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CECAA850, Yes. But that's exactly what I can see myself doing. Leo

Hi Bruce, I pretty much got things sounding good enough to enjoy music and that's what I've been doing with the Chorus and RF7 systems. I guess with that enjoyment I continued to expect more as I explored different types of music. Choral music (comparing versions of Morton Lauridsen works by Polyphony and Los Angeles Master Chorale to be exact) exposed the diaphram resonance and distortion issue. That fixed, I'm bach to enjoying the music more than ever. As far as the two Lauridsen recordings, it turns out they're both exceptional recordings of exceptional material .. many of the same works .. one with a small chorus (often 1 voice per part) and one with a very large but very coherent chorus. They're tough on a system, but very beautiful when things work. Much thanks to this Forum, without which I would never have achieved this level of audio performance. Good to hear from you. Leo

Thanks DavidF .. that seems to address the issue .. as tight as it has to be and balanced. I may use a torque driver with this method to try to avoid getting the coil out of true. I'm just beginning to realize how many ways there are to make perfectly good equipment sound less than optimal. Leo

I don't think the screws/nuts are backing out. I think the diaphram holder and spacing material are compressing (creeping) causing the relax in compression force, or in my Chorus-II case, possibly I didn't apply sufficient force at installation. But, whatever is the problem, I would like to know how tight to make them in the first place, before applying something to prevent loosening. Thanks, Leo

I've changed the mid and tweeter diaphragms in my Chorus-IIs a couple of times. I purchased them used and they were damaged and then later I upgraded to very nice parts from Bob Crites. Over time I noticed a resonance somewhere in the low KHz range. Eventually it occurred to me the horn screws clamping the diaphragms might be loose. It turns out although they weren't exactly loose they weren't real tight for such beefy screws so I cranked them down. Resonance gone and way better sound and imaging. Today I checked tweeter nuts .. not real tight either so I tightened them. Then I checked the horns on my RF7s. Those assemblies have lock washers which were no longer completely crushed (I assume they should be). I tightened them to flatten the lock washers and then some. That "I assume they should be" is what I am looking for. Does anyone know how tight these screws/nuts should be? Are there torque specifications? All I know now is they should be tight enough to keep the diaphram holder from moving and not so tight they strip or crush something. But then, I don't really know what that is. Thanks, Leo

The Hypex modules used in the Channel Islands amps are pwm, but derived from very high gain binary feedback instead of the traditional ramp/comparator approach. My take on it is that the advantage of feedback in limiting distortion is achieved, but feedback noise, which usually trashes the low power purity of a feedback amp, is shifted to the mid to high hundreds of KHz. What's left in the audio band is super-clean. I think the concept is brilliant and the sound of the modules, for me, is the proof. There are a few white papers on the Hypex.nv website. Look at the distortion: Under 0.03% from 60 or so Watts down to something like 3mW. That's about 5 orders of magnitude of power under.03% distortion. I don't know of another approach that can do that. By focusing on keeping low power distortion low rather than extending power to the KW range,the Hypex approach is optimized for efficient speakers like those made by Klipsch Leo

Can you audit the Channel Islands D•100B Monoblocks? Clean low power that I think is better than SET and plenty of high power that is just as clean. Leo

I have to agree with the folks suggesting that an inverter may be noisier, in more ways that will degrade your audio, than what you get from the power company (modified by every device that's using that power plus a lightning strike or two). I 've used isolation transformers in industrial applications and have considered it for my oudio system (especially since I'm beginning to suspect that power surges have killed two power transfsormers) Sola makes some real nice power conditioning stuff for industrial applications, but they might make the audiophile stuff look cheap. Check it out. Leo

I think, for several reasons using the 4 Ohm tap would be better: It essentially provides better control, by the amp, over the speaker. Could be the reason highs sound rolled of is that the highs are not really more rolled off, just less distorted. Leo

Hi Dean, Thanks. I've been having a good time listening these days. Leo

I've never had success with biamping. There are some technical issues that might be part of what didn't work. For frequencies outside the pass regions (highs into the woofers crossover and lows into the horn crossover) the amp sees an open circuit. That might not be real good for some amps. In the crossover region amps see higher than normal impedances which would cause a high output impedance amp (the tube one especially) to accentuate that region. There may be phase of delay differences between the amps further confusing the issue. Also, I doubt a whole lot of effort was made by any speaker designer to optimize this mode of operation because the amp drive is so unpredictable. I think it is mostly a marketing feature. Bi-wiring might be a better use of the ability to separate the high and low sections of the crossover, and may be more of what the crossover designer had in mind. But again, the crossover designer wasn't using your cables which in a biwire config are now part of each crossover. So, since for me it didn't seem to improve anything I gave up on splitting the crossover and just use a pretty hefty set of wires from the amp. Leo

Higher power is not used and with pulse modulation amps using the same technology, low noise generally occupies about the same dynamic range. So the range of low distortion will extend to lower minimum powers with the lower power amp. The low distortion at lowest power possible is what makes an amp sound natural and clean. High end distortion is generally clipping, and I don't think that is an issue with either the D-100 or D-200. S, I suggest optimizing for low distortion at low power which points to the lower power amp. Leo

Yes, I would think the Channel island (lowest power available) would be a good bet. Maybe a dealer would make one available with a return policy, or a demo version could be borrowed. Leo

