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Quicksilver tubes on the midrange panels/ribbons - MGIIIa's

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Posted on April 25, 2015 at 08:46:14
ejhoove
Audiophile

Posts: 102
Location: Maryland
Joined: December 10, 2005
 I have heavily modified MGIIIa's (Maple Frames and Bracing)which are triamped using Acurus A200 amps. After experimenting with several tube amps for the Midrange and treble panels, I inserted a pair of Quicksilver M60 mono blocks (60 watts each)on the midrange panels and am very happy with the results. Anyone with suggestions for the Ribbons? I am going to insert a pair of Quicksilver Mini Mono blocks (30 watts each) on the ribbons, but have not been able to get the volume/drive out of them that the Acurus A200 provides. They do have 2 ohm taps which is why I bought them originally.
Regards,
Jim

 

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RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's, posted on April 26, 2015 at 09:57:42
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 Were you talking about triamping with the minis on the ribbon? or biamping with them?

I don't think the mini QS is really capable of driving the mid/treble on the MGIIIa they are just not sensitive enough. But if you are OK with limited output then it is just a matter of adjusting the A200 down at the electronic XO or sing the XO1 if you are passive biamping.

 

RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's, posted on April 26, 2015 at 10:14:23
ejhoove
Audiophile

Posts: 102
Location: Maryland
Joined: December 10, 2005
 Tri-amping. I have not been able to get the amount of volume out of the riboons with the Mini monos (30 wats each) and will continue to push them with a Acurus A200.
Regards,
Jim

 

RE: "I have not been able to get the amount of volume out of the riboons with the Mini monos (30w each)" ..., posted on April 26, 2015 at 16:05:21
andyr
Manufacturer

Posts: 12548
Location: Melbourne
Joined: September 2, 2000
 Then why not use the 60w Quicksilvers?

BTW, I have been using 25w ss amps on my ribbons for the last 12 years (3-way active system) and have had no issues. 25w into 8 ohms - about 40w into 4 ohms ... and 50w into 3 ohms.


Regards,

Andy

 

RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's, posted on April 27, 2015 at 08:34:15
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 OK, I don't know why I was unclear on your setup, it was obviously stated in clear terms.

You would have a problem even with a 2ohm tap as the amp will not produce as much output at that load and may have a FR droop there, unless the amp is designed with bigger output trannies, which I don't think it is. Having a 2ohm tap does not guarantee the ability of the amp to deliver its full power to the load. Can you use KT120 tubes? They produce a more present top end and more current at low loads..
Another thing you can try is to add a 1-1.5 ohm resistor to the ribbon impedance to ease the load and try it with both the 2 ohm and the 4 ohm taps. I had to do that with my Dyna III's.

 

RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's, posted on April 27, 2015 at 09:12:40
Davey
 I don't think your issue is power related. Those two amplifiers (Quicksilver/Acurus) appear to have a large difference in voltage gain. That's why you're not getting the necessary volume with the Quicksilver amps.

As Andy noted, 25w amps should be sufficient for ribbon-only usage.

Just to confirm, I would connect onto the 8 ohm taps of your Quicksilver amplifiers.

Voltage gain issues have fooled folks into thinking they have power issues for many years. Your experience is not unusual.

Cheers,

Dave.

 

RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's, posted on April 27, 2015 at 10:29:40
ejhoove
Audiophile

Posts: 102
Location: Maryland
Joined: December 10, 2005
 Thanks for your thoughts. Are you talking input voltage? I can increase the db gain from my crossover, but have no idea how much. is there a formula for impeadance difference? The input impedances are different - 100k for the Quicksilvers, and 20K for the Acurus. The QuickSilver's seem fine on the Midrange panels, but seem very week on the Ribbons. Is it safe to run a 2 ohm load into a 8 ohm output on a tube amp? I always thought this was a huge no-no.
Regards,
Jim

 

RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's, posted on April 27, 2015 at 10:33:30
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 Considering the XOs he has the relative output and absolute voltage available should allow for compensation for a low gain tweeter amp.

