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Mini Review: Electra Fidelity 45 CU stereo integrated amplifier

I've had a crush on integrated amps about as long as I've been into high-end audio. My first amp, a NAD, was an integrated. So was my second, an Ars-Sonum. And third. I didn't get into separates until I got a Plinius SA-250 Mk4/M-16p pair some years later. I currently have integrateds from Luxman, Rogue Audio, Miniwatt and Audio Space. I love integrateds. Exactly why all the love may be hard to explain, but it's probably the simplicity, though I can't say that it's really anything more complicated than "I like things with buttons". I dunno why. I just like 'em. What can you do?

Electra-Fidelity

I first came across an Electra-Fidelity amp at T.H.E. Show in Newport Beach this year, fronting a pair of average-sensitivity, but sweet, little loudspeakers from Fritz Frequencies. This was a surprising room — mostly due to the SET Electra-Fidelity monoblocks on display. 300b tubes. In an SET design. ~8wpc. Into an inefficient loudspeaker. At an audio show?  Color me “bemused” — I mean, that’s hardly “real world”, now is it? And aren’t you kinda just begging for issues? I mean, wouldn’t you want a pile of watts for a such a speaker, even if it’s just a monitor?

If you’re picking up a vibe that’s thrumming out an audiophile cliché or two, can you blame me? But, as always, the proof was in the listening — and this was a damn fine sounding room. So much for preconceptions — my response at the time? “Go figure.” Man, am I eloquent, or what?

Somewhere around this time, I was looking for a low-power SET amp to build a high-sensitivity system around. Tony Chipelo reached out to me and suggested I look at one of his 45-based integrateds. A few rounds of exchanges, a few shows, a few months later, and a lo! Behold! A really cute amp showed up here at Chez Moi. And I do mean “cute”! I really like the look of this little guy. Simple. Classic. And sporting some vintage GE tubes! I might have done a little happy dance, but I won’t swear to it.

The Electra-Fidelity 45-Cu retails for $2,495 and is sold direct. There is a “big brother” version, with custom-wound Partial Stranded Silver Secondary (PSSS) transformers called the Silver 45 SE, which retails for $3,995. The Silver 45 SE is enjoying a very limited production run, and I’m told there are only a couple still available for ordering. My 45-Cu is the same amp, minus the fancy silver input and output transformers. I mean, not minus in the sense that they’re all gone, there are some, but they’re all-copper.

A couple of words about E-F:

Electra-Fidelity is a boutique high-end audio dealer based in Las Vegas, NV that was founded by Tony Chipelo in 2010. In addition to high-end audio products from Galibier Design, Resolution Audio, and Sonist Audio, Electra-Fidelity is the authorized marketing and distribution arm for the electronic circuit designs of Jack Elliano, who is well known as the founder and manufacturer of Electra-Print transformers [from “Silver 45 SE Instructions Manual].

Jack Elliano’s philosophy focuses on manufacturing transformers with the widest bandwidth and lowest distortion possible. He then matches a circuit with hand selected parts for use with the transformers that optimizes overall performance. Rigorous testing with different capacitors, resistors, and other parts has shown no discernible difference in sound quality. However, to pacify the audiophile who wishes to experiment on their own, there is easy access to the circuit and a schematic can be supplied so that you can perform your own upgrades [from Electra-Fidelity website].

There’s a couple of gems in here — I especially like the bit about the “pacification” of the audiophile. At the risk of insulting both golden-ear audiophile and manufacturer who caters to them, this is something I’ve heard before — parts quality is one thing, a good design is another. Amp guru Nelson Pass is well known for saying something similar: “if you use common parts and it still sounds good, it must be the design”. I think Jack and Nelson are trying to tell us audiophiles something, here, kids. Just sayin’. Fancy caps and resistors? Who needs ’em!

Okay, fine — I’ll confess that all this smack-talk makes my inner-audiophile a little uneasy. Moving along.

Let’s talk about silver. Silver, especially in tube amps, is apparently all the rage, but is there a difference? Really a difference? I mean, aside from price? Unfortunately for me, without a side-by-side comparison, I’m kinda stuck with hearsay, so I’m taking it all with a pile of salt … but “reputable sources say” that “in most implementations” silver shifts a tonal balance away from mid-bass richness to upper-mid speed and detail, and finishes it off with a healthy dose of top-end sparkle. YMMV. Here’s what Tony Chipelo provided:

Technically speaking, from Jack’s perspective, the bandwidth due to the silver used in the output transformers is higher than the copper version. This yields greater transparency and dynamics and it is noticeable in side by side listening. We have a local audio group here and according to their feedback the 45-Cu sounds more like a traditional 45 SET. On the warm side of neutral with just enough bass bloom, but never tubby. On the other hand most agreed the Silver 45-SE was quicker and more neutral sounding.

