@georgehifi - The damping factor on the RM-10 is 12.5. You can read more about it here: http://www.ramlabs-musicreference.com/rm10mk2.htmlYou might also be interested in the design philosophy, particularly how much power Roger gets out of the EL-84 versus what is typically the norm we see from other designs. http://www.ramlabs-musicreference.com/rm10design.htmlI have owned my RM-10 for about 12 years now. It has always been one of my favorites. Several push pull amps have come and gone in my system (VAC and Cary being a couple of the bigger names) but this one has always survived. It is a lot of amp for the money. It is also a perfect match for the Lightspeed, as Paul (Pubul57) and I quickly found out. |
I was following your thread and saw your comment on
electronic crossovers. I
agree with you on the advantage an electronic crossover has H\however I am having a hard time finding a crossover that
sounds as good as the passive on my system. I have tried a crown vfx-2a,
audio control, ace, an old ESS from my super quads, and an Audio
Research tubed unit. All of them work but I hear a lot more detail
passive. The closest so far has been the AR. Can you recommend a good crossover?
What do you use?
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@partroysound---ESS Super Quads! I have the Transtatics, which has the same KEF B139 woofers in transmissionline enclosures and RTR ESL tweeters as does the Super Quad. For the Super Quad, ESS used the Quad ESL in place of the KEF B110 5" midrange driver used in the Transtatic. I have a real nice little active electronic crossover, the First Watt B4, designed and made by Nelson Pass of course. It has unfortunately been recently discontinued (Nelson sold them all, and decided to not do another run), but had a list price of $1500. Give him a ring, he may know of someone who has one to sell. Nelson built it with all discrete components---no Opamps, no IC's. It provides 1st-2nd-3rd-4th order filters (6-12-18-24dB/octave), in 25Hz increments from 25Hz to 3200Hz. He has a much more expensive model available in his Pass line-up. REAL nice, but too much moola for me. |
@bdp24--- That sounds exactly what I am looking for and at a price I could handle. When you say give him a ring do you mean call Pass Labs?
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I have tried a crown vfx-2a,
audio control, ace, an old ESS from my super quads, and an Audio
Research tubed unit. All of them work but I hear a lot more detail
passive. We used the Marchand Tube crossover, which IMO is one of the best made, but had the same experience as you- more detail using the passive crossover in the loudspeaker. |
I use a Beveridge RM-3 designed by Roger Modjeski when he worked for Beveridge Audio. The RM-3 was a companion component to the RM-1 preamp and RM-2 power supply which fed the active Beveridge Model 2SW speakers (the speakers had built in OTL amps). The RM-3 has removable high and low pass boards so you can have 6, 12, 18, or 24 dB slopes along with your preferred cutoff frequency. Mine are 24 dB Linkwitz-Riley with 100 Hz cutoff. They also have attenuators for the high and low frequencies. I use mine with ESL speakers, either Quad or Acoustat. Neither has any loss of detail that I can hear. Roger has a couple newish old stock ones lying around the shop that need new homes so if you are interested you can email him at tubeaudiostore@ gmail.com.
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I have never heard ANY active xover (tube, S/S or even digital) sound better in the lower-mids/mids/highs, from >150hz up, into my ESL’s than the 18db passive xover it came with it.
(very very much like the difference in sound quality between active preamps v passive preamps).
But from <150hz down I use a 24db active analogue xover, it sounds better than the passive.
Cheers George
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@partroysound---Yeah, at Pass Labs. Or Reno Hi-Fi, First Watt and Pass Labs' primary retailer. atmasphere’s Marchand suggestion is worth looking into, though their x/o’s contain Opamps (if that bothers you) and are known to have occasional reliability problems. If Roger Modjeski’s (Music Reference) x/o is in your price range, I’d jump on it. Great, great tube design engineer. I may look into it as well, though I use a simple 1st order filter to roll off the bottom end of my loudspeakers, using a capacitor on the inputs of my power amp (Music Reference RM-200 Mk.2), the most transparent (and cheap!) way to do it, if 1st order (6dB/octave) works in your application. The value of the cap is determine by the input impedance of your amp and the corner frequency you desire. The formula for determining the cap value for your application is all over the web. |
Another person to contact about an active tube crossover would be Tom Tutay 1-850-244-3041 He does not have a web presence.
