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Stingray aftermarket 2 band pre

#701
So I finally got that thing to work! Thanks UncleFluffy for the layout. I've home-etched the PCB and it came out pretty good looking:

th_fertig2_zps51f1565d.jpg


th_fertig1_zpsacd0baea.jpg


The rotary switch is active / passive / kill, because I didn't want to rewire the PU for my prototype tests. On the other hand this kind of switching makes it easy to compare what the preamp really does.

I didn't have the chance to compare it to my 3 band in depth, because I've missed to order some PCB connectors... :(

Okay.. first impressions:
It does cut bass! It doesn't sound as puchy as in passive mode (low mids). Passive mode is noticeably louder with the controls roled back. Overall it doesn't really shine with my headphones - at first I was pretty disappointed - but with my Eden WT550 + D210XST this thing came alive.

I took 1M lin for the treble control and I definitely noticed why there should be a rev log in place. Treble comes up at the very last bit of the taper .. downside: I don't know where to get those 1M rev log as 24mm - preferably alpha with 3/8 mount or Bourns.. If you know a place in Europe give me a hint!

Here are some quick graphs I did today:

Passive mode:
th_Arta_Passive_zpsc113871b.jpg


Active mode, Bass & Treble full counterclockwise:
th_Arta_BassampTrebleCC_zps89c5c03c.jpg


Active mode, Bass & Treble adjusted to passive level / linearity:
th_Arta_BassampTrebleLin_zpsab70830b.jpg

That's approx. Bass 1/4 Turn, Treble nearly all the way up..

Active mode, Bass full counterclockwise, Treble lin:
th_Arta_BassCCampTrebleLin_zpsa86a225e.jpg
 
#702
Sinclair said:
I took 1M lin for the treble control and I definitely noticed why there should be a rev log in place. Treble comes up at the very last bit of the taper .. downside: I don't know where to get those 1M rev log as 24mm - preferably alpha with 3/8 mount or Bourns.. If you know a place in Europe give me a hint!
Click to expand...

Once I built my LTspice model of this preamp I tried subbing in a 500K antilog pot, first in the model, then in real life. Works just fine for my purposes, and "left hand" 500K audio pots are easy enough to come by. Here are a couple of sims, using 180K for the feedback resistor, 1uF coupling caps, LT1351 opamp. This reflects the actual config I am using. The sims include loading effects of the two pickups in my particular bass, mixed at full up and 88% respectively, each with a 500K pot wired pickup-output-to-wiper:

Bass=5, Treb=5, 1 meg rev audio treb pot:

Link Removed

Bass=5, Treb=5, 500K rev audio treb pot:

Link Removed

Bass=8, Treb=8, 1 meg treb pot:

Link Removed

Bass=8, Treb=8, 500K treb pot:

Link Removed

As you can see, using a 500K pot yields a slightly higher treble center frequency with around 2dB more gain at a given pot setting. That correlates well with what I hear as well. Looks like if you just turn down a little with the 500K pot you're back to darned near the same curve as the 1Meg gives when set a little higher too. Not identical, but pretty close...

Bass=8, Treb=7, 500K treb pot:

Link Removed
 
#703
I got my EB pre amp together and it works!:hyper:
I do have a couple of questions though. To start off I'm no EE I just look at the pictures and put the parts where the are supposed to go figuring if I do it right it will work. I did use all the recommended parts with no substitutes.

1 The treble pot works but boosts counter clock wise. Is that right? And the treble boost is extreme, it will peel the enamel off my teeth. Is it supposed to have that much boost?

2 This pre is being used with an American Precision Deluxe dual coil. I had to wire it in parallel so that it would have a low impedance, 1.98 ohms.
I would like to use this pre with higher out put pick ups and I am confused reading the posts as to whether I can do this. Can it be done?

Thanks Tedward
 
#704
Tedward said:
1 The treble pot works but boosts counter clock wise. Is that right?
Click to expand...

You have it wired up backwards. Swap the two outside wires on the pot.

And the treble boost is extreme, it will peel the enamel off my teeth. Is it supposed to have that much boost?
Click to expand...

Yep. I rarely turn mine up all the way.

2 This pre is being used with an American Precision Deluxe dual coil. I had to wire it in parallel so that it would have a low impedance, 1.98 ohms.
I would like to use this pre with higher out put pick ups and I am confused reading the posts as to whether I can do this. Can it be done?
Click to expand...

You don't have to do that. You can wire the pickup in series. That will also prevent the treble from being too bright.

I use this preamp in one of my basses with a set of my Neo jazzbuckers. It works just fine.
 
#709
Every thing checks out. I even made another one and it does the same thing. One thing I did notice was that the distortion gets worse the lower the frequency. When I play notes in the upper register it sounds good but going down the fret board the distortion starts getting worse.

Tedward
 
#710
Tedward said:
Every thing checks out. I even made another one and it does the same thing. One thing I did notice was that the distortion gets worse the lower the frequency. When I play notes in the upper register it sounds good but going down the fret board the distortion starts getting worse.

Tedward
Click to expand...

sounds like maybe some component values are incorrect or a wire was soldered wrong. Since your treble boost is counter-clockwise the treble pot wires are incorrect. the boost is suppose to be clockwise. the original design treble pot is a 1M rev log taper. Its normal for the treble boost to be that extreme, some bass players seem to like it. good luck!
 
#711
Tedward said:
Every thing checks out. I even made another one and it does the same thing. One thing I did notice was that the distortion gets worse the lower the frequency. When I play notes in the upper register it sounds good but going down the fret board the distortion starts getting worse.

Tedward
Click to expand...

You said everything checks out, but your treble pot was working backwards. So clearly it's not wired up correctly.

Is it the preamp distorting, or your amp? What are you monitoring the bass on?

