G Evans

I'm not familiar with any of the brands suggested are they tube or ss ? I have built both tube and ss preamps and I much prefer the former (tube). Most tube designs have far, far better dynamic range headroom. On tests I had the tube preamp putting out 50V rms while the the ss was clippping at 8Vrms ! The SS sounds very clean but too dry & drab for my taste whereas the tube preamp sounds airy with a very deep and spacious stage. (Both have very accurate RIAA response.) Any chance of seeing a copy of the Adcom schematic ? XXX

Those of you ( Les /Al .. ) who've tinkered with this Heritage xo will know there is what appears to be a thermistor in parallel with a 100 ohm resistor as tweeter protection instaed of the shunt zeners used in earlier designs. My query is whether the mods made to the AL-3 involve removing this prtotection by shoting out the thermsitor/resisor. The thermistor measures about 2ohms COLD. Was this taken into account in the mod ? i.e. by putting in a 2 ohm resistor in place of the thermsitor in order not to shift the tweeter xo frequency. ( as 2 ohms is a fair fraction of the tweeter 8 ohm impedance). George

See thread on digital amps in the Two Channel item - Is this what you are asking ? ... Integrating digital to analog convertion (DAC) with a power amp may make economic sense but, OTOH, think of the cost/performance of a top notch CD palyer ( $2,000 ++) and a top notch amp ($3,000 +) versus proformance / cost of an intergrated unit ($?? !) . IMHO, integration is not necessarily a significant step forward per se but class D output power amps for producing compact units should make the electronic speaker cross-over & EQ concept more attractive and cost effective obviating current passive speaker XO limitations. Where the DAC is located, as long as it is good quality like SACD, is less important and with separate units at least you've a choice what source & amp to have. Also many still use analog sources like vinyl so an analog amp input will be on demand for a long time to come. In summary I think the G.O.F. analog amp will be around for a very long time still. George

The strength of a sound recording chain is that of its weakest link not necessarily the amp-speaker end. Forget not that however good the repro-end is it still leaves a very long chain of digito-analog links along the recording, mastering, & mixing process. This industry in interested in music sales not in gold plating their studios so their equipment is and will be plain'ol industrial grade stuff. This basic oversight has had many an audiophool in search of Will-o'-the-wisp. Having said that no doubt digital amps will evolve but will undergo the similar & long growing pains CD went through in 'replacing' Vinyl. But I think they will have a hard time getting into 'Hi-End' audio. Forget not also that the new SACD (super audio ) format is a kinda 'type' of class D bit stream system running at 2.8+MHz which to my ears is vastly better than standard CD ( PCM) so there is hope for digital amps if they can approach SACD standards. (BTW, one of the reasons for SACD's goodness is that it does away with digital filtering needing only a gentle analog filter to remove sampling artifacts.) George

Hi mdeneen, is quite right when he compares subjective performance of, say,some single ended triode (SET) amps of 2 or 3 watts with 5% THD to much higher power amps with superlative .0001% THD figures which can sound inferior. The ear-brain system can defy reason at times but part of the reason for this bares on how the different systems are tested to get the specs. Most amps are tested to resistive loads (4/8 ohm) only - how that same amp would handle a read life loudspeaker load can be quite different. This is an ever-green conundrum with many attempted explanations. Some sonic differences between amps are simply down to tonal balance differences , which are not inherently good or bad, just a matter of personal preference. On the other hand from my own experience, is that I much prefer my vintage tube amps with THDs of the order of 1% than a much higher power solid state amp with .001% THD I used to have. The darn thing always sounded thin and grainy( harsh) . The nature of the THD is an issue too ( tube amps are rich in 2nd and low order harmonics which enhance richness) but this still can not explain the difference. Also the generally lower damping factors of tube amps can ( with some speakers/rooms ) boost the bottom-end making them sound fuller in bass deficient speaker /room systems to some sonic benefit but not always as bass boom can become a problem in other systems. George

I've been using new La Scalas since November (minus 4 weeks in Dec ) average 2 hrs a day or 150 hrs ,say. With no tweeks and standard AL-3. Any advances on how much more time they usually take to break-in and what blissfull improvemnts I should expect to hear will it make that much difference. I recall someone's comment on this BB that after breaking-in " they sound just like fresh out of the box .. but more so !" George

MacKlipsch The Dope from Hope drawings do show the best way of doing things IF you have a low imp. out preamp which guards againt L/R crosstalk. Most people these days prefer to go from source to power amp directly via a volume pot driven from a very low z out source like CD (I do) or RIAA preamp with a good line driver (cathode follower ~ 600 ohm). With the resistor values given 27K + 25K pot the cross talk expected (as a function of preamp zout): Zout Xtalk (dB) 600 ohm -43dB 1K -38dB 4K -27dB 10K -20dB ** 50K -11dB 100K -9dB Using lower value resistors in the combiner will worsen these ofcourse .. Many PU cartridges have xtalk figures of around 20dB, so some of you will rightly argue that even highish ** output z's are of no consequence... your choice :-) but would 'degrade' the superlative spec figures achievable with a typical CD player.. BTW, I have a collection of Dope From Hope up to 1978. Untill when were they publisehed by klipsch ? George

Sorry to butt in chaps but following my comment in Three speaker stereo thread : as I mentioned there many vintage Scott amps provided a center channel derived from the 16 Ohm tap , but ment to feed a third amp with a Z in of 100K at least :-) . One version used two 8.2K from L/R and one 1.5k to earth. Another version used 82K from L/R and a 15K pot to earth for level adjustment. Advantages of this is that center channel level tracks L/R flanks automatically and does not interfere with L/R channels balance or introduce crosstalk (L/R coupling). Disadvantages are that the C Ch will be fed any noise ( like hum) and distotion generated in the stereo amp o/p satges and speaker back emf transients . Derived from the preamp volume control, some crosstalk will result always depending on resistor values and the output Z of the stage driving the volume control. Taking the output from the volume pot cursor will worsen this. The only way to prevent crosstalk with this scheme is to use an active mixer like an op-amp but all-tube rigg devotees will not buy this of course , I certainly wouldn't. George Three speaker stereo

All HH Scott tube amps ( like the 222, 299B, 380 etc) provided a derived center channel using the amp 16 ohm outputs via ( I'll check) 10K or 22K resitors. If the center channel amp is a sole power amp without a volume control the center resistor could be a pot to tweek the level as .. Watch the center channel level wrt flanks as it can shrink the sound stage if too high. ( -8dB , as Al. K says :-) I even found that effect with a sub ( even though it rolled off at 30Hz) which is why I use the sub to one side of the room not between the flanking La Scalas. The minus side to using a Heresy or Cornwall as center speaker is that you loose the all horn clean bass which is why the Belle was designed. George