Yearly Archives: 2016

Tube rolling in the PV14L

Electronics

The C-J PV14L preamp is not exactly the best candidate for tube rolling, but I do have some experience with the dfiference that tubes can make.  The PV14L only uses one pair of tubes, as the preamp only has one gain stage.

IMG_20160304_185514The second version of this preamp (which mine is) was built around the Mullard M8080/CV4058 tube.  When I received the preamp, it sounded good with the tubes provided, but I found that they were highly microphonic, exhibiting a rattling noise on certain loud notes.  I had ordered in a pair of Tung-Sol 6C4s to try.  They sounded slightly better, yet there was still some evidence of microphonics.  Just not as pronounced as the Philips ECG 6C4s I had replaced but still unacceptable.

When the Mullard M8080s came in (from a UK seller), right away I noticed that there were no microphonics whatsoever.  Sonically I did not notice a huge difference between these tubes.  If anything, the sound was slightly more mellow and balanced with the M8080 than with the others before it, the Philips ECG tubes perhaps being the brightest and maybe slightly more etched of the pair I tried. However, these latter tubes had an unknown lifespan on them–I believe the seller mentioned they were about “halfway used.”

In the meantime, I had gotten in some silicone o-rings to try as tube dampers.  A bag of 10 properly sized o-rings is only a dollar or two; some audiophile tweak companies charge ten times this amount for the same thing!  There is no difference.  In fact, the silicone o-rings that ship with the PV14L are the same material, just of a smaller thickness.  The inner diameter of these tubes is tighter, so it takes a little more effort to place on the tube.  But, that should assist in better dampening.

As one of the M8080s has gotten noisy (the seller is thankfully sending a replacement at no charge), I placed the 6C4 Tung-Sols back into the preamp.  The thicker tube dampeners have made only minimal difference in the microphonics of these tubes.  Dampeners can help with by reducing some of the vibrations but, of course, will have no effect on any of the tube components physically rattling inside the glass.

Seeing there aren’t many options in this family of tubes, I will stick with the M8080s.  The CV4058 is actually a military spec tube, made to more durable specs and tight tolerances, hence the absence of the microphonics.  There are still plenty out there, and it is not a popular audio tube.  An older McIntosh component used the 6C4, and C-J has used this in three of their preamps.  These tubes do so much right that I don’t really see a point in changing out the tubes for a different sound.

The phono stage dilemma

Audio/Video Hardware, Gadget Corner

While searching for my ideal preamp, one of my criteria was for this new preamp to have a built-in phono stage.  That turned out to be more difficult, as the only way I could find them was in older preamps, or in new preamps that were way beyond my budget.  I finally caved in to the idea of getting a phono stage.

Yet, which one?  I really wanted tubes.  I still do, to an extent.  But my choices in tubed phono stages was limited within my budget.  And when pressed for a choice, tubes might not be my solution after all.

My first candidate was a Jolida JD9 Mk II.  While build quality seemed acceptable, a few Internet forums mentioned that there were additional upgrades that could take the JD9 up to a higher level.  Upgrades include swapping in premium op amps, better output coupling capacitors, and HEXFRED rectifiers in the power supply.  Not to mention swapping in premium tubes.  I also would have installed my own mono switch on the rear panel.

While I like getting into the innards of electronics with soldering iron and voltmeter, the idea of hacking up a brand new phono stage (and voiding the warranty) did not sit well with me.  Once I did the math, I realized the Jolida would not have been a good investment.

The other candidate in valve land was the Pro-Ject Tube Box DS, which has the unique loading adjustment on the front panel.  It is nicely built, sure.  Yet like the JD9, I could not find any mainstream reviews of this model.  I found a killer deal on it, but decided to pass.  I do not put 100% weight in reviews, of course, but they are a helpful second opinion.

My luck came about by way of a lightly used Phonomena II+ by Musical Surroundings.  Mainstream press?  Yep, Absolute Sound had picked it as an Editor’s Choice.  Other reviews thought highly of it, and especially praised the depth and control in the bass.  Perfect.  It arrived within a week of purchasing it, and looked essentially unused.  The sound is, as you’d expect, phonomenal (sorry).

Loading is quite easy on the Phonomena.  A series of DIP switches on the rear can be set in many combinations to get LOMC loading where you need it to be.  For my Dynavector, I am currently at 59 ohms, but feel that I could probably nudge it down to 50 ohms to really smooth it out.

