Silly question, have you checked the ground wire from the turntable? I had a turntable and it was loose and not connecting properly.
AD797 Phono Stage Build and Help Desk Thread
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Silly question, have you checked the ground wire from the turntable? I had a turntable and it was loose and not connecting properly.
GreatTone
Super Member
Yes, I checked it. One of the first things I tried was disconnecting the ground at the phono stage, and that made things worse.
I installed the PCB so it is less than an inch from the input RCA jacks, so those leads are very short. However, the output wires are about 8 inches long. I didn't think of using shielded for that, but I did twist them together. I figured since it is inside the solid aluminum case, that would be fine. But considering the RF seems to be associated with the output jacks, that might be a solution. Also, I was thinking of trying to run short wires from the RCA jacks' outer ring to the turntable ground, creating a kind of star ground with a single grounding point.
At this point, it's a very small amount of interference, inaudible while a record is playing. I may just let it go for a while. It's hard for me to leave it alone though, knowing it could be a tiny bit better.
Question: what would happen if I ran the gain trimmers up all the way to 2K? I know it would probably have too much gain, but would it distort?
Depends on your cart but the higher the gain the more noise you will get.
1.3k is about as high as I would recommend.
superblast
New Member
Awesome! Thank you and good luck on the build!
superblast
New Member
Thanks Sachin!
GreatTone
Super Member
Okay, so I adjusted the gain up to 1.2K. Now it's about where the HTMCPS was at 1K, which is fine. This new one is still maybe a tiny bit lower, but close enough.
I think I've licked the RFI. Even at full volume with an album on, it was not audible, even between cuts, but without an album on and the volume way up, I could hear the local country station. So I added 1nF ceramic caps between the neg of the RCA output jacks and the ground lug on the case, and that did the trick. I don't know why that is, but the neg of the RCA cable was very "alive" -- when I touched a jumper between the case and the neg of the cable, I could hear it scraping through the speakers. They are very good cables too -- Blue Jeans cables. I bought them specifically to try and deal with this problem, and they helped a lot, but not all the way. A side benefit though is they sound way better than the cheaper cables I was using. The BJ's are low capacitance, and the highs really came to life after installing them, which I wasn't expecting.
So I listened to a few tunes at full listening volume, and it was mighty impressive. One of the things I listened to was side 1 of Aja, which I know extremely well. On Black Cow, I've always been able to hear a bit of the room or reverb around Fagen's voice. Now, however, it's like he's standing alone in the room, and the reverb trails out all the way to the edge of my room. But the thing is, he's not alone, there is a lot of other stuff going on around him, but he's so clear and surrounded by his own space, it's like hearing him solo, if that makes sense. The background singers exist in a layer behind him, very 3D.
So the separation is great, the detail is amazing, the bass has major punch. With the detail -- when I got my LOMC cart and HTMCPS, I was able to pick out little details that I'd never heard before in familiar songs. Now, not only do I hear those details, but they're so clear it's like they are major parts of the arrangement, completely clear. There's no straining to hear the little things -- the low level detail is as easy to hear as the big things.
Another thing I've listened for is the sound of the maracas and the police whistle in the long instrumental part of the song Aja. I must say, the maracas have never sounded more real and alive. And with the whistle -- when I upgraded my arm and cart, I noticed I could hear the sound of the pea rattling in the whistle. It's one of the things I listen for to see how resolving the system is. Now, not only do I hear the pea rattling, I hear the DRYNESS of the pea. Nice stuff.
I'm really glad I built this phono stage, so thanks! I have thought before that to get better sound, I needed a better amp or better speakers, but then I upgrade my table, arm or cart, and realize that the amp and speakers aren't what's holding things back. I was starting to get into that mode again, looking at speakers, but this new phono stage has shown me again that there is much more performance available with a better front end. I have B&W DM602s btw, which I found at a garage sale a few years ago. They keep surprising me.
One more thing -- we need a catchy, short name for this new phono stage, like HTMCPS. It would be better than saying, this new phono stage.
I think I've licked the RFI. Even at full volume with an album on, it was not audible, even between cuts, but without an album on and the volume way up, I could hear the local country station. So I added 1nF ceramic caps between the neg of the RCA output jacks and the ground lug on the case, and that did the trick. I don't know why that is, but the neg of the RCA cable was very "alive" -- when I touched a jumper between the case and the neg of the cable, I could hear it scraping through the speakers. They are very good cables too -- Blue Jeans cables. I bought them specifically to try and deal with this problem, and they helped a lot, but not all the way. A side benefit though is they sound way better than the cheaper cables I was using. The BJ's are low capacitance, and the highs really came to life after installing them, which I wasn't expecting.
