Try loading it at 750ohm (this is the max you can go to) I am liking it at present over the recommended 100 ohm loading. After I saw the frequency response graph supplied with the cart, it was measured at 1K, I wanted to try that , however with 1K trimmer I could reach till 750 only. Please update with your listening experience with that.
HT MC Phono Stage AD797
- Thread starter jls001
- Start date
The gain pot is loaded by the two opamps. Remove both opamps and adjust the value. I have mentioned this earlier in the thread too, but Hypnotoad insisted that there is no requirement to remove the opamps. My observation during this build - if one removes only the AD797 or the LME49990 only, there is still some loading. But if one removes both, then the resistance goes all the way up to 2000 Ohms. With opamps on the sockets, the max resistance displayed is about 800 Ohms (instead of 2K).
I am guessing your loading is already 1000 Ohms. I will also try 1K resistive loading.
One thing that struck me again on listening to this phono stage (after a long time as I rarely use it nowadays) is how it accentuates the groove noise and ticks/pops (compared to the Pearl II).
I have been off any vinyl for more than a month. I suspect the culprit is the alignment of my 12 incher but I didn't have the energy to check what's wrong. When the going gets tough, the tough listen to CDs
I have the arm issue almost licked but I still hear a grungy midrange. Need to get to the bottom of this problem and get back to tracing the groove.
Spent the whole evening trying to fix the alignment issue with my 12 incher but no success. So I had to reluctantly transfer the cart to my secondary TT. The snafus continued - I broke one tone arm wire: ) on the second TT.
It's a pleasure hearing pristine highs and mids after a long time.
It's a pleasure hearing pristine highs and mids after a long time.
I have to revise my opinion here: yesterday I was trying the Hypnotoad on the Lenco with a 12 inch arm. As mentioned earlier I had trouble with the setting of the arm, and it used to skip a lot. I struggled a fair bit and decided it was safer to transfer the cartridge to the TD 124 with the Origin Live Encounter arm. I have never tried this cartridge on this TT-arm combo (with the Hypnotoad phonostage). And I must say the ticks, pops, and hisses are not any worse than what I have heard earlier on the Lenco. So the accentuated noises were probably a by-product of the misaligned arm on the Lenco. In fact I've never heard the Thorens sounding this good! A great TT for sure.
Would love to do, if enough interest is generated among forum members. We can start group buy.
Dear Kanwar,
I would like to order a board. How can I do that?
Thanks and Regards,
Bela
Dear
Could you please email me the Gerbers?
My email address is [email protected]
Thanks and Regards,
Bela
Could you please email me the Gerbers?
My email address is [email protected]
Thanks and Regards,
Bela
Hi Bela,
Send a personal message to sachu888, not Kanwar. sachu888 made the PCB (+kit).
Received an email from Hypnotoad (through Sachin) to add 10 and 0.1 uF bypass capacitors to both AD797 opamps.
As usual I went overboard and added 10, 1, 0.1, 0.01 and 0.001 uF caps. 10 and 1 uF are electrolytic caps so one must connect the capacitors correctly to the V+ and V- pins correctly. Pin 4 of AD797 is V- so the negative terminals of the caps must be connected to this pin. Pin 7 is V+.
Since I liked what I heard, I added 0.1, 0.01 and 0.001 uF to the two LME49990 opamps too. The space is very tight so there's no room for 10 and 1 uF caps. The addition of the additional bypass caps to the LME49990 improved the sound further.
The effect of additional bypass caps is a much tighter bass (like I've never heard before on my analog setup), much more specific placement of various voices/instruments in the left-right space, much more resolving of lower level details. It also sounds more holographic than before. Very likeable indeed.
It's an easy mod. Those who've built the excellent Hypnotoad are strongly urged to undertake this mod. I've used no-name caps. I'm fairly certain good caps will improve things further.
As usual I went overboard and added 10, 1, 0.1, 0.01 and 0.001 uF caps. 10 and 1 uF are electrolytic caps so one must connect the capacitors correctly to the V+ and V- pins correctly. Pin 4 of AD797 is V- so the negative terminals of the caps must be connected to this pin. Pin 7 is V+.
Since I liked what I heard, I added 0.1, 0.01 and 0.001 uF to the two LME49990 opamps too. The space is very tight so there's no room for 10 and 1 uF caps. The addition of the additional bypass caps to the LME49990 improved the sound further.
The effect of additional bypass caps is a much tighter bass (like I've never heard before on my analog setup), much more specific placement of various voices/instruments in the left-right space, much more resolving of lower level details. It also sounds more holographic than before. Very likeable indeed.
It's an easy mod. Those who've built the excellent Hypnotoad are strongly urged to undertake this mod. I've used no-name caps. I'm fairly certain good caps will improve things further.
