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Onboard preamp true to Andy Summers' Telecaster - Advice please?

Started by tj7, June 02, 2009, 09:01:26 PM

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mrmorrison

#40
June 05, 2009, 01:42:24 PM Last Edit: June 05, 2009, 01:48:16 PM by mrmorrison
Wow, I spent months trying to find help on this matter everywhere.  I'm glad I'm not the only one.  Basically, your best bet is to get the Clapton mid-boost.  There aren't any differences between the two boards, aside from some slight tolerances.  Here are the differences:

EC Board          AS Board
1nJ100              1nK100
47nJ100            47nK100
82nJ100            82nK100
C9 = brown        C9 = green

On the Clapton mid-boost, the tolerances (i.e. J vs. K [1nJ100 vs. 1nK100]) are such a slight difference that it won't make a difference.  I had an electronic engineer verify this for me.

Now, wiring the thing is another beast all to itself.  I had the damn wiring diagram, but my computer crashed and I wasn't able to retrieve the data.  Talk about crappy luck.

Here's a link to the Stratoblaster.  http://alembic.stores.yahoo.net/blaster.html  It's still made today by Alembic, but it's just called the Blaster.  You have no idea how much searching I had to do in order to find that SOB.  I'll be installing it in my next build, which will be the Hendrix Strat on steroids.  I bet you could extract the circuit from the outside housing and put it into the cavity.  That might be your fix right there, Ben.

Anyhow, I'm still working on mine and should have it assembled within the next month or so.  If I can get my hands on another wiring diagram, I will post it for the world to see.  I'll keep you all informed...

Gus

#41
June 05, 2009, 02:54:22 PM Last Edit: June 05, 2009, 04:49:42 PM by Gus
mrmorrison

    If I understood your post you have seen both boards side by side and the parts are the same values?  The parts are the same values that is interesting.  Maybe this does not sound like the orignal one but something A.S. likes now?

looking at an E.C. schematic I found at another forum

   The parts you posted might be  the .047uf (47nf) input cap to the transistor booster first stage the others are part of the output filters of the opamp section.   Opamp looks to have a gain of about 7.6666 = 100K/15K +1.  Opamp feedback resistor of 100K has a .001uf across it.

The first stage has a fix boost of about 4.6 till about 13KHz (there is a bit more going on) this goes then this goes to a 50K volume pot then the wiper to the noninverting input of the fixed gain opamp about X 7.66 that has a passive .082uf 46.4K highpass into a 46.4K .001uf lowpass at the end.  Now the mid boost is caused by the mixing of the first stage volume pot wiper output and the output of the fixed gain opamp with bandpass filters on the end this is a 250Ka mix pot.  The wiper is the output of the circuit to the amp and the two signals feed to each end of the pot.

The wiper of the volume pot goes to both the +input of the opamp and one outside lug on the 250K mix pot

I will guess the output mix pot is fixed at some setting in the A.S. one(or two fixed resistors) and all you have for control is the volume pot.

You could build something like this with a transistor and a single opamp and some caps and resistors

Does the original A.S. circuit still exist?  I guess that is the question.

tiges_ tendres

#42
June 05, 2009, 03:12:41 PM
Quote from: Gus on June 05, 2009, 02:54:22 PM


Does the original A.S. circuit still exist?  I guess that is the question.

I think we have all guessed no.  Otherwise, I think fender would have included it in their faithful recreation of the guitar.
Try a little tenderness.

tj7

#43
June 05, 2009, 09:52:59 PM
Quote from: mrmorrison on June 05, 2009, 01:42:24 PM
Here's a link to the Stratoblaster.  http://alembic.stores.yahoo.net/blaster.html  It's still made today by Alembic, but it's just called the Blaster.  You have no idea how much searching I had to do in order to find that SOB.  I'll be installing it in my next build, which will be the Hendrix Strat on steroids.  I bet you could extract the circuit from the outside housing and put it into the cavity.  That might be your fix right there, Ben.

Anyhow, I'm still working on mine and should have it assembled within the next month or so.  If I can get my hands on another wiring diagram, I will post it for the world to see.  I'll keep you all informed...

thanks MM.  what's yr opinion on the seymour duncan preamp i've been blathering on about?  the youtube clip is very informative, and i think this might be the way i'll go.  it seems to do everything i want it to and SD have a good rep.

mrmorrison

#44
June 05, 2009, 11:40:17 PM
I think the SD Pickup Booster sounds great.  I was initially thinking of going this route as well.  The whole thing for me was an issue of convenience.  I like the fact that with an onboard preamp, you don't have to lug around an extra pedal or power supply.  However, that pedal does a great job of emulating many different pickups, so if you're leaning in that direction, definitely go for it.   :)

tiges_ tendres

#45
June 05, 2009, 11:41:58 PM
Quote from: tiges_ tendres on June 05, 2009, 03:12:41 PM
Quote from: Gus on June 05, 2009, 02:54:22 PM


Does the original A.S. circuit still exist?  I guess that is the question.

