Pioneer SX-939 & Graphic EQ/Dynamic Expansion

[Alex Estrada]

Hi everyone,

Still a pretty new member so please forgive me if this thread is not properly located, but I found similarly-themed threads in the Solid State category so here goes.

I'm having several components of my stereo looked over by my very capable local tech as I'm currently in the process of moving across town. Hopefully, by the time I'm all moved into my new place, the stereo will be ready to rock. My current system includes a Pioneer SX-939 with the components listed in my signature, all playing through a pair of JBL 4311's.

I've been very curious about augmenting my system by adding some type of graphic EQ like the Pioneer SG-9800, JVC SEA-80, or the ADS Sound Shaper One Ten. I also like the idea of adding a DBX 3BX. My idea is to wire up a combination of these two new components inline between the 'Pre Out' and 'Power In' RCAs on the back panel. I know neither of these components is especially essential.

Now to brass tax: My tech is currently in the process of bringing the 939's power supply up to spec, but also indicated to me that some work needs to be done on the tone control portion of the receiver, which is a lot more involved and expensive than the power supply touch-up work.

My priorities are roughly 50/50 sound enhancement/eye candy with the addition of EQ and the 3BX Dynamic Expansion, but with this unfortunate news about the expensive tone control work, I'm seriously weighing the merits of skipping this expensive job and doing most of my tone shaping with an external EQ unit (more flexibility?) with some slight enhancement to LPs with the DBX.

Any recommendations on:
1) if it's worth it to skip the tone control work on the 939 and do my tone-shaping from a graphic EQ (I do all my EQ adjustments during listening based on the material/mood I'm in)
2) a good graphic EQ unit with some decently good looks & lights, which could handle the job of a faltering tone control section in a 939

Any help is much appreciated. It seems like adding these two components could kill two birds with one stone (save some money on tone circuit work and have some extra gadgets to watch while listening) but I want some second opinions before moving forward.

Thank you very much!!!

 

[ivandezande]

Hi everyone,

Still a pretty new member so please forgive me if this thread is not properly located, but I found similarly-themed threads in the Solid State category so here goes.

I'm having several components of my stereo looked over by my very capable local tech as I'm currently in the process of moving across town. Hopefully, by the time I'm all moved into my new place, the stereo will be ready to rock. My current system includes a Pioneer SX-939 with the components listed in my signature, all playing through a pair of JBL 4311's.

I've been very curious about augmenting my system by adding some type of graphic EQ like the Pioneer SG-9800, JVC SEA-80, or the ADS Sound Shaper One Ten. I also like the idea of adding a DBX 3BX. My idea is to wire up a combination of these two new components inline between the 'Pre Out' and 'Power In' RCAs on the back panel. I know neither of these components is especially essential.

Now to brass tax: My tech is currently in the process of bringing the 939's power supply up to spec, but also indicated to me that some work needs to be done on the tone control portion of the receiver, which is a lot more involved and expensive than the power supply touch-up work.

My priorities are roughly 50/50 sound enhancement/eye candy with the addition of EQ and the 3BX Dynamic Expansion, but with this unfortunate news about the expensive tone control work, I'm seriously weighing the merits of skipping this expensive job and doing most of my tone shaping with an external EQ unit (more flexibility?) with some slight enhancement to LPs with the DBX.

Any recommendations on:
1) if it's worth it to skip the tone control work on the 939 and do my tone-shaping from a graphic EQ (I do all my EQ adjustments during listening based on the material/mood I'm in)
2) a good graphic EQ unit with some decently good looks & lights, which could handle the job of a faltering tone control section in a 939

Any help is much appreciated. It seems like adding these two components could kill two birds with one stone (save some money on tone circuit work and have some extra gadgets to watch while listening) but I want some second opinions before moving forward.

Thank you very much!!!

The 939 should be completely gone through, the tone sections have tons of noisy transistors and the orange caps that always measure pretty bad. Also skeptical of the power supply "touch up". That should be very involved, replacing all transistors, caps, and many diodes and resistors. If anything, it's more work than the tone section.
Sounds like you've got a lazy tech.

I'm in the camp that believes you should never need or use an EQ. Get different speakers or fix your room acoustics if you feel the sound isn't accurate to the source.

 

[Alex Estrada]

The 939 should be completely gone through, the tone sections have tons of noisy transistors and the orange caps that always measure pretty bad. Also skeptical of the power supply "touch up". That should be very involved, replacing all transistors, caps, and many diodes and resistors. If anything, it's more work than the tone section.
Sounds like you've got a lazy tech.