Last edited:
greenhorn
Well-Known Member
The reason for adding two seperate caps is that electrolytics are not so great in higher frequencies, so a ceramic or a polyester cap is added in parallel for HF bypass. If you wanted to go overboard, you should have added a 100uF and a .1uF. The closer they are physically to the vcc and gnd pins the better!
The designer recommends 10 uF and not higher. See here: AD797 Phono Stage Build and Help Desk Thread | Page 47 | Audiokarma Home Audio Stereo Discussion Forums
Even 4.7 uF will do fine.
greenhorn
Well-Known Member
as per the AD797 Datasheet, a 1-4.7uF Tantalum + .1uF ceramic is the recommended.
100uF is if you wanted to go overboard - it's useful in case you are experiencing ripple (100hz noise)
see figure 2 in this link if you want to know more
http://www.analog.com/media/en/training-seminars/tutorials/MT-101.pdf
100uF is if you wanted to go overboard
- it's useful in case you are experiencing ripple (100hz noise) see figure 2 in this link if you want to know more
http://www.analog.com/media/en/training-seminars/tutorials/MT-101.pdf
It's best not to stray too far from the datasheet recommendations. The AD797 is a bit finicky, due to its unique topology and (optional) overcompensation for bandwidth, so it does require care in bypassing. Two good caps, like a 10 uF Cerafine or Rubycon BG STD + 100nF X7R as close to the pins as possible, would work better for sonics than a bunch of lesser caps.
On a related note, I found a cap that measures and resolves better than Black Gate PK for bypass applications. However, it is only available in 4V rating and has not been manufactured since 2007/2008, so it does not solve the unobtainium issue for Black Gates. It would applicable for bypassing both digital and analog rails for various DACs, including the ESS Sabre family and various Asahi-Kasei DACs. I'll experiment further with it in due course - right now, I'm using a bunch of them in a classic Kenwood DP-1001 CDP to bypass the NPC DAC, replacing a bunch of BG PKs which were the previous champs in resolution.
On a related note, I found a cap that measures and resolves better than Black Gate PK for bypass applications. However, it is only available in 4V rating and has not been manufactured since 2007/2008, so it does not solve the unobtainium issue for Black Gates. It would applicable for bypassing both digital and analog rails for various DACs, including the ESS Sabre family and various Asahi-Kasei DACs. I'll experiment further with it in due course - right now, I'm using a bunch of them in a classic Kenwood DP-1001 CDP to bypass the NPC DAC, replacing a bunch of BG PKs which were the previous champs in resolution.
HypnoToad
New Member
The improvement after using a 10uf 50v electrolytic and a 0.1uf film (Polyester) cap across the supply rails of each op amp (pin 4 is neg and pin 5 is pos) is very noticeable, like jIs001 found, one of the recommended ones is Elna Silmic II, Panasonic FC's are good also. The 10uf 50v caps can be placed underneath the PCB.
I would also replace the 0.1uf ceramics already fitted with film caps and the 100uf 35v caps with 10uf 35v.
Linuxguru is right when he says to keep them as close to the op amp voltage pins as possible.
And as Sachin recommends the 2.2uf K73-16 Russian caps are a huge step up from the big Wima box caps.
I would also replace the 0.1uf ceramics already fitted with film caps and the 100uf 35v caps with 10uf 35v.
Linuxguru is right when he says to keep them as close to the op amp voltage pins as possible.
And as Sachin recommends the 2.2uf K73-16 Russian caps are a huge step up from the big Wima box caps.
Hi HypnoToad,
Are you saying that we should replace all the 0.1uF ceramic power rail bypass caps with film caps? I have ceramic bypass ones from rail to ground and Elna Silmic II and film ones across the rails. It sounds really marvelous.
Would film bypass caps in the rail to ground positions bring further improvement?
Would you have a clue why the OPA637s distort in the second position? OPA627s works great though.
Regards,
Bela
Are you saying that we should replace all the 0.1uF ceramic power rail bypass caps with film caps? I have ceramic bypass ones from rail to ground and Elna Silmic II and film ones across the rails. It sounds really marvelous.
Would film bypass caps in the rail to ground positions bring further improvement?
Would you have a clue why the OPA637s distort in the second position? OPA627s works great though.
Regards,
Bela
I've been listening to this great phono stage for a few weeks and I feel incline to write a small review to help others to decide and promote it.
I have to start with a blunt statement that it sounds absolutely mind blowing, though, I have made a few changes regarding RIAA and tried to use very good components in the build.
