erik2A3

Consider rejuvenated vintage valves! Heresies LOVE tubes! Dyna ST70 Scott Eico Baldwin 6L6 organ amp (killer!) Leak Give Craig O. A shout at New Old Stock Valves, he'll fix you up!

I see...it sounds as if they are a bit rough around the edges. Still, if they are structurally sound and don't have rattling panels or front baffle, maybe they could be cleaned up satisfactorily. I'm sure your daughter would think it's pretty neat to have some speakers you worked on with her in mind!

I have an SL1210 MK12. Very comparable sound wise to the two other higher-end tables we have. Incredibly well-built, quiet, and musical.

Rotting foam surrounds? You can DIY the surrounds, but it's kinda...well...potentially messy work. I've done it all of three times over the years. Old networks can easily be freshened up (I DO know you know that)!

Nice! I've used a three step plastic polishing compound for dust covers that also works well. Can be surprising at what decent sound one can get from those tables. Plastic Polish-------> https://www.tubesandmore.com/products/S-CPOLISH-SD

Don -- that system components should ideally be matched to begin with is another (to me) rather obvious consideration. When I have built amplifiers and preamps in the past, I have built them to not only work well with each other, but within themselves. Just as one should consider inout and output impedance specs between components, one must in designing equipment consider the same thing between the different stages of a single component. Get that wrong and no amount of impedance buffering between components will remedy the problem. Nor will any amount of external impedance buffering fix the issue I mentioned above with potentiometers (particulalrly in the case of a passive in-line attenuator. We must also consider the power transfer function that takes place between amplifier and the reactive load of a loudspeaker. Certainly careful impedance matching between these two final components in the signal chain is a critical consideration, especially in the instance of using very low power triode amps, such as the Wright monoblocks mentioned above (by the way, Dean, I happened to work on the very pair you listened to shortly after you had them. I found that the connections related to the secondary winding on one of the amps had not only been reversed, but was not connected to the same secondary tap as that of its monoblock twin). That would explain at least some of what you were hearing, but of course would not address the overall disinterest I recall you and a number of other forum members had at the time for SETs in general. We tended to "visit" that topic often in the early years. So, back to the amp/speaker relationship: impedance buffering is generally associated with line-level components, such as between an amplifier and preamp, CDP and preamp, and so on. If one has a situation where for example one happens to have speakers that present a difficult load (such as very low nominal impedance and/or low efficiency) and one happens to be attempting to drive them (just for example) with a single ended triode amp (keeping in mind that tube amps tend to have higher output impedance characteristics), then one is probably not going to be very satisfied with the result. Additionally, of that loudspeaker is a multi-driver system with a higher order passive dividing network, the problem will be compounded by the insertion losses associated with the crossover. That little amp will be puffing very hard to get virtually nowhere. To that end and in my own case, the second pair of the two main speakers I have in my system have an efficiency of about 106 dB and a nominal impedance of 15 (not 16) ohms. They are extremely SET friendly, and the SPLs I can achieve with this combination is not only very loud (though I tend to listen at lower volumes), but very clean. It is a single very wide band driver that also does not rely on the potentially energy-sapping chokes and capacitors of a passive crossover. There is a problem with the particular drivers I'm using, however, which I knew existed before I bought them: they have a pretty wild impedance curve. The usual cure for this that many Lowther owners install a non-inductive swamping resistor across the voice coil in order to reflect a more even overall impedance to the amplifier. In other words, an impedance buffer. My personal problem with this is that while it may provide a more linear impedance plot, I simply don't care for the way it sounds. The drivers sound much more lively and seem to have greater overall all clarity and transient response without the swamping resistor. It's essentially the same thing some do with the autoformer on Klipsch Heritage networks for the same reason - to reflect a constant impedance to the amplifier. For some, that resistor is a compromise they would rather avoid; not all makers of after-market Klipsch crossovers approve of them. I have mentioned impedance buffering many times on this forum, including back in the earlier years when I first visited this site (2002). Unity gain impedance buffering is fairly common, especially in the DIY community. Decware, along with their selections of tube equipment also offers something called a Z Box (the Z being the designation for impedance, just as L and R are for inductance and resistance). Unfortunately, there are many problems related to component matching that an impedance buffer can't fix.

