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AD797 Phono Stage Build and Help Desk Thread

Discussion in 'Turntables' started by HypnoToad, Feb 11, 2013.

  1. HypnoToad

    HypnoToad Ms Puss Puss Subscriber

    Messages:
    6,041
    Location:
    Melbourne, Australia
    This is for those building the AD797 Phono Stage:

    All questions, answers, reviews, tips etc will be here.


    Here's the latest PCB's (ignore the date):

    [​IMG]

    As a PSU you can use any low noise split rail supply with + & - 12vdc to 15vdc. Or 12v SLA batteries.


    LATEST BOM for AD 797 MCPS - 01/14/18

    CHECK THIS BEFORE YOU ORDER

    Unfortunately I can't check every part number to see if they have them all in stock at all times, so ask if you find something out of stock and we will assist you in finding the right part.




    MOUSER


    Qty X Part Number / Description

    2 X 584-AD797ANZ / ULTRA LOW NOISE OP AMP IC AD797
    OR
    2 X 584-AD797BRZ / ULTRA LOW NOISE OP AMP AD797 SMD (Slightly better than std AD797's but need to be on an SMD to DIP 8 Adapter

    4 X 575-21043380 / IC & Component Sockets 8P SOLDER
    4 X 71-RN60D-F-200K / Metal Film Resistors - Through Hole 1/4watt 200Kohms 1% 100ppm
    4 X 71-RN60D47R0F / Metal Film Resistors - Through Hole 1/4watt 47ohms 1% 100ppm
    4 X 71-RN60D3900F / Metal Film Resistors - Through Hole 1/4watt 390ohms 1% 100ppm
    2 X 71-RN60D-F-16K / Metal Film Resistors - Through Hole 1/4watt 16Kohms 1% 100ppm
    8 X 71-RN60D-F-10/R / Metal Film Resistors - Though Hole 1/4watt 10 ohms 1% 100ppm
    2 X 505-FKP20.015/63/2.5 / Pulse Film Capacitors 63V .015uF 2.5%
    2 X 505-FKP24700/63/2.5 / Pulse Film Capacitors 63V 4700pF 2.5%
    8 X 555-RFS35V100ME3#5 / Aluminum Electrolytic Capacitors - Leaded 10uF 35V
    4 x 555-RFS50V100MG3#5 / Aluminum Electrolytic Capacitors - Leaded 10uF 50v
    12 X 505-MKP2D031001F00KI / Film Capacitors 0.1uF 63volts 10%
    2 X 80-PFR5221J100J11L4 / Film Capacitors 100volts 220pF
    2 X 652-3296Y-1-102LF / Trimmer Resistors - 1K ohms Sealed Vertical Adjust
    2 X 652-3296Y-1-202LF / Trimmer Resistors - 2K ohms Sealed Vertical Adjust
    1 X 737-EBC-03-E / Fixed Terminal Blocks 3P 7mm Pitch
    4 X 534-8846 / 4mm x 8mm Standoffs ***IF NEEDED***

    Select a pair of DC blocking caps below or Source Any Good Film 2.2uf Caps

    The Russian PETP K73-16's below are great sound quality at a super low price.

    2 x 2.2 uF 63V RUSSIAN PETP AUDIO CAPACITORS K73-16 (Available on Ebay)
    2 X 667-ECW-F2225JA / Polypropylene Film Capacitors 2.2uF 250V 5% - Panasonic - Fair Quality
    2 X 505-M102.2/250/5 / Film Capacitors 250V 2.2uF 5% PCM27.5 - Wima - Good Quality


    Off Board Components

    1 X 696-SSL-LX5093IT / Standard RED LED - Through Hole HIR
    1 X 71-RN60D-F-8.2K / LED Current Limiting Metal Film Resistor 8.2kohms
    2 X 568-NYS367-9 / Phono (RCA) Connectors RCA PANEL JACK GOLD/WHITE REAN
    2 X 568-NYS367-2 / Phono (RCA) Connectors RCA PANEL JACK GOLD/RED REAN
    1 X 530-111-2223-001 / Ground Binding Post Nickel
    1 X 691-2M1-DP1-T1B1M1QE / Mini Toggle Switch DP


