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How Can I Bi-Amp with an 800c?

marloubow

marloubow

Best Day Ever
Hi all...
I've got it in my head to bi-amp a pair of AR3a's using the 800c for the low end and a pair of Eico HF-22 monoblocks for the top end.

Is this do-able? :scratch2:

If it is...someone here will know how.:thmbsp:

Thanks
Martin

P.s. Been reading some good stuff here.:thmbsp:
 
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Because if they don't you'll need to modify the spkrs to do so with a DUAL pickup plate. Plus you'll need to splt the crossovers so the woofer only gets up to a set point on the 1st wire, then the Mid's and tweeters pick up from there or with a slight overlap.

The other option is to use the 800c with bass bin's and the eico's with separate Mid/high cab's.

EDIT: I looked thru all my Favorites and found a page on the East Coast Speakers. http://www.classicspeakerpages.net There is a Jumper on the AR3A. Leads should be Marked 1-2-T 1 is the NEGATIVE. 2 is the (+) for the Woofer, and T is the (+) POS for the MID/TWEETER.

See this link. http://www.classicspeakerpages.net/...ing_the_ar-3a/restoring_the_ar-3a_full_pd.pdf

To Bi Amp, Connect the 800C leads to the 1 & 2 LEADS, making sure the jumper is disconnected between 2 and T. Then Connect the EICO's to 1(-) and T (+).

You are now Biamp'ed.
 
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Sorry guys, I should have been more precise in my request and given more info.

Yes, as Larry pointed out, the AR3a's have seperate terminals for the upper / lower ends. Sorry to send you off on a wild goose chase Larry.

It's the other end of the speaker wire I need help with

My question was more toward getting a "sync'ed" signal from the 800c to the Eico's, so that when I used the controls on the 800c, the Eico's would follow suit.

I hope thats clear.

thanks

martin
 
Martin -- Probably the best way to do it, would be to tap a signal for the Eicos from the wiper of the volume control in your Fisher. This would cause the Eicos to react to all the Fisher's controls as surely as its internal power amps do. You could always pad down the Fisher's speaker outputs to drive the Eicos that way, but that really presents more problems than tapping the volume control would. You would just want to make sure that you keep the connecting leads as short as possible, to minimize any HF loss due to capacitance in the interconnect leads. The real way to do it, would be to use an additional tube on the Fisher to act as cathode follower outputs from the volume control's wiper, but short of that, short leads should suffice as well.

So connected, the Fisher and the Eico will be phase correct, but both will still be amplifying the full frequency spectrum, unless you also want to use an electronic crossover ahead of both power amplifier sections. The gain of the Eico amplifier is more than that of the Fisher's internal power amplifier, so you will need to use the Eico's level controls to bring the level in line with that of the Fisher's.

As I understand it, you will still be using the passive crossovers in your speakers to channel the appropriate frequency spectrums to the correct drivers. The problem with the approach I understand you to be using, is that there will be effectively no load on the output of the Eicos at low frequencies -- yet they will still be producing power at those frequencies. This can be averted by placing a load resistor across the Eicos, but then it is stealing power at all frequencies.

The real way to bi-amp is to use an electronic crossover ahead of the power amplifiers, and then connect the appropriate drivers directly to the appropriate amplifiers, which eliminates the problem mentioned above, since the amplifiers will always be loaded for the frequencies they are amplifying. Still, it will no doubt be an interesting experiment. If you do it, let us know how it turns out.

Good luck with your project!

Dave
 
Just a thought...

I wonder if you couldn't remove the reverb jumpers and tap into a electronic x-over, then feed either the highs or lows back to the Fisher, the other to the Eicos. That tap was origanally intended for the space expander I think
 
Not a bad idea Perch -- except those jacks appear before the volume control of the Fisher, so it would not control the volume of the Eico as well. I'd have to look at the circuit again, but if the reverb output is driven by a designated cathode follower stage, then these could maybe be reconfigured to drive an external electronic x-over from the wiper of the Fisher's volume control -- through the reverb out jacks. Then, the input of the Fisher's power amps could be connected to the reverb input jacks (the old reverb jack wiring would just be hard wired in place as though no reverb were connected). With no external biamping equipment in use, the same jumpers in the reverb jacks would need to be in place to allow for normal operation, but with them removed, it would be perfectly situated then for a true bi or tri amp configuration.

Dave
 
Ya know Dave, I meant to look at the schematic before posting and got distracted.

I guess I kind of assumed it was like my Sansui integrateds with the pre-out and pre-in jacks. However what you proposed seems like a very worth while mod. At times I like to run bi-amped and this would allow a lot of added flexability. I will keep this in mind when I get around to my 500C
 
dcgillespie said:
So connected, the Fisher and the Eico will be phase correct, but both will still be amplifying the full frequency spectrum, unless you also want to use an electronic crossover ahead of both power amplifier sections.

Dave
Click to expand...