Even in cases where components are ideally matched one is still faced with compromises associated with not only the listening room, but one's own day to day human inconsistency and variability. How many times right here on this forum have I read where someone (very likely including myself) declare how amazing their system sounded one day, only to make a complete about face on another occasion and subsequently decide to sell everything and start from scratch?

There may be a reason that someone, whether an audiophile or not, might have an inclination to turn the volume up. Doing so may in fact mildly improve an already compromised or inadequately matched chain of components, but ultimately will not change the overall fact that certain elements in the signal chain simply don't work well together. That systems should sound good at any vołume seems to me fairly obvious and is of course a desireble trait, but we all are accepting varying degrees of compromise, like it or not. Electrolytic coupling capacitors in source components, output transformers for impedance matching between power tubes and loudspeaker voice coils (OPTs being one of those 'compromises' that led some equipment designers to create tube amps that don't require them), lossy potentiometers (why some designers use transformer based attenuators), and so on. Some consider passive crossover networks, and those in particular that employ myriad circuits for impedance equalization (zobel -- which I can't stand), notch filters, resonant peak filters, etc. to be severely detrimental to vivid music reproduction and sources of phase distortion, and so on, and so refuse to listen to any speaker that consists of anything more than a wide-band, crossoverless transducer loaded in a horn loaded enclosure the size of a refrigerator -- which in and of itself is yet another source of distortion, and in fact happens to be a compromise of choice for me.

Listening to a live musical event (regardless of the sound pressure levels) is significantly different from reproducing a recording. What Mike is saying is arguably correct in a number of ways. One thing that happens at lower vołume control rotations has really less to do with the interface between amplifiers and speakers than it does with an upstream component -- namely the potentiometer on either a preamplifier (as in either an active linestage or passive, in-line attenuator). To state this in simple terms, a potentiometer is a variable resistor which changes in value according to the position of the wiper on its carbon element (or fixed value of resistance on a stepped attenuator built on varying levels of fixed resistance). At low volume settings in general, and in cases where the output impedance of the preamp may not be well-suited to the input impedance of the amplifier in particular, the effects that a potentiometer can have on the overall sound quality of a system can be remarkable. In cases such as this (poor impedance matching between components), lower volume control settings, because of the changes in resistance within the potentiometer, can result in a quality of sound lacking in 'presence' and immediacy. The system's overall high frequency response is compromised and music sounds dull and devoid of clean and sharp high frequency transient response. I wholeheartedly agree with Mike. If a signal chain is already compromised by inadequate matching between the components within that chain, the seemingly benign act of turning down the volume can have a marked influence on the perceived sound. In fact, some designers of musical instrument amplifiers include a very simple form of 'EQ' to ameliorate potentiometer effects on sound at quiet vołume settings: it involves the installation of a small value capacitor (picofarads) on the potentiometer which functions as high pass filter and allows the transmission of high frequency information that would otherwise be choked off -- and which in turns leads to poor low-vołume sound reproduction. When the volume is turned up (again in simplified terms), the electrical characteristics of the potentiometer are again altered, but this time in a manner that benefits the overall reproduction. Moreover, the high pass capacitor that may have been installed on the volume control (which can be switched in and out of the circuit if so desired) to improve the sound at low volume becomes essentially unseen; its effects come into play only at very low vołume settings. There are many other examples.

Richieb: I'd love for you to be able to hear a good single ended triode amp. I have two pair of home-built 300B monoblocks with direct coupled drivers that are marvelous with La Scalas and Klipschorns alike. I feel no need whatsoever to biamp or buffer between them and the speakers in the least. k-horn woofers are extremely fast and efficient, and simply do not need tremendous grunt. Same is true for my 2a3 amps. Try for yourself as much as you can!

Nelson Pass definitely has made important contributions over his many years as an engineer. In this particular case, a single-ended 45, 2A3, PX25, 300B, EL84/6BQ5, etc., on its own, can be magical with Klipschorns or La Scalas. Both are relatively easy loads in terms of nominal impedance, and without a doubt, efficiency, that small amplifiers based on SE triodes (or pentodes) can be in my experience remarkable -- again relative to the listening habits and preferences of the user. As Kevin mentioned, which is something I have also done, is biamp with the single ended triode for middle and high frequencies, only.

