RIklipsch

Craig, Did you try replacing the Xicon electrolytics in the front-end with something better? How about the metal film resistors? Perhaps there is no improvement to be gained here, and is why you left those intact? Room on the board itself probably poses a problem when using other types. Just curious, particularly after seeing the higher grade "sonicaps" installed in your unit. Board is very nice, as are the PS mods. Ryan

---------------- On 10/23/2004 3:38:47 AM djk wrote: What a pedant! Do you obsess about conventional vs electron flow too? I prefer a 150V MOV to a cap across the primary. ---------------- No, I don't obsess about conventional VS. electron flow, I could care less! MOV would work great, *for a while*. It can only take so many "hits" before it goes open though. I guess its life is a function of the current rating on the primary, and how much counter-EMF is "reflected" back on the MOV at turn-on. I'm no MOV specialist, and really can't comment on lifespan. 1000V ceramic disc will get the job done and last longer. If you look at tube products from the 50's and 60's, they all used these ceramic caps, and they are still good (I never had to replace one). -Ryan

---------------- On 10/20/2004 3:36:00 PM mdeneen wrote: For the life of me I can't recall many decent sounding SS amplifiers built before maybe 1973. What amps are you all referring to? The Threshold 400 circa 1974 was a clear breakthrough winner. The PL400 was at least very listenable, as was the Marantz 250. The Electrocompaniet circa 1975 was great, as was the NAIM. But Pioneer? Sansui? Dynaco? HK? Scott? They are given due credit for actually forcing a RETURN to tubes which had been abandoned with the advent of the bipolar power transistor. ---------------- PL400? The only thing that amplifier is good for is brute power I had one blow up in my face, it was quite a show. The things are terribly unstable, and when they do decide to go, they put on one hell of a show! I don't know what you see (hear) in the PL400, it's just a quasi-complementary amplifier, primitive to other 70's "innovations". 1970's were very important to the development of solid-state circuitry. Prior to about 1969, bipolar transistors were basically used in tube circuits, and performed horribly. The early H.H. Scott and Sherwood "transistorized" receivers come to mind, utterly horrible with brittle sound. Many Japanese companies (like Sansui) built state-of-the-art amplifiers and receivers, I especially like the Sansui AU series of integrated amplifiers. The lower powered models do seem to perform better, have you tried them? The monster receivers like Sansui 9090-DB and Pioneer SX-1050 do sound bad at low volumes, with immense distortion. In my opinion, the products made prior to the "wattage wars" were the best. With high wattage, there is a definite price to pay, and that price is sound quality and distortion factors. There were a fair amount of lower powered receivers and amplifiers in the early 1970's, and to me, they exceed the performance of most anything being produced today. I got to hear a Pioneer SX-990 today through horns (990 is rated 28W/Ch), the sound was very nice, not too harsh for me. My SX-1050 (100W/Ch), sounds like crap through the horns. I think power output and output transistor operation characteristic curves, and the range that the transistors are operated in play a large role in sound quality. -Ryan

---------------- On 10/21/2004 6:30:28 AM djk wrote: When the switch is opened the cap begins to charge and the load current now flows through the cap. ---------------- sorry, no. No current ever flows through the cap,(except leakage current) unless it's faulty. Current may flow in the *circuit*, but never through the cap itself. A better place to install the supression capacitor is in parallel with the power transformer primary. IT will absorb the counter-EMF created by the inductive kick-back of the trans primary. I do not like to place capacitors in parallel with a switch, as AC voltage is present across the power trans primary. While the current is very low,(leakage current) it can still give you a "tingle" should you come into contact with it. When I turn off a power switch, I want complete isolation from the AC mains. -R.Inman

Sansui AU-9500 photo gallery and comments from Sansui US: http://www.sansui.us/AU-9500.htm Have a look. -Ryan

