erik2A3

Nice job! The 6SL7 is a really nice tube -- along with the 5687, one of my favorite input/drivers. The 6SL7 is also great with both sections paralleled and direct-coupled to the final stage -- thus getting rid of those pesky but often necessary coupling caps. Your chassis layout is particularly well-done, with the power supply physically well isolated. Granted the rectifier's job is, depending on one's viewpoint, perhaps a bit more plebeian when compared to the signal-handling valves in the front and final stages, and is usually quite less expensive -- particularly compared those large power triodes -- but, I don't know, maybe it would have been kind of fun to have the rectifier a notch or two more visible. That octal hole behind the PT is also a good place for a large chassis-mount single or multi-section electrolytic can. Keeping 60Hz alternating current as far away from the music as possible is always paramount, and you've done a great job in that respect. PS: Tubes can also function as a pilot light! Super-clean work - lucky new owner!

I miss VTV

If this doesn't work out, I have one I will give you for free - if you'll pay shipping!

Well said KT88. I can’t recall how often I’ve come across cases where blame was put...rather shallowly in my honest opinion...on a specific output (or input for that matter) device with complete disregard for the circuit in which it’s used.

Good! I get it. Audio adjectives can be interpreted many different ways... Accurate Fast Warm Sweet bright muddy ...the meaning of each often different depending on the person. What's 'warm' to one person might be too 'cool' or 'bright' for someone else.

So a paralleled 6N2 RC coupled to the output - I'm assuming. Great, have fun!

What does ‘warmest sounding’ mean?

That's what I did to my SE 6V6 Decware Mini Torii - replacing the small OEM output transformers with much larger OPTs with UL tap.

Nice! Is the SRPP driver part of your modification or the original design? CLC is definitely better if you have room! Very cool little amp! edit: And here we also have an example of elevated filaments off the voltage divider on the output of the PSU. Just curious (George!) It seems you've already achieved some great noise rejection, and wondering if you tried just grounding the filament supply center tap.

For what it's worth, it's not unheard of that some loudspeakers have some degree of midrange peak in their response. In fact, it can be a characteristic related more to an intentional design objective than one that's associated with an anomaly, a problem, or some other negative attribute. I can of course can only speak for myself and my own values and objectives in terms of what I like to hear, and I can say that I've tended to not gravitate toward speakers that possess an overly flat, dynamically restricted, or otherwise disconnected response. I suspect I would argue that the perception of a bump, peak, or mild sharpness in the midrange was one of the most attractive aspects of the sonic signature of Klipsch speakers; and was what, when I first heard them (a pair of Heresies), got me just really hooked. I had heard some extremely expensive loudspeaker systems that just left me sort of....well...kind of bored. For me, music has a kind of organic life or quality that, when reproduced truthfully and realistically (let me qualify - I should say what TO ME - is truthful and/or realistic) will most definitely have peaks and valleys (topography, if you will). Speakers that were designed specifically to navigate or travel such musical territory rather than fill in the voids of the valleys or flatten or chop off the sharp peaks and tops of the mountains, which is what Klipsch speakers do (again FOR ME), are what make listening to music an adventure that puts me on the edge my seat in anticipation of what's going to happen next! Another consideration here, though, is the recording itself. I find that the nature of Klipsch (as well as my full-range Lowther drivers -- and others like them) is one that lays bare the recording, whether of poor or very high quality - which, once again, and in and of itself, boils down to nothing more than personal preference. I guess what I'm struggling to say here, and I apologize for the way a go off on crazy tangents (I feel bad for my old students when I was teaching -- though they did seem to enjoy it for the most part), is that in trying to ameliorate, iron out, repair, fix, change, modify, etc., etc., etc., we can sometimes end up, as another forum member astutely observed recently (sorry, I can't remember who he or she was right now) taking a step backwards rather than ahead; and, in solving one perceived problem, create a host of others that may be worse than where we started. And I am most definitely speaking from experience! I have made so many audio mistakes and blunders over these past decades, but I also most definitely made every effort to learn from them. OP: I don't know if these Heresy IVs are your first pair of Klipsch, but, just possibly, perhaps leave them as they are for a bit. With some time, maybe that peakiness you mention will soften on its own the longer you have the speakers. Or not! It's of course totally your right and prerogative to change anything as you wish, and no-one else's to tell you not to! Regardless, you have a great pair of speakers!

