Fodera, Sadowsky, aguilar, and other bass preamps

Stompboxes circuits published in magazines, books or on DIY electronics websites.

Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby lietuvis » 07 Jan 2017, 22:32

clintrubber wrote:No problem at all, only glad it might be of use. Was just curious where I had posted it - DIYSB ?

Have a good wknd


https://groupdiy.com/index.php?topic=26157.40
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby clintrubber » 09 Jan 2017, 10:02

Thanks
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Cort for Kramer/Spector (ns2a Kramer circuit) preamp

Postby karul » 13 Apr 2017, 18:33

1990 Spector ns2o - https://www.talkbass.com/threads/specto ... d.1084448/
https://www.talkbass.com/threads/kramer ... p.1098176/

This preamp was manufactured by Cort for Kramer/Spector. It was used in the NS2o basses back in the 90's.

Regarding origin, this circuit schematic was included in my original purchase. You can read 'Cor-Tek Corp' which is known as Cort and they are in S. Korea.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 24 Oct 2017, 13:53

Interestingly the Cort Curbow that rcustoms posted on page 8 is some form of rip-off of a Seymour Duncan preamp. Its like the two band with a few values changed and a mid control added.

It might be like the old through-hole Seymour Duncan 3-band.
Can anyone check the values on one of those?
The newer SMD version seems to have different part values.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 24 Oct 2017, 14:00

This preamp was manufactured by Cort for Kramer/Spector. It was used in the NS2o basses back in the 90's.


I believe this one is used in many places:
- Kramer Spector
- All HAZ preamps I've seen so far even ones with different shaped PCBs
- Some Tobias bases
- Ibanez SR500 wirhg 2-bands around 1994-1996 (US but maybe not EU or JP). The one where the controls are in diamond but the diamond axis is along the strings, not pointing down like the SR800.
- many Custom/high-end basses which have the controls in a the mentioned diamond pattern.

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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 25 Oct 2017, 12:39

The 90's Ken Smith and Fodera basses also use the same Haz Labs circuit.
The 3-band Ken Smith adds a mid control board that plugs into the other board.

One thing to note is the Ken Smith uses a smaller bass cap.
There's a few other minor variations you can see on the schematic.
The new Ken Smith preamp with the dip switches is apparently voices the default Bass setting even higher, although you can get 15n setting via the dip switches.

I'm still not 100% sure about one of the caps on the mid board and the gain pot schematic might be a little off.

If anyone has a means of checking it please do!

Ed: Oh, one thing I forgot was the Ken Smith swaps U1A and U1B parts. Doesn't affect the circuit but it will confuse you if you check it against the PCB. U1 is an LF422 like U2. I think the treble cap is 2n2 - sorry. A few mishaps in the cut and pasting.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby lietuvis » 25 Oct 2017, 14:42

george giblet wrote:The 90's Ken Smith and Fodera basses also use the same Haz Labs circuit.
The 3-band Ken Smith adds a mid control board that plugs into the other board.

One thing to note is the Ken Smith uses a smaller bass cap.
There's a few other minor variations you can see on the schematic.
The new Ken Smith preamp with the dip switches is apparently voices the default Bass setting even higher, although you can get 15n setting via the dip switches.

I'm still not 100% sure about one of the caps on the mid board and the gain pot schematic might be a little off.

If anyone has a means of checking it please do!

Ed: Oh, one thing I forgot was the Ken Smith swaps U1A and U1B parts. Doesn't affect the circuit but it will confuse you if you check it against the PCB. U1 is an LF422 like U2. I think the treble cap is 2n2 - sorry. A few mishaps in the cut and pasting.

Here you are, ignore input bias value it has to be 499k
Image

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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby karul » 25 Oct 2017, 20:46

https://reverb.com/item/1283619-haz-lab ... nd-spector

If you're looking at this, you probably know what this is. It's a mid 90s HAZ labs preamp. These are what came in older Foderas, Spectors, and Smiths. This is type of preamp Victor Wooten has in his first Fodera. They are crunchy and aggressive. Plus, they are getting really hard to find. This one came from a 1994 Smith. It is two band with push/pull active/passive. It's got two slots for jumpers (one jumper included). I'm assuming this is for different voicing of the pre using jumpers or switches. If you know the exact details, please feel free to hip me to 'em.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 25 Oct 2017, 22:07

Here you are, ignore input bias value it has to be 499k

Very cool. Thanks a lot for that.

The good thing is the two schematics largely agree. You have fixed a few areas that weren't clear to me.
I think the 12k and 2n2 on the first stage are swapped but it's not going to affect the sound.

With the 4n7 mid cap we should see mids: 410Hz, Q=0.80, boost/but +/- 12.5dB. The specs say +/-15dB but I rarely believe those anyway.
Last edited by george giblet on 25 Oct 2017, 22:39, edited 1 time in total.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 25 Oct 2017, 22:10


The mids-board plugs into the black connector on the left.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby karul » 26 Oct 2017, 01:20

HAZ labs preamp with mid-board.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 26 Oct 2017, 02:29

HAZ labs preamp with mid-board.

That's it!
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 26 Oct 2017, 06:37

The Tune "Bass Maniac" (late 80's early 90's Japanese basses) also had a higher bass frequency.
The bass models are TBJ02 & TBJ41 but there may be more as Tune made
a number of variants of the fretted 4-string as well as 5-strings and fretless basses.

TB05B is the preamp PCB number.

Go here for the a Schematic, Gut-shots and mods
http://alexdsp.livejournal.com/106519.html
(Alexey bags-out the circuit and suggested a few mods; which I agree with. He doesn't change the frequencies.)

