The Phonoclone and VSPS PCB Help Desk

It has been several months since I built the VSPS 6.0b phono preamp, so I am posting few photos of my build. This is a prototype version of the VSPS, and Richard was kind enough to share the design files with me, so I ended up getting few boards printed. I mainly stuck to the default BOM, with few slight changes. For the RIAA circuit, I used +/-0.1% tolerance resistors and +/-1% tolerance capacitors. Since there are 3 capacitors per channel for the RIAA circuit, I matched those values between the channels. For C3 I used Clarity Cap CSA capacitors. I tried the OPA2134 op amp first, but it had little too much hiss for my taste, so I ended up using NE5532. I bought Muses8820D as well as LME4562 op amps, but never got a chance to try them. Although I purchased the released version pcb from Richard, I never build that version so I could not compare the two. At first I used twisted pairs of solid wire for the input and output connections, but then decided to use higher quality shielded cable. Single box build, as you could see in the photos. I have some 80-100 hrs of listening time on it, and the preamp works and sounds beautifully. Unless you stick your ear right next to the speaker and increase your volume control to 80% or more of the range (you hear little hiss at this level), it is silent.

Big thank you goes to Richard for his work, and outstanding support that he provides to many of us. I asked him hundreds of questions, and he answered every single one of them. You will not find better product support from anyone or any company out there. Thank you again.

Now onto the next project, the Emerald!

GDA
 

Attachments

  • IMG_2796.jpeg
    IMG_2796.jpeg
    450.1 KB · Views: 106
  • IMG_2797.jpeg
    IMG_2797.jpeg
    533.2 KB · Views: 102
  • IMG_2798.jpeg
    IMG_2798.jpeg
    484.3 KB · Views: 95
  • IMG_2799.jpeg
    IMG_2799.jpeg
    463.8 KB · Views: 87
  • IMG_2800.jpeg
    IMG_2800.jpeg
    465.8 KB · Views: 86
  • IMG_2801.jpeg
    IMG_2801.jpeg
    397.4 KB · Views: 88
  • IMG_2803.jpeg
    IMG_2803.jpeg
    396.7 KB · Views: 97
  • Like
Reactions: 1 users

rjm

Member
Joined 2004
Paid Member
@gda23 Thanks for sharing your amazing build. It looks great!

To be clear, this version of the VSPS should be a significant upgrade from the regular version. I don't offer it myself because the Emerald should be better still - and once you get this far (so my thinking goes) - with the case and power supply and all - you may as well put a pair of Emerald boards in there in place of the single VSPS 6.

Yes, the OPA2134 will be noisier than the NE5532, but it should be very close for most MM cartridges. The NE5532 may sound a little grittier, the 2134 a little airier. I've always liked the sound of the NE5534/32.
 
@rjm Thank you Richard. That is exactly what my plan is; replace the single VSPS 6 board with a pair of Emerald boards, and keep everything else from the VSPS 6 build. I may add a rotary switch to allow to switch between 37 and 57 db gain, or I may just use the jumpers and not complicate things too much. I'll do this as soon as I receive the Emerald boards that I purchased from you earlier this week.

Thank you again.

GDA
 
recently completed asembly of my VSPS board, and now working on the power supply. I have acquired a +- 12vac transformer, and have assembled a prototype power supply.

A couple of problems need solving:

1. The rectifier section has an issue, on one bridge, if connected, the transformer heats up quickly. I cannot see or determine if there is any short in the wiring, so I think it is the rectifier. I have ordered replacements, but how does one check for a defective bridge? The bridge that when connected runs the transformer hot, delivers the same DC voltage as the 'good' one, in addition, the resistance between terminals on teh two bridges measure the same at about 3.75MOhm.

2. This PS will be connected to my selector preamp. I have it wired such that only the selected input board (phon, dac) gets power. So, I believe that I can run the dac with just the positive 12 rail of the PS. The issue then is the relays. The operational selection will require a constant current, consuming about 140 mW. Is this enough power to unbalance the powering of the VSPS while running? I expect to run the VSPS board with the +12vdc, -12vdc rails, and the relay from only the +12vdc rail.

