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The Phonoclone and VSPS PCB Help Desk
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Old 16th April 2020, 03:50 PM   #4281
rjm is offline rjm  Japan
Richard Murdey
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@chromenuts

Very elegant wiring there on the input selection switch. I'm impressed!
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Old 16th April 2020, 06:43 PM   #4282
bonzini is offline bonzini  Canada
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Hi all, me again, feeling very sheepish as I totally missed the calculator in the BOM spreadsheet...

Long story short I'm comfortable with using that to calculate a reasonable value for R2 for my AT-OC9/III.

Sorry for the unnecessary noise. And thanks to Richard for making these wonderful designs available!
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Old 17th April 2020, 01:35 PM   #4283
chromenuts is offline chromenuts  United States
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Hi Richard

Thanks very much for the kind words. It was much easier to wire the selector switch right between the inputs as opposed to mounting the switch on the front panel as I did on my last phono amp.

Things have been a bit hectic with everyone being in the house 24/7. I ended up staying up until 3AM last night so I could finish assembling my power supply.

A quick test across my rails told me I had about 38V DC. Itís a little high, but when I tested my mains voltage at the IEC inlet it was slightly over 120V AC. I know there are fluctuations in the mains throughout the day anywhere from 5 to 10V. Iím thinking it was just at a high point at that time of night.

Iím going to try and build my umbilical later today. Then I can test voltages on the amp boards and hopefully pop in IC1 and give it a try in my system.
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Old 17th April 2020, 11:44 PM   #4284
rjm is offline rjm  Japan
Richard Murdey
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It's clear from the photo you know what you're doing. 38 V is ok, it's unloaded and you have capacitors at the rectifier output. 30-40V range is fine.

By the way you may find it sounds better when you remove those electrolytic caps on the rectifier board. The phono boards already have sufficient filter capacitance, and for some reason splitting the capacitance near/far from the amp introduces some weirdness, sonically speaking.
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Old 18th April 2020, 04:57 AM   #4285
chromenuts is offline chromenuts  United States
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Hi Richard

Thanks for your comments again.

I wasnít sure if I should include any additional capacitance at the supply or not.

Iíve read more than once in the past that when separating a power supply from a sensitive circuit with an umbilical that it was a good idea to have some capacitance in the supply case and at the circuit.

This rectifier board had the option of adding a snubber which would have resulted in having much larger caps at the supply which I decided against.

As it is, there is only a small 35V Silmic 100uf on each rail. One leg can be easily lifted to test the supply without them.

I finished the umbilical this afternoon and moved on to firing the amp board up and testing my voltages in the circuit.

Iím very glad you were able to send me the original instructions and that I followed all of your start up advice.

I immediately found an issue when I went to test for -10V at pin 4 of the IC1 socket on the first board. There was no voltage.

After rechecking the data sheet for the opa27 and your circuit board diagram in the manual I realized that the original owner of these boards had populated the IC1 socket with its notch reversed to the diagram. I wasnít testing at pin 4, I was testing at pin 8.

I didnít really want to have to take the board out and de-solder an 8 pin socket...especially since I recently ran out of soldering wick.

I noticed there was no ďkeyĒ preventing the op amp from being inserted in the socket with the correct circuit orientation. I simply filled the original notch at the wrong end with some liquid tape and put a notch on the correct end of the socket for my own reference and peace of mind in case I were to ever go back in thinking of trying any different op amps.

After that everything went pretty smoothly. Getting those little bugs into their sockets was a bit of a pain. I have big clumsy fingers and no tool to hold them properly. The legs started to bend on one, then it jumped out of my hands and onto the floor while trying to straighten it out. I donít think it got damaged as I retested everything once they were installed and all seemed OK.

I didnít have time to switch the amp into my system today...too much going on. Hopefully tomorrow I will be able to listen to it.
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Old 18th April 2020, 12:23 PM   #4286
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Richard Murdey
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Looks good. And no, there is no insertion key for DIP packages, nor transistors for that matter, nor ... if you think about it, any polar two terminal devices like diodes or electrolytic capacitors. It's on the builder to align the component to match the pattern on the silk screen.
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Old 21st April 2020, 03:30 PM   #4287
Dint is offline Dint
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Default Parts advice

Hello All,

First time poster. Iím building a VSPS with premium parts and have two questions-

1st: Is there any reason not to use a Muses-01 opamp instead of an OPA2134? I found a YouTube video showing the same but it is in Japanese...

