Mar 122018
 

I’ve been using the sweet little Almarro A205A EL84 integrated amplifier to power my vintage Altec 832A Corona loudspeakers that I’m using in my bedroom system, and it’s a really nice match for them.

The volume pot has been kind of noisy in the A205A so I thought I’d pop the bottom off and squirt a little DeoxIT F5 on it to quiet it down.

I popped the bottom off and gave the volume pot the DeoxIT treatment and worked it back and forth a bit to spread it around and let it do its thing.

I’ve never had the bottom plate off the A205A (reviewed for 6Moons back in May of 2004), just the A205A Mk II version that I reviewed for 6Moons way back in March of 2006 (below).

Almarro A205A Mk II interior.

A popular hot rod mod of the Almarro A205A Mk II at the time was to replace the stock coupling caps – the two grey ones towards the bottom of the photo above – with some better caps, with some preferring the Teflon V-Cap’s and others Jenson PIO’s.

Also, one could make the little Almarro A205A sound a bit warmer by replacing the stock 0.047uF coupling caps with 0.068uF coupling caps.

Almarro A205A interior.

After I finished with the lubing the volume pot I was looking over the circuit and I noticed the original grey coupling caps were disconnected and had been replaced with some nice Jensen PIO’s.

There were quite a few changes that were made between the original A205A and the A205A Mk II, but the Jensen PIO coupling caps go a long way for explaining why I preferred the musicality of the older A205A to the newer A205A Mk II.

Back when I reviewed the A205A Mk II I said, “What we have here with the MkII is an example of the classic HiFi conundrum: The MkII version of the A205A sounds noticeably better at least on well-recorded material but the original A205A is more musical and easier on the ears particularly with less well-recorded material.”

So the original A205A I reviewed had the coupling caps upgraded before it ever got to me, which helps explain its richer and more musical tone.

Almarro A205A with a quad of Duelund CAST tinned-copper 0.01uF coupling caps added in parallel to the Jensens.

But that aside, I couldn’t help wonder what would happen if I bumped the Jensen 0.47uF coupling cap capacitance up with some Duelund CAST 0.01uF tinned-copper coupling caps.

Closeup of the quad of Duelund CAST tinned-copper 0.01uF coupling caps.

So I decided to add two each of Duelund CAST 0.01uF tinned-copper coupling caps in parallel with the Jensen’s to give a combined coupling capacitance of 0.067uF.

Another closeup of the Duelund tinned-copper coupling caps.

After getting everything buttoned back up, I put my hot-rodded Almarro A205A back into the system.

Almarro A205A powering the vintage Altec 832A Corona loudspeakers.

The freshly lubed volume pot was silky smooth and totally quiet, so the volume pot refresh was a resounding success.

The addition of the quad of Duelund CAST 0.01uF coupling caps to the Jensen PIO coupling caps gave more of a mixed result.

The addition of the Duelund CAST 0.01uF coupling caps opened up everything considerably, but did not warm up the presentation as I’d hoped for with the little Almarro A205A (it could use a little extra warmth).

The enhanced openness of the Duelund CAST 0.01uF coupling caps in the Almarro A205A was flattering for the lows and mids of the Corona’s, but up top it may turn out to be too much for the already fussy high-frequency presentation of their vintage Altec crossovers.

I’ll report back in this post after I get some more time on the Almarro with its additional coupling caps, perhaps they’ll settle in a bit more and smooth out in the highs.

¸¸.•*¨*•♫♪¸¸.•*¨*•♫♪¸¸.•*¨*•♫♪

Update: It’s surprising how much things can change in 24 hours. The A205A’s presentation has really smoothed out so that the highs are mostly blended-in in a flattering fashion, but there’s still a little more that needs to happen.

Those of you who have been following the developing story know that the 0.22uF Duelund CAST tinned-copper caps that I put in my MX110Z cathode follower positions were stunning right from the start, as they were when I tried them in my Altec A5’s crossovers in the HF circuit. Ditto with the 0.01 Duelund CAST tinned-copper coupling caps when I tried them in the A5 crossover.