I've attached a schematic with some fixes. I was sure the bass control has symmetrical resistors and if you look at the gut shots on that site you can see two 5.1k's and also the 10uF tantalums. The trim-pot is an internal mid boost/cut control. Most basses had this set to a slight cut.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 28 Oct 2017, 07:42

Regarding the Fodera. I found this thread which is about Haz Lab copies,

https://www.talkbass.com/threads/custom ... s.1255033/

On the "Fodera" version, can see,
Bass: 15n
Treble: 2n2
Mids: 2n2, 1n5 (for 800Hz)

Wiring diagram shows, 400Hz mid:
Add parallel 4n7 so mid caps are 2n2+4n7=6n9 & 1n5

Calculated:
1) f0=726Hz, Q=0.72, boot/cut = +/-13.1dB
2) f0=410Hz, Q=0.89, boot/cut = +/-10.8dB

At 410Hz "Fodera" has a higher Q and less boost than the Ken Smith.
(Ken Smith f0=410Hz, Q=0.80, boost/cut = +/-12.5dB)

So Fodera mids are different to Ken Smith, or, that board doesn't
represent Fodera in all respects.

The Bass and Treble are the same as the Ken Smith.

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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 28 Oct 2017, 13:37

I found out something interesting!
All HAZ Preamps are not created equal.

The different Bass/Treble cap values seen in the Ken Smith inspired me to check over
the variants of HAZ preamp. My information is by no means complete. I've traced quite a few of these so it's getting a bit monotonous to do another. Anyway it paid off.

What I found was the Steinberger variant was different to all the others. There are three or four Steinberger PCBs formats - I could only check the treble cap of two of those.
- The bass cap is 10nF. Yes even smaller than the Ken Smith.
- The bass resistors were 3x22.1k This will shift change this a small amount.
- The treble cap was 4.7n. A bit smaller than the Spector value.
- The treble resistor was 12.1k for boost and 2.21k for cut.
There is normally no cut resistor on the HAZ preamps.
(There were a couple of other minor differences as well, like the volume pot being post EQ.)

There's a quite a few PCB variants of the Spectors. I assumed the circuit is the same in these.
However I did find one where the volume pots are wired post EQ like the Steinberger but the cap values were like the other Spectors.

So, we have:
- The Spector variant, the most common variant, which includes the Tobias preamp and the Mighty-Might preamp.
- The Ken-Smith Variant.
- The Fodera variant which has the same bass/treble as Ken Smith but the two possibly have different mids.
- Now the Steinberger variant.

The others that come to mind are the early Warwicks (say mid 1980's) and the Pedullas.

It seems a silly saying a Haz preamp is good when the frequencies vary so much. With the cap differences they are essentially different preamps.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby karul » 28 Oct 2017, 23:26

Does anyone have info about sadowsky's mid boost circuit used on Will Lee's. Is it discrete as the preamp or not ?

It's frequency selectable at 500 or 800 Hz, wide or narrow bandwidth.


You can engage the mid boost via the toggle switch and on the back you have 4 dip switches to select the frequency of the mid-range. Plus, there are two screws which allow you to adjust the Q (bandwidth) and the amount of boost you want.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 29 Oct 2017, 00:57

Does anyone have info about sadowsky's mid boost circuit used on Will Lee's. Is it discrete as the preamp or not ?

Sorry, I'm out of the loop on that one.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 29 Oct 2017, 01:07

For the Steinberger Haz preamp, I found this, it agrees with what I traced (saves me a job making a schematic)

http://www.headless-europe.eu/Files/HAZbassEQ.pdf

Looks like what I traced. Except 22k = 22k1, 12k = 12k1, 5k's =4k99 etc.
[Ed: On the balance control, The Neck pickup should be the C taper and the bridge pickup the A taper.]

Notice the slight differences to the Spector circuit:
1)
- different Bass treble caps
- treble cut resistor
2)
- post eq volume
- the 25k volume pot loads the de-emphasis network. This creates a small mismatch between the pre-emphasis and de-emphasis which affects the "flat response"; perhaps even compensating for the slight treble cut in the detent position.
- the 100p input cap is moved to the other side of the 47nF cap
- there's no 1M input resistor.

The rectangular Spector boards, with PCB's marked "P204A", perhaps circa 1994, have the same second set of minor differences except the pre-emphasis resistor on the first opamp is 43k and not 49.9k. This correctly compensates for the 25k volume pot loading.
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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby george giblet » 29 Oct 2017, 07:08

Does anyone have info about sadowsky's mid boost circuit used on Will Lee's. Is it discrete as the preamp or not ?


Through the use of mirrors and small piece of cheese I manage find this, see point 5,

http://docplayer.net/44568490-Sadowsky- ... model.html
http://docplayer.net/docs-images/60/445 ... es/8-1.png

Looks like it is opamp based.

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Re: Fodera, Sadowsky, aguilar, and other bass preamps

Postby lietuvis » 29 Oct 2017, 21:08

Hello, here I have traced Ibanez onboard preamp with variable mids. I actually built this preamp for my washburn t24 bass and happy with it.
Midrange has good Q and wide range 100hz-5kHz. The midrange circuit topology I see on moog lab series preamp.
I never had original preamp and worked from pictures only + someone to help measure components on original board.
Potentiometer for midrange can be obtained from here:
https://www.aliexpress.com/item/High-Quality-Alpha-C100Kx2-B20k-Dual-Concentric-Three-Level-potentiometers/32340398009.html
Few more files pics, sprint layout etc here:
https://www.dropbox.com/sh/ashbnr0cghknzv4/AAAWkJEyISGIqmw1nB17TltDa?dl=0
Anu questions please ask.
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