Something much less expensive than a new DSP that (might) help and be simple to implement is a Zobel network. It is NOT truly a part of the crossover, although that's the location they are usually found. A Zobel is the last in line before the driver, and is connected across the + and - of the driver (essentially the voice coil). You do not have to solder into the crossover network. It can be temporarily installed across the terminals -- a resistor and capacitor are soldered in series (there are on-line calculators that are simple to use), and this series RC (resistor/capacitor) network is then connected in parallel with the driver (meaning the remaining free end of the cap and resistor). There is no high voltage present, but of course this would be done with the amplifier off. Only one solder connected needs to be made, but it would be very easy to use a simple, small AWG wire nut to connect one end of the cap to one end of the resistor. It might help in this case. Are schematics of the Heresy IV dividing networks released? I'm curious if there is already a zobel in place. Calculating the values of R and C is as simple as this: https://www.diyaudioandvideo.com/Calculator/ImpedanceEqualizationCircuit/

Rich_Guy, That is great to hear. I installed RF-7 horn lenses and drivers over the weekend, and there is definitely a more expansive and open sound - even without changes (yet) to the crossovers. I have the RF-7 network schematic, and it's pretty straightforward to build, likely using the same board as the OEM RF-5 crossovers. I ordered inductors, caps, and a couple of resistors this morning, so looking forward to finishing this modification! There is a series notch/resonant peak filter across the driver (in parallel with it), which may or may not fit on the stock crossover board. If not, I can install it on a small board inside the cabinet, and run leads to the driver from it. Thanks for sharing your thoughts in this great RF series speaker! I agree that it's not just a good, but really kind of an astounding cost/performance ratio. Even with the RF-7 compression driver it doesn't seem overly bright or forward to me. It's the kind of sound I like, but I can easily install an variable L-pad in order to attenuate as needed, if needed. I used to run a Heresy center channel with both our K-horns and La Scalas in the past, and the person who sold me the RF-5s had a seemingly new and right-out-of-the-box RC-7, as well as a great SW-12 sub, and I bought everything - RF-5s, the RC-7, and the sub for $500. Far and away the best sound I have EVER gotten for such a modest price....and the 5s actually do incredibly well on their own without the subwoofer. The scale and expanse of the sound from these things is just so far beyond their physical dimensions -- IMO. They amaze me!

I think this may be something of a shot in the dark, but I'm looking for a pair of the above networks to use with the larger compression drivers I've purchased for our RF-5s. I have the schematic, and they would be very simple to make -- even using the original boards and removing old values of C and L with new -- but it would be just easier to make the modification with already finished networks. I have enough magnet wire to wind my own chokes, but I swore to myself I would never do that again. Thanks! erik

Sure, good point. Even when I started building my own speakers and crossovers in the early 90s, I found I tended to prefer the HF response a couple of dBs or so higher than LF. That's one of the advantages, at least as far as my own experience, of having an variable L-Pad on the tweeter. Other well-known companies like JBL and Altec, just to mention two from a multitude, approved of them for the same reason. Otherwise, they wouldn't have put such a user-adjustable element into the equation. But you bet! I have the means to measure output levels and will definitely take your advice on that!