---------------- On 10/20/2004 6:15:33 AM Glimmertwin wrote: Lower power + older amplifier = better performance http://forums.klipsch.com/idealbb/images/smilies/1.gif"> The best sound, to me, came from my collection of 1967-1975 vintage solid-state amps. ---------------- 1965 - 1975 was the best era for solid-state, IMHO. After 1975, quality took a nose dive. Which vintage solid-state units are you running? One of the finest solid-state amplifiers I ever heard was the Sansui AU-9500. It was produced in 1972, and was the top-of-the-line model for that year. It is rated 75W per channel. I am currently using the amplifier with horns (not Klipsch), and I don't get a hint of harshness from it. If you ask me, it is superior to most other SS units and some tube units. There were several lower powered versions in the AU-9500 series, such as AU-8500, AU-6500, and AU-3500. Each of these has a unique sound that is very pleasing. If you wanted to try one of these, you can pick up any of them on ebay for a song, they typically sell for under $200 and are some of the finest amplifiers you will ever hear. The AU-9500 is the rarest in the series, and also the highest powered. For your Cornwalls, I would recommend the AU-8500 and AU-6500. The AU-3500 is only 20W per channel and is a bit underpowered. Sansui was a cut above Pioneer, Yamaha, Kenwood, and other Japanese manufacturers of the era. Best regards, Ryan

---------------- On 10/19/2004 6:08:44 AM InventiveAudio.com wrote: What is a speaker switch? ---------------- You fix vintage amplifiers and have never seen a speaker switch? What the heck do you work on?

---------------- On 10/19/2004 8:14:41 AM rigma wrote: If I turn off my Crown amp via a switch on a power strip I get a loud thump. Using the amp switch, no thump. Question is could I add a capacitor across power cord to stop this as Erik mentioned about the switch? ---------------- Yes, you can. Use an 0.047 uF 1000V ceramic disc capacitor. The capacitor is placed in parallel with the switch contacts, and the idea is that the capacitor opposes any change in voltage. The capacitor will "supress" the momentary switch "bounce", or pop. R. Inman

---------------- On 10/18/2004 7:56:43 PM InventiveAudio.com wrote: Save your money and buy a satellite radio tuner. CD quality, no hiss and tons of content. ---------------- Have you ever heard a quality tube tuner like the Scott 350-B? If you did, you would never be recommending satellite radio. Satellite radio is nothing but compressed garbage, at least with FM there are still some good quality broadcasts. BTW: There is little to no "hiss" using a Scott tuner. Armstrong designed FM and H.H. Scott was the first to implement FM MPX Stereo. I'd say they know a thing or two about tuners. R. Inman

---------------- On 10/15/2004 5:32:32 PM jheis wrote: R. Inman Thanks for the advice. My instruction manual doesn't go into that kind of depth nor does it provide schematics. I don't have a service manuel. Are you talking about a DC voltage from an output terminal to ground or measured across the terminals? Obviously the amp whould have to be powered up for there to be any voltage and I assume the measurement would be done without any input. James ---------------- Correct, James. The DC Voltage would be measured across the actual speaker terminals. You can safely make this measurement with no speaker load connected. Once you verify that this is indeed the problem, you may save yourself some money, being able to mention this problem to the repair tech. If you take the measurement and get over 30 mV on either channel, shut it off immediately. Generally, when a solid-state amplifier begins to make a loud THUMP when powered down, it is about to fail. The output transistors would be the first to fail, and they are rather costly for your high powered amplifier (probably Mototola MJ21194 or equal) -R.Inman

James, It would be pretty difficult to make this adjustment without a service manual. The best advice I could give you is to find an authorized Carver service center in your area to make the needed adjustments or repair work for you. And Erik is certainly correct about the potential shock hazard. With over 300W of output, you're looking at 85V+ positive and negative rails in this unit. If you had the service manual, it would be easy, but going in blind is never a good idea. Sorry I could not be of more help. -R.Inman

