HT MC Phono Stage AD797

[jls001]

Not to hijack this thread, has anyone tried AD797 Op-Amp in a CNC MM Phonostage or SSP Pre-Amp?

The AD 797 is not a drop in replacement for the OPA2134 or dual LME49990 (with appropriate adapter) that is used in CNC or SSPre. I think it will need extensive modifications to both circuits to accommodate the AD 797.

 

[sachu888]

AD797BR(SMD version of Ad797) mounted on SOIC to DIP adapter can be used with CNC or SSP http://in.mouser.com/ProductDetail/...GAEpiMZZMv9yaQC4TiGCZp%2bzjCMT2SR84BXp0s2YqI=

Regards,
Sachin

 

[murali_n]

The AD 797 is not a drop in replacement for the OPA2134 or dual LME49990 (with appropriate adapter) that is used in CNC or SSPre. I think it will need extensive modifications to both circuits to accommodate the AD 797.

Hi joshua,

I know that it has to be used with the adapters, my question was about its performance in either CNC or SSP, if anyone has tried. :licklips:

N.Murali

 

[jls001]

I know that it has to be used with the adapters, my question was about its performance in either CNC or SSP, if anyone has tried. :licklips:

Sorry, I won't be able to try it on either of these - I have given away my CNC MM phono stage to a friend, and I never got round to building the SSP though I bought the board and parts.

 

[linuxguru]

Link to information about the Diamond Cascode, a Diamond-like Buffer/Current Booster:

Diamond Cascode, a Diamond-like buffer/current booster - diyAudio

The first implementation (the LF07 v1.0) is a current booster for SOIC-8 opamps, in a DIP-8 form-factor. It's already been tested with an LM318M in a MyRef Rev C.

The AD797 already has a diamond-buffer as its output stage, so there isn't likely to be much benefit from using a SOIC-8 AD797 with the LF07 - but just about any other SOIC-8 *single* opamp, like the TL071, NE5534, LF356, OPA604, OPA627, OPA827, LME49710, LME49990, ADA4627, etc., should work seamlessly on the LF07.

In all cases, it should improve the sonics of the base opamp significantly due to the Class-A output-stage biasing, and near constant-current (typically 0.5 to 2 mA) output-stage biasing for the opamp itself. It also has no current limiting circuitry, so it could be used in a low-power headphone amp like a CMoy or similar, for better output-stage sonics.

If there's any interest in beta-testing these modules, PM me or email me at siva dot chander at gmail dot com.

 

[HypnoToad]

Link to information about the Diamond Cascode, a Diamond-like Buffer/Current Booster:

Diamond Cascode, a Diamond-like buffer/current booster - diyAudio

The first implementation (the LF07 v1.0) is a current booster for SOIC-8 opamps, in a DIP-8 form-factor. It's already been tested with an LM318M in a MyRef Rev C.

The AD797 already has a diamond-buffer as its output stage, so there isn't likely to be much benefit from using a SOIC-8 AD797 with the LF07 - but just about any other SOIC-8 *single* opamp, like the TL071, NE5534, LF356, OPA604, OPA627, OPA827, LME49710, LME49990, ADA4627, etc., should work seamlessly on the LF07.

In all cases, it should improve the sonics of the base opamp significantly due to the Class-A output-stage biasing, and near constant-current (typically 0.5 to 2 mA) output-stage biasing for the opamp itself. It also has no current limiting circuitry, so it could be used in a low-power headphone amp like a CMoy or similar, for better output-stage sonics.

If there's any interest in beta-testing these modules, PM me or email me at siva dot chander at gmail dot com.

Would the LF03 work as a drop in replacement for the AD797 chip?

Are you going to get PCB's made for DIY'ers?

 

[linuxguru]

Would the LF03 work as a drop in replacement for the AD797 chip?

Are you going to get PCB's made for DIY'ers?

The LF03 is an earlier design - a fully discrete all-BJT dual opamp in DIP8 dual form-factor. It is a replacement for dual DIP8 opamps like the NE5532, OPA2134, LM4562, etc.

The LF07 is the one referenced above - it is a single-opamp, driving a current booster output stage. It will work as a direct replacement for any DIP8 single opamp, as long as there is a SOIC8 version of that opamp. In principle, it will work with the AD797 also, but without much benefit, because the AD797 already has an internal diamond buffer, so driving an additional discrete diamond buffer doesn't improve things much.

I have already received PCBs and all the discrete parts, which I can offer, but not many SOIC8 single opamps (except a few for testing, including TL071, LM318, NE5534, and similar). If you have high performance SOIC8 singles like the LT1028, LME49990, OPA627, OPA827, LME49710, etc., you should be good to go.

The ideal applications are small-signal and line-level filters/amps/IV-converters, but a low-power CMoy should also be workable.

 

[jls001]

Finally found the time to give the AD 797 HT MC PS a half decent cabinet:

This is thin, cheap sheet steel.


I took the opportunity to roll caps to an Indian made capacitor called DEC/MER (from the Russian PETPs that I had been running). I will allow it some burn in before any serious listening.

