How to Pass a little time ...cont

Discussion in 'DIY' started by dBel84, Oct 22, 2018.

  1. JeffYoung

    JeffYoung Friend

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  2. dBel84

    dBel84 Friend

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    Depends on what you want to drive - my nearfield system does not demand a lot of power but I have a sneaky suspicion this version will drive my maggies resonably well too ( perhaps not to ear splitting levels without clipping, but I tend to be a low spl guy )

    It is not too complex to add the additional 20W as long as you have adequate heatsinking - mine will not handle the additional heat requirements. Sinks are sitting at a healthy 47 deg C. I have the little add on boards and contemplated adding another pair of FETS in parallel with the output pair but figured I would build it this way and keep options open if there was room for more. The stock recommendations are 1A bias but the general consensus is that 1.2A really opens up the amp nicely ( hence my choice to add a trimmer at R13 to allow for such an adjustment ) . My power supply is beefy enough to support the additional FETs should that be something I decide is needed at some point. Because my rail voltages are 19V DC ( as opposed to the stock 12 V ) my amp is probably closer to 20 W anyway.
     
  3. Cspirou

    Cspirou They call me Sparky

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  4. dBel84

    dBel84 Friend

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    Instead of starting a new thread will just add a short note about building the budget 100W AB amp / Griddle amp / FH9HVX

    This is a variant of a very popular clean sounding 100W amp on DIYA referred to as the 100W Ultimate Fidelity Amplifier.
    This amp has been cloned by several manufacturing houses and is available through aliexpress or ebay for very little money - I cannot vouch for the ebay version although I did buy one before X's board became available.

    My original plan was to use the ACP+ ( a Nelson preamp / headphone amp version of the J2 --- more of less ) as a preamp feeding the amp boards and all in a compact chassis that could be used in the office at work.

    I used one of the HK chassis that I was not able to resurrect - major oscillation in the HK775 and I didn't want to sacrifice any more time on it.

    Boards assembled - one of the , no, THE thing that attracted me to this build was the beefy inductors

    [​IMG]

    I used the original torroid from the HK775 , added a small 12V for the output protection and a 24V SMPS for the ACP+ and the front panel VU meters. I built a simple CRCRC filter point to point and crammed it all into the chassis.

    [​IMG]

    The ultimate plan for the ACP+ didn't work out

    1. a lesson in stupidity - I had pretty much everything i needed in my parts box and pulled out N fets instead of P fets which made things not work and nearly blow up

    2. after all the resoldering etc I ended up with one of the ACP+ units producing a major hum

    [​IMG]

    So I pulled the AVP+ units out , just added a volume pot and put it to the test

    ..dB

    [​IMG]

    I needed to reroute one or the ground wires to resolve a very faint hum but it is working perfectly and sounding much better than I expected - it has very good control of the music, has a quick response to transients but isn't the micro detail monster that my SIT amp is. It still sounds very good and well worth the money to build it.

    ..dB
     
  5. dBel84

    dBel84 Friend

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    I can't seem to help myself , the acrid smell of flux mixed in with the occasional skin singe because my eyes are not what they used to be and the angst when flipping the power switch for the first time - will I see twinkling lights or release the faerie dust and on the rare occasion a spectacular bang as a capacitor explodes... the cycle continues but let me present to you an F4 that neither smoked nor banged but let its lights dance to a sigh of relief

    Front

    [​IMG]

    Back

    [​IMG]

    Internal

    [​IMG]

    Setting bias

    [​IMG]

    Speaker SSR working

    [​IMG]


    Still needs to be thoroughly cooked before I can test it on my speakers but this has been gradually built for some time and I finally took some time to get the panel work done.

    ..dB
     
  6. rhythmdevils

    rhythmdevils MOT: rhythmdevils audio

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    I wish there was a double like button.
     
  7. Cspirou

    Cspirou They call me Sparky

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    It looks like you have some extra boards there.

    What do you have connected to the transformer and the two boards in the corners?
     
  8. dBel84

    dBel84 Friend

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    Extra boards are a soft start next to the transformer and the 2 boards at the back are solid state DC sensor/protection boards.

    I decided, with this build, I would try and make it as robust as possible as I think this is going to be my long-term primary amp (if it lives up to expectations)

    .. dB
     
  9. dBel84

    dBel84 Friend

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    all buttoned up - but crappy cellphone photo

    [​IMG]

    I had this very odd "waxing and waning" loss of volume in the left channel - I was convinced it was the uber rare input Toshiba Jfets and was dreading trying to hunt down a matched pair but it seemed to resolve when messing with the input RCA connector but ultimately narrowed it down to the little SSR speaker protection unit ( which I didn't build ) - the spade connector had a dry solder joint and would lose connectivity randomly but frequently enough for it to not be obvious as to what it was.