I haven't seen anyone else here saying their preamp is distorting. That's certainly not an issue I have had either.

So something is not right.

Use a 200k resistor on the feedback loop of the op amp, instead of a 180 or 100k as some are doing. That lowers the gain. You can also try increasing the 220K resistor at the input. But I see no need for that as these can handle pretty hot pickups with no problems.
 
#712
You are right about the treble pot being wired back wards they have been switched. I got so involved with the board that I over looked the pot. Sounds like the distortion is gone. Man, these things sound great!:hyper::bassist:

I really want to thank you for your patience and help.

I'm monitoring with a GKMB 200 into a BF Jack 10. All the controls are set at 12:00 and gain is at 9:00. Can't wait to hear this pre in my GreenBoy 12/6.

Thanks again
Tedward
 
#714
domdec314 said:
I've heard this a few times, but it don't believe it's right. I wired an active/passive switch so I could compare the tones and when I rolled the bass all the way back, it was definitely cut. It was significantly thinner than the unaffected passive tone. When I put the bass knob in the middle, it sounded very close to the passive tone. Also, there's this:
Page%201.jpg

This page, from an old manual, states both knobs are cut/boost.
Click to expand...

My current guess on this is that this MusicMan literature was describing the 1976 or the 1977-78 Black Epoxy Type 1 circuit, whereas my understanding is that the Bajaman/UncleFuzzy circuit is the 1977-78 Black Epoxy Type 3 circuit, as described at Link Removed
If I'm off on the wrong tangent with that I hope someone will explain it to me.
 
#715
snowman910 said:
My current guess on this is that this MusicMan literature was describing the 1976 or the 1977-78 Black Epoxy Type 1 circuit, whereas my understanding is that the Bajaman/UncleFuzzy circuit is the 1977-78 Black Epoxy Type 3 circuit, as described at Link Removed
If I'm off on the wrong tangent with that I hope someone will explain it to me.
Click to expand...

I don't believe there were any major changes throughout the history of the original 2-band preamp. In the 80's they changed from tantalums to electrolytics and added a protection resistor, but that's about it. The circuit itself has pretty much stayed the same.

In my experience with the Bajaman preamp, of which I've built at least five, it's is without a doubt a boost/cut circuit on both the treble and bass pots. When I had one in my G&L, I kept the active/passive switch so I could compare the two, and with the bass pot turned all the way down it is definitely cutting the lows. It sounded extremely thin compared to the unaffected passive sound.
 
#716
domdec314,

Thanks for your response, and for your many informative posts on the subject of these boards. I wish I knew more, and am grateful for the many users who have extensive experience with these circuits who have posted about them, but all I know is gained from the threads on talkbass and the information at Link Removed.

I think going from three wires to the bass pot, using it as a potentiometer, which could be cut and boost, to two wires to the bass pot, using it as a variable resistor, which can only cut, is a significant change in the circuit, and could provide the answer to the many posts in the threads on this subject by owners of 1977 MusicMan basses which appear to their owners to function as cut and boost, but no one seems to know anything about the the 1977-78 Black Epoxy Type 1 circuit variant, all comment seems to be about the 1977-78 Black Epoxy Type 3 circuit, which I believe is the Bahaman/UncleFluffy circuit, though there are comments about the resistor values based on original examples that may be about the original examples that are the 1977-1978 Black Epoxy Type 1 or even the 1976 circuit. The 1976 circuit is reportedly a different circuit from any of the 1977-1978 Black Epoxy types, but I don't have original examples of any but the 1977-1978 Black Epoxy types except my working 1977-1978 Black Epoxy Type 1, which I plan to keep original and unmolested and am unwilling to sacrifice to the cause. I keep hoping someone has figured out what changed, but so far, no information is turning up. Maybe those who have posted about their 1977 models that appear to be bass cut and boost will open up their control cavities and check to see if they have the three wires to the bass pot, to verify this. If so, then perhaps I'm on the right track.
 
#717
I can only tell you what I know from experience. The Bajaman circuit most definitely boosts and cuts on all the ones I've built. It's way too thin sounding with the bass knob all the way down for it to be boost only. Especially when compared to the bass in passive mode, which would be flat.

EDIT: Just an idea, if it's true that the bass pot is technically boost only, they may cutting the lows before the bass boost circuit to give the impression of a boost/cut.
 
#718
domdec314 said:
I can only tell you what I know from experience. The Bajaman circuit most definitely boosts and cuts on all the ones I've built. It's way too thin sounding with the bass knob all the way down for it to be boost only. Especially when compared to the bass in passive mode, which would be flat.

EDIT: Just an idea, if it's true that the bass pot is technically boost only, they may cutting the lows before the bass boost circuit to give the impression of a boost/cut.
Click to expand...

Sorry, I'm not being clear. The bass is not boost only on the Bajaman/UncleFluffy, it is cut only - the discussion has been whether it is cut only or cut and boost. Unless I misunderstand something, with only two wires, it is just a resistor, so it cannot boost (a pot wired to one lug and sweeper is a variable resistor). It may be perceived as cut and boost by the ear, but in the circuit I do not see how it is possible for a variable resistor to do anything but cut, but I may be misunderstanding something. I'm no expert.
 
#720
snowman910 said:
Sorry, I'm not being clear. The bass is not boost only on the Bajaman/UncleFluffy, it is cut only - the discussion has been whether it is cut only or cut and boost. Unless I misunderstand something, with only two wires, it is just a resistor, so it cannot boost (a pot wired to one lug and sweeper is a variable resistor). It may be perceived as cut and boost by the ear, but in the circuit I do not see how it is possible for a variable resistor to do anything but cut, but I may be misunderstanding something. I'm no expert.
Click to expand...

The argument has always been whether or not the bass control is boost/cut or boost only.
 

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