I'm giving up with UV boards. I'm looking for a cheap laser printer to try direct etching.
It looks easy. Print onto magazine glossy paper with a laser printer, iron the design onto a copper clad board anfd then wash off the paper.
Result is a waterproof / etchproof design on your board ready for etching.
With laser printers about £30. It seems foolproof.
It looks easy. Print onto magazine glossy paper with a laser printer, iron the design onto a copper clad board anfd then wash off the paper.
Result is a waterproof / etchproof design on your board ready for etching.
With laser printers about £30. It seems foolproof.
I need to ascertain wether it is the A4 or the Pumpkins that are oscillating at start-up.
Its odd that they settle down after a few seconds and then work flawlessly.
Its odd that they settle down after a few seconds and then work flawlessly.
Hi Zen,
I've had a hernia inducing morning carting around my Aleph 4.
Anyway, here are the results of my problematic set-up.
First, lets recap on what we are testing.
1. POWER AMP = Dual Mono Aleph 4. Both amps are COMPLETELY SEPARATE except that they are each connected to a single Mains Earth via a 12R resistor.
2. PRE-AMP = DUAL MONO Shuntky / Pumpkins. Both amps are separate but share a single transformer. There is a single STAR 0V at the transformer but no Mains Earth.
3. POWER IN = Unbalanced RCA.
4. PRE IN/OUT are both balanced XLR.
With the Power Amp connected to the Pre-Amp but no power on the Pumkins the Power Amp is SILENT.
If I turn ON the Shuntkys I get a "Whooshing" noise from the set-up.
If I short the inputs to the Pumkins the amp falls quiet again, except that I get a minor hum.
I've had a hernia inducing morning carting around my Aleph 4.
Anyway, here are the results of my problematic set-up.
First, lets recap on what we are testing.
1. POWER AMP = Dual Mono Aleph 4. Both amps are COMPLETELY SEPARATE except that they are each connected to a single Mains Earth via a 12R resistor.
2. PRE-AMP = DUAL MONO Shuntky / Pumpkins. Both amps are separate but share a single transformer. There is a single STAR 0V at the transformer but no Mains Earth.
3. POWER IN = Unbalanced RCA.
4. PRE IN/OUT are both balanced XLR.
With the Power Amp connected to the Pre-Amp but no power on the Pumkins the Power Amp is SILENT.
If I turn ON the Shuntkys I get a "Whooshing" noise from the set-up.
If I short the inputs to the Pumkins the amp falls quiet again, except that I get a minor hum.
Slight Hum:
Have a look at the common ground in the dual mono power amp and look at the common ground in the pre-amp.
Next area. The Main Audio Ground appears to be at the PSU Zero Volts. Could that be a hum problem?
As to the whooshing:
What about an output mute on the pre-amp during start up?
Have a look at the common ground in the dual mono power amp and look at the common ground in the pre-amp.
Next area. The Main Audio Ground appears to be at the PSU Zero Volts. Could that be a hum problem?
As to the whooshing:
What about an output mute on the pre-amp during start up?
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I always turn the PRE on first anyway to stop turn on thumps.
This was an enquiry as Zen-Mod stated that the whooshing was not normal from the Pumkins.
I've just disconnected the two 12R resistors that connected amplifier 0V to mains Earth in the Power Amp.
Hum has gone.
Chassis is still earthed for safety but nothing inside the amplifier is connected to EARTH.
One Channel on the Pumpkin is still slightly noisy. The "Whooshing" noise has gone. LH Channel is quiet RH Channel has a slight "HISS".
This prevails even with inputs shorted.
Hum has gone.
Chassis is still earthed for safety but nothing inside the amplifier is connected to EARTH.
One Channel on the Pumpkin is still slightly noisy. The "Whooshing" noise has gone. LH Channel is quiet RH Channel has a slight "HISS".
This prevails even with inputs shorted.
Zen, Can you provide a line drawing of how you connect up your Pumpkins.
I'm using a single mains transformer with two Shuntkies and two Pumkins. The only common point is the transformer.
It still hums (quietly) but annoyingly. And one channel hisses (quietly) but annoyingly.
I'm using a single mains transformer with two Shuntkies and two Pumkins. The only common point is the transformer.