    All is good - this might be the best of the FirstWatt amps yet , early days but it is going to remain in the stable

    ..dB
     
  10. dBel84

    dBel84 Friend

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    I thought I would post a little summary of the LuFo Lite here - main thread is over at DIYA

    The name is derived from the Mosfet Follower amp which uses a single mosfet and is choke loaded = MoFo ( a very large thread dedicated to it over at DIYA ) , The LuFo is a JFET (LU1014D) follower and also choke loaded but in this case, it uses a microwave transformer primary as the inductor load - MOT ( microwave oven transformer )

    The LuFo Lite is a headphone amp derivative of these simple circuits and uses a single JFET ( the LU1014D) . I decided to try this out because I had most all of the parts lying about and had bought 50 JFETs to match with the intent of building the First Watt F3 someday and it turned out I got a batch in sequence and so far they all measure identically.

    My plan had been to assemble this P2P but there were a small batch of prototype boards made and I had the good fortune of receiving a set.

    I assembled the heatsinks from 3 separate pieces and bolted them onto a square core of alu bar with lots of thermal paste at the junction. Here is the end result with the Vicor Flatpac smps power supply I intended for the project

    [​IMG]

    I assembled the boards with bits I had in my spares drawers

    [​IMG]

    and I fired it up earlier without any catastrophic surprises

    [​IMG]

    After I confirmed sound emanated from those little speakers, I hooked it up to the test rig on my bench and it made some sweet sound. Nothing to write home about but I suspect the circuit needs a little tweaking as the voltage at the Drain of the FET is much lower than I had been anticipating.

    more to come ..dB
     
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  11. dBel84

    dBel84 Friend

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    I see I left out some of the fun since this last post.

    The 12V rails were dropping to 7v at the drain of the fet and not moving much current. so I strapped the 2 12V rails in series and used the 24V rail. This livened things up quite a bit and those 10W power resistors were suddenly pushing 4.7A through them. Needless to say, 110 deg C in no time at all. this is when I decided to add a power resistor, bolted to the heatsink. A bit of a pain to drill and tap with the amp board attached but only 2 holes

    [​IMG]

    After making sure all the voltages were good, I left it running for about an hour

    [​IMG]

    The bias is only 1.3A (target is 1.7A)

    The jfet gets to about 35 deg C , the resistor housing is just shy of 50 deg c and the heatsinks matched the jfet at 38 deg c

    sounded good - driven directly from dac so no major volume but enough to hear the quality of sound and to make sure no gremlins
     
    Last edited: Aug 24, 2021
  12. dBel84

    dBel84 Friend

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    A mate of mine recently pinged me that he had found a pair of Realistic Minimus 7's for $20 and was all excited about them being a kickback to the 80's "dorm" sound. Not being in the country at the time, let alone knowing anything about radioshack, I took a quick dive into "the google machine" and discovered a treasure trove of reminiscence and tweaking that had been done to these micro speakers of old. I also discovered something else ..... they looked vaguely familiar. My friend had sent me a picture of his little walnut veneered boxes but the online images showed plenty of small cast aluminum speakers with metal grills - I was sure I had picked up a pair from a yard sale / goodwill a decade ago - and yep, sitting abandoned on a shelf in my basement I discovered a pair of dusty "Optimus AV7". It turns out these speakers came in many varieties and the pair I had been hoarding for possible patio use had been shielded for use next to monitors. I had already agreed to modify my mates Realistic minimus 7's so I figured - "what harm can be done"

    [​IMG]

    I gave them a quick sand and primed / painted them (in "Dr Who Blue" - left over from a project for my daughter - although that looks a little lighter than the trusty Tardis) , Luckily the small binding posts from PartsExpress fit snuggly, I added a switch to be able to bypass the recommended L-Pad in case I preferred the tweeter without attenuation. ( about 3dB )

    The big issue with the original was that the crossover only cut the top end, the little mid/woofer was allowed to run full range and the cone breakup caused some nasty spikes in the 2-4KHz range. So upgraded the crossovers per one of the many threads on the forums. - this one seemed to have the most agreement and measurements looked good.