As a reference I have used the following components:
1, Sachin latest board. Very professional quality
2, 0.1% 10-20ppm metal film resistors (holcos etc.) further sorted and channel matched
3, changed the RIAA values to 200K, 16K9 and 16nF, 4440pF respectively to get more accurate RIAA response. RIAA caps are channel matched 2*2225pF polystyrenes and 2x8000pF 0.3% SGM silver mica caps
4, output capacitors are channel matched 0,47uF (FT-3 teflon)+0.01uF (MBM PIO)+0,001uF (FT-1 teflon) or 1uF (K75-10 Hybrid PIO)+0,1uF (FT-3 teflon)+0,001uF (FT-1 teflon) or a single 1uF (K73-16 PETP). Difficult to settle on my preference. The first combo by a tiny bit leads but all are superb. My amp has a 100K input impedance so I dont need high value caps.
5, first stage op amps are AD797BRZs, RIAA stage are OPA627BPs (OPA637BPs are not stable unfortunately due to less than 5 gain in high frequencies. I have also tried the LME49990s in the second stage that are also good but are a bit lean to my liking. The OPAs has more body without losing any details so I prefer the OPAs in my system.
6, + and - power rails are bypassed to ground with 47uF Elna Silmic II and 0.1uF MKP2 caps
7, +/-15V power rails are bypassed with 4,7uF Elna Silmic II and 0.1uF MKP2 caps
8, powered at +/-15V from an upgraded Muffsy Dual Power Supply using LT1085/LT1033 instead of the original LM317/LM337 combo. I have also added 10uF Cadj bypass caps to reduce ripple and changed to GREE SiC Schottky rectifier diodes instead of the specified 1N4004 to eliminate any diode switching pulses.
Now to the sound or at least to what I am hearing:
System: A vintage but very nice DUAL 721 turntable with Audio Technica AT-F3/FF cartridge into - above detailed AD797 HTMC Phono stage (100 Ohm and 220pF cartridge loading, 1100R gain resistor setting) into - Jolida Fusion 3502 integrated amp (with matched Psvane 12AX7-T/TII and 12AT7-T/TII preamp and a set of quad matched Psvane Philips Holland Metal Base Replica EL34PH or KT150 tubes, using mostly the KT150 ones that are simply unreal) into - KEF R500 speakers without any room treatment.
Sound stage is utterly real. I can pinpoint the location of every piece of instrument or any sound sources within inches. Sound stage is wide and deep yet utterly realistic. Not overblown at all.
I have the strange singer-in-the-room feeling every time I hear voices.
I close my eyes and the speakers disappear completely.
Frequency extensions are very nice up and down. Bass is very well controlled. Sound is liquid and silky.
What can I say? I am loving it!!!!
I wish a had a better turntable in the Rega PR8 or VPI Prime or Classic category with say a AT-OC9ML/II cartridge. It would be paradise for sure but I am not complaining at all, just dreaming.
I am happy about what I have and what I am hearing.
I have to thank Phillip (HypnoToad) and the DIY community for giving us such a beautifully sounding yet affordable phono stage.
Now back to listening and enjoying music!
Regards,
Bela
I have to start with a blunt statement that it sounds absolutely mind blowing, though, I have made a few changes regarding RIAA and tried to use very good components in the build.
As a reference I have used the following components:
1, Sachin latest board. Very professional quality
2, 0.1% 10-20ppm metal film resistors (holcos etc.) further sorted and channel matched
3, changed the RIAA values to 200K, 16K9 and 16nF, 4440pF respectively to get more accurate RIAA response. RIAA caps are channel matched 2*2225pF polystyrenes and 2x8000pF 0.3% SGM silver mica caps
4, output capacitors are channel matched 0,47uF (FT-3 teflon)+0.01uF (MBM PIO)+0,001uF (FT-1 teflon) or 1uF (K75-10 Hybrid PIO)+0,1uF (FT-3 teflon)+0,001uF (FT-1 teflon) or a single 1uF (K73-16 PETP). Difficult to settle on my preference. The first combo by a tiny bit leads but all are superb. My amp has a 100K input impedance so I dont need high value caps.
5, first stage op amps are AD797BRZs, RIAA stage are OPA627BPs (OPA637BPs are not stable unfortunately due to less than 5 gain in high frequencies. I have also tried the LME49990s in the second stage that are also good but are a bit lean to my liking. The OPAs has more body without losing any details so I prefer the OPAs in my system.
6, + and - power rails are bypassed to ground with 47uF Elna Silmic II and 0.1uF MKP2 caps
7, +/-15V power rails are bypassed with 4,7uF Elna Silmic II and 0.1uF MKP2 caps
8, powered at +/-15V from an upgraded Muffsy Dual Power Supply using LT1085/LT1033 instead of the original LM317/LM337 combo. I have also added 10uF Cadj bypass caps to reduce ripple and changed to GREE SiC Schottky rectifier diodes instead of the specified 1N4004 to eliminate any diode switching pulses.
