Vintage Bartolini TCT Bass Guitar Preamp: Testing & Pedal Build...Marcus Miller's Tone Secret?

This is the same onboard preamp that Marcus Miller has in his 1977 Fender Jazz Bass. It was installed by Roger Sadowsky in the early 1980's. In this video I turn one into a guitar pedal. After some testing, I decide the pedal needs a fet buffer on its output.
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Using a P-channel mosfet as reverse polarity protection:www.geofex.com/...

[@nanoluciani]

The amount of quality (not to mention INSANELY interesting) content you put out is second to none. That build ended up as great as one could ask for! Cheers, mate 🍻

[@RobMods]

Thanks for your kind words Nano. I'm glad you like my channel!

[@JasonWright-mc6dz]

Thank you so much for doing this!! The amount of material which covers technical aspects of bass instrument specific circuits like this is incredibly scarce. And not just YT videos, this is also true of books, online resources, technical articles etc.. Frankly, the only place I’m aware that gets into this kinda thing, Is diy amplifier & stombox forums. Which can certainly be a nice resource, however they’re like the Wild West; Opinions, Misinformation, and pure voodoo audio mojo theories frequent. The toughest thing is the disparity between user knowledge level & experience. Which runs the full spectrum from to absolute novice to professional E. Engineer. I don’t know if all your viewers fully understand your content, but I do and sincerely appreciate it!! 😊

[@Eugensson]

I have seen mosfets being used as reverse polarity protection on the modern Ibanez bass preamps. Now I understand why, thanks!

[@RobMods]

Thanks Dimitri. I was almost going to cut the polarity protection stuff out because the edit was getting pretty long. I'm glad you liked that part mate!

[@seanedwards9787]

Super cool build! I've taken your idea of running the wires of the circuit board out one side and wrapping the whole thing in shrink wrap. It really works well. Love the content! Keep em coming!

[@trevorblair5552]

Thanks for the video. I have 70s jazz basses with this preamp and all sounds good awesome! 🙏

[@nyclamusician]

Great video! I think I am interested in building my own TCT pedal!

[@rexertek]

Very nice work! I wasn't previously aware of printable decals. I'm now wondering what I can stick to my motorcycle gas tank! Also, nice sounding bass.

[@RobMods]

Thanks mate.

[@ErixSamson]

Really nice! Sounds great.

[@dfybyn]

Hi Rob - I've always been interested in your content, but I actually have a TCT pre in my Pedulla MVP signauture 4 from 1989 (PJ config). Awesome pickups and preamp. Sounds just as great today as the day in 89 in New York when I bought it. Keep up the great vids.

[@dfybyn]

and for the record, mine is a boost and cut pre, but definitely has "TCT" printed on it

[@dfybyn]

And only orange wires - I think Mike Pedulla may have had his ones customised by Mr Bartolini

[@RobMods]

Nice one. I'm still kicking myself for not buying a fretless pentabuzz I saw in a 2nd hand shop years ago in the US. I know Mike Tobias has used custom tweaked preamps from Bill Bartolini for decades. Actually I got to meet Mike Pedulla on that trip. Harvey Citron and Stuart Spector as well...

[@JasonWright-mc6dz]

Aww me too, particularly the fretted P/J Pedulla buzz! Such incredible instruments that are now super difficult to find on the used market and the ones you do see seem to go up in $$ daily!!

[@chriscuthbertson]

I loved the Yamaha Nathan East preamp in a box. I sounded great with a passive bass.

[@het_gele_teken]

I really dislike those blue LEDs that unfortunately are so common these days. In a darkend room or stage these blue LEDs become só bright (Purkinje Effect) it's impossible to see knob settings on my three Keeley pedals. I prefer good old red LEDs. That aside, really interesting video once again Rob. Love these videos.

[@RobMods]

Yeah, for me blue LEDs just remind me of the late 90s when it seemed every boutique pedal and piece of audio gear had a bright blue LED. I had a recording interface that had several of them on its front. But you are right, it's not uncommon for pedal LEDs to actually be too bright for dark stages! I've heard about little plastic caps you can put over them to dim them a little. Or I guess you could mod them and change them to another colour or decrease the current with a resistor inline with them. This one matches the artwork, plus my mate plays a lot of daytime gigs in the airforce band, so I think it'll be okay... Thanks for watching mate, glad you like my stuff!

[@tonyflies1]

Rob great channel, what sort of usb scope do you use. Thanks

[@tekglitch6596]

Great video. I wan't to ask, do you think its possible to apply this to one of the Sire preamps thats are available to buy? Would be cool to try and put one in a pedal type enclosure.

