I would say the alot of the "Classic Spector Tone" does come from the EMG's themselves.
I agree, I think the EMGs color the tone a very specific way after hearing Spectors with Barts and Nordy pups.
The Spector 9V Circuit (Haz) or Haz copy or Spector TonePump Pre will add Growl and grind to the tone.
Yes. In the video below - thank you Sam for sharing it... I explain all of the history.
It's probably NOT clear in this video, because the video was already long enough and not about the USA 9v circuit... that the Spector USA 9v circuit IS OpAmp based. And it uses an array of OpAmps to get around the oversat issue. Which has an overdrive effect, thus the growl from the circuit.
It's not that Stuart set out to create a really growly circuit. He set out to create a bass with a tonal range that would sit in any mix and have a unique voice... its own sonic territory to play in.
The growl and grit in the USA 9v Circuit which he created WITH Henry's assistance (Henry owns HazLabs and makes the circuits for Spector) was a mixture of the limitations of the available tech options at the time and an unavoidable side-effect of the approach Stuart and Henry took to "get around" those limitations.
If you haven't seen this video regarding the Tonepump check it out. It will explain how the Tonepump works.
https://www.youtube.com/watch?feature=player_embedded&v=b9x1TNtUKI0#t=107
To be completely honest. And this may be blasphemy... but the TonePump is really a superior circuit to the USA 9v from a tech standpoint. JFET circuits are the standard now, OpAmp circuits are used in cheaper import basses or not at all anymore.
The USA 9v Circuit and the NS-2 since 1998 when Stuart and PJ relaunched the Spector brand after its demise with Kramer in 1991, has been about tradition.
Sincerely the best way to give someone the tone from those early, mid and late 1980's Spector basses is to build them as close to the originals as possible.
The NS-4 is a more modern take on the NS-2. As is the Euro4LX. Stuart really tries to experiment with the Bolt-Ons and other models. He sincerely tries to keep the NS-2 as close to the original as possible. Realizing that it's a classic and people want them because of that classic 1980's tone.
The Tonepump with the Trim will be a big change in the Tone of your Euro. Once the Trim is lowered down to 30-50% the bass and treble will sound much different then the non-trim version.
Yes. I've owned both. See attached. I had an early Euro4LX with the non-trim pot model and a new (brand new at the time) Euro4LX with the adjustable TP.
WORLD of difference in the tone... the older model was pretty much hot as all get out. The newer once it was adjusted, was tamed down but still very much Spector in tone.
Regarding the USA 9-volt circuits, I was speaking to PJ about that today. Remember they are hand made by HAZ Labs and the components in the circuit are getting harder to get in. They barely get enough in for new NS-2's so that is why there are no extras at this point.
I have been trying to get one for about 6 months... and I keep getting told, "Nope. None are available."
So don't feel bad. They may NEVER be available for purchase individually again.
Lol. I can't handle the blood. I'm not as hardcore as you or Webster. Any gigs I do these days will be church gigs. I guess I could say it was representative of Jesus' blood?

No offense meant to anyone.
You know as the guy who designed that blood drip pattern I laugh every time I see something like this.
FYI - there are 5 component patterns that can be mixed and matched, therefore the Czech shop can adjust the mix of the 5 (2-3 of these 5 patterns can be used to create the total drip pattern). So each bass can sort of have a unique pattern. But after a while you can start to see repetitions in the patterns.
Bunk's Alex (which was mine) has the original pattern design first created for Alex and his prototypes. That pattern *with three of the components) is to me the optimal design for it's the true original design I came up with. Which is why it is on that bass. That one was built for me and is the one used in all of Spector's marketing.
Anyway... as the guy who designed that blood drip paintjob, I totally agree. LOL. Alex is a good friend. I've gotten to know him and his wife really well and I think they are sincerely great people. But that bass is totally NOT my style.
I do have to admit that the idea that a church bassist could play it and that blood represent Christ's sacrifice is very interesting. For that, it'd be worth seeing if PJ would do a special order gloss white Alex Bass with the blood. Then you have the white of the dove or of the lamb and the blood.
Regardless, I am not the least bit offended by either statement. I designed that bloody paint job and it's not something I'd play - thus after sitting in the corner for a year I sold it to Bunk because that bass SHOULD be played.
And the idea of a church bassist using it is actually symbolically cool in my opinion.