So I listened to a few tunes at full listening volume, and it was mighty impressive. One of the things I listened to was side 1 of Aja, which I know extremely well. On Black Cow, I've always been able to hear a bit of the room or reverb around Fagen's voice. Now, however, it's like he's standing alone in the room, and the reverb trails out all the way to the edge of my room. But the thing is, he's not alone, there is a lot of other stuff going on around him, but he's so clear and surrounded by his own space, it's like hearing him solo, if that makes sense. The background singers exist in a layer behind him, very 3D.
So the separation is great, the detail is amazing, the bass has major punch. With the detail -- when I got my LOMC cart and HTMCPS, I was able to pick out little details that I'd never heard before in familiar songs. Now, not only do I hear those details, but they're so clear it's like they are major parts of the arrangement, completely clear. There's no straining to hear the little things -- the low level detail is as easy to hear as the big things.
Another thing I've listened for is the sound of the maracas and the police whistle in the long instrumental part of the song Aja. I must say, the maracas have never sounded more real and alive. And with the whistle -- when I upgraded my arm and cart, I noticed I could hear the sound of the pea rattling in the whistle. It's one of the things I listen for to see how resolving the system is. Now, not only do I hear the pea rattling, I hear the DRYNESS of the pea. Nice stuff.
I'm really glad I built this phono stage, so thanks! I have thought before that to get better sound, I needed a better amp or better speakers, but then I upgrade my table, arm or cart, and realize that the amp and speakers aren't what's holding things back. I was starting to get into that mode again, looking at speakers, but this new phono stage has shown me again that there is much more performance available with a better front end. I have B&W DM602s btw, which I found at a garage sale a few years ago. They keep surprising me.
One more thing -- we need a catchy, short name for this new phono stage, like HTMCPS. It would be better than saying, this new phono stage.
I am glad you got your RFI sorted out, it's one of those things that's trial and error.
One track I like to play to test out detail is Because by The Beatles on the Love album.
I have said this before, there is a fly that buzzes around at the start and I can hear it clearly now, with my other stages I could hear it but it was hard to tell if it was a fly or not, now it's easy.
As for the name I have been calling it the AD797 Phono Stage but you are right we need a catchy new name.
How about Vinyl Heaven Phono Stage or VHPS?
One track I like to play to test out detail is Because by The Beatles on the Love album.
I have said this before, there is a fly that buzzes around at the start and I can hear it clearly now, with my other stages I could hear it but it was hard to tell if it was a fly or not, now it's easy.
As for the name I have been calling it the AD797 Phono Stage but you are right we need a catchy new name.
How about Vinyl Heaven Phono Stage or VHPS?
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GreatTone
Super Member
Something funny about "Because" -- I remembered that you mentioned that a while ago, and a few months ago I got a new copy of Abbey Road, and I kept listening to "Because" listening for the fly and not hearing it, thinking my system must be deficient. I must have listened to it 20 times. Then I realized it was on the "Love" album version...
Soldering SMD Chips onto Adapters
Here's some tips on soldering those tiny SMD chips onto the adapters.
1. Since the chips are so tiny (a magnifier is a great help here) I place one onto the adapter board holding it in the right spot and grip the whole thing with a spring clamp. Some extra flux helps a lot too, I can then solder one side, remove the clamp turn it around and solder the other. You only need the iron to touch the pad and leg for a second and brush the solder over it while pulling the iron tip backwards. Or as Sachin said you can pre-tin the legs of the SMD chip and also have a little solder on the tip of the iron so you just have to touch each leg. I use my chisel tip turned sideways so it's about the same width as the pad.
Make sure you get the orientation of the chip correct with the silkscreen on the board.
2. The easiest way to hold the pins in place is to put them into a machined socket.
3. Then put the PCB with the chip you just soldered onto the pins like this so you can solder them in place.
Here's some tips on soldering those tiny SMD chips onto the adapters.
1. Since the chips are so tiny (a magnifier is a great help here) I place one onto the adapter board holding it in the right spot and grip the whole thing with a spring clamp. Some extra flux helps a lot too, I can then solder one side, remove the clamp turn it around and solder the other. You only need the iron to touch the pad and leg for a second and brush the solder over it while pulling the iron tip backwards. Or as Sachin said you can pre-tin the legs of the SMD chip and also have a little solder on the tip of the iron so you just have to touch each leg. I use my chisel tip turned sideways so it's about the same width as the pad.
Make sure you get the orientation of the chip correct with the silkscreen on the board.
2. The easiest way to hold the pins in place is to put them into a machined socket.
3. Then put the PCB with the chip you just soldered onto the pins like this so you can solder them in place.
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What, you just found the best ones and now you want to pull them?
I can talk I am always swapping things around.
No, it's a case of gently levering them up with a very small screwdriver.
The LME49990's are the easiest because of the adapters.
