Issue matching pre amp and Dax

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Issue matching pre amp and Dax

Postby DarthDiva on Wed May 17, 2017 10:11 am

After many years of being shut down I am reviving my system . I'd like to keep my 4 mono Lumley amps because they did a wonderful job driving my Divas through the original DAX . I had been using a custom built pre amp by the guys who started Sonic Frontiers .
I'm thinking of getting a Coincident Statement Phone with line stage instead . But I fear an impedance mismatch . The Coincident outputs 250k ohms and the DAX input is 80k . I've heard that the mismatch could roll off the high and low frequencies as volume is turned up . Perhaps not a happy match ? I'd very much appreciate comments and direction
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Re: Issue matching pre amp and Dax

Postby apogee_admin on Tue May 23, 2017 11:06 am

Think you misread the spec says output impedance is 250ohms, so you are ok.

I probably shouldn't say this, but I have tested the DAX against upgraded crossovers and found it very bland and lifeless sounding in comparison.
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Re: Issue matching pre amp and Dax

Postby DIVA_Paris on Fri Jun 09, 2017 10:20 am

And what about upgrading the Dax in order to keep a biamp configuration?
Or maybe a better active crossover exists?

Thank you for any advice

BTW I recently mesured the frequency respons of my divas with a microphone.
There is a continuous drop above 12 kHz. Is it due to the Med/treb filter?
Also a drop around 50hz on the bass
The Dax is working ok up to 20 kHz, so it is not a problem coming from DAX or the preamp
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Re: Issue matching pre amp and Dax

Postby Zardoz on Fri Jun 09, 2017 1:30 pm

Certainly upgrading the DAX would help it, but I don't have any idea if it would be economical or not. If you are using 4 identical amps, you can still biamp with the passive cross over. John can tell you better about that, but that is my understanding of biamping.
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not screaming in terror like his passengers..."
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Re: Issue matching pre amp and Dax

Postby DarthDiva on Tue Jun 20, 2017 2:01 pm

Thanks so much for the reply.

So, I should be thinking of addressing the DAX / cross over upgrade issue. Which path is the best, upgrade the DAX or avoid that entirely and replace the cross overs all together?

In either case, who might be the right person to do the DAX upgrade or the crossover upgrade?
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Re: Issue matching pre amp and Dax

Postby DIVA_Paris on Wed Jun 21, 2017 12:29 pm

One issue with Dax is the remaining medium /treble passive filter . The medium filter is only a an inductance and everybody agree on the value 0.055mH. But what about the tweeter filter values ?
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Re: Issue matching pre amp and Dax

Postby DarthDiva on Mon Mar 05, 2018 9:52 pm

Thanks to all for your kind replies. Luck was with me and after 15 years of down time, the Divas are up and running. No bass buzz, no foam rot. One midrange ribbon stretched and waves in the wind a bit. Seems to sound ok but perhaps needs replacing.

They still sound amazing. Those 4 mono Lumley amps were and are a match made in heaven for these Divas.

But time has passed and I understand newer passive crossovers may be better than the DAX. There is a guy in Quebec that offers an upgrade. I wonder if anyone has done the upgrade? Here is the link.
http://www.audiodoctor007.com/am%C3%A9l ... apogee_dax

If I go to the new passive route, what is the preferred source for that?

And I wonder if anyone has tried forgoing passive crossover all together and going direct through a dsp/equalizer?

I would love to have a chance to hear what Graz has done . Don't know if any of his work has made it to the Toronto area.
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Re: Issue matching pre amp and Dax

Postby Zardoz on Tue Mar 06, 2018 1:56 pm

I rebuilt my Xover myself and just used higher quality caps and inductors (huge improvement), but I am pretty sure the two Apogee guys in the USA offer that service. While you are at it, you ought to consider having them reribboned as well. The new ribbons make a big difference on their own.
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Re: Issue matching pre amp and Dax

Postby DarthDiva on Tue Mar 13, 2018 12:58 pm

Thanks for the response ;) I’ve reached out to one of the rebuilders but no reply yet. I’m also looking into direct connect through an active DSP and equalizer from DEQX or DBX.
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