The power supply is from two 12 Volt, 2 Amps AC-DC adapters wired like two 9V rechargeable batteries (which I was using earlier). I do not notice any loss of dynamics by using these AC-DC adapters.

Notice also the DC "bus bar" running from the cabinet mounted sockets to the circuit board (red, black and white wires). This is to physically separate the output (signal) cables crossing the DC-carrying cables in close proximity.

Current gain is set for 0.25 mV cartridge with 100 Ohms loading.

 

[sachu888]

Looking nice Joshua,
Which wire did you use?It looks very neat.
Qwin tried quite a few output caps before settling down to Mundrof Supreme.Here is the review AD797 Phono Stage Build and Help Desk Thread - Page 36 - AudioKarma.org Home Audio Stereo Discussion Forums

Regards,
Sachin

 

[jls001]

Looking nice Joshua,
Which wire did you use?It looks very neat.
Qwin tried quite a few output caps before settling down to Mundrof Supreme.Here is the review AD797 Phono Stage Build and Help Desk Thread - Page 36 - AudioKarma.org Home Audio Stereo Discussion Forums

Regards,
Sachin

Signal carrying cables are RG-174 coax cables from Toyo. Thin and flexible, with proper braided shielding. This is a 50 Ohms IF/RF cable.

The DC carrying cables are generic, teflon-shielded, tinned copper multistrands of about 14 AWG (too thick for this application!).

I will try swapping out the 560 Ohms resistor to 390 Ohms as recommended by Hypnotoad. Some extra gain and some additional "air" has never hurt anyone
Yes, I read about the Mundorf Supreme cap. Will have to see where to source it from. But before that that I will try the DEC/MER as well as the default Wima cap.

 

[jls001]

I will try swapping out the 560 Ohms resistor to 390 Ohms as recommended by Hypnotoad. Some extra gain and some additional "air" has never hurt anyone
Yes, I read about the Mundorf Supreme cap. Will have to see where to source it from. But before that that I will try the DEC/MER as well as the default Wima cap.

I managed to find 390 Ohms resistors among the electronic knick-knacks and swapped out the 560 Ohms resistors. Since I was already used to the sound of the Russian PETP capacitors, I put those back in the circuit and removed the DEC/MER capacitors for now.

One immediate effect is the increased gain of the phonostage - I need to turn down the volume by about 5 to 6 dB for comfortable listening volume.

I have been too busy with the Pearl 2 build to devote time for any critical listening, but I think I could discern more details, especially in the highs (is that more air????), and marginally improved mid bass.

 

[dillihifi]

Well here's putting down my build of the AD 797 phono.

Well having recently procured a project expression 2 with a ortofon rhondo red cartridge I was in search of a nice LOMC phono stage for the same.

I initially contacted sachin (sachu888) for some pointers about the phono stage as well putting out a wanted ad in the forum. I promptly received the message that in case you want to go DIY then there is a nice AD 797 phono stage which would cater to the type of cartridge that I had.

Since the cost was not too much and having already dabbled into the DIY domain with the CNC phono stage build (only one channel was working and I having never got around to troubleshoot the same) volunteered immediately for this build and sachin sent me all the parts and the pcb for the same.

After the kit arrived I started to build the same over a weekend and though being a novice in DIY (having read umpteen threads over the net including the present one), I bravely attempted to complete the build on my own. Having struggled for the better part of the day in the evening I thought that my build was complete. After making all the connections I switched on the unit but alas there was no sound. I tried to troubleshoot but soon convinced myself that this is not for me and maybe I am better off buying completed units. Then I contacted sachin and asked him whether he can troubleshoot the board for me. Sachin directed me to Om (omisra) who gladly agreed for the same.

Yesterday the boards arrived having been thoroughly repaired and tested by Om (looked like a professional had rebuilt it) and I was itching to try out the same. In the evening got myself a pair of 9V batteries (my OPS is still WIP) and after connecting the phono stage I switched it on and the rest is history. I could not believe what I was hearing, this must be amongst one of the finest phono stages that I have heard. The sound was you can say with absolutely no hum, three dimensional sound (now I appreciate the mc carts, how it extracts the smallest nuances).

Well I have set the input impedance at 100 and the gain trimmer at 1k. There is no problem with the gain, it equivalent or a little more than the CDs.

Now looking for some suggestions for a cabinet for the same.


PS. : Thanks to Om and Sachin for helping me out for discovering this beauty of a phono stage.

 

[jls001]

Now looking for some suggestions for a cabinet for the same.

First of all, congratulations! on completing the build. The Hypnotoad AD 797 phonostage is a very good phono stage. And I am sure with such a fine cartridge, it must be singing a sweet tune.