I think we have all guessed no.  Otherwise, I think fender would have included it in their faithful recreation of the guitar.

Or maybe! it's just a big smoke screen of Mojo!  The original unit never died, he just said it did and then didnt want to share it with the world!
Try a little tenderness.

tj7

#46
June 05, 2009, 11:44:49 PM
Quote from: mrmorrison on June 05, 2009, 11:40:17 PM
I think the SD Pickup Booster sounds great.  I was initially thinking of going this route as well.  The whole thing for me was an issue of convenience.  I like the fact that with an onboard preamp, you don't have to lug around an extra pedal or power supply.  However, that pedal does a great job of emulating many different pickups, so if you're leaning in that direction, definitely go for it.   :)

to clarify, i meant i am leaning towards the onboard preamp circuit SD makes, which is based on the pedal :)

http://www.guitarelectronics.com/product/PASFX/Seymour_Duncan_Pickup_Booster_Circuit.html
http://analogguru.an.ohost.de/193/schematics/SeymourDuncan_PickupBooster.gif
http://www.youtube.com/watch?v=3xIXw9JIqjk

far as i know, the preamp circuit above will give me the clean boost as opposed to changing the pickup resonance, which the pedal can do....   

Gus

#47
June 06, 2009, 10:57:01 AM Last Edit: June 06, 2009, 11:04:12 AM by Gus
The stratoblaster and the Tillman.  Unless you understand something about FETs good luck setting it up correctly, if you don't pick the right FET IDSS and Vgsoff range.  It helps to have a scope and signal generator and have it connected to the load it will drive to find the best operation point for the FET.

Next they are circuits you can find in textbooks and maybe you want to set it up a bit different.

Things to think about what min and max gain do you want? and what drain resistor and operation point(Id or drain current)? Then you need to select the FET.

Do you want a gain pot in the source leg or a fixed gain stage and a volume control after it.

A TL071 circuit I described should work as well as the S.D. 3 transistor opamp one and you can build one it has a low parts count.  I see people build teles from all kinds of wood and parts at http://www.tdpri.com/forum/index.php  .

The reason I brought up the NPN boost was it has a NPN Si gain stage and the E.C. boost has one as well as a first gain stage,  The NPN has a min boost of X2 and gain control in the emitter leg no output volume control.  The E.C. has a fixed gain first stage NPN first stage of about X 4.7 until about 13KHz.
You can find the schematic of the EC on the web.

tj7

#48
June 06, 2009, 07:23:39 PM
Quote from: Gus on June 06, 2009, 10:57:01 AM
The stratoblaster and the Tillman.  Unless you understand something about FETs good luck setting it up correctly, if you don't pick the right FET IDSS and Vgsoff range.  It helps to have a scope and signal generator and have it connected to the load it will drive to find the best operation point for the FET..

thanks gus but i'm after a complete ready-made as i can't build these things.  i'm leaning towards the sd for several reasons:

1. i have been able to hear it in action (albiet via youtube) and it seems to do what i want
2. it's tiny compared to other onboard preamps i have seen (eg the EC is huge)
3. folks i've been asking generally seem to think that it would be suitable

gain range is +6  to +25db.
i have asked guitarelectronics.com to clarify how precisely it models the SD circuitry and what componentry it uses but who knows if they will see fit to respond in detail.

your suggestions are obviously grounded in experience but there are so many 'ifs' and 'or's etc - too many options and as mentioned i just can't build these things.  has to be ready made or i'll never get this done.   i do very much appreciate all your advice though and the questions i raised with guitarelectronics.com are based on some of your questions to me. :)

Gus

#49
June 07, 2009, 02:09:34 PM
I drew up a  boost schematic and some wiring of an idea for a hum single tele inspired by this thread.
  It uses an opamp and has a few tuning sections.
interested?

donald stringer

#50
June 07, 2009, 05:05:50 PM
I certainly would !
troublerat

tj7

#51
June 07, 2009, 07:08:05 PM
Quote from: Gus on June 07, 2009, 02:09:34 PM
I drew up a  boost schematic and some wiring of an idea for a hum single tele inspired by this thread.
  It uses an opamp and has a few tuning sections.
interested?

sure, if it covers the ground i've been talking about - let's have a look :)
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