---------------- On 10/15/2004 11:23:41 AM mike stehr wrote: How can you decipher those little ceramic dog bone shaped caps that just have color bands for values? ---------------- Easy, Mike. Most color-coded capacitors followed the EIA standard, and are read from left to right (following the arrow), just like a resistor: Example Red----Red----Orange The first two colors are significant, the third is the multiplier. 2----2----3 22,000 micro,micro farads OR 0.022 microfarads -R.Inman

---------------- On 10/15/2004 8:14:28 AM mdeneen wrote: IME, the tone control setups on most preamps - especially vintage jobs - are seriously compromised by cheap pots and really super cheap caps, Often 5-cent ceramics. And they don't center correctly in most cases unless there is a bypass switch. And so it's a real dillema. Adding a cheapie tone control hurts the serious appeal, adding a proper one raises the price very significantly for something used "once in a while." I dunno. mdeneen ---------------- I respectfully disagree with your analysis of vintage units, Mark. I'll use H.H. Scott as an example: If you take a look at their LC-21 or 130 preamplifiers, you will find CTS potentiometers and Mylar capacitors, no "cheap pots or ceramic caps". Most of the decent HiFi manufacturers used higher quality components in critical signal paths. Ceramics were generally only used in feedback circuitry. H.H. Scott used little ceramic discs, if any in some models, they typically used Silver Mica caps for feedback. Maybe by todays twisted audiophile standards CTS pots are reffered to as crap, but I honestly don't buy that. A good working CTS brand pot has a velvety smooth rotation and excellent performance. Even most of their integrated amplifiers used these higher quality parts. It wasn't until the early 60's (64 - 66) that ceramic caps came into play in tone control circuits, and even they don't have a perceptable affect on sound for the stages they are used in. "They don't center correctly". Perhaps the knobs on the units you've seen were misaligned? Or perhaps DC from the EQ stage amplifier was affecting the circuits performance, a common problem due to leaky capacitors. I wouldn't blame the pot itself. I also disagree that tone controls add a cheap appeal of the product. Everyone hears differently, has different room acoustics, and to offer a means of adjusting the tone characteristics to some degree is "ideal" in my view. It is possible to market a preamplifier with tone controls to both crowds, those who want them, and those who don't. Many manufacturers incorporated "defeat" switches which totally remove the EQ from the signal path. The only additional item in the signal path would be a pair of switch contacts, and surely those will not have any audible impact on sound in defeat mode. -R.Inman

---------------- On 10/15/2004 1:30:04 AM jheis wrote: I have a Carver TFM Amp (375w) that works fine except that I get a rather loud POP when I power down. I know that this can't be good for my speakers, so, since I'm runing it through a Niles Audio speaker selector, I disconect the speakers before I turn off the amp. Any idea what is wrong with the Carver? It didn't do this for the first 6-8 years of its life. Any advice/comments would be appreciated. James ---------------- James, The problem has nothing to do with the power switch. Modern amplifiers such as your Carver use a differential input amplifier, and OCL (output-capacitor-less) output stage, also known as DC Coupled. This eliminates an output coupling capacitor for improved sound. The differential input stage allows for 0VDC on the output stage. You have DC (direct current) voltage on one of your speaker channels. Using a DC VOM set to the millivolt range, measure the voltage of the affected channel from the speaker outputs. Refer to the instruction manual on how to adjust DC Offset (may also be called DC Balance). The manual will refer to a potentiometer, for example "VR-301". Remove the bonnet on the amplifier to access the driver board where the pot will be mounted. Follow the service manuals instructions. With a simple VOM, this is very simple. You want to adjust the output voltage so that it is 0, +/- 30 mV. Over the years, transistor characteristics drift, causing the DC Offset to be off. DC on the speaker outputs in excess of 30 mV can damage speakers, especially efficient speakers. Be sure there is no DC Offset voltage before you power up the Carver again. -R.Inman