    Select a pair of op amps for the second stage, the LME49990 are no longer in production but work well if you can get them, they need to be on an SMD to DIP 8 Adapter,

    2 X 926-LME49710NA/NOPB / OPAMP AUDIO MONO AB HIFI 8DIP - May be hard to get also

    2 X 595-OPA1611AIDR / OPAMP Low Pwr Prec Op Amp - These need to be mounted on a SMD to DIP 8 Adapter

    Another option is a pair of OPA627's (OPA637's won't work) or a pair of the Burson V5i single which are both more expensive. (No Affilliation)
     
    Last edited: Feb 23, 2018

     

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  2. GreatTone

    GreatTone Super Member

    Messages:
    2,290
    Location:
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    Are you saying you leave the 2 batteries connected, plus to minus, then charge both batteries at once with the 24V charger? It's too late for me, as I already bought a good 12V charger, but I just want to understand.

    I'm getting close to finishing mine. I drilled the chassis holes and populated the board this weekend. Now I just need to wire it up (and install the missing input filter caps when they arrive in a few days). I'm hoping to be listening by next weekend.

    I'm really hoping this phono stage won't be plagued by RFI. My HTMCPS sounds great and mostly quiet with 9V batteries, but with 12V of lantern batteries or the SLAs, it's very noisy with both hash and actual station interference.
     
  3. WntrMute2

    WntrMute2 AK Subscriber Subscriber

    Messages:
    1,734
    Location:
    Royal Oak, Michigan
    I really try and buy locally to support our local merchants. So I stopped by the local Batteries + on my way home from work to look at the SLAs and 24V chargers. Well the SLAs were $32.00 each and the same little charger described in the B-town thread was a whopping $52.00. Now the batteries are 2.5 X as much as on Amazon and the charger was almost 10 X. Sorry local guys, I'm shopping for these at Amazon!
     
  4. jimreeves

    jimreeves Poopy & Me Subscriber

    Messages:
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    Location:
    New Port Richey, FL
    A link to those amazon parts would be handy...

    are they similar batteries to these?

    [​IMG]
     
    Last edited: Feb 11, 2013
  5. WntrMute2

    WntrMute2 AK Subscriber Subscriber

    Messages:
    1,734
    Location:
    Royal Oak, Michigan
  6. HypnoToad

    HypnoToad Ms Puss Puss Subscriber

    Messages:
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    Location:
    Melbourne, Australia
    Yes, I leave my batteries connected together, and I use the same plug on the charger (minus the ground connection) as I have on the phono stage, I can then unplug the phono stage from the batteries and plug in the charger.
     
    Last edited: Feb 11, 2013

     

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  7. HypnoToad

    HypnoToad Ms Puss Puss Subscriber

    Messages:
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    Location:
    Melbourne, Australia
    Setting the Trimmers for Impedance and Gain

    The trimmers for the impedance give a range from zero to 1k ohms, do not go too close to zero or you are shorting out the inputs, it won't damage anything you will just lose sound. I would say that 50 ohms is the lowest I would go, so you have a range of 50 ohms to 1k to play with. The trimmers come set at around 500 ohms. I set mine at 100 ohms which seems to be the optimum for most moving coil carts. If you have a high output moving coil this phono stage is not for you.

    Impedance Adjustment: (Never connect the DMM to the phono stage while its on!)

    Turn Off the phono stage and disconnect the turntable interconnects from twith blue circles for eachhe phono stage, then connect your DMM to the inputs of the phono stage, I have marked the points with red arrows for the right channel, use the same points on the left channel. The trimmers are ImpR (right) and ImpL (left). Turning clockwise lowers the resistance, so with the DMM connected just turn slowly, you will find you can get very accurate readings but you will need to go really slowly when reaching the desired setting. Just turn back and forth if necessary to get it spot on, these things keep there settings extremely well.