So I was a little surprised the same thing didn’t happen with the 0.01uF Duelund CAST tinned-copper coupling caps in the little Almarro right off the bat. I’m thinking it would be better if I ran a pair 0.047uF or 0.068uF Duelund CAST tinned-copper caps alone instead of supplement the Jensen’s, but I went with what I had on hand.

I’m going to let it play some more over the next week and will report on any further developments.

Secret: I was going to share a Duelund secret with you in this post and forgot. Frederik mentioned to me he is contemplating building an insulated version of the DCA12GA wire suitable for use in a power cord. I don’t have any details or know anything about the timing yet, but I’ll keep you posted as I find out more.

If/when that comes to pass I think I’ll do a project where I build a power chord for the Almarro A205A (hard-wired), and a detachable AC power cord terminated with a 15A Marinco 8215 NEMA hospital-grade power plug and a matching Marinco 320 IEC connector that I can try on a couple different pieces of gear.

¸¸.•*¨*•♫♪¸¸.•*¨*•♫♪¸¸.•*¨*•♫♪

Update 2: Now, after 3 days of run-in time, the 0.01uF Duelund CAST tinned-copper coupling caps have blended in seamlessly and offer a very nice presentation of the music. Cymbals, and percussion in general, sounding rich and startlingly real at the same time, and the sense of space has opened up significantly, as is typical with Duelund’s tinned-copper capacitors.

I was just doing this for a “for fun” experiment, but if you were going to do a coupling cap mod to your own A205A I would recommend either a 0.047uF or 0.068uF Duelund CAST tinned-copper capacitor as the coupling caps, depending on what you’re trying to accomplish.

Ok, that’s it for now.

As always, thanks for stopping by, and may the tone be with you!

 Posted by at 1:15 pm

  21 Responses to “Almarro A205A EL84 Integrated Amplifier Duelund Coupling Cap Mod. Update x 2.”

  1. Nice work Jeff!

    Pete

  2. I bet one of these speakers with a MC-30 and a EMT mono cartridge would make one heck of a mono system.

  3. Hi Jeff
    I think you would have better luck sticking with one value of cap, as well as one manufacturer. That has been my experience when changing stock caps for something else.
    Best
    Keith

    • I think you are exactly right, Keith.

      I added in the coupling caps as a spur of the moment thing with what I had on hand to see what would happen, just for fun, but I second your recommendation, a single cap is a better way to go.

      Kind regards,

      Jeff

  4. My experience with capacitor bypassing is that 1% is optimal, 5% is fine, even 0.1% is OK, but 10% or more causes smearing. For a 0.047uF cap, try bypassing with a 0.001uF, such as the Jupiter copper foil & wax.

    • Hi Glenn,

      Thanks for sharing your experiences with bypass caps, appreciated.

      Back when modding the Almarro A205A was at its height of popularity, replacing the stock bypass caps with better 0.047uF or 0.068uF caps was one of the first things enthusiasts did, and it helped the musical & sonic performance quite a lot.

      In fact, designer of the A205A, Yoshihiro-san, encouraged experimentation with the cap values and told me that “the value of C1 affects the bass response frequency and its sound quality. The value of the C1 capacitor can be varied from 0.01uF to 0.1uF. The C1 value for the stock unit is 0.047uF (630V). By substituting PIO (paper in oil) or Teflon capacitors, you can tailor the sound to your preference. We have found that the value of the capacitor tends to have more of an effect than the type used. Smaller value capacitors tend to make the bass response lighter and more polite, higher values the opposite …”

      Although my little A205 sounds pretty good with the PIO Jensen’s in it, I was curious what bumping the 0.047uF’s up to ~ 0.68uF’s would do.

      The pairs of Duelund 0.01uF bypass caps actually worked pretty well in that little experiment. The results were pretty much the opposite of the smearing you described as experiencing, with the presentation of the music sounding more focused, transparent, and resolved, while still maintaining musicality, which I guess is about what I have begun to expect from the various Duelund tinned-copper cap experiments I’ve done.

      Anyways, it was a fun little experiment!

      All the best,

      Jeff

  5. I am curious about the two coils mounted on the aluminum plate opposite what looks like a transformer or choke. They are not part of the original circuit and I do not see them in the schematic from the 6Moons article .