Safety Warning Re: 24v Scooter Chargers.
If people buy one of those cheap 24v chargers with a XLR plug on the end they can run into problems owing to the pin connections when charging two 12v SLA batteries in series.
The pin connections should be same as this diagram:
However the wire coming from the charger only has two conductors, so what they do is short the negative and ground connections together in the XLR connector with a bare solid wire. So pin 2 & pin 3 are shorted and both negative.
For safety I would open up the XLR connector and snip the wire shorting Pin 2 & 3 leaving only Pins 1 & 2 connected.
We have two batteries in series with a center ground point for our phono stage, this is not the same as the ground for the charger.
If you connect the ground from the charger to the center point of the batteries you are shorting out one battery. This will cause things to fry and maybe even a fire or explosion.
Cut or Ignore the ground connection from the charger XLR connector altogether, you don't need a ground connection anyway when charging batteries in series.
I removed the XLR connector from my charger lead and it has a Red wire which is Positive and a Black wire which is negative. These are connected to the Positive and Negative outputs of the batteries in series when charging. Make sure you have the phono stage off or disconnected when doing so.
I have a female 3 pin molex connector coming from my phono stage, and a 3 pin male connector coming from the batteries. Pin 1 is Positive, Pin 2 is Negative and Pin 3 is ground or the center point.
I put the same female 3 pin molex connector on the leads from the charger, and just connected the red Positive to Pin 1, the black Negative to Pin 2 and left Pin 3 out.
Now when I want to charge the batteries I just unplug the phono stage and plug in the charger.
If people buy one of those cheap 24v chargers with a XLR plug on the end they can run into problems owing to the pin connections when charging two 12v SLA batteries in series.
The pin connections should be same as this diagram:
However the wire coming from the charger only has two conductors, so what they do is short the negative and ground connections together in the XLR connector with a bare solid wire. So pin 2 & pin 3 are shorted and both negative.
For safety I would open up the XLR connector and snip the wire shorting Pin 2 & 3 leaving only Pins 1 & 2 connected.
We have two batteries in series with a center ground point for our phono stage, this is not the same as the ground for the charger.
If you connect the ground from the charger to the center point of the batteries you are shorting out one battery. This will cause things to fry and maybe even a fire or explosion.
Cut or Ignore the ground connection from the charger XLR connector altogether, you don't need a ground connection anyway when charging batteries in series.
I removed the XLR connector from my charger lead and it has a Red wire which is Positive and a Black wire which is negative. These are connected to the Positive and Negative outputs of the batteries in series when charging. Make sure you have the phono stage off or disconnected when doing so.
I have a female 3 pin molex connector coming from my phono stage, and a 3 pin male connector coming from the batteries. Pin 1 is Positive, Pin 2 is Negative and Pin 3 is ground or the center point.
I put the same female 3 pin molex connector on the leads from the charger, and just connected the red Positive to Pin 1, the black Negative to Pin 2 and left Pin 3 out.
Now when I want to charge the batteries I just unplug the phono stage and plug in the charger.
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Another possibility is to cut the plug off and wire the polarized cord to one side of a DPDT switch, the center of which goes to the batteries and the other side to the preamp, polarities observed. Throwing the switch to preamp-off will connect the batteries to the charger with the pre' disconnected, the center, 'neutral' stays connected and is not part of this ckt.
That's originally what I had planned but I just went with the easy (read lazy) method of having the same connector on the charger lead as the phono stage.
But yes that would work well.
I would even suggest an On, Off, On switch which gives you a Center position where everything is off.
You could have a green LED for the phono stage on and a red LED for the charging position.
The possibilities are endless.
GreatTone
Super Member
Just want to check in and say again how excellent this phono stage is! I have never had a phono stage that is CD-quiet the way this is -- certainly never a LOMC stage. Several times I have turned up the volume and thought that it wasn't turned on. Soundstage is wall to wall, imaging is pinpoint precise and rock solid, detail is out of this world. This thing is the bee's knees. If you haven't built yours yet -- get on it!
Now a question about batteries. I have two black sealed 12V batteries like the ones in HT's photo. In the instructions for the charger, it said that these types of batteries run 12.75 or so volts when full, and only go down to 11.5-ish when "empty." I guess I'm wondering when I should charge them again. When they get down to 12.0V, or what? After a week of lots of play time, the batteries are still 12.72/12.65. Any thoughts?
Now a question about batteries. I have two black sealed 12V batteries like the ones in HT's photo. In the instructions for the charger, it said that these types of batteries run 12.75 or so volts when full, and only go down to 11.5-ish when "empty." I guess I'm wondering when I should charge them again. When they get down to 12.0V, or what? After a week of lots of play time, the batteries are still 12.72/12.65. Any thoughts?
