Hi,
I would very strongly suggest that all the audio grounds be brought together in a star and all the power and decoupling grounds be brought together in a power ground star. Then the PG and AG and PSU 0v can all be connected. But separate from the safety (chassis) earth.
In simple language, copy power amplifier topology.
and
could that be the problem?
I would very strongly suggest that all the audio grounds be brought together in a star and all the power and decoupling grounds be brought together in a power ground star. Then the PG and AG and PSU 0v can all be connected. But separate from the safety (chassis) earth.
In simple language, copy power amplifier topology.
I guess that could be the problem but there are plenty of designs that don't separate the GNDs and don't have problems though.
Hi,
Judging by the number of requests on this Forum for help in solving hum and buzz problems, I am inclined to think your conclusion
Judging by the number of requests on this Forum for help in solving hum and buzz problems, I am inclined to think your conclusion
is based on hearsay and maybe a bit of luck (not design) on the part of the builders.
Max,
Don't give up on it, you can likely make it work. I would suggest you focus on the case/wiring/PS and the line stage itself. You may wish to take a listen to the line stage with nothing more than two resistors forming a voltage divider at the input with one resistor to GND. If you still get the buzzing then you need to focus on the line stage and its PS.
Cheers!
Russ
Don't give up on it, you can likely make it work. I would suggest you focus on the case/wiring/PS and the line stage itself. You may wish to take a listen to the line stage with nothing more than two resistors forming a voltage divider at the input with one resistor to GND. If you still get the buzzing then you need to focus on the line stage and its PS.
Cheers!
Russ
Hi there, well 13 months after reporting my endless strugle to get a PIC programmed in this thread... yes its that old, I have a USB programmer and I'm not afraid to use it! Completed my first PIC project this week, the inductance and capacitor meter, which gave me a cursory introduction to pics and talking to LCDs, so I thought I'd give this circuit a shot now...
BUT the pcb from page 4 is no longer available... is this just a server being gone in history...? I would love a copy if it is still available as public domain..
BUT the pcb from page 4 is no longer available... is this just a server being gone in history...? I would love a copy if it is still available as public domain..
Another Hum/Noise/Hiss Issue
Hello, I have just connected a stereo JT attenuator to my audio chain (CD -> JT -> dual-mono block Leech amp). I've tested this chain w/out the JT with a series pot without issues.
The issue is: as I rotate through the different relay combinations, I get pops at certain transitions (basically when transitioning from all 1's to all 0's and a MSB 1). I'm not sure if this is to be expected. Beside this, the larger issue is noise/hum/hiss that shows up in varying degrees, depending on the relay combination. The worst case is when R1 - R6 (on the controller board) show ~5V and R7 0V. The noise at this step is extremely high and just touching the control pot causes different buzzing aural sensations. Touching different nodes on the controller board also causes hiss tones. This seems odd to me, as the controller board should be isolated from the audio signal, except through any power-rail or control-signal leakage/path on the relays. One more turn to the right and the 1st through sixth relays turn-off and last relay turns-on, leaving the noise floor back to acceptable levels. Any idea what this could be. I checked my 5V rail (I'm feeding this directly in to the controller board via an external regulator, bypassing the on-board AC-to-DC circuitry), and it seems reasonably stable. I'll get a scope to check for glitches. What is strange to me is that if this were a power issue at high draw, why wouldn't I hear any noise when all 7 relays are turned-on (R1 through R7 on control board reading ~5V). I've visually reviewed the attenuator board for any cold-solder joints are bad connections - I'm not seeing any.
Well any ideas or suggestions will be appreciated. I may try an AC transformer input to the on-board regulator to check if that fixes the issue.
Thanks, Willus
Hello, I have just connected a stereo JT attenuator to my audio chain (CD -> JT -> dual-mono block Leech amp). I've tested this chain w/out the JT with a series pot without issues.
The issue is: as I rotate through the different relay combinations, I get pops at certain transitions (basically when transitioning from all 1's to all 0's and a MSB 1). I'm not sure if this is to be expected. Beside this, the larger issue is noise/hum/hiss that shows up in varying degrees, depending on the relay combination. The worst case is when R1 - R6 (on the controller board) show ~5V and R7 0V. The noise at this step is extremely high and just touching the control pot causes different buzzing aural sensations. Touching different nodes on the controller board also causes hiss tones. This seems odd to me, as the controller board should be isolated from the audio signal, except through any power-rail or control-signal leakage/path on the relays. One more turn to the right and the 1st through sixth relays turn-off and last relay turns-on, leaving the noise floor back to acceptable levels. Any idea what this could be. I checked my 5V rail (I'm feeding this directly in to the controller board via an external regulator, bypassing the on-board AC-to-DC circuitry), and it seems reasonably stable. I'll get a scope to check for glitches. What is strange to me is that if this were a power issue at high draw, why wouldn't I hear any noise when all 7 relays are turned-on (R1 through R7 on control board reading ~5V). I've visually reviewed the attenuator board for any cold-solder joints are bad connections - I'm not seeing any.
Well any ideas or suggestions will be appreciated. I may try an AC transformer input to the on-board regulator to check if that fixes the issue.
Thanks, Willus
Re: Another Hum/Noise/Hiss Issue
Hi Willus,
I am still mulling this over, but a couple questions come to mind...
1) Is there any DC component to the signal you are attenuating?
2) Is there any continuity between the signal and the digital/power circuits at any attenuations step? If there is, then there is a solder bridge, or possibly a bad relay.
I will post more ideas as they come.
Cheers!
