Adding Pre out/Amp in

[schaale]

I want to add pre out and amp ins to my Sansui QRX-7001 so I can use the 7001 amp plus add an sub amp. Coming out of the front pre I will be putting a Y adapter. One will go to the sub amp amd the other from the Y will go to the 7001 amp in. In doing this will it cause any sound problems orload problems to the Sansui splitting the signal like that?

 

[JoeESP9]

Running preamp section outputs in parallel will usually cause no harm. The fact that you ask the question suggests that you're not a technician/engineer. If this is the case I'd be very careful about doing this.

If I'm incorrect or out of line I apologize.

 

[schaale]

Sansui QRX-7001 pre outs

No i'm not an engineer/technician just learning for fun. I'm working on a Sansui QRX-7001 that I want to add the pre outs to. From looking at the schematics it looks like I would take the 4 wires that go from the 2428 board to the 2436 driver boards. I would take the wires from the 2428 board to the RCA pre outs , then go from the amp in RCA to the 2436boards. Does that sound right?

 

[mmc350]

I'm not familiar with your specific Sansui model, so I don't know which - if any - of these will work for you, but I'll throw them out there anyway.

Most powered subs (which I assume you're referring to since you're planning on using a line level input) have BOTH a line level input jack as well as speaker (hi level) inputs and outputs.

If your amp has two or more sets of speaker outputs and it also has the ability to use more than one set of speakers at a time, hook up one set of speaker outputs to the sub's hi level speaker input terminals.

Another option would be to run a set of speaker wires from the amp to the sub's speaker inputs and then run wires from the sub's speaker outputs to your regular speakers.

The last possibility is to feed the sub's line level input from the headphone jack. I've done this before, with what I'd consider to be quite satisfactory results.

Just my opinion, but I'd much prefer one of these options to physically re-engineering the equipment. However, you're free to do as you choose.

Hope this helps, and good luck,

Jim

 

[schaale]

The subs i'm building wont have an amp plate, I was going to use a Heathkit aa-1640 amp to drive the subs. I'm restoreing a Sansui QRX-7001 quad receiver and while I had it open I figured I would add the pre outs. How is the sound quality when using the headphone jack and I have to check if I can use the speakers and headphone jack at the same time.

 

[JoeESP9]

I don't have a copy of the Sansui schematics so I can't help you there.

I'm wondering what kind of signal you're going to feed to the subs. You don't want a full range signal going to them. You should have a low passed signal going to whatever amp will be driving the subs.

Ideally the signal going to the amp that drives your mains should have high pass filtering. One of the benefits of using sub woofers is removing the low frequencies from the main speakers. Unless the signal to them (mains) is high passed they will be reproducing the lows right along with the subs. That's counterproductive.

 

[schaale]

I'm going to be using the subs mostly for movies. My main speakers have enough bass for most of the music I listen to. When I build the subs i'll make a crossover that takes over where my mains let off or I could go with a active crossover before the sub amp. My mains the woofers have a F3 of 30hz and the subs will be tune to 15-18hz. I would also like the pre-outs incase some day I want a little more power. I figured while I have it opened up it would'nt cost much to add the outs and ins. Ive changed out about 180 of the 207 electrolytic caps so far. There where a couple of differences from the schematic to what was actually installed. The rest of my caps should be here by friday so hopefully that part of the project will be done this weekend.

 

[JoeESP9]

IMO an active crossover is the way to go.

 

[schaale]

Are you using the CX2310 for the 2 subs or are you using it to bi-amp the mains? Do they make an active crossover just for a sub? I'll be rebuilding my main speakers in the near future. They are ported now but I want to make sealed version that will sit on top of 15" front firing subs. I'll have to make new crossovers for them but how difficult is it to set up a active crossover? Looks like cost wise it will be about the same. The plans I used to build the crossovers tells what the crossover frequancies are for the tweeter ,mids and woofers.

 

[KentTeffeteller]

Can't be done without butchering it. Get a receiver which has preouts.

 

[mmc350]

Well, I guess I'm more ignorant of this whole subwoofer thing than I thought.

I've always felt the beneficial use of a sub was more along the lines of an 'addition' to - or 'reinforcement' of - bass frequencies that were either missing, or had insufficient strength, from the main speakers.

I didn't realize that one should attempt to completely remove all bass frequencies from the mains through filtering when using a sub. Main speakers are usually designed to handle nearly the full audio spectrum. I never contemplated any reason to deprive them of doing just that. But it appears I'm mistaken.

