Stingray aftermarket 2 band pre

[SGD Lutherie]

hmmm.. since you have an authentic Sabre preamp in front of you there is no dispute in the values. The Sabre abd Stingray preamps I built have enough gain and sound great with the 100K in the feedback loop. I noticed the Sabre guitar schematic has a 220K in the loop. I'll swap it for a 220K and see if it sounds better. Since I use LT chips I always left pin 8 empty. Thats what I love about being a DIY'er, I can tweak and modify the builds as I go along.
thanks for the info

It's not just the gain, that's also where the bass tone control's feedback loop is.

What I did was to build one of each and then A/B them in the same bass. 220K sounds better. It wasn't all that much louder, but it just had a better overall tone.

Here's the Sabre circuit that tipped me off and made me study the real preamp. And here's a modified Bajaman schematic.

 

[Dominic D]

SGD Lutherie, your revised Bajaman schematic still has the old typo. One of the 1u caps should be 10u. The parts layout portion is correct.

 

[Stealth]

Good find, David.

 

[4848277]

SGD Lutherie, your revised Bajaman schematic still has the old typo. One of the 1u caps should be 10u. The parts layout portion is correct.

Can I ask which capacitor has the typo so I can correct my diagram...?

Perhaps somebody could post the corrected diagram.

Thanx

 

[SGD Lutherie]

SGD Lutherie, your revised Bajaman schematic still has the old typo. One of the 1u caps should be 10u. The parts layout portion is correct.

Oh I forgot that! The output cap. Fixed.

 

[BassLife77]

It's not just the gain, that's also where the bass tone control's feedback loop is.

What I did was to build one of each and then A/B them in the same bass. 220K sounds better. It wasn't all that much louder, but it just had a better overall tone.

Here's the Sabre circuit that tipped me off and made me study the real preamp. And here's a modified Bajaman schematic.

I already mentioned I was going to hear how it sounds like. So that would be the tone

 

[SGD Lutherie]

I already mentioned I was going to hear how it sounds like. So that would be the tone

Give it a try and see what you think.

I came here to report this issue because I have been building these preamps and just found the mistake. The real thing uses 220K, and I felt it sounded better. Something seemed missing to me with the 100K.

If it works good for you, that's fine. But the real thing uses 220K. I would damaging with very high output pickups that 100K might work better.

 

[delta7fred]

David

There seems to be some variation of component values for different basses.

The resistor values of 100K and 1M5, as originally posted by Bajaman over on FSB, are correct when compared to my fairly recent Stingray.

fred

 

[SGD Lutherie]

David

There seems to be some variation of component values for different basses.

The resistor values of 100K and 1M5, as originally posted by Bajaman over on FSB, are correct when compared to my fairly recent Stingray.

fred

I saw someone posted that over at freestompboxes. The preamp I was looking at is an original '78 Sabre preamp. I also had a hand drawn Sabre schematic, as well as a hand drawn '76 Stingray circuit layout, and they both had 220K resistors for the gain, and 2.2M for the quiescent current setting.

Since the two preamps are almost identical, I decided to replace the 100K with a 220K, and I prefer the tone with more gain.

Apparently these parts have changed over the years. But since I found a discrepancy, I thought I'd come and share the info.

So now we have two variations known.

 

[BassLife77]

I have a theory it might have been one of those "secret revisions" of the preamp. Since the Sabre wasn't selling as well as the Stingray they were scrambling trying to improve the sound. They figured the consumer wouldn't check the value of every component on the board, especially if it was sealed in epoxy. Or it might have been a QC issue with stuffing boards which probably wasn't the case

 

[SGD Lutherie]

I have a theory it might have been one of those "secret revisions" of the preamp. Since the Sabre wasn't selling as well as the Stingray they were scrambling trying to improve the sound. They figured the consumer wouldn't check the value of every component on the board, especially if it was sealed in epoxy. Or it might have been a QC issue with stuffing boards which probably wasn't the case

Well this was never sealed in epoxy. Also I have two other schematics showing the 220k resistor, one from a Sabre and one from a Stingray.

I was actually going to replace the gain resistor to something larger when I found the the three other versions.

I think they started with the higher gain and then reduced it. The original instruction book that came with the bass said to leave the volume about half way up, but it must have been kind of loud.

Either way, I think it sounds better with the 220K resistor. It was punchier and had better transients to me.

 

[4848277]

Oh I forgot that! The output cap. Fixed.

Thank you for posting the revised schematic. Much appreciated.

Cheers!

 

[SGD Lutherie]

Thank you for posting the revised schematic. Much appreciated.

Cheers!

No problem. From what Bajaman told me, leave the resistor connected to pin 8, 1.5M. That improves the high end and transient response.

Also it seems both 100K and 220K resistors were used.

 

[rubato]

but didn't wan't to spend the money on the East preamp.

actually, you did wan't to...

 

[Red Planet]

Subscribed.

 

[brenner182]

I can vouch for the seymore duncan 3 band. It's awesome

 

[SGD Lutherie]

I want to give a small report. I installed one of these in my '87 Ibanez with my Neo Jazzbuckers and did a gig last night. My previous tests had been at my shop.

With the 220k resistor, the gain is pretty hot from the preamp. So if you have high output pickups, you might want to stick with the 100k. I might switch mine back. It works fine, no distortion or anything, but is a lot louder than my passive basses.

 

[Dominic D]

I'm thinking about wiring my bass with a passive treble cut knob and only use the preamp for volume and bass. How would I wire the preamp to bypass the treble section?

 

[SGD Lutherie]

I'm thinking about wiring my bass with a passive treble cut knob and only use the preamp for volume and bass. How would I wire the preamp to bypass the treble section?

The treble control actually works fine for cutting. The bass control on the other hand doesn't do as much. The treble control can do a lot more boosting.

I never have an issue where I need the treble control to cut more than it does. With the bass boosted the treble half way it's a pretty thick tone. With the treble all the way off it's in dub land.

The treble control is part of a feedback loop. Probably the easiest way to do that would be to use a trim pot for the treble control and set it where you want it, and then hide it away inside the bass. The passive tone control would go before the preamp.

I just did a custom control plate for someone that had a stacked volume and passive tone control, a blend and a stacked bass/treble control. It also had a bypass and a passive tone bypass:

 

[Stealth]

That does remind me - the current PCB layout is rather unsightly, considering it needs several long-lead jumpers. Has anyone tried to optimize the layout so more is routed using regular paths on the PCB? And yes, I'm fully aware of the "if it ain't broke" adage.