I found your thread yesterday, jjptkd, and it's good to hear or see, depending on how one's looking at it, that others have gotten great results from the change -- despite what others say to dampen the enjoyment or personally perceived improvement. That's just how it's been here sometimes, and I've been coming to this forum since about 2004 (at that time under my user name (which is my name) Erik Mandaville. So, excellent! Thanks for sharing. It's something that helps broaden the experience associated with this specific modification -- and in so doing helps others new to the RF-5s benefit. What I am considering (as of about 10 minutes ago when I thought about it) is removing the networks from the cup altogether, and connecting only the drivers to their respective binding posts (on the inside of the cabinets). I would then rebuild the crossovers externally in order to find the best balance in terms of capacitor type/brand (I've used the very reasonably priced Daytons in the past in been just fine with their performance). The woofer filter will remain as is, except for perhaps larger AWG for the .5mh choke on the woofer. The Zobel network would also stay the same. Using an external crossover frees up space on the back of the input cup, and there is flat area just above the binding posts that would accommodate a variable (rather than fixed) L-pad to balance the HF section to my own personal taste. We must keep in mind, of course, that ANY change -- such as suggesting to someone a different brand or type of capacitor -- is a deviation from Klipsch's already extremely competent engineering. The point is that we all have personal priorities, tastes, etc., regarding how we want our reproduced music to sound; and all are legitimate if the end result is one that doesn't compromise the electrical safety and working tolerances of the equipment being used. Years ago here, we would go to battle over the use of resistor-based L-pads (either fixed or variable) vs the autoformer (which Klipsch no longer uses) as a means of attenuating the bandpass driver in a 3-way Heritage system. Instead of the work required to desolder and resolder autoformer positions, I found it far easier, more efficient, and ultimately more accurate in terms of achieving finer steps of attenuation, to use a variable L-pad. It does not change the reflected impedance the way autoformer steps do, and so the value of the input-to-network capacitor does not have to be changed in order to maintain the same crossover frequency. There were always arguments about how resistors waste amplifier output as heat, but I just never had a problem with that in terms of what I actually heard -- and I had been using extremely low power amplification with our La Scalas and K-horns. Moreover, I actually found the a-former to sound sort of veiled or lossy. If others can hear distinct differences between capacitor brands and dielectrics, I can hear the difference between a resistor and a multi-tapped choke (aka: autoformer)! I applaud and support your experimentation, and it helps me think that I may be on a similarly good track with our new/old RF-5s! Looking forward to the arrival of the new compression drivers!

Ok, great

Approximately 45 minutes ago.

A couple of days ago I mentioned our recent acquisition of a pair of RF-5s. We know the reference series was designed with two pairs of binding posts: one for HF, the other LF. This of course makes it possible to bi-wire the speakers with your wire of choice for midrange and high, and, perhaps larger AWG for the woofers - both of which connected to either a stereo amp, or single channel monaural amplifier. The owner's manual also encourages bi-wiring over a single run (with binding posts strapped). Since I have the means to do this with a number of matching solid state and tube amplifiers, instead of bi-wiring or simple bi-amping with a mono amplifier, I decided to vertically bi-amp each channel with a pair of stereo transistor power amplifiers (Hafler DH-120s). Note this is NOT bridging the amps (which can be done with them) for mono operation, but rather using them in stereo, with one channel driving the HF section of the RF-5s, and the other channel (of the same amp) connected to the Low. For the signal input, a Y jack is connected to each channel of the preamp, and a dedicated interconnect for the L and R inputs on the amp is connected to the opposite end of the Y. For those of you familiar with Vandersteen loudspeakers, this is an approach that is also strongly recommended beyond bi-wiring and/or mono bi-amping. And the results here were immediately apparent to me over the use of either a single stereo amplifier or my mono block 300B or 2A3 amps. My dear wife is taking a nap after very early morning meetings for work, so volume is much lower, but I'm impressed by what I'm hearing in terms of improved frequency response and separation of instruments (really overall stronger three dimensional soundstage) even at these low levels. Amplifier pairings of hence greatly expanded, where it would be possible to use a lower power valve amp on the HF, and something stronger on the low end. I have also ordered a pair of RF-7 compression drivers to replace, or at least audition, the OEM HF drivers, and can make some small adjustments to crossovers (primarily driver impedance at crossover point) as needed -- which may or may not be audible. We'll see. Moreover, I can control output levels of my amps, and thus adjust the HF and LF crossover branches (really two separate networks) individually. I haven't had more fun with this in a long time....for lots of reasons...but it's so nice to be able to have this kind of flexibility with a pair of speakers that already sound very, very good!