    I have never doped drivers before and seeing as there was some consensus that this did wonders for this little driver, once again , "all in" :) - amazon supplied me with some artist varnish called "Grumbacher's Damar Varnish" - again , this was the recommended muti of choice and I have no prior experience.

    Now, you would think that I might have listened to them in stock form before going to all this effort , but no, I just snatched a few minutes here n there and went along my merry way, whistling while I worked.

    I am very pleased to report that it was a very worthwhile effort - they sound precise and expansive. Exceptionally natural decay and very responsive ( ie quick without any audible distortion or nasty peaks ) They roll off quite quickly below 100Hz so will need to be paired with a sub or dedicated bass unit but pushed up against a wall , they deliver a very full sound and have now replaced my monitors at work. I would encourage anyone to grab them if they saw them sitting on a goodwill shelf or in a box at a yardsale - they scale well beyond their meagre size and deliver exceptional sound ( with a little tweaking - but may sound great as is too )


    I may as well post the slow progress of another project too

    With all the amps and speaker fun , especially when there is a small gathering, it became apparent to me that I needed a way to more easily switch between gear ( especially after some close calls with people "hot swapping" speakers )

    I knew that the ADCOM GFS series speaker selectors had a whopping big resistor inside to protect amps against shorting and load variation. So I picked one up for cheap - $50 ish

    [​IMG]

    The major issue with these units is the weird twist type wire connection and obviously you can only switch speakers

    I decided to upgrade the binding posts to more traditional 5-way posts and add a robust ceramic switch which could handle the currents for the power amps

    It is not complete but this progress shot will give you a sense of what it will be

    [​IMG]

    I will then need to build a switcher for the source to the amps so that I can use a single source and then select amp and speakers of choice - might have been more simple to follow the traditional shut it all down and add new component but then I wouldn't have tinkered with this :) . more to come...

    ..dB
     
  13. dBel84

    dBel84 Friend

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    some more random stuff

    Switcher wired up and working, waiting for a paddle type knob for the front

    [​IMG]

    and an adapter for our mad planar scientist = RD has a franken Glass which has no Noval capacity and I could not find adapters for octal to noval anywhere , so I made up a set for a good cause

    [​IMG]

    epoxy took longer to set but it all worked out and it works like a charm

    ..dB
     
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  14. dBel84

    dBel84 Friend

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    put the LuFo Lite in a box so that I could reclaim my work space ( and to finally be able to test this thing as a headphone amp

    [​IMG]

    survived the casing up process, now to add a 4 pin xlr and TRS jack
     
  15. dBel84

    dBel84 Friend

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    and now for something a little different


    [​IMG]

    I really had no intention of buying another deck, but @dsavitsk posted this early series Linn LP12 for sale and .... how could I resist. I know it is not regarded as the best table around and generates some polarizing views but having grown up in Brit-Fi, it as akin to picking up an E-type for a great deal.

    Wrapped safely for shipping and arrived in time as a little gift to myself

    [​IMG]


    First thing - I am not a purist and have no qualms in modifying for practical reasons.

    My intent is to refresh the LP12 and set it up to play music where it will be enjoyed

    Step 1. Dismantle

    a view from below

    [​IMG]

    pulled apart and cleaned / oil drained etc

    [​IMG]

    [​IMG]

    I made a few interesting discoveries in the tear down

    - although this is an early series Table , it is a bit like "Trigger's broom"
    The sub chassis was replaced around 1992 and the bearing likely around the same time - just pre-circus (black ring and liner for LP12 fans) . The arm-board as also replaced from original ply to the MDF laminate of the later series.

    I added corner braces to the plinth (both for stability and to allow me to add some decent feet) and sanded it down , ready for new life in espresso stain

    [​IMG]

    [​IMG]

    I received the new set of springs today and am waiting on the oil ( couldn't source it locally and although shipping was a little more, the oil itself is cheaper ) . The belt looks in decent shape but I have sent an inquiry to a Linn dealer to see if i can get a new one. ( The oil supplier didn't have any belts in stock or that would have been the obvious choice )


    and while I was waiting for everything to arrive - I started exploring motor controller options.

    I put together the phoenix motor controller by user Pyramid on DIYA

    [​IMG]

    - just waiting for the programmed chip to arrive before I can test it

    and built an arduino based tachyometer to go with it

    [​IMG]

    I also happen to have bought a second option which only became available after I had bought everything for the previous one but might be better for this assembly, in which case I have a spare one to find a new home for .

    more to come as parts arrive and I finish putting it all back together.

    my thanks to @dsavitsk for aiding this romanticized idea become a reality

    ..dB
     
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  16. dsavitsk

    dsavitsk Friend

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    @dBel84 that's more work in 3 days than I did in 30 years. Clearly it has found its proper home.

