His turntable ground lead is summed to the right channel negative signal lead which means the turntable is grounded to the board itself. However he did not ground his board to his pre chassis as far as I know.
Is he using batteries or a PSU?
Here It Is: The All Singing All Dancing HTMCPS
- Thread starter HypnoToad
- Start date
Is he using batteries or a PSU?
Big Bill
Summertime Rolls.....
Hello Phillip, he is using two 9 volt battery's.
That's odd Bill, he should not have any noise at all, I would get him to check his gain resistors to make sure they are less than 1k ohm. Even try 500 ohm.
Also what is he plugging it into, no one else has complained of noise or way too much gain.
Big Bill
Summertime Rolls.....
Good question, it sounded great to me here in the shop before he left with it.
I guess he will get back to us, Bill.
bearchuck
Active Member
Alright, I'm back! Maybe "way too much" is putting it too strongly, but I definitely think there's more gain than I'm comfortable with. I'm running the pre into an aux line stage of a Luxman L-80V integrated. If I assign imaginary numbers to the volume control, I start to hear noticeable white noise and hum at "3" and to me it sounds like I'm getting some distortion / clipping when I play music at around "4." On the other hand, if the volume is at "2" everything sounds awesome ... crystal clear.
Hopefully I'm describing it correctly. I'm still a novice at these type of things, but I'm pretty sure that if you all heard my system, you'd agree that something was amiss.
As I mentioned, I'll switch the 390 for the 470R and see where that leaves me.
Bill - I'm not sure why we didn't notice the noise in the shop; maybe we just weren't paying close attention to it while the music wasn't playing.
As for the grounding thing, I thought that maybe the board wasn't grounded to the chassis, but I wasn't sure. What's the best way to do that?
I'll attach some photos. You can't see much detail, so if you'd like to view them in giant, glorious hi-res, go here. FYI - the grounding post just arrived a couple days ago so I still need to install that.
Attachments
Fasterdamnit
Super Member
#1. Your input and output leads are too long. They act as antenna. The shorter (especially input) the better.
2. twist those leads so they are evenly wrapped around each other.
3. You said you had 1K feedback resistors. Try somewhere between 600 to 750
ohms. Exact value is not a worry, just get two that are less than what is in there.
That will lower your gain.
4. Sure you are not plugging your RCA leads into your phono input?
2. twist those leads so they are evenly wrapped around each other.
3. You said you had 1K feedback resistors. Try somewhere between 600 to 750
ohms. Exact value is not a worry, just get two that are less than what is in there.
That will lower your gain.
4. Sure you are not plugging your RCA leads into your phono input?
Hi,it's nice build.
I don't see any issue except one. You have to twist the input leads of each channel and make it of required length only. Same could be applied to output wires, keeping input and output routed away from each other. If space permits then rotate the board by 90 deg CCW.
Though I don't have good cabinet like you, but look at the wiring.
By boundry at 2012-06-17
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Pio1980
AK Member
Received, Thnx!
Okay process of elimination, check these in order:
1. You are using a Denon DL-103D?
2. Double check what you are plugging it into, and try another input on your amp, say the Cd input for example.
3. You can put the ground wire to the point where it says Gnd on the PCB.
4. Try putting those 470R resistors in place of the 990R in R2/R10.
ConradH
Lunatic Member
I like this circuit, though haven't built one. Just some armchair comments. The input is a virtual ground. Even though there's 33 or so ohms on the non-inv side to ground, that doesn't make the input look like a 33 ohm impedance. Depending on the frequencies involved and the actual HF input impedance of the opamp, filtering out RF and such using just capacitors might be difficult. One might want to try some ferrite beads if living near a radio station, if caps alone aren't doing the job.
My experience with the LME opamps is that they have to be treated like the 50 MHz parts they are. Typical audio layouts aren't usually good enough and my guess is they aren't preferred in many comparisons because they aren't living up to their potential. I'd add HF bypass caps right at the pins or within the socket itself before trusting them to behave as advertised!
My experience with the LME opamps is that they have to be treated like the 50 MHz parts they are. Typical audio layouts aren't usually good enough and my guess is they aren't preferred in many comparisons because they aren't living up to their potential. I'd add HF bypass caps right at the pins or within the socket itself before trusting them to behave as advertised!
GreatTone
Super Member
Also, could someone talk me through (or send a simple schematic) of the battery hookup? I'm thinking it's positive to negative between the batteries, then the pos to pcb, and neg of the other battery to pcb.
One more: should the switch break both legs of the batteries connection? ie, pos and neg. thx a bunch. I've placed my Mouser order and am deciding on a case. Maybe this one:
http://angela.com/hammonddiecastaluminum571x374x177enclosure1590j.aspx
One more: should the switch break both legs of the batteries connection? ie, pos and neg. thx a bunch. I've placed my Mouser order and am deciding on a case. Maybe this one:
http://angela.com/hammonddiecastaluminum571x374x177enclosure1590j.aspx
dodog
Addicted Member
Unless it's different than the CNC version, this should work:
http://www.audiokarma.org/forums/showpost.php?p=4900082&postcount=317
GreatTone
Super Member
Thanks, that's perfect. And turntable ground goes to that same gnd connection as the batteries? How about connecting the ground to the phono stage chassis?
Another question: if I used 6V lantern batteries, would I use 2 or 3? I believe the opamps can use anything up to 18V iirc. All this battery and opamp stuff is new to me. I usually work on 1960's era tube amps...
sachu888
Spare the tigers, kill me
Hi,
TT ground should be separated from chassis ground.You can use insulated banana plug for TT ground.You will need four 6V lantern batteries(2per side)to get a +/-12 V.Most opamps can take +/-18V but that is max.You can use 3 pin connector for connecting batteries http://www.audiokarma.org/forums/showthread.php?t=448089
Regards,
Sachin
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GreatTone
Super Member
I guess I'm not understanding...is anything grounded to chassis? I thought I read that the tt ground should be connected to "gnd" on the pcb. That is, I think, the ground point of the batteries too. Does that get grounded to the chassis? Or does the tt ground connect to one of the "-" connections at the inputs?
Sorry for all the questions, I don't want to screw this up. Thx.
dodog
Addicted Member
I'm confused as well. For the CNC build, the power grounds to the PCB which shares a ground-out wire with the binding post/chassis. Is there something different about the HTMCPS that you wouldn't do this as well?