[@marklowe7431]

Sure if you want your canvas to be the same as Marcus, it's simple. An Ash jazz bass with maple board, Fatbeams, 70's pup spacing and a TCT. The only thing missing is the biggest part, Marcus. A canvas is nothing without his chops.

[@sebastianbisurgi9970]

You should start a complete series of video tutorials. Electronics for totally illiterate. Like me. Not because you can, but because you manage to make me follow your videos even if I have no idea what the hell is going on.

[@RobMods]

Ha ha. Thanks Sebastian.

[@Eugensson]

I am really curious about the XTCT preamp, especially the extra mid boost control module which is suspicious, it has only one input and one output, which means it is just a passive component (inductance?). And is designed to replace the mid cut 25k trim pot with this module + 50k pot.

[@RobMods]

Yeah I saw that as well a page or two further down on that PDF I printed out. I'm guessing there's an op amp in the second gain stage and the brown wire is from its inverting input. With an LCR in the little module you could create a mid boost. Having said that, I still have no idea why the output Z would be so high. This was designed in the 80's so maybe it's a discrete opamp with fet input. (That second stage had a very high input Z).

[@waynegram8907]

ROB, any reasons why the Marcus Miller onboard preamp is High Impedance output? when using 250K or 500K pots loads its going to cut the output volume in half loosing 3dB or 6dB not sure why they designed the preamp to not work correctly impedance with 250K pots and 500K pots.

[@JanVanderKuylen]

Hey rob, I'm Jan Vander Kuylen from Belgium. I follow your youtube channel on a regular basis. Fantastic posts. I myself am a bassist who practiced electronics and computer technology in a past life. Since my retirement I have devoted myself full time to music and everything related to it. Recently I came across several youtube videos regarding the variety in sounds of a Wal bass. I went looking and came across a Lusithand website. As an electonician I would have liked to get hold of the electronic diagrams, but apparently they cannot be found on the www. I would like to equip my Sterling Music Man StingRay Ray5 HH with this fantastic sound source. Can you help me with that? Kind regards Jan.

[@RobMods]

Hi Jan. Hi from Australia, and I'm glad you like my channel! A few years ago I posted a simple preamp design on TB in a thread about filter preamps. I think the Wal and Alembic preamps are based on a state-variable filter topology. My design was simpler and used a sallen-key filter with switchable caps for the high/low resonance. I can't post a link here, but if you go to pickups and electronics and do a title search on "a different kind of low pass filter", you should find the thread. You can probably skip the first few pages... I think stingray pickups, with their low inductance and high resonant freq are great pickups for filter preamps. Cheers.

[@JanVanderKuylen]

@@RobMods Thanks very much for your response. I found your design and will try it out with different caps. Have a nice creative new year. Jan

[@bassstudent4life]

Huh... I thought he installed a Sadowsky 2 band pre-amp in Marcus' bass.

[@glennrichardson1087]

Will this pedal be available on Sweetwater or Amazon?

[@Bleats_Sinodai]

You don't measure impedance with a multimeter. Impedance is resistance over signal. You *can* cheat a bit tho, if you put a series trimpot as a variable resistor and adjust it till the signal is the same amplitude over it and the input/output you're trying to measure, the trimpot will be about the same value of the impedance of the circuit, so just measuring it gives you a more accurate ballpark.

[@RobMods]

True, but for an output z, the test load is in parallel, not in series.

[@timedwards5600]

Bartolini is still the best bass stuff .

[@thejoetandy]

Isn't the module flipped on the vertical axis, on the diagram? Wires underneath, not on top.

[@RobMods]

Yeah, that's what I thought as well. But all the ones I've seen on google images are like the diagram... Weird.

[@LuizFernando-tq8tb]

Top de mais

[@arnoldday5412]

*promo sm* 🎉

[@robzecc]

My guess is it is probably a fet circuit like the sadowsky/aguilar circuit. There are some schematics around

[@RobMods]

Yeah maybe, but it has quite a modest input z. The input stage had a very weird clipping characteristic as well. I'd love to see a schematic. I did look around a bit before this project but didn't have any luck. Either way, it's a great sounding circuit. My mate loves it.

[@chrisbrazierx]

Hi Rob, I'm a big fan of the TCT and have some modifications done to mine that's on my bass. I was wondering if we could chat over a direct message to go over some tech stuff. We might be able to help each other out 👍🏻 let me know what you think