Keep the original look! -- of course just my opinion, you should definitely do as you like! Very cool!! I'm wondering about the distortion you mentioned. with Heresies, you should be able to turn up the volume quite high without distorting. I wonder if you may be over-driving the input/driver stage (if you using a modern source, such as CDP). Or if it's simply clipping. If all is good at the volume/s you prefer, with a bit of headroom beyond that, sounds like it's doing fine. I make my own cables, although many on this forum have been very happy with products from here: http://www.bluejeanscable.com If you have long runs of IC, as one response mentioned above, the lower the capacitance, the better, and this company has well-priced low-capacitance cables available at your specific lengths. I agree that many companies go to great lengths to glorify their wire with descriptions of propriety geometries, perfect surface conductors, etc., etc., and dress them up in fancy jackets that do nothing but add to overall cost in the name of cosmetics. I'm sorry if I sound negative! I've become a bit more that way in recent decades.... Love your new amp -- it's amazing how rough (in a really neat way!) something can look and still sound amazing. Have fun!

Curious George, You are braver than I for sure! I'm well aware of the 211 requirements, and I think I'm probably just too much of a wimp to work with those. Half that voltage was bad enough when, I also must admit with shame, I was soldering in a plate load resistor, thinking I had unplugged and discharged filter caps. That's another important thing to remember! Even caps that have sat for a long time can, if there is no bleeder resistor on the output of the PSU, still have enough charge to give a super bad shock. Years ago I had an amp (another big OTL) sent to me to look at, and there was still a monster charge in the big reservoir caps after a few days shipping. I shorted them to ground (which actually isn't the best way to bleed off a charge -- that I also admit -- but I just didn't think there would be much of anything still in those things. POW!!!

Thanks for reading and contributing. I don't have experience with the 3s, and we are using the 5s exclusively for music (we've got a decent sound bar from that other company that, for the kind of movies we watch - definitely more dialogue oriented than special effects - fulfills that just fine). And for sure, they do well without a sub. I've been using the Lowther full-range drivers up until now, and at about 105 dB/watt, they are obviously super efficient. There is just very little in the way of lower octave info. with them. I listen to tons of guitar, and the Lowthers seem to get the timbre and textures of that instrument, as well as the same of other strings and woodwinds, really well. They have an open and immediate quality that's unlike most other loudspeakers I've heard, but they are not even close to the RF-5s for everything else -- and I paid $300 for an essentially like-new pair! The PM5A drivers now in my back-loaded horns cost about $2,500 (that's just the raw drivers, no cabinets).

Langston, What a fascinating story, and thank you for sharing your professional experience in this thread! Totally true, watch out for plate voltages! I'm glad he was ok. It's happened to me too, and every single person I know who has spent any significant amount of time working on tube equipment. I will definitely look forward to listening to those sound files later today. Thanks so much for including them! erik

