After the clone, I built the VSPS 300 and a larger (100AV) power supply inside alum case. When I first tried it, I laid the power supply on the TT dustcover and had notable hum until I moved it away. Once moved, there is near silence at high volume settings @50dB gain setting.
Last edited:
I'll return to pfcs49's excellent build report shortly. First a quick comment about the power supply placement.
Internal will most likely work fine, if you are moderately careful. External is pretty much idiot proof.
I have found that the interference from the transformer is most severely transmitted directly to the phono cartridge, not the inputs of the phono stage itself. From this view, it's not so important to separate the boards from the transformer, but the transformer from the turntable. If you like to have your phono stage sitting next to the TT, then I recommend an external supply.
The other issue is grounding. With an external supply there is no reason to earth the phono stage chassis, and this avoids the possibility of ground loops developing with the amplifier, which is usually earthed. With a one-box build you may have to connect phono GND to the chassis via a 50 ohm || 0.1 uF link to break the loop.
In truth, no one who has build a one-box phonoclone has reported problems, so I might be worrying over nothing. It's only been 2-3 people, however, a very small minority and all of them definitely fit into the "know what they were doing" category.
Internal will most likely work fine, if you are moderately careful. External is pretty much idiot proof.
I have found that the interference from the transformer is most severely transmitted directly to the phono cartridge, not the inputs of the phono stage itself. From this view, it's not so important to separate the boards from the transformer, but the transformer from the turntable. If you like to have your phono stage sitting next to the TT, then I recommend an external supply.
The other issue is grounding. With an external supply there is no reason to earth the phono stage chassis, and this avoids the possibility of ground loops developing with the amplifier, which is usually earthed. With a one-box build you may have to connect phono GND to the chassis via a 50 ohm || 0.1 uF link to break the loop.
In truth, no one who has build a one-box phonoclone has reported problems, so I might be worrying over nothing. It's only been 2-3 people, however, a very small minority and all of them definitely fit into the "know what they were doing" category.
Last edited:
If you use toroidal transformers you should be OK as long as you put the phono board on the other end of the enclosure (added metal shield would be best). That said, my phono preamp has a seperate enclosure for the regulated PSU... I did that so I could swap phono boards and keep the power suply the same. Build a new box with different phono section, just unplug the embilical and swap. It's all good.
Cheers,
Bob
My new supply has 3 outlets-
two on one end of the box and a third on the PC end.
I built a clone and two VSPS 300s. I don't expect to use three at a time, but it's at least a possibility. Two at a time will be normal.
And that left me with the 35VA compact supply from the clone build so I can use any preamp elsewhere whenever I want to.
PS: I didn't mention that I have 2x6 rotary switches that could be easily squeezed in near the gain switch. I may do that, certainly to the 2nd VSPS, for MM use to adjust input load and capacitance.
two on one end of the box and a third on the PC end.
I built a clone and two VSPS 300s. I don't expect to use three at a time, but it's at least a possibility. Two at a time will be normal.
And that left me with the 35VA compact supply from the clone build so I can use any preamp elsewhere whenever I want to.
PS: I didn't mention that I have 2x6 rotary switches that could be easily squeezed in near the gain switch. I may do that, certainly to the 2nd VSPS, for MM use to adjust input load and capacitance.
Last edited:
Rectified, unregulated split supplies from 2x12 VAC 35 VA or larger transformers makes a very useful general purpose power source, good for just about anything from phono stages and DACs to line level to headphone amplifiers. Using multiple, common sockets and cables means you can swap different projects in and out without having to build a power supply each time.
Returning to your VSPS300 build : it's nice to learn that switching the gain resistors can be done on the fly, without the extra wiring leading to instability issues or noise pickup.
If I was doing it-
I would have used a much larger case. As things are, you cannot access the boards without disassembling the front and rear panel jacks and switches. Components have been bent to fit, which is always a bad sign.
I would have made a daughterboard with multiple sets of the gain set resistors pairs, and probably a DIP switch on the board to select. Just three wires back to each VSPS board. Keeps the wiring length down to a minimum, and VSP board layout free of any extra clutter.
Returning to your VSPS300 build : it's nice to learn that switching the gain resistors can be done on the fly, without the extra wiring leading to instability issues or noise pickup.
If I was doing it-
I would have used a much larger case. As things are, you cannot access the boards without disassembling the front and rear panel jacks and switches. Components have been bent to fit, which is always a bad sign.
I would have made a daughterboard with multiple sets of the gain set resistors pairs, and probably a DIP switch on the board to select. Just three wires back to each VSPS board. Keeps the wiring length down to a minimum, and VSP board layout free of any extra clutter.
"I would have used a much larger case. As things are, you cannot access the boards without disassembling the front and rear panel jacks and switches. Components have been bent to fit, which is always a bad sign"
I love these cases for their accessibility. Remove the 4 upper screws and the top half lifts off as in my pictures.
Remove the other 4 and the ends come off with all connections intact. Then simply slide the boards out of the bottom through the grooves in the case and everything is on the bench ready to run and totally accessible.
