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  • If you don;t believe...

    I have suggested several times, old equipment needs re-caping. I have never provided objective measurements. Well here it goes.

    Parasond Z3 amp.
    Original noise floor from -100 to -60 dB. About 5dB hash along the entire spectrum.
    60 Hz -43 dB. 120 -44dB Spikes all the way up to 2K.
    Replaced the 4 4700 uf 50V caps.

    Noise floor remains about the same level, but straight line from 2K up. Barely off my IO box.
    But 60 Hz, GONE. 120 Hz 68 dB. remaining harmonics all in the 68 and lower range.

    Now, I would not call this an excellent supply. As has been noticed the tiny package just does not provide enough physical space for large enough heat sink and PS caps. The lesson is just proof you need to re-cap your old stuff.


  • #2
    Suggested??? I think you have done more than suggest.
    Anyhow, which caps in what part of the amp are you referring to? The larger power supply caps or every cap in the amp?
    http://techtalk.parts-express.com/fo...khanspires-but
    http://techtalk.parts-express.com/fo...pico-neo-build
    http://techtalk.parts-express.com/fo...ensation-build

    Comment


    • #3
      A lot of people say things emphatically with no backup. Just thought I would add some. You may be surprised how many people think their 40 year old amp is still the best sounding amp they ever heard. In some cases with maintenance, it can still be. I expect most here can wield a soldering iron. It is a shame many real music lovers do not have such skill and the very idea of a repair shop went away 20 years ago. Worse, not all schematics are available to inspect. You would think after 10 years they would be.

      In this case, just the four power supply main caps to provide the objective measure. The caps not in the signal path will not degrade the sound. Curious, again probably space restrictions, no decoupling caps on the main board for the audio section. If I were keeping it, I would change the caps in the protection circuit, power on delay etc. They have no effect on sound quality. The only two electrolytics in the signal path are the 10u input caps. I would replace them with .33u film as a subsonic filter if I were going to use it for music. For now, it remains just my bench test amp.

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      • #4
        Curious, as replacing every cap on the boards could be a major pita. Just the generally larger power supply caps a bit less involved. If a schematic can be found, I may try this on a 30yr. old Carver.
        http://techtalk.parts-express.com/fo...khanspires-but
        http://techtalk.parts-express.com/fo...pico-neo-build
        http://techtalk.parts-express.com/fo...ensation-build

        Comment


        • #5
          My Z3 schematic cost $5. Worth it. A PC based spectrum analyzer can verify your work. Just be sure you have a proper divider probe and a 4V Zener so you don't blow up your sound card, ( SOP, ARTA manual) I use RTA for a lot of things, but have several others as well as an old Tek scope. To measure noise, you only need a Watt or two so a big load is not needed. A 20 Ohm 10W resistor is fine. You are looking at a difference, not an absolute.

          Another way to look at it is if you have a board pulled out, that is half the work so go ahead and do anything in the audio path. If your PS is big bolt in cans, then you don't have to pull the boards so I see the difference in effort.

          Never seen the schematic for the Carver. I would be curious, They had a pretty fair rep back in the day. Bob was a pretty clever engineer pulling ideas from several other disciplines not common in audio.

          Comment


          • #6
            This would be one of their more plain jane multi-channel amps, the 705x. No fancy tracking down converter, etc.. If you are interested, I can pm the schematic.
            http://techtalk.parts-express.com/fo...khanspires-but
            http://techtalk.parts-express.com/fo...pico-neo-build
            http://techtalk.parts-express.com/fo...ensation-build

            Comment


            • #7
              Just measured the AC on my MOSFET amplifier. Only 50 dB from rated power. Looks like I have more work to do.

              Yes, I would be curious to see the schematic. The only one I saw was the "magnetic" amplifier which gave me a good laugh as it was so close to the driver we used on our tape reel motors. We did not bother with the integrator though. Description sounds impressive. https://hometheaterhifi.com/volume_4_2/av705.html

              Comment


              • #8
                Meh, it's an amp. Its flaws are probably more of omission than excess. You will have pm shortly.
                http://techtalk.parts-express.com/fo...khanspires-but
                http://techtalk.parts-express.com/fo...pico-neo-build
                http://techtalk.parts-express.com/fo...ensation-build

                Comment


                • #9
                  Got it. Thanks. As I mentioned, besides the main filter bank, I would replace the cap on the spreader and let it rip.

                  Comment


                  • #10
                    Follow up. When I built my MOSFET amp, I upgraded the Hafler 6600uF caps to a pair of 22,000 off e-bay. Now can't find any with the physical dimensions, so building a bank of 8 5600uF. ( 4 on a rail.) Only other electros in my amp are on-board bypass, so getting new 100u for them.

                    A bank of small is a pain, but lower ESR and can take higher ripple current. Cheaper actually.

                    Comment


                    • #11

                      To expand on something tvrgeek mentions in PM about the Carver 705x schematics concerning the possibility of intentionally mimicking some aspects of 'vacuum tube' sound.

                      Carver 705x ... it is an easy sounding amp, even when things should be sharp and harsh it tends to sweeten them up a bit. Music seems to come from, to use an audiophile term, a 'black background' until listening to a pair of Acurus amps. These amps do set the scene on a black background, don't sugar coat the sound, are more capable of 'floating' the sounds in the 'soundstage', and can 'pick fly$hit out of pepper' without being harsh. The difference is noticeable after only a short listen. Not having seen the test results, I would guess the Carver may not have a ruler flat frequency response. It may sound like the Carver 705x is a poor performer but it's not. It is a solid performer whose sins may be more that of omission than excess, or smoothness vs harshness. I'm an 80's teenager and remember the over the top treble pushed on early cds. I'll take smooth over 80's cd harsh any day. If you are the type of person that likes to sit back, grab a cool beverage, and have a long listen, you will probably like the 705x. If you are the 'pick fly$hit out of pepper' type, it may not be your favorite amp.

                      Again supporting tvrgeek theory is Bob's 'Carver Challenge' https://www.stereophile.com/content/carver-challenge Basically, Bob Carver states he can intentionally tailor his $700 Model 1.0 amp to sound indistinguishable from any $$$ 'reference' amp. Read the link to see if he succeeds.

                      I found this intentional tailoring of sound very interesting.

                      YMMV, IMO, $.02, ...
                      http://techtalk.parts-express.com/fo...khanspires-but
                      http://techtalk.parts-express.com/fo...pico-neo-build
                      http://techtalk.parts-express.com/fo...ensation-build

                      Comment


                      • #12
                        The ironic thing about his challenge is in the process, he built one of the finest tube amps ever! (Silver 7)

                        Well, time for one of those cool beverages. Highland Gaelic Ale. I have found none better. I'll clean up the workshop tomorrow. Just finished my SSR controlled power strip that can trigger off either the standard 12V audio trigger, or from a USB. Waiting on caps for my HT crossovers.

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