 is from the output of the opamp and it goes to the emitter of Q2.  Another form of bootstrapping the emitter
Output of Q2 is inverted that goes into the inverting input of the opamp.  Output of the opamp goes to the emitter via a 220K (note the lack of any other DC paths)
So the emitter is driven in phase with the input signal at Q2s base
You don't need jfets for high input resistance.

After you try it with a 741 you might want to try something like a 5534.  Note the 100pf might/will need to be adjusted with other opamps.

What years was this sold?  I ask because the use of the 741 and how the high input resistance part of this circuit was designed.  I am guessing early to mid 70's

[digi2t]

The pic that you're alluding to looks to me like it was pulled out of the Japanese electronics book. Amazingly enough, at quick glance, the circuit, and all the components values are the same, but like you point out, power switching is handled at the input side. Beats me as to why TCE decided to split the duties. Maybe they feared some kind of copyright infringement?

As far as I can read, from internet scuttlebutt, this unit was put out in the 80's.

Just wondering; would there be any advantage to using bipolars, or tantalums, for C4 and C5? I see the old Japanese schematic specs tantalums here.

[Gus]

A bump  
I thought about this circuit yesterday after reading this thread
I think this is a very good circuit design
I might even build it to try it.
Clever how it has 6.8meg input resistance

Input resistance is a part of the sound of effects along with the cable and guitar or bass.

C4 and C5 might make a difference as tantalum caps
If the value matters for the EQ
The ESR is lower
You would need work out what changes in the EQ and operation of the circuit when you change the cap values

Film caps are available in 1uf and 4.7uf values

[Gus]

some sim screen shots
did not include the EQ and first transistor
note the DC values
Sim is sensitive to supply voltage and the R6 and R2 resistor values
Note the input voltage range going to the + supply voltage

green in blue out

[digi2t]

I did try the tantalum caps, and they ended up staying. Not because they made a huge difference, but I do believe that any difference that is there, might be placebo effect to my ears. Besides, I didn't feel like swapping the other ones back in. I have it running at 24vdc now, only because I happened to have the power supply available, and not in use for anything. Since it's first in the chain, that is way more than adequate headroom or gain for my application. 15vdc is fine if, like me, you're running this first in line after your guitar. If you're planning on pumping hotter signals into it, or want to use it as an overdrive, then you can experiment with the higher voltages (32vdc max.)

The buffer that I've been using at the front end of my pedalboard to date (same as the one in the Klon), has served me well to date. But, tests today, vs. the TCE, have booted it off. The response of my entire rig with the TCE is much better to my ears. With the EQ knobs set flat (the tone knobs run -15db to +15db, with 0 in the middle), and the volume set to unity, the bass end seems tighter, punchier, and the treble is brighter and crisper. For my purposes, I have the treble flat, the bass at about +2, and the volume just a hair over unity. I find it an improvement over the buffer I was using before, no matter what effects chain I run afterwards, clean, or dirty.

Here are some pics of the build;











If you're looking to punch up your tone, this might be a good option for you. Doesn't take long to breadboard, and is a pretty easy build. A TL071 gave me the same results with all the same components, and is easier/cheaper to source. Doesn't affect the layout of the vero either, but of course, as we all should know by now, the mojo genie lives in a can. Right?

Many thanks to Gus as well, for taking the time to sim this, and to give us a glimpse at the response. A scholar, and a gentleman, as always.