On the phase issue, why do tweeters (esp. horn tweeters), sometimes sound better out of phase? I can only come up with Klipsch at the moment, but I know some other companies also do this. From what I've read, when Paul was asked why he did it on certain models, he said simply because it sounded better to him and his team.:dunno: When I was tri-amping horns a couple years back, I used a Berhinger active crossover up front and 4 tube amps, (two monos and two stereo). IIRC a ST70 on bottom, ST35 for mids, and 2A3s for 10k and up. Seems like I paid around 125 for it off CL and it even had a horn compensation feature that did in fact make the horns sound better to me. It was a good system, but it seemed that each person that heard it, liked a complete different setup on the active crossover. I'm definitely in the cross it over before the amps group, as you then are asking less of the amp.
 
I read some where that Bi wiring (not to be confused with Bi amping) was ineffective.
can't remeber where maybe Roger Russell not sure .
 
Crossovers are lead/lag networks consisting of inductors and capacitors, as well as resistors, which are phase neutral unless they have inductive properties. I can't recall if it's the inductor that leads or the inductor that lags phase-wise. Caps would be the opposite.
What happens is that the crossover to the tweeter often modifies the phase due to the lead/lag that the phase is greater than 90 degrees out. Therefore when you reverse the phase from the HF output of the crossover to the tweeter, it's actually closer to the phase of the woofer.
Many three ways reverse the phase of the middle driver.
 
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Wow guys!
A lot of great input. I was certain it would take a mod of some sort or another.
I even considered just splitting the signal at the source. Of course I would lose the ability to sync the 800c and Eicos together, having to adjust the gains seperately and leaving it as such till the listening session was finished.
But at least it may give me an idea of what the AR3a's might sound like before I commit to a more perminant mod....yes / no?

I just finished a restore / presentation for a customer, so I'm kinda tired.
Most of it was cosmetic. Reskinned and repainted a pair of Seeburg Discotheque DDS1's, a repaint / polish on a Grommes PG-24 and a piano black plinth for an Empire TT. Everything in silver and black. He was quite happy...I'm glad it's done. Big job.

Sorry for rambling.

Anyway, thanks for all the input....I'll look at it closer in the morning when my heads a little clearer.

martin
 
Martin -- Probably the best way to do it, would be to tap a signal for the Eicos from the wiper of the volume control in your Fisher. This would cause the Eicos to react to all the Fisher's controls as surely as its internal power amps do.
Click to expand...

I've actually done this before on DYI project, an Aksa TLP preamp. I needed a sub "out" for powered sub. That required a pair (right and left channel) RCA's.

Whether or not to use a pair of existing RCA's, like "tape monitor, or a pair of RCA's off the chassis is the question. An 800c with a "tail":scratch2:

martin

DSCF0009.jpg
 
You will want output that goes through the volume pot then, correct?
You have two pairs of speaker outputs.
None of the input RCAs are volume knob sensitive and full bandwidth.
 
Don,
Again, me not giving enough info...sorry.
Yes, two pair of leads coming off the 800c's volume wiper and either wiring them to an external board with 2 RCA's off chassis (a tail). Or disconnecting a pair of existing on chassis RCA's and use those instead.
Am I on the right track?

martin
 
I can't see how you'd really gain anything going through the preamp and all of the 800-C before going out to the other amp. If you got an active crossover, that'd be another thing.
The trick here is that I believe you want a preamp to go to the tweeters so you have gain control. That's the snag. If you had an attenuator on the amp for the the highs, this would be easy, right?
I'd still try bi-wiring first.
 
I swear....I must be as dense as the day is long.
I really neglected to see the big picture here and specifically, the need for a crossover.
I can tell that take need to take a better look at what you guys have offered up and put aside my "good ideas".

thanks
martin
 
martin,
I guess I am the one that threw the x-over into the mix. The reason being is because that is the set-up I am used to, where the speaker does not have biamping capability built in. For hat your doing it most likely is not required but does allow a lot of teaking as far as x-over points and slopes and such. sorry to cloud the issue
 
Okay guys...
I appologize...I've been looking at this whole idea from a very limited perspective, meaning my narrow scope on biamping
After spending some time in the Speakers forum and reading a thread on biamping...I discovered I didn't know squat about bi-amping. Quite ignorant as a matter of fact.

http://audiokarma.org/forums/showthread.php?t=25231&highlight=biamp?

I suppose I should have studied a bit before starting this thread. I just thought it was a way to provide more power to power hungry speakers. Obviously it's that and much, much more. I had no idea.

A lot of what was posted earlier, is clearer to me now.

So, wanting to use a receiver and a pair of monoblocks, while, certainly possible, does seem to have it's limitations.

The way I see this happening as first proposed would be...
source into 800c.

2 pair of leads (+/- & R/L) off the volume wipers, terminating in a set of RCA's, one for each of the Eico's.

But from what I understand, the draw back here and the need for xovers before amplification is to limit each pair of amps to the frequencies of the drivers, thus making them (the amps) more efficeint, and I suppose the drivers more "tweekable".

Correct?

Just trying to learn here guys.


Thanks for the effort gentlemen.

martin

Don, even though bi wiring appears to be getting a bad rap around here, it certainly would be an easy try. I'm bound to give it a go sooner or later. thanks
 
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