# pre-outs on MF3.5 to BFD-Pro?



## Guest (Sep 22, 2006)

Hi all... my first post and I have a question regarding the use of left and right pre-outs on my Musical Fidelity A3.5 to hook into a BFD-Pro via a Y-connector. I am using #4 on the BFD-Pro to power my SVS 20-39 PC-Plus subwoofer in conjuction with my a/v/ receiver for movies. I want to use the "spare"#5 on BFD for "stereo" listening using my Goldi's. Will the left and right pre-outs on my MF 3.5 be compatable with the the BFD inputs, using the proper adaptors. I guess what I am trying to say is that I want to use the same sub in the same room, with two different sources and two different sets of speakers! Thanks for any help!:dizzy: Huck


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## brucek (Apr 11, 2006)

> I want to use the "spare"#5 on BFD for "stereo" listening using my Goldi's


Don't quite understand this statement. Do you mean Program #5? The BFD has 10 available programs you can use.



> Will the left and right pre-outs on my MF 3.5 be compatable with the the BFD inputs, using the proper adaptors


Yes.



> I want to use the same sub in the same room, with two different sources


How do you plan to connect this? with switches? Can you be more specific.

brucek


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## Guest (Sep 22, 2006)

Hi brucek and thanks for the reply! The BFD has 10 preset programs, programs 4 and 5 are already set up for PA(Parametric EQ). I am using #4 right now with 8 filters for movies only! I want to use #5 for two-channel only, with another source. I plan to use the same sub for different duties. The sub has a left and right inputs, so
right now I am using the left input on the sub, being fed by the output on the BFD, which is being fed a signal from the sub-out on my receiver. I plan to use the other input and output on BFD to take the combined left and right signal, via a Y-connector from my 3.5 and an extra sub cable from the spare output on BFD to the spare(right) input on the sub. I am not sure if these pre-outs on the 3.5 will work,being that they are a "full-range" signal. Obviously, one or the other source would probably have to be turned off, depending on whether I was watching a movie , or listening to two-channel! Anyone using one sub with two different sources (signals)? Thanks, Huck:T


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## brucek (Apr 11, 2006)

> right now I am using the left input on the sub, being fed by the output on the BFD, which is being fed a signal from the sub-out on my receiver


No problem there.......



> I plan to use the other input and output on BFD to take the combined left and right signal, via a Y-connector from my 3.5


How will you combine them? A Y-connector will short the left and right outputs of the pre-amp. A no-no.

You would have to split the left and right signals from the pre-amp and fed them to an *active combiner* and then feed that single 'combined' signal to the BFD.

brucek


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## Guest (Sep 23, 2006)

brucek said:


> No problem there.......
> 
> 
> 
> ...


Hi brucek: I guess I won't be combining the two pre-outs! What about going from the left and right outs on the integrated with two separate cables and THEN going into a Y feeding a single cable to one of the spare engines( I am not sure which one I am using right now) on the BFD? It's probably the same thing(shorting situation)! Maybe this is all a "bad idea".... I just got ta thinkin and it sounded to me like it would work......but what do I know! :coocoo: Thanks anyways! Huck:T


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## brucek (Apr 11, 2006)

> two separate cables and THEN going into a Y feeding a single cable


Still a short and not allowed.

There's nothing wrong with buying a proper mixer/combiner though. That would certainly work. You don't even need to use a different program on the BFD - just use the other channel of the Program 4 and set different filters.

brucek


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## Guest (Sep 23, 2006)

brucek said:


> Still a short and not allowed.
> 
> There's nothing wrong with buying a proper mixer/combiner though. That would certainly work. You don't even need to use a different program on the BFD - just use the other channel of the Program 4 and set different filters.
> 
> brucek


Thanks, Huck!


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## Guest (Sep 23, 2006)

brucek said:


> Still a short and not allowed.
> 
> There's nothing wrong with buying a proper mixer/combiner though. That would certainly work. You don't even need to use a different program on the BFD - just use the other channel of the Program 4 and set different filters.
> 
> brucek



Hi brucek: Can you point me to a link, or product name? Thanks, Huck:T


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## brucek (Apr 11, 2006)

> Can you point me to a link, or product name?


You have to be careful when purchasing a mixer for stereo signals. Combining two line level signals is quite simple and can be carried out with a couple of fifity cent resistors. In fact quite a few 'passive' combiner/mixers are simply that inside the case (unless they're transformer based). This resistive passive method has problems though when applied to stereo signals in the form of increased crosstalk and distortion resulting from high output impedance. So you have to be careful what you buy. You don't want to mess up your pristine mains signal. Unfortunately when you find an inexpensive combiner on the internet, they don't include specs, so it's hard to evaluate, and I'm not that familiar with product types.