Running a MM cartridge, though, I have the option of two different resistive loads, and capacitive loads.  The only drawback is that MM loads are limited to 47k or 100k ohms; ear bleeders like the Audio Technica MM carts are happier with different loading, maybe in the 22k range.  The next available setting is 2k ohms.

For gain, there are 13 steps available from 40 to 60dB.

I did notice a bit of “rush” (faint white noise) when turning the volume way up.  I am going to inquire whether this is normal or not, and if a better power supply (than the small wall wart) would help that.  This phono stage uses so little power that a battery power supply may be an option too.

Overall, I have not had much chance to listen to it yet, but the sound is very clean and full-bodied.  If the soundstage was improved with the C-J preamp, this really locks it in further when playing vinyl.  I do want to tweak loads a little more, but it is really sounding nice at 59 ohms.

I will have more impressions over the coming week as I evaluate some high-quality vinyl.

Preamp upgrade: Conrad-Johnson PV-14L

Music

It only took me 34 years, but I finally have a new (to me) preamp in the system, and I am finally a member of the “valve audio” club.  The PV-14L arrived two weeks ago, and I have been getting familiar with it.  My unit has had the “S2” upgrade, which features improved caps, Vishay resistors, etc., and a new spec for the tubes.

Having only seen photos of the front panel, I was afraid it was going to be silver.  Instead, it is a pale gold color, which looks nice with the engraved front panel.  Operation is by pushbutton, with most features available via the remote.  Switching and volume are done internally, so worries about oxidizing potentiometers is eliminated.

The tubes were changed out at some point, as the factory spec Mullard M8080s were replaced with the Philips ECG 6C4WAs. For a quick replacement, I ordered in a pair of Tung-Sol 6C4s which were marked for FAA use.  I have the M8080s shipping from the UK, as they are reportedly less microphonic than these 6C4s are.  The Tung-Sols do sound nice in the system, slightly less bright or “etched” sounding than the Philips pair.

One thing I have noticed with this preamp is that the imaging is rock solid.  Instruments are more clearly placed left to right in the soundstage, and vocals are spookily centered between the speakers.  Clearly my speakers are the weak point (for that “last mile” of improvement), yet I can still hear the differences.  One critique of this preamp was weak bass (boooo….), but the S2 upgrade cured that.  The bass is definitely weighty in the improved version.

It also appears to be a good match to the Nelson Pass-designed Stasis amp (Nakamichi PA-7).

The only thing it does not have is a phono stage.  But, that issue has been solved as well…

I will be back with a long-term update, as well as an update once I get the Cardas interconnects built.

Interconnect Update

Music

I’ve lived with my Silver Sonic cables for several months, which I wrote about this past April.  While they are a clean sounding cable, I am finding the sound to be somewhat thinned out.  Perhaps the silver in the mix is not to my liking.

I have decided to embark on another cable project and make up a few sets of interconnects usinc Cardas 2×21 interconnect wiring.

This particular Cardas cable uses a “golden ratio” of conductors in an arrangement where the inner strands are smaller than the outer.  More notable is that Cardas produces these using litz wire, where each individual strand is insulated with a clear lacquer coating, similar to how windings in a transformer are insulated.  I won’t go into the technical and electrical advantages, but others who have heard Cardas cables mention that they are less bright (some even say they are dark) while the sound is more full-bodied.

This cable is not so expensive that I need to worry about buying enough to make the interconnects.  With that in mind, I am going to go with the Cardas 2×21 and, again, the Neutrik ProFi RCA plugs.  I had considered the Cardas Silver RCA plugs (their lowest cost plug), but it still uses a similar brass core that the Neutrik uses.  Since my RCA jacks on the new preamp (you’ll find out more in a few days 😉 ) will be gold plated, having gold on both the plug and jack will prevent metal mismatches.

Since it has the separate shield, again I will use the floating shield method of building the cables; my Silver Sonic cables remain dead quiet even today.

What’s nice is that I can mix and match these different sets of cables as needed.  If the phono playback is too dull, I can swap in one of the Silver Sonic cables.  If digital is too bright, I’ll stick with the Cardas over the Silver Sonic.

The only caveat with Cardas litz wire is that it requires special preparation–a rosin flux, and tinning.  I may not invest in a solder pot for this project, but the flux is a necessity to flow the solder and melt the lacquer insulation.  (I need to use a heat sink to prevent melting the insulation further up the wire.)