20 to 30 watts might be fine, and also might not be what this individual is looking for in terms of the KIND of sound and or sound QUALITY he may be seeking. Wattage alone is nothing more than a quantitative value. Moreover, I don't think we have knowledge of this person's listening preference as far as desired listening levels, music genres, and so forth -- all of which are important considerations.....in my view.

I would like to submit that output power capability (as in wattage) is not the only consideration in determining the kind of control a given amplifier will have over a woofer, horn-loaded or not. I have a class A OTL amplifier that is good for about 1.5 watts/channel that has a better grip on low end response than a couple of PP valve amps with significantly higher outout ability. There are reasons for that. Al makes quality passive networks that are excellent in terms of both design and craftsmanship. The high order (Extreme Slope) networks can also be very good under the right conditions. The drawback is that higher order passive networks require heavy amounts of inductance and capacitance in order to achieve their design goals. High series L and C introduce insertion losses that for a low power amp (as with the one mentioned above) are considerable and amount to significant attenuation where headroom is already in short enough supply. There are other networks available for these big horns that IMO are much better suited to such low output (but exceedingly good sounding) amplifiers -- my favorite being the 6dB/octave slope type A network.

PrestonTom. Precisely. While specs and measurements will not always reveal how one may subjectively respond to a given design, specifications of input/output impedances and input sensitivty are not only important, but really mandatory in determining fundamental electrical compatibility between components. In designing a preamp or power amplifier, for example, those same specs are required for determining interstage impedance relationships. While it's true that it's difficult to make a decision about the sonic qualities of those components that share similar specs on paper, in my view it is arguably beneficial to consult basic operating parameters of pieces of gear in order to begin the auditioning process. A more mundane example: When I go out to buy a pair of shoes, there will be a million varieties of the size 10 species, and knowing my size requirements, size 10 is what I will ask for as a starting point. We all know that shoes labeled the same will not always fit the same, so we look for the size (which may be a half or even whole size up or down) that best fit our particular needs.

Perhaps the OP is giving greater weight to their music reproducing abilities than he is their mild resemblance to another speaker in the Heritage line. If I were in search of La Sclas (which I'm not since I already own a pair) the full-face grille on the pair shown here would be entirely insignificant. As a serious listener, 'looks' are very much of a secondary concern for me. They are Klipsch La Scalas in very good condition for an excellent price -- the thin piece of cloth in the front does nothing to change the basic infrastructure behind it. I say grab em'! If down the track Speed Racer wakes up one morning and decides the fabric is not for him, I suspect it would be a rather simple thing to tear it off.

Definitely a near-field listener. One of the benefits of this approach is that the listening space seems, in my instance (though I have heard others say the same thing), less of a critical role than it must in a situation where the listening position is significantly further back. The potential interference and distortion of wall, floor, and ceiling reflections are greatly diminished in the near-field, particulalrly in the case of lower SPLs, which in our room have the subsequent advantage of being less likely to excite room modes in the range of a couple of hundred Hz, or so. I have known more than one professional musician who also happened to really like Klipsch Heritage speakers (in this case La Scalas), and one of them, a very talented french horn player who was also incredible on fretless bass, said what he liked so much about La Scalas was not their ability to play loud, but rather what they can accomplish with very low input levels. Sure it's fun to crank the volume a bit with certain material, but when I listen critically, it's in the near field, in the sub-watt range, and almost always from a single-ended amplifier. And of course there will be the other end of the spectrum, where one's boat fails to float unless the volume is turned up very high on equipment capable of that particular approach to listening. Each to his or he own.

Hi, Maynard A friend of mine recently gave me a vintage Quad 303 stereo power amp. He had initially sent it for power supply and ouput stage recapping, which I have already done, but I recommended new components, trim pots, etc. (the originals are dirty in the extreme, and had a reputation for drifting). He had since invested in some other components, and so very kindly just told me to keep the Quad to do with it as I liked. That's what's on my bench right now, with several other projects going on when I have time. My amazing wife also bought me the new 300B Transcendent Sound preamp/headphone amp kit, which is needed for room changes that necessitate long lengths of IC between preamp and amplifiers. I love building from scratch, and kits are fun to do too, especially since my time is very tight now during the school year and teaching. The TS kits are done very well by the way! Again, great upo non this amp. I have always been one to appreciate simple chassis that contain innovative and interesting circuits! Good to have someone like you around here.

