unknown spector bass preamp

[billdylan]

Hi guys ...got this preamp long ago...I've never seen any pics or info on it..stacked bass and treble and vol and balance..any information would be appreciated...here's some photos...pots are normal values not emg type ...thanks
this shows the photos

 

[billdylan]

and more photos ...fingers crossed <a href=""><img src="" title="source: imgur.com" /></a>

 

[billdylan]

and....<a href=""><img src="" title="source: imgur.com" /></a>

 

[billdylan]

Wow...I'm amazed ...Its got spector bass on the pre...has no one got any idea at all...can't be that rare ....any help much appreciated guys....bill

 

[billdylan]

yearly bump to see if anyone can tell me which spector this preamp comes from....spector on the board itself...passive 250k pots...its the great mystery to me...hunted the internet....nothing...zilch...comeon make my day guys...gratefull thanks for any ideas..cheers...billdylan

 

[RobbieK]

I think I have this same preamp in my "Project Berocca" bass. Can you post a photo of the top of the circuitboard?

If you skip to the 19min mark in this video, you'll see some frequency sweeps I did on this preamp.



Also, I found a schematic for what I think is this preamp...

 

[billdylan]

Thanks rob....been away so sorry for delay getting back to you.....yup !!...its the same .....great to see your videos...seems like a good pre and will stick it in my stingray type build with a duncan MM pickup...still got no idea where it came from..ha..ha..thanks for taking your time to share your video...much appreciated...

 

[billdylan]

It would be good if you could stick the schematic up....cheers..bill

 

[RobbieK]

I'm currently working on the next Project Berocca vid. I'm building a new 2-band pre. Once this is in the bass and I've taken out the spector pre, I'll be able to get another close look at it to confirm that this is truly the schematic. Right now I'm not sure. In fact I think my pre has a 50K treb and bass stack for starters, plus there wasn't a pot soldered to the board like your photos...

I'd also like to credit the guy who wrote this out and came up with the stripboard layout, but I'm afraid I have no idea what site I found this. If you are out there mate, please say hi!

It is an interesting circuit. The first stage has a big treble boost, then there's a treble roll-off (roughly equal) at the output. I'm guessing this is some kind of pre-emphasis/de-emphasis noise reduction. (If memory serves, the boss 7-band EQ pedals do the same thing.) The 062 is a notoriously noisy opamp. OTOH, it has very low current consumption (200uA). I guess back in the 90's there was much less choice for low-current audio opamps. The treble control is quite strange too, boosting so low in the spectrum. It actually boosts a lot of upper mids as well...

 

[catcauphonic]

OP, you likely would have more views on this if you were to post it directly in TB's 'Spector Club' thread. I don't have the link handy, but if you're still looking for more info on it, it'd be worth doing a search to post your inquire of anything Spector related there.

Good luck, and rock on

 

[ThisBass]

I'm currently working on the next Project Berocca vid. I'm building a new 2-band pre. Once this is in the bass and I've taken out the spector pre, I'll be able to get another close look at it to confirm that this is truly the schematic. Right now I'm not sure. In fact I think my pre has a 50K treb and bass stack for starters, plus there wasn't a pot soldered to the board like your photos...

I'd also like to credit the guy who wrote this out and came up with the stripboard layout, but I'm afraid I have no idea what site I found this. If you are out there mate, please say hi!

View attachment 3523091

It is an interesting circuit. The first stage has a big treble boost, then there's a treble roll-off (roughly equal) at the output. I'm guessing this is some kind of pre-emphasis/de-emphasis noise reduction. (If memory serves, the boss 7-band EQ pedals do the same thing.) The 062 is a notoriously noisy opamp. OTOH, it has very low current consumption (200uA). I guess back in the 90's there was much less choice for low-current audio opamps. The treble control is quite strange too, boosting so low in the spectrum. It actually boosts a lot of upper mids as well...

Unfortunatelly cap magnitude readings are very wrong (likely an issues with reading of decadic multipliers).
You won't get a decent response out of it with this faulty magnitudes for capacitance numbers.

 

[MPU]

Cap values has been corrected in this thread. Help needed for schematic/layout match
That schematic works and the preamp sounds great.

 

[billdylan]

Hey ...another year...another chance for someone to identify this unknown Spector marked pre amp.....2 years and no one knows what it is...I'm amazed ...and ...constantly intrigued...Any New Ideas Guys ......thanks ...Billdylan