I've not attempted to remove all high frequencies from getting to a sub any more than I've attempted to to remove low frequencies from getting to a set of full-range mains. After all, I had assumed the sub manufacturer wouldn't want (or allow) his speakers to attempt to reproduce violin notes or cymbal brushes. I was under the impression that this filtering out of high frequencies was done by the sub itself. Furthermore, I never even considered removing an entire frequency spectrum from speakers (mains) that were designed to reproduce it. To me, that would seem counterproductive.

Also, since very low frequencies - coming from the sub(s) or the mains - are relatively non-directional in nature (am I correct in this assumption?), I see no harm in allowing the mains to reproduce whatever they're capable of.

Unless, of course, the bass from the mains is so distorted as to destroy the musical content . . . in which case I would think a better course of action, rather than filtering out the lows, would be to replace the mains.

I'm always willing to learn, so please educate me, if you will. I don't see where allowing the mains to do what they were designed to do would be counterproductive.

Jim

 

[schaale]

I'm new to this also. My plan is to build 2 subs that will do the low freq. that my main speakers can't. I was going to make a passive crossover and mount it in the sub box. I think the idea of using active crossovers is that your amp is only amplifing the signal the speaker is going to use instead of the whole signal. A friend of mine swears by bi-wiring his speakers ,his speaker wire cost $110 a foot. I tried it with my speakers and I can't tell a differance but I used 2 seperate speakers wires instead of a speacial cable. He said that way the only freq. on the cable is the one that driver is going to use(lows on the woofer and highs on the mids and tweeter) I would think using a passive or active crossovers that the end result of the sound coming out of the speakers would be the same.

 

[schaale]

Hi Kent What can,t be done without butchering it? Adding the pre-outs or using a active crossover or both?

 

[audiofred]

There are active crossovers that will do exactly as you want without getting into circuitry and causing more problems. I have a RANE MOJO active crossover and it does a nice job. Getting into the existing amp might not be a good idea.
I used to own a Heath AA1640...you still use yours?
I don't think it was the greatest amp around for its day. There are mods to give it a lot more punch and overcome some design issues from Heathkit. It seemed to be happy with an out put of 100 watts per channel. Getting the meters toward the red or 200W per was not a pleasant listening experience.
Subs for movie effects would need a modern 200W amp and tuned cabinet with 10 inch or 12 inch speaker.
Fred

 

[JoeESP9]

Are you using the CX2310 for the 2 subs or are you using it to bi-amp the mains? Do they make an active crossover just for a sub? I'll be rebuilding my main speakers in the near future. They are ported now but I want to make sealed version that will sit on top of 15" front firing subs. I'll have to make new crossovers for them but how difficult is it to set up a active crossover? Looks like cost wise it will be about the same. The plans I used to build the crossovers tells what the crossover frequancies are for the tweeter ,mids and woofers.

My mains are full range electrostatics. I use the Behringer to feed everything from 85Hz down to the subs. The CX 2310 is an active two way stereo crossover that also has a separate mono sub woofer output (which I don't use).

BTW: I agree with Kent about getting a receiver or integrated that has preouts. In addition the 7001's rating of 35WPC makes it rather underpowered.

 

[schaale]

The Heathkit aa-1640 is on the shelf waiting to get redone with the mods. The mods take it to about 300w per channel. The 7001 is just to get my feet wet so to speek. When I get the 7001 done it will be doing bedroom duty or to the kids, next inline will be the 9001 at over 100w per channel. Whats the differance between buying a receiver with pre-outs or adding them yourself? I have the denon for hometheater now. Its about 2 years old and its having problems already. It sounds good for movies but lacks it for music. I only use it in 4.1 now so I figured I would use the 9001 with a oppo universal player with analog outs and that will cover me for music and movies and besides the 9001 looks cool with the wood case and meters. Sure beats the plain black box look of the new gear.

 

[JamesDean59]

<----

I recognize your avatar! Pierson's Puppeteer!

 

[JoeESP9]

Yep! I like to think it's Nessus.

 

[JamesDean59]

Ahh one of my favorite books. Ender's Game is up there as well as the Rendezvous with Rama series.

 

[sanyofreak]

Here's a simple rule regardless of how technical or non technical you are -- Its OK to split any low level output to drive multiple input sources, but NEVER "Y" two outputs to combine and drive a single input. Even low level higher impedance outputs.