I'm in the camp that believes you should never need or use an EQ. Get different speakers or fix your room acoustics if you feel the sound isn't accurate to the source.

My tech is pretty much the authority in town (Abell Audio in Columbus, OH). Actually talked to him twice today over the phone and between the two calls he had completed the power supply work (just several bad caps). As I understand it, the tone control work and fixing of the Low, High, and 20db cut functions involves a lot more disassembly of the unit and will basically double my service charge.
I'll easily forgo the 3BX unit, but if it came down to spending almost $300 to completely bring the onboard tone-shaping up to spec or just skipping the work and using a seemingly more versatile EQ unit, I'm at a loss as to what I should do.

 

[ivandezande]

My tech is pretty much the authority in town (Abell Audio in Columbus, OH). Actually talked to him twice today over the phone and between the two calls he had completed the power supply work (just several bad caps). As I understand it, the tone control work and fixing of the Low, High, and 20db cut functions involves a lot more disassembly of the unit and will basically double my service charge.
I'll easily forgo the 3BX unit, but if it came down to spending almost $300 to completely bring the onboard tone-shaping up to spec or just skipping the work and using a seemingly more versatile EQ unit, I'm at a loss as to what I should do.

Hmm I mean considering you can just take the tone controls out of the circuit on the 939 with a switch, and you want to seriously EQ things, just buy an EQ. Should be cheaper and simpler.

Your town has a lack of authorities. Lazy, plain and simple. I've rebuilt two 939's and I charged maybe $200 for the restore. Getting to those boards isn't hard at all, takes maybe 5 minutes to get to it. Just the fact that he didn't overhaul the power supply makes it sound like he's hoping it fails in the next few years so you come back and dole out more money.

 

[xero-D-hero]

What I would do...
Fix the tone controls.
I'd get the SG-9800 EQ as well.
I'd put the EQ in the tape 2 loop where it belongs,not in the pre-out/amp-in loop.
Forget about the DBX 3BX entirely.

If I wanted a light show (ie: eye candy) to go with the rig I'd probably get something like a Kenwood SA-90 -or- SA-90II -or- a BSR SA-3X.
These can go in the same loop as the EQ.

BTW welcome to AK.

JM2¢ ~ FWIW

Bret P.

 

[Alex Estrada]

What I would do...
Fix the tone controls.
I'd get the SG-9800 EQ as well.
I'd put the EQ in the tape 2 loop where it belongs,not in the pre-out/amp-in loop.
Forget about the DBX 3BX entirely.

If I wanted a light show (ie: eye candy) to go with the rig I'd probably get something like a Kenwood SA-90 -or- SA-90II -or- a BSR SA-3X.
These can go in the same loop as the EQ.

BTW welcome to AK.

JM2¢ ~ FWIW

Bret P.

First off, thanks for the great suggestions!

What practical/sonic differences would I get from placing the EQ in the tape 2 loop as opposed to in between the pre-out/power in?
I'm just a little apprehensive about using up one of my two tape monitors as ideally, I have my Nak hooked up to tape 1 and my R2R hooked up to tape 2. I'd imagine I could get around this with some kind of tape-deck specific switcher with rca ins and outs (I already have a plain 5-to-1 input switcher to make up for the 939's one aux in) but I haven't been able to find anything like that for tape machines.

 

[fernarias]

The 939 should be completely gone through, the tone sections have tons of noisy transistors and the orange caps that always measure pretty bad. Also skeptical of the power supply "touch up". That should be very involved, replacing all transistors, caps, and many diodes and resistors. If anything, it's more work than the tone section.
Sounds like you've got a lazy tech.

I'm in the camp that believes you should never need or use an EQ. Get different speakers or fix your room acoustics if you feel the sound isn't accurate to the source.

For a tech, the tone controls are the more expensive repair. There's a lot of disassembly/assembly that has to be done to get to the tone boards plus the chance that you cut the tuner cord whereas the power supply is much easier to access (remove bottom, release board and flip over). See pics I got here: https://www.audiovintage.fr/leforum/viewtopic.php?t=57475



I think you should rebuilt the whole 939.