    You can off course set these on the fly, by ear, but I would check with a DMM later as I have found my ears are not good enough to get both channels the same. Once you like the sound then you can fine tune them with the DMM using the procedure above.

    Gain settings: (Never connect the DMM to the phono stage while its on!)

    Moving coil cart outputs range from around 0.2mv to 0.8mv which means one size does not fit all. A stage that gives the correct volume for 0.2mv will be too loud when one with an output of 0.8mv is used and vice verse.

    You can see in the photo I have marked the testing points for the right channel with purple arrows, it's the same for the left. It's a good idea when soldering these resistors in place to not have them too close to the PCB, leave a little room so if you have a DMM with mini-grabber leads you can attach them to the legs of the resistors.

    The trimmers are GainR (right) and GainL (left).

    The range of the trimmers is 0 ohms to 2k ohms, the lower the resistance the less gain you get, turning them clockwise lowers the gain. They come set at around 1k which is good for carts around the 0.3mv region. I have a medium output cart with 0.8mv's so I set this to 500 ohms and another 0.26mv which is fine at 1k.

    You can again adjust these by ear but check them later with a DMM using the instructions above to make them equal, I have found my ears are around 100 ohms out :D.

    Set the gain of the stage so your volume control is around 12.00 o'clock for normal listening or to be in line with your tuner, Cd player etc.


    [​IMG]
     
    Last edited: Jan 13, 2018
  8. HypnoToad

    HypnoToad Ms Puss Puss Subscriber

    Messages:
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    Location:
    Melbourne, Australia
    Fixing The Missing Trace

    [​IMG]

    The missing trace is only 5mm and goes from the 4700pf cap C22 to the 47 ohm resistor R2, so I just soldered the leg of R2 to the leg of C22, a very simple permanent 10 second fix.

    So just leave the leg of R2 closest to C22 long, bend it towards the closest leg of C22 and let it touch it against the PCB, then solder at R2 pad and C22 pad making sure you solder the R2 leg to C22 leg, snip off the excess and you're done.

    If more PCB's are made there will be no missing trace. :yes:

    [​IMG]
     
  9. superblast

    superblast New Member

    Messages:
    3
    Oh shoot, I was hoping this might work for my setup but I guess not. Started reading on another forum and saw a post referencing your mods to the Cambridge Audio 640p and then found AK and have been reading up on the various DIY options.

    Do you think the CNC or HTMCPS amps would be better suited for my setup? I'm really intrigued by these after reading comparisons to highly regarded phono preamps. My TT is a Rega P25 with a Sumiko Blackbird which has an output of 2.5mV. I've been using a Sony E80ES preamp which is supposed to have a respectable phono stage for a built in. I thought I'd see what else is out there though.
     
  10. WntrMute2

    WntrMute2 AK Subscriber Subscriber

    Messages:
    1,734
    Location:
    Royal Oak, Michigan
    I'm trying this build for the same cart. I'll let you know in a few days hoy it works out. Waiting for sla batteries
     
  11. sachu888

    sachu888 Spare the tigers, kill me Subscriber

    Messages:
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    Location:
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    This Phonostage works best with LOMC.I recommended HTMCPS for your HOMC http://www.audiokarma.org/forums/showthread.php?t=418308

    Regards,
    Sachin
     

     

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  12. OldSch00l

    OldSch00l Seeking a Happy Medium

    Messages:
    879
    I'm totally going to build one of these, looks like this will be the thing that persuades me to become a subscriber... :yes:
     
  13. GreatTone

    GreatTone Super Member

    Messages:
    2,290
    Location:
    Falls Church, VA
    Ok, so I finished mine last night. It was too late to play loudly, but even at modest volumes I could tell a major difference between my HTMCPS. That's been a good one, but this new phono stage is a major, major upgrade. Very silent -- the music just seems to emerge from the blackness. Also much greater focus, with a more 3D quality where things hang in a very specific space. More detailed, but not at the expense of musicality. Excellent strong bass, but not bloated. Nice job! I think I'm really going to like this one.