    Where are they added in the circuit and how do they help?

    • Hi Paul,

      Actually, the coils are part of the circuit of the original A205A, as discussed HERE. That changed with the Mk II version, where they were omitted.

      To quote from my 2006 review, “The A205A has coils (L1) that affect the high frequency extension by making it roll off around 14 kHz. If you remove the L1 coils, the A205A won’t roll off until 20 kHz. The L1 coils are used with some of the older full-range speakers in mind, to cancel their driver resonance which occurs at around 15kHz. For more recent drivers, this L1 coil is not needed.”

      I think the coils are to the A205A’s benefit with my vintage Altec’s, for which it is a nice match.

      That’s the scoop on the coils!

      Kind regards,

      Jeff

  6. Hi Jeff,
    I am Just wandering if almarro company still exist in japan? I went and check the old website, but got nada.

    daniel-

    • Hi Daniel,

      I don’t know if Almarro is still around or not. I couldn’t find a web page for them either, so I’m guessing not.

      That’s too bad, they made great sounding gear!

      Kind regards,

      Jeff

  7. Hi Jeff,
    have you a prefered modern brand for EL84 tubes?
    Thanks

    • Hi Giovanni,

      It has been a long time since I’ve listened to what’s available in EL84 tubes, so I am out of touch with the current offerings.

      During an earlier survey I listened to and liked the line of HARMA EL84’s offered by Watford Valves in the UK, but I don’t know how they compare to the latest EL84 offerings out there.

      Kind regards,

      Jeff

  8. Thank you very much

  9. Hi Jeff,

    Recently I bought the Almarro A205A Mk2 amplifier and it came with a V cap coupling capacitors (.068uF) and russian tube 6p14p & 12ax7 .The amplifier looks clean and it was in a good condition.
    The only issue when I played the Almarro with my Zu Audio Union (99 db) speakers is that I am getting too much gain where a slight movement of the volume pot will result a very loud sound. I can barely go past 7 1/2 o clock.At first I suspect there is a problem with the volume pot but I have tested with a cd player that has a volume control and I set the volume of the cd player to very minimum level and the Almarro volume pot work just fine where I can go past 10 o clock without any issues and getting more headroom. Do you have any idea what’s the value of the ALPS volume pot that came with the standard Almarro?

    Is there any known issues with the russian 6p14p power tube that can relate to the high gain? Can I solve it with any NOS European E84 tubes?
    Or this too much gain issue on the Almarro can only be solve by putting in resistor that mod the gain to suit my high efficiency Zu Union. Or changing a to a better volume pot will bring a significant improvement for the high gain issues? Appreciate you advice. Thanks

    Best regards,

    Hasraff

    • Hi Hasraff,

      First of all congrats on the Almarro, it is a fine little amplifier.

      My A205A volume pot was doing the same thing as yours, so I suspect that the volume pot of your A205A Mk 2 needs the same treatment that mine needed recently, to be lubed with some CAIG Laboratories DeoxIT FaderLube.

      All you should have to do is squirt a little FaderLube into the volume pot and work it back & forth for a bit, and it should be good as new, without the issue you describe.

      I don’t think the Russian 6P14P would be the issue, as they are just ruggedized versions of an EL84, but you could always try changing them and see what happens.

      I hope that helps!

      Kind regards,

      Jeff

      • Hi Hasraff and Jeff,

        If Jeff’s suggestion doesn’t do the trick you could try to substitute the 12AX7 with a 5751 tube. It has less gain than a 12AX7.

        Kind regards,
        Peter

        • Hi Peter and Hasraff,

          I’m glad you mentioned the 5751, Peter, and in fact I run a NOS GE 5751 in my Almarro to nice effect.

          Kind regards,

          Jeff

      • Thanks again Jeff for your response. Now the high gain issues has been solved. The technician has replace the 2 small caps & adding on 2 resistor. Now my Almarro can sing!

        • That’s great, Hasraff! I’m glad you were able to implement a simple fix for the gain issues you were experiencing.

          Happy listening!

          Kind regards,

          Jeff

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