2nd: Would it be worth using please premium capacitors like V-Cap ODAMís for C8,C9 (to bypass the voltage regulator electrolytics)? I am going to use these capacitors - which are simply amazing, for C3, and will use them here as well if it is worthwhile:

Thanks in advance for your help,

Aron
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Old 22nd April 2020, 02:51 AM   #4288
rjm is offline rjm  Japan
Richard Murdey
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Quote:
Originally Posted by Dint View Post
1st: Is there any reason not to use a Muses-01 opamp instead of an OPA2134? I found a YouTube video showing the same but it is in Japanese...

2nd: Would it be worth using please premium capacitors like V-Cap ODAMís for C8,C9 (to bypass the voltage regulator electrolytics)? I am going to use these capacitors - which are simply amazing, for C3, and will use them here as well if it is worthwhile:
1. Muse 01 is a dual, Jfet input op amp broadly comparable to OPA2134. You can use it in the VSPS circuit without further adjustment. Input offset voltage (max) is about 50% worse than the OPA2134, but this shouldn't be a problem unless the device is right on the datasheet worst case.

2. For C3, worth it if you like the caps. For C8,C9 doubtful but this is a "try it and see" thing, no?
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Old 22nd April 2020, 01:56 PM   #4289
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Thank you for this... I will proceed with the Muses and with ODAM’s for C3, mess with C8, C9 later, after I become familiar with the sound...
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Old 23rd April 2020, 06:53 PM   #4290
chromenuts is offline chromenuts  United States
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I’ve had the VSPS 300 up and running in my system now for several days. I pulled everything off my shelves over the weekend and did some dusting, cleaning and rearranging.

I was happy with what I heard. I am enjoying the system quite a bit lately as I had just finished a pair of F2J monoblocks a few weeks back and have been listening every day.

Having changed the amps so recently has made it difficult to seperate what I am hearing as a result of the amp change or the phono change.

I don’t normally make more than one change at a time because I take quite a long time to build projects. This one just came together quickly since I acquired the VSPS boards populated and used some cases I had bought for power supplies instead of building from scratch as I usually do.

I would like to be able to compare the sound of the VSPS in the system head to head with the JFET phono amp I have been using for a while that is based on a Boozehound Labs kit. It is a derivative of the “Le Pacific” circuit which as I understand it originated with Jean Hiraga.

The VSPS currently produces more noise than the JFET phono. My test was to connect both and turn my system up to the “enthusiastic” listening level, which is almost exactly at the 50% point of my pots of my preamp (depending on the recording). The JFET phono amp is almost completely silent at this level even when listening inside the mouth of my horns.

I can go a little further with the JFET phono before I experience feedback through the system during listening, perhaps to 60%, but I am not interested in hearing distortion or damaging anything in the system. I have not tested what the maximum level the VSPS will go to without feedback or distortion yet.

My idea to compare them is to put a switcher in my system directly after the MC head amp so that I can switch back and forth between the VSPS and the JFET phono amps connected to different inputs on my preamp. Both are set up to produce 40dB of gain.

It will require getting up to change two switches at the same time...less than perfect...perhaps I will get a switching volunteer from the troops currently locked up in the house with me.

I’m not sure this will be a fair comparison without trying to also run the VSPS off of a battery supply.

I was having nothing but problems trying to find a quite power supply for the JFET phono when I first built it. That is why I resorted to using a rechargeable NiMH power supply for it.

My idea is to buy two more 18 or 19.2 V NiMH battery packs to create a bipolar supply for the VSPS. The research I did indicates that if I connect them in series I can then take the positive rail from one pack, the negative from the other and a common from where they are connected in series positive to negative. I’m wondering if this is correct, if others have already done this and what the optimal voltage for the battery packs would be?

Just for reference, my preamp is based on the Salas DCB1 design which I have modified with Jensen transformers on the output to pick up 6dB of gain. There is not a lot of gain in the system when you consider the F2J down stream and the ZYX MC head amp upstream. I am relying on the sensitivity of the DX3s in the horns as well as using 6 high sensitivity drivers in each dipole bass panel which is driven by some bridged Rotel HT amps.
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