Very nice, Maynard - an absolute lesson on well-done P-to-P. Thanks for the description, as well. Input jacks up front and close to the input stage is excellent -- frequently a better practice IMO than immediately adjacent to mains inputs and other PSU components.

Here is an example of an impedance buffering I mentioned above (I am providing the link for illustration purposes, only and as an example) http://www.decware.com/newsite/zbox.htm

A sort ironic thing about preamps: more often than not, they are used not to boost a signal but to attenuate it; to reduce its strength. Sounds odd, I know, but here's what I mean: take an average CD player with a fixed output and connect it directly to an amplifier with both very high input impedance and voltage sensitivity (many tube amps, particulalry vintage examples, fit this description) For example, I recently rebuilt a LEAK ST20, which has a notoriously high input sensitivty. What would happen If I were to connect a CDP to this amplifier without first going through a device (either active or passive) with an attenuator of some kind? I would instantly blow out the windows of my house and shatter my ear drums...... So, we use a preamp which, even though it may be capable, as the case may be, of 10,15,20,30 dBs of gain, would be used to attenuate and moderate the CDP's full-strength signal rather than boost it. Of course that's not always the case, in that there are many amplifiers that not only would benefit from an active linestage, but in fact where one is mandatory for optimal performance. A primary benefit of a preamp has really less to do with an increase in gain, but rather impedance buffering between the preamp ouput and the amplifier -- in essence making the two more electrically compatible with one another. One can even make or buy unity gain buffering stages for the same purpose -- to provide suitable inter-component impedance matching.

What Mark said. The source ouput impedance (DAC, CDP, etc), the value of the potentiometer used in the passive, and the input impedance/sensitivity of the power amp are important considerations. As a rough guideline, the usual standard is a 1/10 ratio between source output impedance and the load it sees. For example, if the output impedance of a linestage preamp is 1k ohms (which is on the high side), the input impedance of the amplifier should ideally not be lower than 10k ohms. In practice, these two figures tend to be quite a bit different, particulalrly in the case of vacuum tube amplifiers, which generally have both quite high input impedances and high sensitivity -- which for passive preamps are good and desirable characteristics. I have made many 'passive' in-line attenuators over the past couple of decades. Unless we are talking about TVCs, as mentioned above, a passive preamp is nothing more than a vołume potentiometer between the source and amplification. Even though such a passive device does NOT amplify (and in fact does the complete opposite), I use the term 'preamp' simply to identify its position in the signal chain -- as in the fact that it (the passive device), as far as the audio signal is concerned, comes before and is in front of the amplifier. Thus, PRE - amp. Audio always involves choices between compromises, and this can also be the case with passive in-line attenuators. If we have an amplifier with an input impedance of say 100k ohms and an input sensitivity of 1 volt (or in many cases even less), a passive preamp becomes (subjectively) a very possible option. But what happens if one simply plunks in a vołume control between the source and this amplifier? The inter-stage impedance relationship becomes greatly changed. The load seen by the signal is now NOT that of the amplifier (which at 100k -- or even 1meg ohm in some cases) but rather the value of the potentiometer. Of course one could choose a VC with a resistance value of 100k (which is the same as that of the amp), and that would be nice for the source signal, but it's what happens on the output side of the vołume control that things become less desirable. As someone also mentioned above, a conventional pot will alter the impedance relationship considerably depending on the position of the wiper on the volume control. So, one must necessarily find the best compromise between the value of the volume control and the impedances of the source and amp. One vintage power amp I recently completely took apart and rebuilt has an input impedance of 1meg ohm, and the potentiometer I installed on it works fine because the ratio between it (the VC) and the 1 meg ohm grid leak resistor (which is what establishes the input impedance of the amplifier) is suitable. So, to put all this in light of Justin W's amp, which I'm just guessing may have an input impedance of approx 100k or so, a more suitable value for a passive in-line potentiometer would be in the range of 10k or so. But this bring about another possible compromise in that the impedance seen by the source is now lower, too, which is less desirable. BUT, it's again what happens on the output going to the amplifier that is important: the 10k pot will have a more appropriate impedance relationship with the amp than did the higher value 100k potentiometer. But because a passive does not possess gain (again, a TVC is an exception to this in that they, depending on how they are configured, CAN in fact step-up the strength of the signal between the primary and secondary winding), one is then confronted with the effects of cable length and the associated increases of capacitance and resistance. Higher output impedances (as in the case of high value conventional potentiometers) have difficulty driving capacitive loads (ie long interconnects), and these issues present themselves most commonly in the form of high frequency losses. However, there is something of a remedy for this: a very small value capacitor (as in picofarads) can be used as a high pass filter on the VC, and this will provide a small amount of EQ at lower vołume rotations -- allowing for less attenuation of high frequency information. On music instrument amps this is sometimes referred to as a 'bright switch' and it can be switched in and out of the circuit as desired. One solution for Justin's amp, which I have done more times than I can remember, would be to replace the resistor on the grid to ground of the first stage with a vołume control of the same value. In other words, the volume control would not only provide the necessary working impedance for the amp, but would also provide adjustable gain. Channel to channel tracking is not always ideal on those less expensive carbon strip pots, though, and one way get around that problem is to either use dual mono pots for individual channel adjustment and balance, or buy a better contro such as a blue Alps, which are not only very quiet, but generally have much more even channel to channel tracking between the two mono sections of the potentiometer. Goldpoint also sells very nice stepped attenuators using surface mount resistive networks. Because these consist of precision switches, the cost is far greater than the usual kind of control. Goldpoint also sells nicely built passive preamps with choices of stereo, dual mono, source selection switches, etc. In-line attenuators are incredibly easy to make if you know how to solder. Good luck!