    Makes sense about the circa '92 updates. That's about a year before I got it, and the prior owner sold it having just upgraded to something all new.
     
  17. JeffYoung

    JeffYoung Friend

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    I got a lot of miles out of mine over 20 some years before moving to a 230V country. Should have brought it along and built a motor controller for it....
     
  18. dBel84

    dBel84 Friend

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    Small update

    I assembled the external motor control unit and tested it - seems to be operating as designed

    [​IMG]

    - the 60 is a 60Hz wave form for 33.33rpm , there is a switch to bump it to 81Hz for 45rpm

    I am not sure how to upload videos to show it working but you can trust me, it does.

    Not pretty - cased up in recycled psu from a server

    Front : the window on the front face is the arduino controlled rpm tachyometer , the window on top is the frequency display for setting the control unit

    [​IMG]

    rear : the potentiometer adjusts the final output voltage - this can also be done in the software but I had already added a pot to be able to set it up initially. The 3.5mm TRS is for the sensor lead to measure TT rpm, power jack/switch and IEC outlet for 120V ( or whatever the final setting is for a rumble free but appropriately running motor )

    [​IMG]

    and the sensor hooked up to my u-turn :

    [​IMG]

    a fraction slow but good enough to get the job done

    and finally started to assemble the Linn

    I had wanted an integrated psu as I don't really want more clutter. The power supply I was initially after was developed by Steve Cobham on DIYA and called the Zeus power supply - it also generates a clean wave form at both 60 and 81 Hz but has PID feedback from the sensor to accurately control the TT platter speed. I had attempted to grab them coming up for sale as they are no longer available for DIY - commercial interest bought out the rights and it will be available as an aftermarket Linn accessory. I had initially emailed Steve to ask if there were any still available and only after I had committed to buying all the parts for the external motor controller did I hear from him that he had a single assembled and tested board available.

    It arrived yesterday so I drilled out the holes to accommodate the board and could finally start the reassembly :

    [​IMG]

    The new Zeus power supply comes with a new printed switch that controls the unit , printed enclosure for the sensor which tucks in under the platter and a sensor display holder that I need to find an appropriate place to fit.

    I had ordered the "Valhalla" spring set - I originally thought that I would have to be updating the 1973 tired parts but my discovery of an early 1990's update probably made the new springs less important but as I had already bought them, I replaced them.

    Waiting on the oil to arrive from the UK but have found a cirkus subchassis and bearing .... trying to decide if this nervosa and uprgaditis craziness is justified :)

    and speaking of nervosa :

    Cantilever and stylus of my AQ404B

    [​IMG]

    - image taken with my aging S8 and a monocle :)

    It is an elliptical diamond stylus on a hollow sapphire cantilever ( although this appears to be boron - which some of the AQ404 series had )

    I had been toying with having soundsmith retip it as the audionervosa has slowly been creeping up but aside from a little bit of dust, I am guessing many more hours of nervosa listening ahead

    still more to come ..dB
     
  19. Biodegraded

    Biodegraded Friend

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    Kudos for the orange practice puck on the U-Turn. Heavier and more effective than the black game pucks.
     
  20. dBel84

    dBel84 Friend

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    seeing as I was on a roll, I set up the armboard last night and adjusted the "bounce" - they say to do this by feel and should allow a few seconds wobble. Not quite done yet as I need to set up the software on the arduino and make sure the sensors are all in the best location - but this is essentially it.

    [​IMG]

    I made the phono cable by cutting up some of the cables I had and used an angle din for the tonearm.

    and the glam shot

    [​IMG]

    ..dB


    EDIT :
    didn't think a new post was warranted - "programmed" the Zeus controller EEPROM last night - took me 2 hours to figure out the interface and 30 seconds to program it . I couldn't figure out why I couldn't get accurate speeds with the PID feedback - turns out that there is a ratio in the calculation that used the line frequency - when I changed the formula to use 60Hz, it all worked as expected.

    It is actually pretty slick - simple press of the switch starts the platter and it gets to a stable 33.33 in about 1 minute. Hold the button for 3 secs and it ramps up to 45rpm, similar process to get it back down to 33.33 and then a 1 sec push to switch it off.
     
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    Last edited: Jan 13, 2022

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