Deang Posted April 24, 2007 Share Posted April 24, 2007 There's a good deal of difference between the original SI and the Super-T, spending the extra $100 is a no brainer. Most use the Tripath 2024 chip for about 10 wpc. The Winsome Labs Mouse uses two Tripath TP2050 chips for about 40 wpc -- probably better for something like the Cornwall. As is often the case, if you put a preamp into the mix the sound changes and takes on a lot of the character of the preamp. I actually prefer the sound at the lower to moderate volumes without something in front of them, but if you like to dial it up they sound better with a preamp. Quote Link to comment Share on other sites More sharing options...
sfogg Posted April 24, 2007 Share Posted April 24, 2007 Dean, "The Winsome Labs Mouse uses two Tripath TP2050 chips for about 40 wpc --" As I recall that is the same chipset (modulator and output stage are on different chips) that the Teacs run. Shawn Quote Link to comment Share on other sites More sharing options...
Deang Posted April 24, 2007 Share Posted April 24, 2007 I imagine you removed the board with the junky volume pots on your TEACs? Do you believe that board degrades the sound -- I sure thought so. Quote Link to comment Share on other sites More sharing options...
meagain Posted April 24, 2007 Share Posted April 24, 2007 sfogg - what is the model of Teac you like so much? thx. Quote Link to comment Share on other sites More sharing options...
Deang Posted April 24, 2007 Share Posted April 24, 2007 The TEAC's aren't available anymore -- Shawn bought them all. Quote Link to comment Share on other sites More sharing options...
sfogg Posted April 24, 2007 Share Posted April 24, 2007 Dean, "I imagine you removed the board with the junky volume pots on your TEACs? Do you believe that board degrades the sound -- I sure thought so." The board is still there, the junky pots are not. I replaced the pots with fixed attenuation as needed to maximize SNR out of the crossover per driver. I wanted all nine channels exactly balanced (relative to each other for L/C/R) which wouldn't have been easy/possible with the junky pots. Leaving the attenuation on that board made working on the attenuation easier. I could just pop out that board and adjust attenuation as needed then plug it back in instead of having to disconnect all the input/output cables and bring the whole thing over to the bench. As homage to you I also changed the input caps on that board to film caps. Nothing special.... just did it as I had them. Those could be bypassed all together as the amp cards themselves have input caps on them too. The other changes I did to the Teacs were changing the Tripaths operating parameters to lower its hiss which was a problem in my room when bi/tri-amping. Shawn Quote Link to comment Share on other sites More sharing options...
leok Posted April 24, 2007 Share Posted April 24, 2007 pauln, The statements about pwm output impedance being a function of frequency is more hype than reality, especially with the Tripath amps that use modulation frequencies around 1MHz (which is high enough so that there is little impedance change even at 20KHz). PWM is, in fact, remarkably immune to impedances of the speakers it is driving: real problems being excess current which could fry the output FETs (although there is a pretty good protection scheme in place for that) and opens. These problems could damage the amp (as they might damage other ss or tube amps). Treat the amp with the kind of care you would any other amp. If you hear it clip, turn it down .. and if it clips you'll hear it. Resist the temtation to see how hard you can drive it until in completely collapses .. you might have an answer, but no amp (as might be the case with any number of amps treated that way). Leo Quote Link to comment Share on other sites More sharing options...
sfogg Posted April 24, 2007 Share Posted April 24, 2007 "The TEAC's aren't available anymore -- Shawn bought them all.:)" Nahh, I only have five of them. They surely made at least a few more then that. Shawn Quote Link to comment Share on other sites More sharing options...
sfogg Posted April 24, 2007 Share Posted April 24, 2007 Leo, "The statements about pwm output impedance being a function of frequency is more hype than reality" Check out the measurements linked to earlier in this thread. 5ohms output impedance at 20kHz, something like 0.35 ohm at 20hz for the Sonic Impact Super-T. Have you ever measured the output impedance of your amp at different frequencies? One of these days I'll measure the Teacs. Shawn Quote Link to comment Share on other sites More sharing options...
Cut-Throat Posted April 24, 2007 Author Share Posted April 24, 2007 I haven't ordered one yet. I think I may bypass the stock version and try the Michael Mardis modifed version ($279). I'm also tempted to move to a higher powered version like the Winsome Labs Mouse: http://winsome-labs.com/products.htm The low watters get loud enough, but you're not going to shake the pictures off the walls. Considering the low prices, it's worth it just to buy one and see what you think. Dean, You can get a kit for the Trends Amp for about $46 - to bring it up to the musical level of the Mardis modified version. Also, you do know that the shootout preferred the Trends over the Winsome Mouse. Quote Link to comment Share on other sites More sharing options...
leok Posted April 24, 2007 Share Posted April 24, 2007 Shawn, I'll take a look at that. The way pwm works I'm a bit skeptical .. both numbers look high. Also, I'm not sure what the lower frequency "impedance" measurements really mean in that the output straddles the target output voltage at all points, meaning the output can't loose any amplitude due to "impedance." I'll take a closer look and see if I can add anything helpful. PWM tends to be tough to measure using standard methods. Leo Quote Link to comment Share on other sites More sharing options...