It still hums (quietly) but annoyingly. And one channel hisses (quietly) but annoyingly.
ZenMod,
After re-routing all the 0V connections the Pumpkin is still very noisy.
I have got it configured so that all 0V are connected to a single start connection at Transformer 0V.
Measuring the noise at the output of the Shuntkys, there is a considerable 50mV of noise at the DC (both + and -) of both Pumpkins.
This occurs even with the inputs shorted.
Next step will be to try a regular regulated PSU to see if I can improve on the noise.
The STAR 0V is on top of an insulated pillar and is not connected to anything other than the star.
You will note the odd transformer arrangement - this is because I had 2 x 40V transformers going spare.
Andy
After re-routing all the 0V connections the Pumpkin is still very noisy.
I have got it configured so that all 0V are connected to a single start connection at Transformer 0V.
Measuring the noise at the output of the Shuntkys, there is a considerable 50mV of noise at the DC (both + and -) of both Pumpkins.
This occurs even with the inputs shorted.
Next step will be to try a regular regulated PSU to see if I can improve on the noise.
The STAR 0V is on top of an insulated pillar and is not connected to anything other than the star.
You will note the odd transformer arrangement - this is because I had 2 x 40V transformers going spare.
Andy
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Is the rectification and smoothing done inside the first "shunty".
If so then you must not connect your Main Audio Ground upstream of smoothing.
The charging currents passing from transformer through rectifier and smoothing caps back to the transformer MUST BE SEPARATE from the audio stages.
If so then you must not connect your Main Audio Ground upstream of smoothing.
The charging currents passing from transformer through rectifier and smoothing caps back to the transformer MUST BE SEPARATE from the audio stages.
Yes, the rectification and smoothing is done on the Shuntys.
There is no provision on the boards to incorporate a star earth between the main caps which is where I would put it.
I could use off board bridges and caps but the Pumpkin / Shuntky has rave reviews so there must be something wrong.
I get better results by using raw supplies than I do with the Shuntkys.
I think I've got defective Shuntkys because the noise is AWFUL.
Not only 50Hz but HF hiss and popping as well.
There is no provision on the boards to incorporate a star earth between the main caps which is where I would put it.
I could use off board bridges and caps but the Pumpkin / Shuntky has rave reviews so there must be something wrong.
I get better results by using raw supplies than I do with the Shuntkys.
I think I've got defective Shuntkys because the noise is AWFUL.
Not only 50Hz but HF hiss and popping as well.
Don't locate the Main Audio Ground on the wire/trace/plate between the smoothing capacitors.
Locate the MAG where it can best do it's job and then use a wire to connect the Zero Volts line to the MAG.
I saw a very clever interpretation of this in a Sugden Power Amplifier.
The trace connecting the smoothing caps was, as usual, on the bottom side of the PCB.
The MAG where the Speaker return was bolted was on the top side of the PCB. The bolt connecting the two was effectively the wire between. Perfect separation of the charging current pulses from the smoothly changing audio currents.
Locate the MAG where it can best do it's job and then use a wire to connect the Zero Volts line to the MAG.
I saw a very clever interpretation of this in a Sugden Power Amplifier.
The trace connecting the smoothing caps was, as usual, on the bottom side of the PCB.
The MAG where the Speaker return was bolted was on the top side of the PCB. The bolt connecting the two was effectively the wire between. Perfect separation of the charging current pulses from the smoothly changing audio currents.
The Hum isn't the real issue here. It's the awful "Whooshing" noise that emanates from the amp at start up. It takes a good few seconds to calm down.
These PCBs were ZenMods early ones and they are AWFUL.
These PCBs were ZenMods early ones and they are AWFUL.
Can you disconnect the amplifiers from the supplies and then test the supplies individually through the start up and warm up phase.
You will probably have to connect some dummy loads to the shuntys.
You will probably have to connect some dummy loads to the shuntys.
Just measured the "Noise" at the output of the initial caps, ie before the Shunt Regulator. Its below 50mV. Seems as though the Shunt Regulators are actually making noise. Unless of course it is being fed back from the Pumpkins.
I'm hoping that ZenMod might poke his oar in here and defend his product somewhat.
My experience has been that these are POOR - I would even go as far to say VERY POOR.
My experience has been that these are POOR - I would even go as far to say VERY POOR.