Sorry I missed this earlier, Until a few months ago my favorite amp for the RF-7s was a pair of 2A3 SETs .. very natural and detailed sound. I used that for years and was very happy with it. I have since switched to a custom implementation of one of the original, lowest power Hypex modules which I am running at power for 60W / channel: optimized for lowest distortion at low power. This is way cleaner than the SET .. I can hear much more low level detail (for example: acoustic room reverb including acoustic reverb in studio recordings that don't use electronic reverb). Sound, due I guess to the very low distortion at al levels, is even more natural sounding than the SETs. Massed strings are very nice. High power is obviously much better and remains clean. I have also found a nice 26Watt class A, but some mods are required to remove a small DC offset so that one remains on the bench. I continue to be impressed with the fantastic sound (really lack of "sound" .. fantastic capabilities) of the RF-7. Leo

It would be interesting to compare SET with the Scott. The Scott has a relatively low impedance output due to the use of feedback, so you will get a good frequency response (not "shouty"). The lack of feedback traditionally in SET designs is one reason for SET's very high impedance output. However, feedback can have its own sonic signature (possible distortion of sibilances among other things). I encourage you to try a pair of SET amps if you can. You can listen through the frequency response variations and hear a clarity that comes with a no feedback design. Leo

You might consider trying SET rather than buying. SET amps tend to be no feedback designs with high impedance outputs. The Forte (and Chorus) speakers (I've used both with SET amps) have impedance (or efficiency) peaks in the midrange and amps with high impedance outputs will accentuate that region resulting in what is often referred to as a "shouting" quality to the sound. I have 2 tube no-feedback amps and found both unuseable with the Forte or Chorus designs (I've had the -II versions of both). Both of those tube amps work well with my RF-7s. I recommend a ss amp with low distortion at low power for the Forte and Chorus. I am happy with a Crown D-45 which will cost you less than half of your $2K budget. It is designed to be used with high efficiency horn loaded loudspeakers. I'm not saying don't try SET with the Forte. The clean sound of SET is attractive, but the coloration eventually got to me. Leo

I had one and the rumble was very bad. I physically separated the motor from the base and provided an isolated sprung mount for it. Then the rumble wasn't bad. I also replaced the tone arm. Then it was stolen. I wouldn't do it again. Leo

Hello Marty, Nice job on the amp. Interesting design too. Use of the ECC83 in a no feedback design with a cathode follower driver is a differen approach (at least for what I can remember) . Makes me wonder if my tube amps are a bit under driven. A couple of thoughts Hum will be tough without a ground plane right next to the wires. Some re-dressing of the wires around the ECC83, isolating signal from everything else might help. If your 3rd wire line power safety Gnd connects to the amp signal and power gnd you might cut that and insert a big (10MegOhm or so) bleeder resistor between safety and signal gnds and let the amp get its Gnd from the signal source. Keep the safety Gnd connected to the metal plate (for safety). On the sound: maybe try disconnecting the 100uF 6L6 cathode caps (disconnect the cathode side not Gnd side). You can always reconnect them. Also, a 6922 instead of the ECC83 might help. Check the pins: they might not all be the same. Can't think of anything else. Looks like a lot of fun and hours of tinkering. Enjoy!! Leo

I have used a pair of 2A3 SET amps to drive my RF-7s until I made the Hypex amps. I prefered the RF-7s with the 2A3s over the Chorus-IIs because the high impedance upper midrange of the three ways caused more accentuation of that region than I liked. The Forte-II might be a nice compromise if you can get a low impedance output from your SET amp .. the Forte is nice. In any event, I don't know what speaker besides Klipsch that I would use with a SET amp.

I second, or third the cautions about using Chorus II with a high output impedance amp (no feedback amps ar generally high impedance). The problem is not power, it's impedance. The Chorus has very high impedance in the midrange and a high impedance amp will play that range louder, making it sound thin. Neither of my tube amps works with the Chorus II. I use the Tripath, Hypex, or Crown (see below) with my Chorus IIs and love them. Played a little Mighty Sam McClain through the Chorus II / Crown combo this AM .. WOW. Leo

I agree with Marvel. Leo

I didn't know about the belt. I'll look into the Revolution. Thanks for the tip. Leo

I have the Basis 1400 (It replaced a Dual). The current cartrige is a Benz high output ("Blue"). The arm is a Graham 1.5. I've had the table for a couple of years and have yet to have even the slightest complaint. I don't even know it's there: it doesn't have any sonic signature I can detect. It does have only soft rubber bumpers on the bottom of the feet for suspension. I have it mounted in a wall rack because my old wooden floors would transmit too much motion and vibration. I use it several times / week. I paid $1800 for the table and arm two or three years ago. Leo

Max, Thanks for the response. I tend to use such low power I forget a lot of people use a lot more. Certainly if you need the power and it's not there the amp wouldn't work. Leo

Hello Max, Did you use a preamp with your Hypex amp? If so, it may have contributed to your disappointment. I have never seen preamp distortion as low as that of the Hypex modules, and if you were using a pre. that's probably what you were hearing, not the Hypex. The hypex input impedance is 100K Ohms so even if your phono pre is tube, a high resistance potentiometer will serve as a lower distortion amplitude controller than an active preamp. Also, I've now tried the Hypex amps with the Chorus-IIs and the result is just as spectacular as it was with the RF-7s. Leo