About bending stuff: I could have not bent anything (I inclined the 4 RIAA caps) but access to the R3 terminal block would be difficult. Also, R4 flush with the board would be against the R3 block and I thought moving it over a little and insulating the legs w/teflon tubing a better plan. And the gain switch and wiring are easily removed and R2/R3 installed across bays 1&4 of their respective terminal blocks. The rotary swx fits with room to spare around unmolested components.
As an aside, I measured the input capacitance: long side 93pF/short side 87pF.
I kinda expected a little less. ???
I love these cases for their accessibility. Remove the 4 upper screws and the top half lifts off as in my pictures.
Remove the other 4 and the ends come off with all connections intact. Then simply slide the boards out of the bottom through the grooves in the case and everything is on the bench ready to run and totally accessible.
About bending stuff: I could have not bent anything (I inclined the 4 RIAA caps) but access to the R3 terminal block would be difficult. Also, R4 flush with the board would be against the R3 block and I thought moving it over a little and insulating the legs w/teflon tubing a better plan. And the gain switch and wiring are easily removed and R2/R3 installed across bays 1&4 of their respective terminal blocks. The rotary swx fits with room to spare around unmolested components.
As an aside, I measured the input capacitance: long side 93pF/short side 87pF.
I kinda expected a little less. ???
So I'm running my Sumiko Blackbird into my DIY VSPS but I want to listen to it through the Phonoclone I've built. Assuming I select the correct resistors for R1 and R2, will this work without damaging something? The output of the Blackbird is 2.5 mv and the internal resistance is 135 ohms. This works out to R1=135 and R2=540. Any disasters up ahead if I do this?
I've just measured the capacitance of the VSPS 300 board inputs (bare board), and it is 10 pF. I would expect <20pF for the short length of twisted wire and connector, for a total "true" capacitance of about 30 pF.
Anyway, it's all small and of no consequence compared to the capacitance of the phono cable itself. Nothing to worry about.
OK, I just got my resistors for the above Phonoclone and have another question. For R1=135, should I undershoot with a resistor value of 121ohms or overshoot with 150ohms? Same thing for R2=540, under at 511ohms or over at 562ohms. Thanks in advance.
Dave
Newbie help
Building my Phonoclone 3 and power supply. Just a couple of newbie questions:
1. What gauge wire should I use for the connections to the RCA jacks? Should it be solid copper or stranded wire?
2. What kind of wire is used for the connector between the power supply and the audio plug that plugs into the phono preamp? A microphone cable? A power cable? Can I just cut up a PC power cable and use that? It looks like it is a three wire cable, but I can't seem to find a source for less than a 100 feet of three wire cable.
3. My transformer did not come with any hardware. What is the metal cap in the pictures below called? I don't know what to look for on Digikey or Mouser. I guess I don't need one, but it looks like it holds the transformer in place nicely.
I am using these pictures as my guide, which I found on this help forum.
Thanks.
Building my Phonoclone 3 and power supply. Just a couple of newbie questions:
1. What gauge wire should I use for the connections to the RCA jacks? Should it be solid copper or stranded wire?
2. What kind of wire is used for the connector between the power supply and the audio plug that plugs into the phono preamp? A microphone cable? A power cable? Can I just cut up a PC power cable and use that? It looks like it is a three wire cable, but I can't seem to find a source for less than a 100 feet of three wire cable.
3. My transformer did not come with any hardware. What is the metal cap in the pictures below called? I don't know what to look for on Digikey or Mouser. I guess I don't need one, but it looks like it holds the transformer in place nicely.
I am using these pictures as my guide, which I found on this help forum.
Thanks.
You can use whatever you feel comfortable with. Solid core 24 AWG works quite well.
YES!! That works just great.
Unless your transformer has a potted "plug" with a hole drilled in it, you will need those rubber/metal plates and the bolt. I doubt these are available off the shelf at digikey, I've only ever seen them included with a transformer. However it's not too hard to make a bracket yourself from a bit of wood or plastic. It doesn't have to be round.
I used wire from this guy. Very easy to deal with and great quality stuff.
eBay My World - navships. I used the 24 gauge stuff.
For the power cords and umbilicasl, hardware stores as well as Home Depot type stores have 14/3 black cord in bulk for a buck a foot type prices.
eBay My World - navships. I used the 24 gauge stuff.
For the power cords and umbilicasl, hardware stores as well as Home Depot type stores have 14/3 black cord in bulk for a buck a foot type prices.
I went with the overshoot resistors. Sounded fantastic on start-up! Have ran a few albums thru it and it keeps getting better. The wife came down into the basement to fold clothes and said "I've never heard the instruments sound so distinct from each other or it sound so lifelike." Really, I swear! Phonoclone with HOMC works just fine at least so roar.
lol , 24 g , just grab a few feet of cat5 . it's already twisted
I've often wondered about recycling Cat5... What do you do??? Strip the shielding off and break it down into the 4 pairs???
Thanks,