If this is a problem, is there a way to get +12vdc from the +-12vdc rails into a balanced +12vdc/ground?

I know that a latching relay would be the answer as it would only require power during switching, but I already have the selector portion of the pre-amp designed and built, and would like to not have to redo it.

Thanks in advance,

Roger
 
Richard,
I purchased a 24vac dual secondary +-12ac. I connected it up to the bridges as pper schematic. I have installed the new bridge rectifiers, and the transformer heating issue has ceased.

So, I have wired it to my pre-amp, selector through a mini XLR connector with the two outputs connected together as per PS schematic. Everything up to there is perfect.

Now, while I have a +12dc rail, and a -12dc rail, plus, what would you call it? Neutral? These are connected to the VSPS board, and now I am trying to use this configuration to achieve a 12vdc power to supply the relays in the selector portion of the pre-amp.

The issues now are that with the +12dc rail and 'common' connected to the relay board, the measured DC voltage is 19vdc. When I check the voltage between the power supply output on the mini xlr connector, it is only +- 14vdc. So I have no idea where the extra voltage is coming from. I added a 220uf cap across the +12vdc rail, and common, it did not change the voltage, but I suspect that it will help with ripple on the relay coil circuit.

I think I fried my DAC board powered by the relay board, as the 19vdc had a severe ac ripple on it I suppose, the DAC board had a small wiff of smoke when I selected it, upon which I turned it off. I have not reversed the power circuit back to my 12dc wall wort to power the selector board and DAC to see if it survived.

I suspected that I would have to configure a ground somewhere in the circuit in order to use the +12vdc incoming line, but do not know how that should be accomplished, as I think your VSPS board would not 'like' the common to be connected to ground.

If I have to have separate power supplies for the VSPS board and the relay selector board/DAC then, I can do that but it would make for a pre-amp with two incoming power lines, not the most refined design.

Anyway, that is my currect situation.


attached are two diagrams, the first is with the previous phono pre, it required only +12vdc from wall wart supply, which also supplied +12vdc to relay coils. I used one side of the relay to connect the output ground to the grounds of the two boards, phono and DAC. This allowed the power only to be applied to the boards if they were selected.

Second diagram is with the vsps board included. I would like to provide a +12vdc line, plus ground, to supply the relays and DAC board.
 

Attachments

  • relay_schematic_2.pdf
    225.9 KB · Views: 37
  • relay_schematic_vsps.pdf
    167.5 KB · Views: 36
looking at the situation a little closer, I think that I can use the rectified +12vdc rail to feed an LM7812 regulator, with a 220uf cap across the feed to ground, and the output 12vdc can be used to drive the relays, I will also use a 220uf cap across the output to ground to help clean it up. See revised drawing.
 

Attachments

  • relay_schematic_vsps_reg.pdf
    168.8 KB · Views: 38

rjm

Member
Joined 2004
Paid Member
The VSPS is connected directly to the output of the bridge rectifiers.
The 12 VAC secondaries with produce about 18 VDC when connected to the VSPS V++, and -18 VDC connected to the VSPS V-- with respect to COM. This is normal. The voltages are internally regulated back to 12 V by the VSPS before powering the op-amp.
Note that you'll only measure about +/-12 VDC at the XLR before you connect the VSPS, because there is no filter capacitor attached yet.

If you want instead to power the VSPS from +/- 12VDC supplies you have to remove the on board regulators and bridge over the pads, as denoted by the "U" graphic on the silkscreen. This is explained in the design manual excel file.

You can, in principle, connect the ~18VDC V++ rails to another LM7812 regulator to generate a 12 VDC line to power your relays.

The main thing that's incorrect/inclear about your diagram is you are showing 12 VDC going into the VSPS, rather than the nominal 18 V unregulated DC you'd get from the diodes.
 
Thanks Richard.

Yes, I am only labeling the outputs from the rectifiers as +-12vdc, they are indeed higher as you describe.