We owned both a pair of La Scalas and Heresy Is when the original RF series of floor standers was introduced. I loved the LS and Heresies because they were the only speakers to which I'd listened that truly approximated the sharp transient attacks and dynamics of live music. When the first RFs came out, I went to an audio store in Houston to ask if I could listen to the RF-7s....which I did. The salesman turned them up way too loud, trying to impress me with how loud they could play (which they did very well), but I told him I was more interested in what they could do a lower SPLs. He asked me what we were using now, and, on telling him about our La Scalas, he laughed, and explained that I obviously didn't know how music was supposed to sound, and that the LS was intended to be used ONLY as PA speakers or by disc jockeys. I told him I was sure he was right, but suggested that preferences in music playback equipment was, at best, a pretty subjective and personal sort of thing. Sort of like mayo or ketchup on fries or pomme frites. I prefer mayonnaise; mi esposa, ketchup. I though the RF-7s were gorgeous slabs of speaker though! But despite how cool I thought they were in that sense, they just seemed unbalanced to me in terms of frequency response; and that fact may actually have been the result of the comparatively upward tilt of our pair of LSs. As confident and self-assured as the salesman had been (sort of rude might be a better description his character....at least during my encounter with him), in retrospect, maybe he wasn't too far off the mark. For a long time afterwards, then, I just forgot about the then-new RF series, and enjoyed all of our Heritage speakers, which included a couple more pairs of La Scalas, Heresies Is, Heresy IIs (which I gave my dad) Klipschorns, and Chorus IIs (which were pretty awesome, actually). I had also been using and enjoying the crazy-efficient Lowther full-range drivers in rear-loaded horns, which were as efficient as our K-horns, or slightly more so. I still use them, and for some kinds of music, that crossover less full-ranger simply can't be beat. But for anything with real bass -- think of some modern bands like Tool, Perfect Circle, Sound Garden, Audio Slave, Alice In Chains -- all of which my wife loves (and much of it me too!), the Lowthers just can't cut it, and finding a sub fast enough to keep up with them in order to fill in the bottom octaves seemed next to impossible. And so, just last week, I was looking through CL here in Tucson, and found a very nearly mint pair of RF-5s for $300. I went to see them the same afternoon, and they were setup in the seller's garage. They were playing along with an older, but great-sounding Klipsch subwoofer, which, just like the audio store in Houston, was turned up way too loud. I asked him if I could play with the controls a bit to even things out......and I was mesmerized. Even inadequately setup up in a garage they sounded like a completely different speaker than what my acoustic memory serves regarding the RF-7. The 5s were balanced and just amazingly articulate -- truly the equal of any Heritage speaker we had owned and used. But, to me (just my opinion, mind you....) they had an organic, sort of living quality that the big mid-range horns of the Heritage stuff didn't. I'm thinking, though, that the coherence I'm getting from these things is likely more due to the fact that they are two-way systems rather than the three-way of the Heritage. Which makes me now understand why lots of LS owners I've known have gone to some trouble and effort to transform both their LS or K-horns into two-way systems using horn Altec horns. That's something I actually never tried myself. We have a large listening room with a vaulted ceiling, and the way these medium-sized speakers, the RF-5s, are able to fill this quite big space is just kind of amazing. They are capable of very loud undistorted sound, which just seems incongruous with their physical dimensions. I was worried we were going to drive amps into clipping in order to get enough volume, and it's not even close to that. Even with the several watts of single-ended 300Bs they are fantastic, and provide deeper insight into recordings than I think any other speakers we've owned. With the far more powerful Parasound Halo, they can play painfully loud (just as a test), yet remain totally in control. These RF-5s are end-game speakers for us, although I would like to replace some of the crossover components - particularly with respect to inductors. They already have film capacitors, which are likely mylar types, but I may opt for some nice electrolytics, particularly in the critical midrange/tweeter branch. wink wink erik

