3dzapper Posted November 5, 2003 Share Posted November 5, 2003 Actually those square waves aren't bad for a fourty odd year old amp. The waves at 20Hz shows a drop off on response of the subharmonics and probably as stated above the limits of the power supply it tries but gets short of breath like us old men. From about 150 to 5k the there is a small overshoot which is harmonic distortion, not a great amount. over 10Khz the waves show the limits of the upper frequencies. It won't reproduce 100Khz. The power levels are within a DB or two except for 20Hz. There are just over 3 divisions at 800HZ the lowest is just under 3 divisions. If that is 17V to 14V what's that? 1.5db max? Still not bad for a fourty year plus old amp without adjustable feedback. I think the 800 and 1500Hz traces are the most telling about this amp. Where most of the the energy of music is concentrated it is close to perfect. My opinion. Rick Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 5, 2003 Share Posted November 5, 2003 Michael, An example of an integrated SS amp at 1kHz: Same amp at 1kHz but with the bass control turned down.... Of course it is worth mentioning that except for only a few speakers square waves through your speakers will look *MUCH* worse then this. And square waves don't exist in music. Shawn P.S. The above amp was Acoustic Research integrated amp from somewhere around the mid 70s. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 5, 2003 Share Posted November 5, 2003 I realize that square waves don't exist in music, but thanks anyways. The pics posted show that the amplifier closely followed the waveform, and that's pretty much what I was wondering. Btw, a solid state amp driven to clipping starts to deform, and flatten off the top of the sine waves, does it not? I have never seen what that looks like on a scope. Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 5, 2003 Share Posted November 5, 2003 A couple of examples of square waves through speakers: Which speaker sounds better? Shawn Quote Link to comment Share on other sites More sharing options...
sfogg Posted November 5, 2003 Share Posted November 5, 2003 Michael, " Btw, a solid state amp driven to clipping starts to deform, and flatten off the top of the sine waves, does it not? I have never seen what that looks like on a scope." Yes, picture a sine wave and basically clip off the top of it... that is basically it. Though just like everything else the actual clipping of an amp will vary depending upon its design and implementation. Shawn Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 5, 2003 Author Share Posted November 5, 2003 Okay some more interesting findings. I first did as Mark suggested and fiddles with the controls to get as flat as possible at 1Khz and set the output to 5 Watts at 1Khz pretty much Identical results not worth the trouble of posting. I thought Hmmm then I remembered that with the HF81 you can bypass the preamp section and drive just the power section using the Tape out jacks. Results varied here big time ! I will have a second one here later this week and will redo this testing. 20Hz 50Hz 100Hz 200Hz 800Hz 1.5Khz 2Khz 5Khz 10Khz 15Khz 20Khz Quote Link to comment Share on other sites More sharing options...
Painful Reality Posted November 6, 2003 Share Posted November 6, 2003 Your amp is overshooting. You should fix this. Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted November 6, 2003 Share Posted November 6, 2003 His mouth too. Quote Link to comment Share on other sites More sharing options...
Painful Reality Posted November 6, 2003 Share Posted November 6, 2003 LOL! Quote Link to comment Share on other sites More sharing options...
Deang Posted November 6, 2003 Share Posted November 6, 2003 It's that great Eico output iron at work, doing what it's best at -- midrange. Quote Link to comment Share on other sites More sharing options...
Painful Reality Posted November 6, 2003 Share Posted November 6, 2003 ---------------- On 11/6/2003 12:35:31 AM DeanG wrote: It's that great Eico output iron at work, doing what it's best at -- midrange. ---------------- Dean, if you want to judge about how an amp will sound by the quality of a square wave reproduction, you are in for a big deception. It can indicate some problems though. As an exemple, the overshooting and ringing in the midrange seen here is definitively one problem that should be fixed. But I guess Craig saw that and will assess the problem tomorrow. Quote Link to comment Share on other sites More sharing options...
Deang Posted November 6, 2003 Share Posted November 6, 2003 How does one really go about fixing that sort of thing? I thought this test primarily focused on the performance of the OPT. What the hell do I know -- I'm waaay out of my league here. Quote Link to comment Share on other sites More sharing options...
Painful Reality Posted November 6, 2003 Share Posted November 6, 2003 ---------------- On 11/6/2003 12:55:25 AM DeanG wrote: How does one really go about fixing that sort of thing? I thought this test primarily focused on the performance of the OPT. What the hell do I know -- I'm waaay out of my league here. ---------------- The square wave test does give a pretty darn good idea of the OPT ability to reproduce square waves, yes... Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 6, 2003 Author Share Posted November 6, 2003 Jeff, Your absolutley correct the amp is over shooting badly and is rolled off pretty bad also. This amp has all coupling caps replaced and cathode resistors replaced. All Electrolyes replaced . Keep in mind this last test is only of the output section which narrows the option for fixing this to very few parts count ! So tell me what do you think the problem is ? Craig Quote Link to comment Share on other sites More sharing options...
Deang Posted November 6, 2003 Share Posted November 6, 2003 Sit an anvil on top of the OPT? Quote Link to comment Share on other sites More sharing options...
Painful Reality Posted November 6, 2003 Share Posted November 6, 2003 ---------------- On 11/6/2003 1:02:04 AM NOSValves wrote: So tell me what do you think the problem is ? ---------------- Didn't I recommend you a book with a nice chapter on stability networks? Remember, it was one of those books I recommended you that were only scratching the surface (as you once wrote). Quote Link to comment Share on other sites More sharing options...
NOSValves Posted November 6, 2003 Author Share Posted November 6, 2003 Jeff, I wasn't asking your advise on how to fix this problem. I was asking what in your opinion the problem is . I already know what is it myself ! Craig Quote Link to comment Share on other sites More sharing options...
mike stehr Posted November 6, 2003 Share Posted November 6, 2003 You might be able to noodle with the feedback resistor and compensation cap values and clean that up. After replacing the more important needed parts of course. Quote Link to comment Share on other sites More sharing options...
Deang Posted November 6, 2003 Share Posted November 6, 2003 Amps are people too. Fords suck. Quote Link to comment Share on other sites More sharing options...
sunnysal Posted November 6, 2003 Share Posted November 6, 2003 btw ford sucks! my chevy will eat any ford for lunch! 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.