This, I am having trouble understanding:

"If you want instead to power the VSPS from +/- 12VDC supplies you have to remove the on board regulators and bridge over the pads, as denoted by the "U" graphic on the silkscreen. This is explained in the design manual excel file."

I guess I do not have the +/-12VDC supplies, only the rectifier outputs.

Revised drawing attached.

I am confused over the grounding strategy. In my previous version, the power supply neural/ground was attached to the chassis. All of the low level input shield/ground were isolated from the chassis, connected together and connected to the output shield/ground, again isolated from the chassis. The separate phono ground was attached to the other phono board at a designated terminal. The previous phono board, and DAC board were controlled by running the ground circuit from the relay coil output through the selector switch. It is unclear if I can do this with the VSPS. Would it work to connect the 'common' through the selector switch as with the other board? My previous phono board, and the DAC have LEDs to indicate it they are indeed 'on' so I could test the circuit to see if it was working.

Anyway, progress is being made, I have some LM7812 regulators on order. I have a bunch of 50v 220uf caps I can use to filter the relay supply, and the DAC supply, is there a recommended higher value? They ran fine on a typical wall wart, I do not know how much conditioning those supplies usually provide.

Roger
 

Attachments

  • relay_schematic_vsps_reg.pdf
    168.9 KB · Views: 34
I think I have found a way to do what I need with the addition of another relay. I know this isn't direct support of VSPS, but perhaps if you look at the attached, you could comment. Since my selector switch has two poles, (originally directly switching inputs) I can select the VSPS and have two relays driven on. One will connect the phono outputs, the other will connect the unregulated outputs of the bridge rectifiers. The remaining questions are, is the grounf hooked up correctly, and will the LM7812 plus a 220uf cap condition the regulated 12vdc supply to drive the relays without 'contaminating' the rest of the circuit? (the ground from the bridge rectifiers is unfiltered and needs to be connected to the system ground (I think).

Anyway, I have eliminated the other relay circuits for clarity.

Roger
 

Attachments

  • relay_schematic_vsps_2relay.png
    relay_schematic_vsps_2relay.png
    48.5 KB · Views: 42
So I think what you have there is connected correctly. I just question the value of powering on the VSPS with a relay, as the relay circuit itself (which must be kept powered on for you to be able to switch on the VSPS) consumes about as much power as the VSPS does. You might as well leave off the relay and power everything up with a single physical switch.

As for "contamination" relays are notorious for backwash, but only when switched. The supply doesn't have to be especially clean or well filtered, an LM7812 and 220 uF should be sufficient. The bigger issue is when you combine digital circuits like a DAC with sensitive analog amplifiers like a phono stage. It's generally better not to run them off the same power supply.
 

rjm

Member
Joined 2004
Paid Member
The traditional preamp options are

line pre + phono stage + DAC as separates
analog pre (phono + line stage) + outboard DAC
"receiver" (line pre + phono stage + digital receiver (DAC, etc.) in one box)

I imagined you would connect your (DAC+phono) box to an integrated amplifier, but an integrated amp would also have a line selector so that doesn't track.

It just strikes me to be a lot simpler (and more versatile) to build a phono stage as a phono stage, and a DAC as a DAC, and plug each into the integrated amplifier / line pre.
 
  • Like
Reactions: 1 user
My 'amp' is a single input valve amp with volume control, it is fairly sensitive. So, with the need for input selection, this is more or less what I designed.

I guess, it would be perhaps better (or not) to separate the various sources and just use the selector as a selector.

In the previous version of this pre/selector, I had a very inexpensive phono board, powered by a 12vdc wall wart, and it worked fairly well, better than expected from a $10 board off of Amazon, but not quite the HiFi I was looking for. Just a board for proof of concept to see if I could actually do it. That being successful, I proceeded with the DAC, another $15 board, again powered by the same wall wart at 12vdc. Worked fine, switched between the two without much switching noise (but not completely silent either).