This is ancient. I must have written about filament hum reduction in valve amps hundreds of times here in the early 2000s. There are MANY sources of noise in tube amps. They traditionally have both inherently high input sensitivity and high input impedances - both of which make the potential for noise worse. The schematic above this post represents a filament circuit, with the filament winding (usually green as also shown above) connected to a hum-null potentiometer (aka: humdinger). There reason a hum-null pot - which simply balances current across the filaments WHERE AC IS USED TO HEAT THE FILAMENTS and helps reduce 60 cycle hum - is because, as is also evident in the schematic above, there is no GROUNDED center-tap present in the filament winding. The same is the case with the OP's reference to two 100 ohm resistors on either side of the filament winding to ground. In that case, the two resistors form a simulated center-tapped filament winding, which can similarly be used as a sort of FIXED hum-null device. However, the resistors naturally do not have the benefit of a potentiometer, which can be adjusted in a manner that 60 Hz hum across the output of the amplifier into a speaker voice coil can be both heard and measured, and thereby reduced to the lowest level possible. There are also other ways the center tap can be used to reduce hum, one of which involves connecting it to source of 40-60 VDC (or so), such as the top of the cathode of a cathode-biased output stage - in other words, raising filaments above ground. In choosing between the use of a grounded, center-tapped filament winding and the two-resistor-pseudo-center tap, I prefer the more robust and ultimately safer grounded center tap. Cost savings was often a priority, however, and two small resistors don't cost very much. In older amplifiers, AC current was used to heat the cathodes of tubes, and this increased the potential for its (the AC's) related noise components, due to proximity between cathodes and their associated heaters, for audible hum at the output stage. This can be a problem for indirectly heated cathodes, but is of much greater concern with directly heated single-ended (push-pull topologies are different) output devices like the big triodes (45, 2a3, 300B, etc.). These filamentary cathode tubes present to the builder/user/listener an even greater challenge in terms of residual noise than smaller signal tubes and/or indirectly cathode heated output stage valves. A 2a3's or 300b's cathode IS its filament, and attention must be given to the 60Hz filament hum that almost invariably becomes combined with audio output. Almost all of the instances above can be quite effectively solved by using well-designed and filtered DC current to heat a tube's filament rather than alternating current. What we often run into in the case of DC filaments, however, has to do with the subjective and often debated efficacy of one type of current vs the other. Which SOUNDS better, AC or DC? And that is something I'm not going to address. But filament related noise is only one example of many, many possible sources of hum and buzz in tube equipment. Poor grounding, which results in ground loops; inadequately filtered B+ (for plates/anodes); EMI and RFI. All are possible causes of unwanted noise that must be dealt with individually and differently. Simply adding a simulated center tap on a filament transformer with two 100 ohm resistors, for example, is going to do absolutely nothing for 120 Hz hum that's coming from a lack of filtering in the high voltage plate supply, or poorly handled lead dressing, or the angry buzz coming from the dimmer switch in one's listening room. Have fun, erik (who on these pages many years ago used the avatar Erik Mandaville - which also happens to be my name) edit: And so. If you are somewhat new to tubes and are having problems with bothersome or excessive noise with your preamp or amplifier, please DO NOT turn the poor thing upside down, take the bottom plate off, and start digging around inside for the filament wiring. To only consider a component's heater supply as the source of noise is a gross over simplification. Find an experienced technician who is familiar with the high voltages associated with tube equipment to help you. Chances are, in fact, that whatever residual noise you are experiencing is NOT coming from tube heaters (which is a fundamental aspect of designing tube amplifiers, and something for which a competent designer will have already considered). Noise can exist in lots of different forms: high pitched oscillation, cracks/pops, 60Hz hum, 120 Hz hum, fine buzzing, course loud buzzing, extremely strong hum (as in faulty input ground connection or heater/cathode short), and a knowledgeable technician can most often diagnose and repair problems without the use of signal tracers and scopes. I once rebuilt a large amplifier for a friend who decided to poke around inside his amp to move wires around in the hopes of solving a noise problem. The amplifier was energized, and he both got severely shocked and blew up the power supply .....quite literally. In another case, I knew someone who was similarly unfamiliar with tube electronics, but made the decision to change coupling capacitors (to see if he could hear a difference) in his 22 tube (yes, a total of 22 tubes) OTL amplifier -- again, while the amp was energized and upside down on a pillow. This involved soldering an unsoldering inter-stage coupling capacitors in situ in a live amplifier. Same situation, and I completely rebuilt a very complicated power supply board. Everything was taken out, rectifiers, resistors, filter caps, all of it. Be safe. There are lethal voltages in tube equipment. If you have tried such things as, possibly, a new pair of interconnects (sometimes ICs can have a faulty ground return that can cause noise; or changing tubes; or mains filter -- simple things like that -- and the problem persists, please take it to someone who knows how to safely work on the more involved and potentially dangerous aspects.

I am always amazed at how much our Outback can carry!! Can't get the pic to upload for some reason, but my wife and I (thank you my dear!) got them in without destroying the headliner. What a truly fun transaction. With what we sometimes run into as far as inflated-to-popping ego in this hobby, or already well-fed sharks looking for every last cent of profit margin and/or taking advantage of others, Christopher is an absolute gentleman. Thank you sir!