I took a look in google and didn't find any inexpensive active stereo mixers that I could recommend, but I did find a transformer based combiner that looks good. It seems to have the correct impedances and should work OK, and the price is right.

http://www.edcorusa.com/sound/matchers/s2m.htm

If you find something on a web site and you want me to give an opinion, I certainly will.

brucek


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## Guest (Sep 23, 2006)

brucek said:


> You have to be careful when purchasing a mixer for stereo signals. Combining two line level signals is quite simple and can be carried out with a couple of fifity cent resistors. In fact quite a few 'passive' combiner/mixers are simply that inside the case (unless they're transformer based). This resistive passive method has problems though when applied to stereo signals in the form of increased crosstalk and distortion resulting from high output impedance. So you have to be careful what you buy. You don't want to mess up your pristine mains signal. Unfortunately when you find an inexpensive combiner on the internet, they don't include specs, so it's hard to evaluate, and I'm not that familiar with product types.
> 
> I took a look in google and didn't find any inexpensive active stereo mixers that I could recommend, but I did find a transformer based combiner that looks good. It seems to have the correct impedances and should work OK, and the price is right.
> 
> ...


 Thanks a lot brucek for taking time to find me something! I appreciate it! I will order one first thing Monday. Thanks, Huck


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## Guest (Sep 24, 2006)

Hi: Maybe I am looking for something the BFD cannot do,that is "adding" bass for "two-channel" listening. Maybe I should be looking at a graphic equalizer instead, that way I van have some tone controls for my stereo speakers, plus control the sub! Can someone recommend a good equalizer that I can use with my integrated, plus add and subtract bass!I have no way of adjusting the bass on my integrated amp when listening to two-channel, other than jumping up and turning the gain dowm on the sub when the bass is too much. Maybe I should just use the BFD for watching movies only, the way it is now! I will have to buy the stereo to mono combiner,two extra rca cables, two adaptors, plus two extra sub cables and if it no work!? Thanks for everyones( especially brucek!) help on this! Huck:surrender:


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## Wayne A. Pflughaupt (Apr 13, 2006)

> You would have to split the left and right signals from the pre-amp and fed them to an active combiner and then feed that single 'combined' signal to the BFD.


I’d be concerned that the other (i.e. uncombined) pair from the splitter would end up with a mono signal in both channels... ? After all, the side going to the main amp and the side going to the combiner have continuity. Or will the combiner eliminate that problem?

Sorry if this is been discussed and I just missed it, but why not combine the BFD’s two outputs for the sub? That would fully isolate the combining from the pre-amp – I think (brucek, please comment!). They you can set up two BFD EQ programs, one for music, one for music, as planned.

Regards,
Wayne


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## brucek (Apr 11, 2006)

> Or will the combiner eliminate that problem?


The crosstalk from one channel to the opposite channel is the drawback with the simple passive combiner. That's the reason I cautioned Huck away from that type.

Huck has one channel of his BFD used already for a feed from a mono LFE signal on system #1. He wants to feed the other BFD channel from system #2 that doesn't have a mono LFE signal. So, he must combine that stereo mains signal first before he can accomplish this. 

He will of course have to get creative with the BFD since that combined signal will be full range. Presumably he has defeated the LPF crossover in his sub as a consequence of feeding LFE from the system #1, and so a crossover in addition to equalization will be required from the BFD filters for system #2's full range signal. Certainly possible. 
Personally I would have accomplished the combining and the LPF crossing with a device like the Paradigmn X-30, since that would have solved both problems at once, but they aren't cheap. I think they're around $150, but I've seen them on ebay for less.....

Combiners are a juggling act with impedance matching. A passive combiner using simple resistors will either have an input impedance that is too low, causing crosstalk to the opposite channel as you suggested, or (if you modify it to have sufficient input impedance) it will have too high output impedance causing distortion. The solution is to impedance match with active components or a transformer. Fairly simple devices.

Hopefully the cheap device I suggested will work fine. They never supply enough information, but you can't lose for $20.........

brucek


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## Wayne A. Pflughaupt (Apr 13, 2006)

> Huck has one channel of his BFD used already for a feed from a mono LFE signal on system #1. He wants to feed the other BFD channel from system #2


Ah – I missed that there were two systems... 

Yup, they never give you enough info with those things. Hopefully Huck will let us know how it works out. 

Regards,
Wayne


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