Tweaking, modifying or updating a phonostage

pcosta

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Jul 25, 2010
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Windsor, Ontario, Canada
I recently bought a phonostage and I was considering updating some of the caps and resistors in the signal path. A tech would do all the work, and a friend that has the same phonostage has already done these mods.
They mods mainly consist of Mundorf silver caps and Vishay resistors.

Anyone here ever have work like this done and liked the results.

Any other cap or resistor choices I should consider?
 

opus112

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Feb 24, 2016
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I'd suggest power supply mods before anything else, power supplies are almost always the lowest hanging fruit.
 

Folsom

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Which phono stage that you own, are you talking about?

It's pretty impossible to declare exactly what resistors and capacitors without knowing the device. I modify stuff for people, and I consider the resistors and caps to be lower on the totem poll for modifications, often. But it really depends on what.
 

bonzo75

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Feb 26, 2014
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Which phono stage that you own, are you talking about?

It's pretty impossible to declare exactly what resistors and capacitors without knowing the device. I modify stuff for people, and I consider the resistors and caps to be lower on the totem poll for modifications, often. But it really depends on what.

What is higher on the totem pole
 

microstrip

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I recently bought a phonostage and I was considering updating some of the caps and resistors in the signal path. A tech would do all the work, and a friend that has the same phonostage has already done these mods.
They mods mainly consist of Mundorf silver caps and Vishay resistors.

Anyone here ever have work like this done and liked the results.

Any other cap or resistor choices I should consider?

IMHO you are playing roulette. The best you can do is comparing your friend unit with yours in your system. If you prefer it and consider the money well spent go fo it.
 

pcosta

Well-Known Member
Jul 25, 2010
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Windsor, Ontario, Canada
Which phono stage that you own, are you talking about?

It's pretty impossible to declare exactly what resistors and capacitors without knowing the device. I modify stuff for people, and I consider the resistors and caps to be lower on the totem poll for modifications, often. But it really depends on what.

The unit is a Foundation Research V5 from Canada. There are aprox. ten of them built. The company in no longer making anything, but they were more known for their power cords or power filter/conditioners.
They also made a line stage.
1076231-foundation-research-v5-tube-phono-preamp.jpg
 

YashN

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Jun 28, 2015
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I'd suggest power supply mods before anything else, power supplies are almost always the lowest hanging fruit.

I totally agree with the first part: for Line Level, the power supply is extremely important. Anything occurring at Line Level output will subsequently be amplified,so the cleaner it sounds here the better. It is helpful here to think of what you are hearing as a modulation of the power supply, so that you know it's super important and audible, and it's no surprise you should spend a lot of time optimising this.

Here are a few things you could potentially try, but if you're not too comfortable, ask someone to help as mistakes made in this area can be detrimental to you or the gear or both:

(a) Replace the diodes in the rectifier by Schottkys

(b) Twist the wires AC-side before and after the Toroid. Someone like Ric Shultz may advise some additional mods here, like for how to make a physical mod to the toroid (have to be careful of not shorting the core here)

(b) Add a snubber on the Toroid secondary(ies)

(c) Examine the filter post-Toroid and make it a CLC, a i.e. use a Choke there

I can't say from here how the regulation section is, but there should be one (probably the chip on heatsink and surrounding area on the bottom right). You could potentially replace the man chip there, but the best thing to use in this area is a shunt regulator or a super regulator if it hasn't been installed. You could build or get a crop-in replacement or mod this area if you get schematics or can analyse it.


Now, this doesn't mean you cannot get further SQ with other parts, like with changing the capacitors and so on.
 
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Folsom

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What is higher on the totem pole

opus112 is on track, power from the inlet to the actual circuit is where the most important improvements are typically found. Corrections in the actual circuit might be an option depending on time, money, and availability of a schematic. (schematics aren't necessary for almost any PSU, but for amplification/buffer/digital sections they can be due to time to money constraints)

Resistors and capacitors can improve sound a lot, so I'm not saying to avoid them. In fact the first resistor that is often between the gain stage and the turntable is worth the time to upgrade for an impressive improvement. I've found LDR's in this location to easily best many resistors such as Dale's, PRP, and Caddock TF.
 