The selector is in a chassis that matches my valve amp, and they sit stacked. There was a lot of room left over in that chassis so it invited the phono and DAC additions.

I did not have any noise or cross talk issues the DAC and phono stages performed remarkably well considering what they were.

I thought perhaps it was better to have the boards un-powered when not selected, there is no 'mains' switch on the selector unit, something perhaps overlooked. I did not want an IEC mains connection on that unit as the whole assembly (valve amp, selector) would be crowded with mains wiring.

In any case, thank you for all of your thoughtful comments and help. I will see how this goes and perhaps rethink moving the VSPS unit outboard, and just use the selector to switch inputs, and maybe house the DAC. I am REALLY pleased with how good this cheap DAC, using Cyrus Logic chipset works with the rest of my system. In my system, I do not think I could hear the difference of a different/better DAC, though I expect the VSPS to be an improvement..

Roger
 

rjm

Member
Joined 2004
Paid Member
It's a pity the amplifier didn't have a simple 2-source input switch. Then you could have a fairly tidy traditional stack of integrated amp + DAC + phono stage.
When I was faced with a similar situation I built myself a simple input selector box, connecting my DAC and phono stage to it, but I can see why you took the route you decided to take.
 
I built the amp in a chassis only 10"x5"x2". Squeezing in a selector switch would be a challenge! I matched the size of the selector chassis to the amp so they could stack. Thee IS room in the selector for these boards, but not a PS and boards plus relays.

I am on a fairly tight budget right now. Future possibilities as things loosen up though. Might consider a three tier stack, phono/DAC/Selector/Amp. Lots to ponder, and thanks again. My PS is on another chassis, and hastily done, I need to redesign for a neater version with a proper IEC mains connection.

Thanks again, you have been a significant help. I could not have done this without your assistance. Still waiting on a few parts, and then I will let you know how it sounds finally!!!

Roger
 
Ok, I guess it would be easier to just use a switch. So I added a DPST switch to the incoming unregulated +-vdc from bridges. Connected switch output to both VSPS power inputs. Used the +vdc to power an LM7812 to provide regulated +12vdc to power the relays, and indicator LEDs. (see attached)

Now the question. On my previous phono board, and on my DAC, I use the selector switch to connect the relay power to ground, as well as the board grounds. This completes the power circuit for the boards. The VSPS schematic is unclear to me whether the 'common' in connection is required to power up the VSPS board, or can I run the 'common' input through the selector switch to ground? There is no path to chassis or system ground from the VSPS except from the turntable ground. The phono inputs and outputs have the ground connections to the shield on the cable, which is connected not to the chassis, but to the shield/ground on the source (coax, phono, aux). I guess I could try and see, I do not believe it would cause harm. My switch and LM7812 should be arriving this week, so I am looking forward to completing this project. Oh and not indicator LEDs for each selection!
 

Attachments

  • relay_schematic_vsps_switch.png
    relay_schematic_vsps_switch.png
    43.8 KB · Views: 27

rjm

Member
Joined 2004
Paid Member
@rogerayotte

The VSPS schematic is unclear to me whether the 'common' in connection is required to power up the VSPS board, or can I run the 'common' input through the selector switch to ground?
COM, GND, IN-, and OUT- are all connected within the VSPS board. The labeling designates what you are expected to connect the pads to: the power supply, chassis/ground lug, input RCA, and output RCA, respectively. This scheme assumes that those parts don't connect at any other point (i.e. that the RCA lugs are isolated from the chassis with plastic spacers, etc.)

If you connect the power supply COM to the chassis, and the chassis to the VSPS GND, then you don't need to connect the power supply COM to the board COM because the connection was already made at the chassis.

Would that work? Most likely, yes. At this point, though, I tend to wash my hands of the whole thing. I feel it's up to the person making these decisions to troubleshoot things themselves if problems arise.
 

Attachments

  • guide_vsps1g.png
    guide_vsps1g.png
    9.3 KB · Views: 31
  • guide_vsps1g.png
    guide_vsps1g.png
    58.8 KB · Views: 32