 

[xero-D-hero]

What practical/sonic differences would I get from placing the EQ in the tape 2 loop as opposed to in between the pre-out/power in?
I'm just a little apprehensive about using up one of my two tape monitors as ideally, I have my Nak hooked up to tape 1 and my R2R hooked up to tape 2. I'd imagine I could get around this with some kind of tape-deck specific switcher with rca ins and outs (I already have a plain 5-to-1 input switcher to make up for the 939's one aux in) but I haven't been able to find anything like that for tape machines.

Tape loops are fixed level loops (line level).
Pre-out/amp-in is a variable level loop controlled by the volume knob (output level).

EQ's work best using a line level signal,as the good ones usually have their own input level control to adjust for unity gain.

That SG-9800 instead uses two selectable attenuator buttons for that purpose.
But the net result is largely the same,just not as precise as a knob/slider style input level control.

As for "losing" a tape loop,dont worry you dont actually lose it to begin with,as there's a replacement tape loop on the back of the EQ itself.
You just select that loop via the button on the EQ instead of a button on the receiver,that's all.

Hope that explains it all clearly.

FWIW

Bret P.

 

[ivandezande]

For a tech, the tone controls are the more expensive repair. There's a lot of disassembly/assembly that has to be done to get to the tone boards plus the chance that you cut the tuner cord whereas the power supply is much easier to access (remove bottom, release board and flip over). See pics I got here: https://www.audiovintage.fr/leforum/viewtopic.php?t=57475

View attachment 1572711

I think you should rebuilt the whole 939.

I'm aware on how to get to the boards....I've rebuilt two 939's, let alone many more in that lineup. However, on the tone boards it's just capacitors and 4 transistors. On the power board, it's 4 TO-220 transistors that need to be regreased and replaced, at least 6 resistors, capacitors, more than 6 normal style transistors, and many, many diodes. It's not just about how hard it is to get to it. Which isn't that hard. Take off the faceplate, take out the 4 screws holding each board. I literally spent more time typing this than it takes to do it.

Also there's no way you could cut the tuner cord taking out the tone boards unless you are the world's clumsiest person and thought the tone boards were top access.

 

[Alex Estrada]

Tape loops are fixed level loops (line level).
Pre-out/amp-in is a variable level loop controlled by the volume knob (output level).

EQ's work best using a line level signal,as the good ones usually have their own input level control to adjust for unity gain.

That SG-9800 instead uses two selectable attenuator buttons for that purpose.
But the net result is largely the same,just not as precise as a knob/slider style input level control.

As for "losing" a tape loop,dont worry you dont actually lose it to begin with,as there's a replacement tape loop on the back of the EQ itself.
You just select that loop via the button on the EQ instead of a button on the receiver,that's all.

Hope that explains it all clearly.

FWIW

Bret P.

Thanks for that explanation, very helpful.

I've decided to have the 939 100% worked over before saving up for new toys for the system.
On a slightly related note, do you have any recommendations for tape switching devices? If I do eventually go down the road of using my tape 2 loop for spectrum analyzer fun, it would be nice to be able to switch between decks within tape loop 1.

If I could have record/playback functionality within tape loop 1 across all 3 of my tape machines (2 cassette decks and a R2R), maybe even with some expandability for more tape decks, that would be ideal.
I've found some info on the dbx 200/400 and the Numark TC4100, but any recommendations on devices like these are much appreciated

 

[KentTeffeteller]

The 939 should be completely gone through, the tone sections have tons of noisy transistors and the orange caps that always measure pretty bad. Also skeptical of the power supply "touch up". That should be very involved, replacing all transistors, caps, and many diodes and resistors. If anything, it's more work than the tone section.
Sounds like you've got a lazy tech.

I'm in the camp that believes you should never need or use an EQ. Get different speakers or fix your room acoustics if you feel the sound isn't accurate to the source.

Fix the Pioneer's tone section first, and see how good it really sounds. The only dynamic expanders I care for are built into broadcast processors and must be adjusted with care, a musical ear, and knowledge. The only somewhat affordable consumer EQ I like is the new one from Schitt.

 

[sKiZo]

Pre Out typically passes the signal thru the integrated tone section before it hits the amp, so if you think you have problems with that, you're better off (usually) using a tape loop, which "should" normally bypass the tone section of the receiver?

I'm a fan of the dbx 3bx and can't imagine life without it. Turn it off here, music goes flat, doubt erased, simple as that. Main thing is to go conservative in your settings. Set the 3bx too high, and it will cause pumping and other undesirable effects. Mine is set to approx 1.3 on both sliders, and only need the slightest nudge to make "problem" music come alive.