[TheRhino]

I have a new Les Paul Recording model guitar which has Hi-Z pickups and a Jensen transformer built-in for an optional Low-Z output. When using the Low-Z output and plugging straight into an amp, the signal is clean but obviously very low. In reading the descriptions for the both the Wald TPC1 and CAE CB1 preamps they both seem to do the same thing as the Jensen. What I am confused about is at what point does the Low-Z signal from these transformers get converted back to a Hi-Z signal for a guitar amp?

What I was thinking about doing was picking up something like a Shure A95UF and plugging it's 1/4" male jack into my amp. The other end would be a female balanced XLR jack. My signal chain would be Guitar > 1/4" to 1/4" cable > pedals > 1/4" to male XLR > Shure A95UF > Amp. This would retain the low impedance signal for as long as possible and be converted back to Hi-Z just as it hits the amp. With the descriptions of the Wald and CAE preamps, I don't see where the signal is boosted back up to Hi-Z.

[milobender]

The signal isn't converted to hi-z with the Wald Buffer, and the CAE... Neither are they simply transformers... they are OPAmp amplifiers... I don't know what the Jensen transformer actually is, if it's simply a transformer, or something else... I'd try the Wald TPC1 or a Stratoblaster clone (which I'm happy to make for you "o)... I've just come into some J230s and Allen-Bradley carbon comps for them, if that's interesting to you) to give the signal a little kick... I'm sure if Waldo knows what the Jensen is, he'd be happy to chime in...

[TheRhino]

The signal isn't converted to hi-z with the Wald Buffer, and the CAE... Neither are they simply transformers... they are OPAmp amplifiers... I don't know what the Jensen transformer actually is, if it's simply a transformer, or something else... I'd try the Wald TPC1 or a Stratoblaster clone (which I'm happy to make for you "o)... I've just come into some J230s and Allen-Bradley carbon comps for them, if that's interesting to you) to give the signal a little kick... I'm sure if Waldo knows what the Jensen is, he'd be happy to chime in...

I understand that they don't convert the signal to Hi-Z, they do the opposite and take the Hi-Z signal and convert it to Low-Z

Wald TCP1: " The preamp onboard the guitar changes the high impedance output of standard passive pickups to a low impedance output rendering NO signal loss and the ability to drive long cable runs"
CAE CB1: "It buffers the high impedance output of the guitar pickup and provides the low impedance drive necessary to send the signal to the effects pedal with no tone loss"

Both of those statements are describing the same thing that is in my guitar which is a Jensen transformer. From the data sheet, the Jensen transformer:

• * Converts unbalanced line levels to balanced mic level output
  * M Stops "hum and buzz" problems in musical instrument hook-ups
  * M Allows use of long cables without high frequency loss

http://www.jensen-transformers.com/datashts/dbe.pdf

My question is that aren't these then acting as transformers to convert the signal to Low-Z and, if so, is there an additional circuit involved that brings the signal back to Hi-Z? I'm guessing there is because they are both referred to as preamps. When I plug my Recording straight into the amp with the Low-Z jack I get a much quieter and seemingly (when the amp is cranked) clearer signal. I would expect both the Waldo and CAE to do the same thing as the Jensen and, if so, there need to be some circuit to amplify or convert the signal to Hi-Z. Hopefully that makes sense. I probably embody the term "knows just enough to be dangerous"

[milobender]

Sorry I should have been clearer... they don't convert the signal 'back' to hi-z. I don't have any experience with the CAE model (I have one still sitting in a box... but I liked my first Wald TCP1 so much, I never use anything else) but the TCP1 converts the signal to lo-z, and amplifies the signal a bit... it isn't strictly a unity buffer. The Jensen is just a transformer... a completely different approach than the TCP1 or the CAE amps. I'm no expert in electronics... I'm sure there are others here that can expand on your questions... I would think that just using a passive transformer would have to cost some signal strength, and that you'd benefit from the TCP1 in the circuit.

[TheRhino]

No worries and thanks for the help. I'm just confused about the fact that the signal isn't converted back to Hi-Z. A regular guitar amp or something like an SMS preamp + power amp combo would expect to see the Hi-Z signal I'd assume. Maybe not. Hopefully someone can straighten me out!

[milobender]

Yes, that's the way they are designed... and I don't know enough about it to tell you how it actually works, but, I do know that the preamp and amp works fine with the low impedance input from the buffer/amps in the guitar. That's pretty much all I use now...

[TheRhino]

I have an older Strat that I am going to use to learn how all this works. I plan on installing the VooDoo '69 pickups which seem to get a lot of praise around here and try both Waldo's preamp and CAE's. I'm going to put in a Stratoblaser (milo, I'll keep you in mind when I get ready to by this) and see how the signal reacts with the blaster on and off.

[hippieguy1954]

There is a good explanation and information concerning the buffers and impedance here:

http://screaminfx.com/tech/why-and-when ... -pedal.htm

[TheRhino]

Thanks for the link! Looks like a lot of good info on that site. I'll try to get into it in more depth tonight.

[Jon S.]

I found this video easy to follow.

[Mr.Burns]

I was under the impression that the Lo-Z output was intended to be plugged directly into a mixing console or something similar for recording. If it was my axe, I'd be looking into adding the TPC1 or CAE to make that Hi-Z output a Lo-Z as well, if it's to be used on stage. These circuits are proven to work well with stage rigs, and the LP Recording's circuit is apparently still unknown, but if the guitar's name means anything I would expect the balanced, Lo-Z output to be less than optimal for that purpose. Hence, the other output, which I assume Gibson intended for amplifiers. But I'm not sure that Gibson intended for this guitar to be used outside the studio. No offense, but it's not exactly a looker, if you know what I mean. It looks like the coil tap (or whatever they call it) is a slider switch? Not meant for use on the fly, obviously. Idk anything about the pups, might not be truly tapping coils anyway.
It just occurred to me that the purpose of Jerry's buffers were to address issues created in the signal chain between the guitar and amp. In a studio, this can be minimized and tailored specifically to each instance, so things like OBELs and buffers aren't quite as vital as they would be in a live setting, where you need flexibility and stability. Or you can just plug the Lo-Z output into your mac or pc based recording rig and forget about all that.