Questions and suggestions:
1) this phono stage deserves a fine cabinet. I have personally not tried it but you can get a suitable one from Silicon Ray in Hong Kong. Alternatively, if you can find enclosure builders in NCR, commission a nice aluminium one. If you plan to continue using batteries to power it, you can get away with a small cabinet. I find improvement in the sound by using two 12V adapters (rated for 1.5 to 2 Amps, though this is overkill) instead of two 9V rechargeable batteries. Besides, adapters don't need recharge. I recommend it over 9V rechargeable batteries for the sonic improvement and the convenience. If you plan to build the OPS and house it in the same cabinet, then you will need a much larger cabinet. If you plan to follow this, isolate the OPS in a different chamber.

2) Are you using the regular counterweight, or have purchased the heavier one meant for heavier cartridges? I just ran quickly through the manual of your TT and it seems the regular counterweight is intended for cartridges weighing 4 to 7 grams. Your Rhondo Red weighs 10.5 grams. So you need the heavier counterweight.

 

[dillihifi]

Thank you all for making this possible. I was indeed inspired to try my hand by reading your thread.

I am thinking of getting separate cabinets for the phono stage and the power supply. I have already populated the OPS board, am yet to get an R-core transformer and a suitable cabinet for the same. Let me think about using two 12v adapters, I think the cost would around 300 bucks. Let me try ebay/neighborhood shops for the same.

Regarding your question of the counterweight. I actually do not know about the same but since this was sold alongwith the cartridge by project I am sure they would have included the correct counterweight. Further I had adjusted the tracking force and could get the proper force with the included counterweight

 

[dillihifi]

Spent a major part of the day listening to various genres of music. This phono stage is really worth it. It seems getting better and better. Any idea on how much listening time a pair of 9V batteries could give ? I have listened to the phono for approx. 5 hours including 3 hours today and it is still going strong.

It was indeed a great idea to build this phono stage. Anybody with LOMC carts should definitely try it out it certainly does punch above its weight. I for one is one happy user :yahoo:

 

[jls001]

Any idea on how much listening time a pair of 9V batteries could give ? I have listened to the phono for approx. 5 hours including 3 hours today and it is still going strong.

30-35 hours is the usual norm.

I have two pairs - "Accuplus" 250 mAH, and "infinite" 300 mAH. Accuplus lasts longer.

 

[dillihifi]

sachin : I noticed from the photos in ak that you are using a nice enclosure for the cnc some details please.

I am inclined to go for a separate cabinet for this and keep the power supply separate. Any thoughts ?

 

[sachu888]

sachin : I noticed from the photos in ak that you are using a nice enclosure for the cnc some details please.

I am inclined to go for a separate cabinet for this and keep the power supply separate. Any thoughts ?

Hi Tapan,
My CNC enclosure is from Hammond manufacturing.I had bought it from Amazon @ $22.One of my friend shipped it for me Amazon.com: 1455N Silver Aluminum Box, For 3U Sized PCBs, With 11 Card Guide Slots, Box = 6.3 x 4.6 x 2.1 in: Everything Else
You can use SMPS box from junk CPU for Power supply enclosure,as it already has IEC connector at back https://www.google.co.in/search?q=c...-a-computer-smpspsu-is-working-or-not;500;335

Regards,
Sachin

 

[dillihifi]

Well as far my experience goes the 9V batteries do not last for more than 10 hrs. Yesterday while listening the sound started deteriorating and I must have been listening to the setup for barely 5 hours. I disconnected and measured the voltage across the terminals it was around 5v.

Going by JLS's experience I hunted for some old adapters and found two nos of 12V adapters though they are rated at 0.5A I tried the method employed by JLS and connected them in the same pattern as the dry cells and found that these were performing as well as expected.

 

[jls001]

Today I completed a Hypnotoad AD797 phono pre build for malvai. Thanks to Sachin for sending me populated Hypnotoad board as well as populated OPS power supply board. Raghu supplied the cabinet populated with an R-Core transformer. It also came populated with the IEC socket and front panel push button (with a cool blue LED lamp built into the switch).

The toughest part was soldering the LME49990 opamp into the adapter. Being SMD, this chip is tiny and needs a pointed solder tip. This is the second time I've done it, so I now got the hang of it.

Gain and impedance loading are calibated for a Denon DL103 Pro (110 Ohms, 0.35 mV). The gain setting is approximate for now as I have used a cartridge with a 0.23 mV output. But it can be recalibrated easily as a 2KOhms Bourns pot is provided for gain calibration.

Like my previous build, this build was also full of missteps. First, the right channel refused to sing. Then the front panel switch conked off. Further, there are so many varieties of IEC sockets, that I always end up in confusion on how to wire them correctly without blowing it up. This one was one of the simplest around, and its deceptively simple layout had me foxed for quite some time.

I knew that the right channel issue had to be dry solder on the input or output leads as I used CAT6 wires. To my ears, CAT wires sound better than any stranded wires I have tried for internal wiring, but they are quite prone to bad contacts due to dry solder. So a tip for anyone who wants to use CAT5/6 strands - tin the wire with solder after scrapping it clean with the side of a blade or emery/sand paper to get proper solder contact. I did all that and still had bad solder. So extra care is called for.

Right now it is burning in. Bass is still flabby. It will improve with more record sides. No noise/hum.