    I still need to twead the gain. My AT33EV runs about 0.3mV. I set the trimmers to 1K, but it seems like the level is just a bit low. If I want it a little louder, how far should I go? 1050 ohms? 1200? I'm just trying to get a sense of how sensitive it is.

    Also, you may remember I live by a giant transmitter. The radio station interference is about the same as the HTMCPS, but without the little bit of hash that was there before. I tried various things, including a cap across the power supply, but that made it worse. Also, a cap from the power supply to case ground made it worse. The only thing that made it better was when I touched the outer barrel of the output RCA jack and the case at the same time, and then it went away almost completely. The RCA jacks are not grounded to the case. Running a jumper from the outer (neg) part of the jack to the case made it worse, but running a capacitor from the neg of the RCA to the case made it better. This was just touching it on the outside with a cap. So I can open it up and solder a cap in, but any idea why this is happening like this? The interference isn't audible during play, but I'd like to get the last bit of performance out of it. Also, if you agree I should add a cap, what value should it be? I used 0.01uF, but I have other sizes. Thanks.
     
  14. jimreeves

    jimreeves Poopy & Me Subscriber

    Messages:
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    Location:
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    Last edited: Feb 14, 2013
  15. jimreeves

    jimreeves Poopy & Me Subscriber

    Messages:
    4,368
    Location:
    New Port Richey, FL
    YES, you should! :yes:
     
  16. GreatTone

    GreatTone Super Member

    Messages:
    2,290
    Location:
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  17. HypnoToad

    HypnoToad Ms Puss Puss Subscriber

    Messages:
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    Location:
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    Your findings of the sound quality are the same as mine, this phono stage really shines, it's easily beat out all my other stages and then some.

    Try 1.2k, and fine tune if from there.

    You can try the 0.01uf, 0.1uf and 1uf to see how they work or any combination of them.

    You are the test bed for RFI it seems so besides installing lead shielding around your house, did you ever try the ferrite beads?

    Someone did and I'm not sure it was you or not, you can put one on the lead from the batteries as close as possible to the phono stage.

    Also I remember Catman suggesting that shielded wired be used to stop RF interference. You should be able to buy it at Home Depot etc by the foot, they have twin conductor with the ground mesh around it which would be ideal for the inputs and outputs to the RCA's. You can also try it for the leads from the batteries to the switch.
     
    Last edited: Feb 14, 2013
  18. sachu888

    sachu888 Spare the tigers, kill me Subscriber

    Messages:
    1,272
    Location:
    Bharat,where Tigers rule
    A shielded Mic cable can be helpful for RF.

    Regards,
    Sachin
     
  19. GreatTone

    GreatTone Super Member

    Messages:
    2,290
    Location:
    Falls Church, VA
    I used shielded wire for the battery harness, and used the shield conductor as the ground. In order to reach the battery contacts, there is a couple of inches of unshielded wire for each connector, but I'm not sure that's enough to do anything. I tried all kinds of ferrite chokes with the HTMCPS, and they never did anything. That cap from the RCA cable neg to the case got rid of all the RFI, so I'll just go with that and hope for the best.

    I will say that when I go to touch the volume control of the amp, the interference goes up quite a bit. When I move away from it, it goes down. Maybe another clue? However, when switched to any of the other inputs it doesn't happen. And I've tried swapping inputs for the phono stage, with no luck.
     
  20. GreatTone

    GreatTone Super Member

    Messages:
    2,290
    Location:
    Falls Church, VA
    I was thinking last night I could get a case big enough to hold the PCB and the batteries, and keep the whole thing shielded that way. If it's a real problem, I may try that.
     

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