Jay, sure! Wolfram: I think he says the new designs are better because he really believes they are -- which of course is a subjective judgement. I have built quite a number of TS products, and have had the opportunity to experiment with a variety of "upgraded" (ie more expensive passive components, and my opinion was not the same as yours. I did not find differences that warranted the greater cost. That's not always been the case, though, with other preamps and amps I have built. I don't choose parts based on cost. I make judgements based on performance in specific circuits, providing that a part is correct in terms working voltages, etc. Were I to do otherwise, I would be compromising my own sense of what is important in creating a component. BTW: I know that he does appreciate well made parts, such as with the usual culprit (coupling capacitor). I would say any designer is pretty good about reflecting faith in his/her new product once it has been thoroughly tested. That confidence has been rather well-illustrated over the years on this forum.

Jay I have not heard any of the new Transcendent OTL amps. Rozenblit is a sharp EE and a designer who is constantly working and experimenting. His newer models depend on a different output tube than the earlier versions and despite what others have said about the greater number of tubes required, there are those who, once they tried an OTL, will never return to transformer-coupled designs. Each to his or her own. For those, the cost of ownership is not really an issue. He also designed a model I am particulalrly interested in that, like his new preamp/headphone amp, uses 300B triodes. It is a very low power amplifier, and uses AC current on the filaments (DC can't be used here), but Rozenblit managed to get around the AC filament hum problem in a way that I think is particulaly smart. The majority of amplifiers I own are not OTL designs.

Jay - I own one Transcendent Sound SEOTL (single-end-output-transformerless - the first version, which has been replaced by another, apparently much better design. I also own two Transcendent Sound T16 stereo amps. I am going to rewire them for monoblock operation. The T16 has also been replaced by a new design.

My point in mentioning OTLs had really nothing to do with a statement about transformer coupling V.S. OTL amplification in terms of which is better. Of course every design is something of a dance of compromises. We were discussing the perceived merits of larger output transformers as opposed to their sometimes a bit misunderstood smaller counterparts. The OTL was an illustration of those that require neither a large nor small OPT of any kind. The designers of the amps for which I provided links know a good bit about this subject, and both have created very successful OTL topologies. The feedback issue is something also often brought up, but, as an owner and builder of both single-ended and PP amps, we should not discount some of the merits of judicious and careful use of negative feedback. Maynard -- I absolutely agree concerning the point you make regarding grid stoppers. Amplifiers can oscillate at such high frequencies to be virtually inaudible, yet still be undesireable. I own two OTL amplifiers, and will say that clarity is very much their forte.'