stax srm717/srm727-11 - Page 4

Thanks for the positive comment Argybargy I have been put off adding to this because of the general negative comment.

                       That I wasn't presenting this by the "way it is done in Head-Fi"

                          And yet looking at some posts they go on for greater lengths to mine --in the same lay-out.

                            My whole approach and attitude is bound up in the way that JLH [john linsay  hood ] .

                                approached it but very condensed- I love music but reproduction of it isn't always perfect

                                 Like John I believe in complete openness so that any fault in the electronic components is shown up    NOT to be "dummed down" to make it smooth by adding many frequency changing and stability components like small value capacitors . To me that is cheating.

                                     A certain ADE wrote in EW/WW that while on a breadboard his new design performed beautifully BUT transferred to a lovely to look at PCB he had to add comp capacitors.They affect the reproduction -yes to stop HF oscillation but also the perceived sound reproduction. 

                         Johns designs were always open -and latterly -high input impedance/high sensitivity any ADE will tell you that that is harder to achieve  low distortion than a low sensitivity/low input impedance.

                           John also used Mos-Fets at that time he was criticised for using them under the heading-"they are not as LINEAR than BJT"-quite right -BUT a lot more neg feedback can be applied as they have a higher bandwidth and as some know here have a more clear presentation.

              MY whole aim here is to achieve  a lot more open and natural sound-as you would hear live at a concert hall 

         Not smoothness for smoothness sake with rounded ends which after a while you feel inside yourself that you are missing something in the music but a feeling you are in the stalls listening to it live. I have no intention of changing my values learned from JLH. I know ADE have blazing  rows with each other on audio issues but I wont be changing mine.

The 727-11 produces quite a bit of heat-it does run in class-A. But heat means noise and this too will have be removed from the amp by  NEG. feedback.[more work for it]

        It is supposed to work by convection but it only takes a quick look at the size of the holes on the base plate to realise that the efficiency will be near nil.

               I understand that companies are  under legal restraints by governments  as tiny fingers could reach underneath and touch a live part. causing a massive legal claim.

      For those who dont have that problem- I got my old 717 base plate   and was going to drill  large holes in it bit as I wont be selling it I just removed the whole area of holes.Try using that base in front of your PC extraction fan and watch the CPU temp rise.

           That isnt enough as the bottom clearance to allow a good stream of cold air isnt enough.

              Using the old base plate I added new feet to it these I got from an old 70s  Japanese record player being used as suspension these raised up the base high enough to allow more air to get in.

                      I realise this isnt for everybody but just as a test  IF you have re instated the feedback as I suggested

                           run the amp without the top cover for 2 days to see if it makes an improvement.

                              I am talking about a very small   improvement as it sounds very good as it stands. 

                                   And remember IMO- SS equipment should never be switched off.

                                        The company I bought all my input equipment says the same -CYRUS Hi-Fi-UK

I said in a previous post that to work on the Stax 717/727 1/2 energizers that you would need  a higher impedance than your normal MM of 10M ohm input  because of the very high  impedance of the circuits and that 10M would cause the safety relay to cut out the power to the units inside.  I said I had a HP bench MM industrial version of very high input impedance.

     But I bought an Avo MK 4 VCM and noticed on the sites on that web page that Valve/Tube Voltmeters  were for sale . While these are old technology they still beat  most SS ones as far as input impedance is concerned and unlike SS measure a high voltage with the meter set at a low one only the needle would be damaged as the valve are nearly "bullet proof". At the moment they sell cheaply on EBay and others as nobody wants them but those unable to work on energizers because they don't have the right MM this is the answer. REMEMBER --there are MANY circuits for them ONLY buy ones that have an input impedance of say around 100M ohm . Many old Heath-kit  only have a 11 M ohm  input -not high enough.

     The only hard part is you might have to adjust a couple of controls  to set them up.And you have usually bought[depending on the circuit] a TT or two.  

Further to my above post I contacted a ex-government equipment seller in the UK as I saw  a Bradley CT471 very high impedance meter for sale[ 100M  ohms above 12V ]  No price was on it as it was on sale . Phoning them  I found it was selling very cheaply as it did not have a probe and no front cover [don't need the front cover and unless you are testing RF equipment   don't need the probe]. It was a total of including shipping of £37  probably $60 or so I ordered one. I have dealt with this company before all their equipment is guaranteed to work. That is a bargain! as one sold on eBay in ropey condition for £150.

                I don't want to mention the company as some business people might want to buy them as they have more and resell at a profit.

                     But if any Head -Fiers are interested I could  post it.