Barry

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Before you do anything ask yourself several questions: 1) do you intend to keep the unit for at least a few years; 2) what your objectives are in improving the overall sound of your system and is the piece really the weakest link; 3) how much are you willing to spend; 4) does it matter if the component's resale value might be compromised or you don't recoup the cost of the upgrades?; 5) do you have good schematics to work from and what is the logical path for upgrading; 6) what is the reputation of the person doing the work and what kind of warranty will they provide; 7) Would it be cheaper in the long run to get a new or better used phono stage than mod this one?

As others have suggested, you must try your friend's phonostage in your system for several days if you can first.

You don't say what Vishays would be used but the TX2575s are widely acknowledged as exceptionally transparent and very expensive ($8 to 15 each depending on R value and source). As to capacitors, everybody's got their favorites and they all sound different. There are several "Mundorf Silvers" variants. Yes the power supply is also a key place to modify.

Oh, answering your other question, most of my stuff is modified including the phono stage. I will never sell any of it.
 

opus112

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Feb 24, 2016
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The unit is a Foundation Research V5 from Canada.

Very helpful to have the picture, thanks.

What I'm seeing here is that the designers didn't pay much attention to mains-borne noise. This is obvious to me because top left you see there's an IEC inlet with mains filter incorporated. These are very generic devices not optimized for audio, they include Y capacitors which have the tendency to pollute your earth.

Next in line we have a toroidal transformer - great for low radiated magnetic flux but the poorest choice for rejection of mains-borne noise. If you're serious about modding these two items (filter and transformer) would be very high on my list to be replaced. If you were to replace just one, change the filter to a custom arrangement designed to give much better rejection of common-mode noise, and one without Y capacitors.

This is just the start, I see YashN has further suggestions - definitely the diodes and caps in the main PSU would be next.
 

YashN

New Member
Jun 28, 2015
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Certainly agree with opus112 here on the inlet filter and cap, because of Leakage Currents caused by these, but not sure you can do much except perhaps add yet another AC Filter/Conditioner to deal with additional noise injected into the mains. However, you can still have additional interaction between these caps and other parasitic characteristics. YYMV here as there's also a lesser form of Leakage Current which occurs because on interaction with other supplies and permitted because of interconnects as well.

A couple of more things I will add since there is a Toroid:

- Try to physically locate the Toroid further from the electronics if possible

- Try a DC Blocker prior to the Toroid (it could be placed before the gear's AC inlet)

And a further thought: if you could examine the Layout and especially how the Ground(s) are made, there could be opportunities to optimise further there as well.
 

Folsom

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Actually the biggest problem with those little crappy boxes for IEC's is that they micro-saturate a lot, but the Y caps are bad too.
 

pcosta

Well-Known Member
Jul 25, 2010
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Windsor, Ontario, Canada
I was told the silver box at the IEC is a LC1 power filter from the same company. I don't know if it is something off the shelf or something he made and wrapped it in a box that looks generic.
 

BobM

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Feb 5, 2014
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Try to get a schematic for the unit, if you can. If you can't then you can probably get pretty close in the analogue/signal processing level because most phono stages are pretty similar. You want to upgrade that one or two key resistor that is directly in the signal path, and any caps that are the same. You don;t need to replace all, that should save you some cash.

True, the power supply is first and the recommendations above are spot on. One more thing though - the power cord makes a difference.

Also, don't forget your connectors. You will be surprised what better RCA jacks can bring to the table.
 

pcosta

Well-Known Member
Jul 25, 2010
364
123
950
Windsor, Ontario, Canada
I will rely on a local tech who is more than capable of doing this work for me and offering some advice. He builds his own amps and mods many other things. My plan right now is to have him bypass the internal SUT so I can use my own and make a real judgement call before any radical mods are made if at all.
 

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