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@clio09 email sent..i have some ESL63 that might benefit.. |
...this might not prove a common story, but here goes. I have the NAD M2 one box dac/pre/power into a pair of sealed Salk Veracity monitors. The NAD has the ability to deliver 2, 4, 5, 6, 7 & 8 Ohms. The Salks are rated at 8 but, after reading that there is a "spread" of deliverance, I tried both the 6 & 7 Ohm position, and found a pleasant welcome increase in musical honesty, timbre in particular, with no apparent downside at 7. Communicating with Jim Salk, he agreed that 7 might be a greater sweet spot for the Veracitys. Just sharing. Life is good! Norm |
I was not previously aware of this ampifier or what they were up to. It appears from the Stereophile measurements that NAD is compensating for the interacion of the switching amps output filter by modifying its drive signal while still in the digital domain. Here are the measurements, to see what is going on here may take some time and thinking , it was not immediately obvious. If there are questions I will be happy to look further into it. https://www.stereophile.com/content/nad-m2-direct-digital-integrated-amplifier-measurements |
compensating for the interacion of the switching amps output filter by modifying its drive signal while still in the digital domain. I believe BelCanto maybe did something similar with their M600 monoblocks and modify the Hypex modules with filters in the front to aid the output filter in trying to rid the switching noise. These amps I didn’t mind listening to, but it was only when they were driving a benign nice flat impedance very expensive large ribbon tweeter, in a two way, crossed over quite low. 3.5k? Also if you have a look at the $50k!!! Mark Levinson #53 Class-D mono blocks they attacked it at the output and from the photo series’d up many output filters judging by the amount of air core chokes in each mono, but apparently they were a bit of a failure. https://www.stereophile.com/images/1212levin.side.jpghttps://www.stereophile.com/images/styles/600_wide/public/1212levin.promo_.jpgCheers George |
I found this interesting in the Levinson #53 review. Michael Fremer notes: The transistors switching the positive and negative voltage rails to the load in Levinson's "class-I" topology are each connected to the load via a large air-cored inductor and to the opposite voltage rail via a diode. Read more at https://www.stereophile.com/content/mark-levinson-no53-reference-monoblock-power-amplifier#FaZxXFFTa...
I am not sure how any of this applies to autotransformers, I will just say that neither the NAD or Levinson have any nor would likely benefit from one except for the following: One problem with switching amps is that the output filter is optimized for a particular resistive impedance. Unfortunately our speakers are neither resistive or constant so the fix is only nominal. I would love to see a swicthing amp's response to driving a 10uF capacitor which is typical of many electrostatic speakers. |
Since we are developing a class D maybe I can chip in.
The filter is there to reduce the amplitude of the switching component; IOW the switching frequency of the amplifier which is present at the output of the amp.
The switching frequency is never completely eliminated; what is still there is called 'the residual'. If the filter is doing its job, the residual will be a pure sine wave between about 1/2Volt to maybe 3 volts or so.
While the capacitance of an ESL will affect the residual, the amplifier will otherwise behave as a voltage source, even if it employs no loop feedback.
Class D amps, like all other amplifiers, have greater distortion into lower impedance loads. So an autoformer can help reduce distortion (while also decreasing output power) and it will attenuate the residual somewhat; a lot depends on the design of the autoformer as to how effective it might be in this regard.
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Since we are developing a class D maybe I can chip in.
The filter is there to reduce the amplitude of the switching component; IOW the switching frequency of the amplifier which is present at the output of the amp.
The switching frequency is never completely eliminated; what is still there is called 'the residual'. If the filter is doing its job, the residual will be a pure sine wave between about 1/2Volt to maybe 3 volts or so. Thats much switching residual would bother me and not pass CE approval. While the capacitance of an ESL will affect the residual, the amplifier will otherwise behave as a voltage source, even if it employs no loop feedback. Several uF will cause a large reduction of the residual. However the problem I am concerned about it the severe falloff in response due to the output filter. WIthout feedback I would think not a very good voltage source Class D amps, like all other amplifiers, have greater distortion into lower impedance loads. So an autoformer can help reduce distortion (while also decreasing output power) and it will attenuate the residual somewhat; a lot depends on the design of the autoformer as to how effective it might be in this regard.
I find class D amplifier are not like all other amplifiers and have special considerations which are obvious in published measurements. |
One problem with switching amps is that the output filter is optimized for a particular resistive impedance. Unfortunately our speakers are neither resistive or constant so the fix is only nominal.
This is why I found the Belcanto 600M's the first Class-D I could listen to for a length of time. Because the speaker as I said were a two way with large benign very flat 6 or 4 ohm ribbon tweeter that went down to around 3.5khz before crossing over the the mid/bass. Cheers George |
I have used this Hughes Performance RV22050 Autoformer to prolong the life of my RV appliances. There are so many things that I like about this 30 amp autoformer: It can withstand rapid changes in moisture and heat inside the RV. It can manage up to 10% voltage boost, which is very good for our appliances inside the RV. Specially, it has LED indicator lights for convenient monitoring.
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