That is unless he bought the mono horn amp which has deliberately reduced gain by 18 db. But that one does not spec a 2ohm tap

Mini Specifications
Power Output 25 watts into 2, 4 or 8 ohms
Power Bandwidth 13 Hz to 50 KHz
Peak Power 50 watts
Input Sensitivity 1 volt
Input Impedance 100 Kohms

88 mono Specifications
Power Output 80 watts into 4 or 8 ohms from 20Hz to 20 KHz
Power Bandwidth 13 Hz to 80 KHz
Input Sensitivity 1 volt
Input impedance 100 K ohms
Damping Factor 15
IM Distortion 1% or less at 80 watts

Mono Horn amp Specifications
Power Output 25 watts into 4 or 8 ohms
Power Bandwidth 15 Hz to 100 KHz
Peak Power 50 watts
Damping Factor 20
Input Sensitivity 6 volts
Input Impedance 100 Kohms

 

RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's, posted on April 27, 2015 at 10:54:50
Davey
 Computing the voltage gain gets a little tricky sometimes because of confused manufacturers specifications, but in this case 1.1VRMS yielding 200wpc/8ohm (Acurus) results in voltage gain of 31db, and 1.0VRMS yielding 25wpc/8ohm (Quicksilver) results in a voltage gain of 23db. So, theoretically, you'd need to up your voltage drive to the Quicksilver amplifier by 8db to provide the same ribbon output level as when using the Acurus. Make sense?

The difference in input resistance of these amplifiers is irrelevant in this case since you're driving with an active crossover.

Attaching to the 8 ohm tap simply couples across more of the output transformer secondary and provides an effective increase in voltage gain. You don't have a preferable impedance match, but this is just a test and you're not going to damage anything.

Cheers,

Dave.

 

RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's, posted on April 27, 2015 at 14:00:26
ejhoove
Audiophile

Posts: 102
Location: Maryland
Joined: December 10, 2005
 It is the mini mono with 2 ohm taps. The output impedance of the Behringer analog outputs are 160 Ohms.
Thanks,
Jim

 

RE: Quicksilver tubes on the midrange panels/ribbons - MGIIIa's, posted on April 27, 2015 at 18:21:34
Davey
 The output impedance of the Behringer and the input impedance of the amps are irrelevant.
These kind of relative voltage gain differences are one of the many issues active crossovers have the ability to solve. If using the Quicksilver amp, simply raise the output level on the tweeter outputs of your Behringer to compensate. If you can't get it high enough, lower the level of the other outputs.

Dave.

 

Did it work?, posted on April 30, 2015 at 16:09:24
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 Have you managed to raise the QS mini tweeter amp's signal at the Behringer XO tweeter output to a high enough level to match the rest of the speaker as Davey suggested?

 

RE: Did it work?, posted on April 30, 2015 at 16:45:14
ejhoove
Audiophile

Posts: 102
Location: Maryland
Joined: December 10, 2005
 The Mini's will be added in the next day or so. Work keeps interfering! :^(

Regards,
Jim

 

RE: Did it work?, posted on May 1, 2015 at 02:26:39
ejhoove
Audiophile

Posts: 102
Location: Maryland
Joined: December 10, 2005
 The Mini's will be added in the next day or so. Work keeps interfering! :^(

Regards,
Jim

 

RE: Did it work?, posted on May 2, 2015 at 03:43:18
ejhoove
Audiophile

Posts: 102
Location: Maryland
Joined: December 10, 2005



First - Sorry for the double post!

Well it will be a good day! The M60's are driving the Midrange panels, and the Mini's are driving the Riboons. Very fluid and smooth with very good drive and attack while showing no signs of glare or bloat. So far I now understand why many run tubes on their Maggies. I will take today to dial them in level wise, then try and tidy up the wiring tomorrow after church. I'm running EL34 tubes in both amps - JJ Blue Bottles in the M60's and Svetlana's in the Minis.
I'm only using 2 of the 3 A200s, 1 for the subs, and one for the Bass Panels. When I get some muscle to help I'll remove the spare A200 from the stack. I ran the system at a pretty high volume for 2 CD's and the only thing that was more than warm to the touch were the tubes which I did not check. :^)

Regards,
Jim

 

RE: Did it work?, posted on May 2, 2015 at 15:13:38
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 What is your subwoofer XO freq?

Did you get slap with the speakers run full range?

 

RE: Did it work?, posted on May 2, 2015 at 19:38:13
ejhoove
Audiophile

Posts: 102
Location: Maryland
Joined: December 10, 2005
 My subwoofers cross over at 42Hz using a NHT X1 crossover. Even running full range they have never slapped.
Regards,
Jim

 

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