kaiser SET say Posted April 24, 2007 Share Posted April 24, 2007 So two pages later Kaiser wakes up to tell Erik he is right on the first call as my wife has a thing for pigs (maybe that's telling me something[]), this thing is heavy with cork feet so I had it setting on two of those cork bottom coaster stones to help with chassis vibration. I could not tell if it made that big a difference but she thought it was athstetically (sp) pleasing so that's how I rolled with it[] Fini, I should have clearified it's now her bedroom system which at the time of this picture it was set up in the sunroom of our old home. Beleieve me my albums are not in any part of her house[] and that would be the 90% I don't put stuff in[:S] Pauln has pretty much convinced me a pair of these should drive LaScalla's to pleasing level with bass to boot[] I just think the difference in the size of the mini iPod and Trends between the Scally's will absolutely blow people away[8] Quote Link to comment Share on other sites More sharing options...
sfogg Posted April 24, 2007 Share Posted April 24, 2007 "PWM tends to be tough to measure using standard methods." Only because of the ultrasonic noise can effect SNR measurements and such. Output impedance is easy to measure. I'll try and put one of the Teacs on the bench to measure its output impedance at a few points. Shawn Quote Link to comment Share on other sites More sharing options...
seti Posted April 24, 2007 Share Posted April 24, 2007 Max, I don't know much on your JVC but my wife's bedroom system Onkyo PS-50 (30WPC @ 8Ohm will absolutely light up any heritage at 100db plus and sounds fantastic and like your little JVC speakers the accompanying speaker on my Onkyo also hold their own well with several monitors I've heard. Exceptional build also but this system originally retailed for $1050.00 at BB back in the mid 90's and I picked it up at closeout for half off and it was a steal IMHO[] Kaiser was nice enough to loan me the Onkyo right after I brought my Belles home. I used them for many months not bad : ) Quote Link to comment Share on other sites More sharing options...
pauln Posted April 24, 2007 Share Posted April 24, 2007 I am using my Wright tubed active preamp to drive the Trends.The highest volume I have run so far is 9:00 on the preamp (scale from 7:00 to 5:00) which puts SPL meter peaks just under 100dB in my listening chair; so I figure the actual transient peaks are higher - guessing I'm using about 2 watts. The Trends output is speced to be clean up to about 6.25 watts, so I have additional headroom. I am quite certain that the level at which the Trends clip is WAY higher than I would ever consider for even very looud listening. My records sound better, my preamp quieter... another way of describing the Trends is that it does not sound like the amp actually drives the speakers - it sounds more like the speakers are pulling the sound from the amp, and that this is really easy for them to do. With the LS there is just no sense at all of any exersion or effort to belt out the music. I would also like to see measurements of the output impedance against frequency. The source of this notion was from two places; a Stereophile review of another 2024 chip amp where this curve was suspected in the listening tests and confirmed in the measurement tests, and discussion about it in the DIYaudio 40 page Trends thread. Whatever the reality it works with high efficiency horns! Quote Link to comment Share on other sites More sharing options...
kaiser SET say Posted April 24, 2007 Share Posted April 24, 2007 I'm sold on them Paul, think I'll see if I can't run a pair with this[] Quote Link to comment Share on other sites More sharing options...
sfogg Posted April 24, 2007 Share Posted April 24, 2007 Just measured the Teac quickly. A stock channel on the Teac measures at output impedance of 0.802 ohms at 20hz and at 20kHz it is at 4.03 ohms. One of my modded channels measures at output impedance of 0.27 ohms at 20hz and at 20kHz it is at 4.14 ohms. Shawn Quote Link to comment Share on other sites More sharing options...
sfogg Posted April 24, 2007 Share Posted April 24, 2007 Forgot to post the reason the impedance increases with frequency on these amps is because of the output inductors which is part of the low pass filtering on a switching amp. Shawn Quote Link to comment Share on other sites More sharing options...
leok Posted April 24, 2007 Share Posted April 24, 2007 Shawn, What was the output power during impedance measurement? PWM, due to output filtering, may be slew rate limited making it appear to have a higher (than actual) impedance at upper frequencies. The power handling capacity of the tweeter of a KHorn, or any other speaker is a small fraction of the power handling of the speaker overall. Slew rate limiting would limit the power available at high frequencies while not really reducing power available (or increasing impedance) for realistic acoustic requirements or demands at those frequencies. Leo Quote Link to comment Share on other sites More sharing options...
Cody_Mack Posted April 24, 2007 Share Posted April 24, 2007 I wonder if it could be linked to a computer...... Again, the L-R output of a computer's sound card is 'Line-Out', same as the output of a CD player, MP3 player, pre-amp out, etc. The PC provides a volume control along with multi-source functions, so it is in essence a pre-amp. Just a little tid-bit for the knowledge base [Y] I presently do most of my 'digital' music listening through my PC. Rick Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.