Now to the sound or at least to what I am hearing:
System: A vintage but very nice DUAL 721 turntable with Audio Technica AT-F3/FF cartridge into - above detailed AD797 HTMC Phono stage (100 Ohm and 220pF cartridge loading, 1100R gain resistor setting) into - Jolida Fusion 3502 integrated amp (with matched Psvane 12AX7-T/TII and 12AT7-T/TII preamp and a set of quad matched Psvane Philips Holland Metal Base Replica EL34PH or KT150 tubes, using mostly the KT150 ones that are simply unreal) into - KEF R500 speakers without any room treatment.
Sound stage is utterly real. I can pinpoint the location of every piece of instrument or any sound sources within inches. Sound stage is wide and deep yet utterly realistic. Not overblown at all.
I have the strange singer-in-the-room feeling every time I hear voices.
I close my eyes and the speakers disappear completely.
Frequency extensions are very nice up and down. Bass is very well controlled. Sound is liquid and silky.
What can I say? I am loving it!!!!
I wish a had a better turntable in the Rega PR8 or VPI Prime or Classic category with say a AT-OC9ML/II cartridge. It would be paradise for sure but I am not complaining at all, just dreaming.
I am happy about what I have and what I am hearing.
I have to thank Phillip (HypnoToad) and the DIY community for giving us such a beautifully sounding yet affordable phono stage.
Now back to listening and enjoying music!
Regards,
Bela
Rather late update to this thread: I had used two 12V AC adapters to power my Hypnotoad for a long time. I built a Blues Magic shunt regulated power supply to power both the Hypnotoad MC phono stage as well as my Kuartlotron buffer. The shunt regulated supply is from fellow forum member doors666. This supply is big enough to supply a third line level device but I've limited it to supplying only two devices. Needless to say, the shunt regulated supply is a big improvement in terms of dynamics and quietness.
I use the Hypnotoad on my Thorens TD 124 TT, equipped with a DIY-ed Schroeder magnetic pivot tonearm and a Denon DL 103 cartridge. This TT is a hybrid idler+belt drive system, with a heavy multi layered Baltic birch plywood plinth. I admit that I've never lavished any attention on this TT (like the Lenco) since I honestly don't know how to improve the mechanicals further.
Recently on the advice of fellow forumer G401fan I tried using ceramic ball based footers from Soundfoundation. I've had these footers for many years and have tried it under various devices but never a TT. I was happily using brass cones footers under the Thorens. Changing to the ceramic ball based footers was a big leap in sound quality. The most obvious improvement was a better defined bass, although improvements were heard across the board.
A little later I tried placing a 12 mm thick slab of slate under this TT, the slab placed on top of the rack shelf (thick maple plank). This helped solidify the sound further. Since I had a second slab of slate I added that below the current slate slab, hoping that more would be better. However, I sandwiched pieces of thick foam between the two slabs. This produced more bass, but it wasn't particularly well defined or textured. This observation is in line with earlier experiments of using a damping footer under amps, preamps and speakers. Two slabs of slate is more massive than one, and my guess is the idler TT thrives on higher mass loading. The combined effect of ceramic ball based footers and massive loading is a much improved sound from the TT. I've owned the Denon DL103 in stock form for years now and I've never heard such nuances, details and bass weight/texture from this humble cartridge.
Idler drive TT owners could experiment with the much more commonly available granite slabs (I'll try it in future since I have a 18 mm slab).
I use the Hypnotoad on my Thorens TD 124 TT, equipped with a DIY-ed Schroeder magnetic pivot tonearm and a Denon DL 103 cartridge. This TT is a hybrid idler+belt drive system, with a heavy multi layered Baltic birch plywood plinth. I admit that I've never lavished any attention on this TT (like the Lenco) since I honestly don't know how to improve the mechanicals further.
Recently on the advice of fellow forumer G401fan I tried using ceramic ball based footers from Soundfoundation. I've had these footers for many years and have tried it under various devices but never a TT. I was happily using brass cones footers under the Thorens. Changing to the ceramic ball based footers was a big leap in sound quality. The most obvious improvement was a better defined bass, although improvements were heard across the board.
A little later I tried placing a 12 mm thick slab of slate under this TT, the slab placed on top of the rack shelf (thick maple plank). This helped solidify the sound further. Since I had a second slab of slate I added that below the current slate slab, hoping that more would be better. However, I sandwiched pieces of thick foam between the two slabs. This produced more bass, but it wasn't particularly well defined or textured. This observation is in line with earlier experiments of using a damping footer under amps, preamps and speakers. Two slabs of slate is more massive than one, and my guess is the idler TT thrives on higher mass loading. The combined effect of ceramic ball based footers and massive loading is a much improved sound from the TT. I've owned the Denon DL103 in stock form for years now and I've never heard such nuances, details and bass weight/texture from this humble cartridge.
Idler drive TT owners could experiment with the much more commonly available granite slabs (I'll try it in future since I have a 18 mm slab).
Purchase the Audiolab 6000A Integrated Amplifier at a special offer price.
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