Russ
z_willus_d said:
Hi Willus,
I am still mulling this over, but a couple questions come to mind...
1) Is there any DC component to the signal you are attenuating?
2) Is there any continuity between the signal and the digital/power circuits at any attenuations step? If there is, then there is a solder bridge, or possibly a bad relay.
I will post more ideas as they come.
Cheers!
Russ
Vishay S102C Resistors
Has anyone listened to the Vishay S102C Bulk Metal Foil resistors?
Wondering how they might sound in the Jacob's Ladder?
S102C's are rudely expensive!
How about using non-inductive resistors for very low noise and reasonable price?
Comments?
Has anyone listened to the Vishay S102C Bulk Metal Foil resistors?
Wondering how they might sound in the Jacob's Ladder?
S102C's are rudely expensive!
How about using non-inductive resistors for very low noise and reasonable price?
Comments?
Channel Crosstalk?
Has any measruement been made on channel separation/crosstalk?
I am interested to make a different ladder with separate SPDT contact Reed Relays per channel. Reeds of course are pratically silent, but hard to get in DPDT.
Thanks!
Russ :>)
Has any measruement been made on channel separation/crosstalk?
I am interested to make a different ladder with separate SPDT contact Reed Relays per channel. Reeds of course are pratically silent, but hard to get in DPDT.
Thanks!
Russ :>)
Re: Channel Crosstalk?
When used in balanced mode, there is virtually none left to right as the entire PCB is used for one channel. 🙂
No I have never actually measured it.
RussT said:
When used in balanced mode, there is virtually none left to right as the entire PCB is used for one channel. 🙂
No I have never actually measured it.
I'm thinking of adding this to my Aleph P1.7 (Veteran's boards) and in the interest of saving money, is there any danger in piggybacking a voltage divider on the 30V secondaries off my transformer (wired in series to get 60V needed by the P1.7) to get the dual 6-12V stated in the Kit Contents page?
Any drawbacks to using this approach, or would I be better off trying to shoehorn another transformer in my case?
My transformer is 80VA btw - I think Nelson Pass spec'ed 2 30VA trafos in the design pdf, so I have some headroom with this one
Any drawbacks to using this approach, or would I be better off trying to shoehorn another transformer in my case?
My transformer is 80VA btw - I think Nelson Pass spec'ed 2 30VA trafos in the design pdf, so I have some headroom with this one
Hi,
you could use a series regulator to reduce from 30V to 12V.
If the power dissipation is too high for just one regulator then cascade a pair on a common heatsink. And repeat for the other half polarity.
you could use a series regulator to reduce from 30V to 12V.
If the power dissipation is too high for just one regulator then cascade a pair on a common heatsink. And repeat for the other half polarity.
twitchie said:
You only need one AC voltage into the rectifier for the JT controller 6-12V. It then creates its own 5V digital supply using a regulator.
I would not feed that circuit from your analog DC rails(even with a regulator) as you will introduce some digital noise into your preamp. I would either just take the AC from a secondary, or use a seperate small transformer. You do not need dual rails. Just one secondary is OK. I think the kit contents page just say "secondaries" because the trafo we have happens to be a toroidal with 2 secondaries which would be used in parallel.
Cheers!
Russ
Of course, one can also feed a 12VDC voltage into the board as well since the input will accept DC as easily as AC!
I tested the board using a 9 Volt Battery. Worked great for the test!
Definitely keep the digital power away from the analogue power as Russ mentioned to avoid digital noise from entering the analog domain.
BTW, the Joshua Tree works extremely well!
I get a faint hint of "zipper noise" but I am sure that is expected. I believe this is caused mostly from slight DC offset of my pre-amp.
Has anyone tried muting the output with a relay just while the volume is changing? I do not know if the audible feedback with this setup would be acceptale to actually listen to. But it would ensure quiet operation during volume changes. Any thoughts?
Some feedback for future revisions Russ: Suggest making the hole sizes perhaps 0.005" or 0.010" bigger on all reisitors and diodes as I found it to be just a tad too tight. I usually use 0.035" holes for 1/4W resisotrs and 0.040" holes for 1N4001 diodes.
Thanks much!
Russ :>)
I tested the board using a 9 Volt Battery. Worked great for the test!
Definitely keep the digital power away from the analogue power as Russ mentioned to avoid digital noise from entering the analog domain.
BTW, the Joshua Tree works extremely well!
I get a faint hint of "zipper noise" but I am sure that is expected. I believe this is caused mostly from slight DC offset of my pre-amp.
Has anyone tried muting the output with a relay just while the volume is changing? I do not know if the audible feedback with this setup would be acceptale to actually listen to. But it would ensure quiet operation during volume changes. Any thoughts?
Some feedback for future revisions Russ: Suggest making the hole sizes perhaps 0.005" or 0.010" bigger on all reisitors and diodes as I found it to be just a tad too tight. I usually use 0.035" holes for 1/4W resisotrs and 0.040" holes for 1N4001 diodes.
Thanks much!
Russ :>)
twitchie said:
Hi,
I will use the same boards. Where do you put the attenuator, at the input or output?
Thanks
Peppe
RussT said:
Hi and thanks! Your feedback is welcome! 🙂
Yes that faint zipper noise is caused by DC coming into the JT. This could be at the input or the output. The cure here is to minimise or eliminate the DC. You could do this by nulling the DC at the source, or by adding a cap. It actually may not even bother you as it is only even evident when changing volume.
Cheers!
Russ
Peppe said:
It would work either way, but I would put it on input first and see how you like it.
If you do put it on the output the output impedance of the preamp will become 750R.
Cheers!
Russ
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