As an example of detail Jack likes to use the Solti recording of Scheherazade, I think the last couple movements as it starts off pretty slow. He listens for … strings and especially the violin … [and the] “scratch” that is caused by the resin used on the bow. To him, this sound is more clear and prevalent with the Silver 45-SE.

The 45-Cu is fairly simple, classic even, and uses a pair of 6SN7 input tubes along with a pair of 45 output tubes. Power regulation/rectification is all solid-state. Again, this output tube is a 45, so 1.7wpc is all you get. Consider yourself warned — you’re not going to rattle the apartment with this guy unless it’s blowing on a horn (or something with a similarly high sensitivity). We’re talking a max of 3dB off your speakers’ sensitivity.

Volume control on this amp is a purely passive affair, borrowing the design from the Magnetic Line Amplifier, a passive preamp also available from Electra-Fidelity.

The volume control of the amp is based on the passive voltage attenuator circuit. This is the same circuit as used in the Magnetic Line amplifier. The circuit is comprised of a pair of input transformers and a 10K potentiometer. The interesting part of this design is not only that it is passive, but the purpose of the input transformers is to step up the voltage from the source. So if you are using a CD player with 2V output, the input transformers will convert that to 16V (1:8 ratio which is Jack’s preference, but the transformers can be wound to produce lower ratios). So essentially we have a passive gain stage where the transformers produce the gain, then you attenuate the voltage using the 10K pot. From Jack’s perspective this ensures proper dynamics swing, which running the signal direct to the 10K pot (traditional passive circuit) would not accomplish.

I should note that I didn’t roll the tubes on the amp, so I have no idea what swapping out the vintage GE tubes would or would not do.

The circuit has been designed to tailor primarily to those 45 tubes manufactured between 1929 and 1959 (US) including ST and globe types. The manual discusses tube rolling and it is worth noting here again that lowest distortion will be achieved with 45 tubes as specified by Jack Elliano. This is not to say others won’t work (the EML 45 is a good choice as one of our customers reported), but again Jack is focused on getting the lowest distortion from this circuit. As for 6SN7 tubes there is more flexibility, but again, some of the 6SN7 variants (especially those not designated with 6SN7 markings) out there may not work ideally in the circuit as Jack voiced it, so buyer beware.

Setup & Sound

There is an interesting option on the back panel — “High Z” and “Low Z”. Tony explains:

Low Z switch for 100 ohm loads mean that is the maximum load that should be seen from the source output impedance (in fact we have tested it with sources with up to 600 ohm output impedance and it works just fine). The High Z is for sources with output impedance up to 10k ohms. That may seem rather high but home theater sources and high output impedance tube sources are best suited for this level.

For loudspeakers, I wired this tidy little guy into a pair of 104dB Volti Vittoras. The Vittoras came with the big 18″ Vittora Subwoofer, so I was able to leverage the sub-outs on the Electra-Fidelity amp (the RCA jacks that sit on either side, closest to the IEC connector on the rear) — a very clever option on an amp that’s probably going to have issues with most loudspeakers.

The sound I was able to get out of this little amp was just lovely. I’m not really sure what I was expecting, but I suppose it was pretty close to what I got. Overall, I heard: warm, speedy, luscious, with a deep, rich tone that made these speakers into romance engines. I hair under two watts was, apparently, more than enough for Getz Meets Mulligan in Hi-Fi. Not the most demanding music, but still, this was all about “straight ahead and strive for tone”. Mmm, mmm. Moving over to the far-more-up-tempo Art Blakey & the Jazz Messengers The Big Beat and Duke Ellington’s Ellington at Newport, was equally enthralling. Okay, so I’m a jazz fan. I surrender! Following up with Chris Jones’ Roadhouses & Automobiles, and a couple of other pop recordings; I found the mid-bass a bit softer than I was expecting even if the bass was pretty much in-line with what I was expecting — a touch billowy. Interestingly, the output was still very powerful — to get the amp to tip over would have required hearing protection. I couldn’t do it, not with living creatures in the house, anyway.

Just as a point of comparison, I have a 300b-based SET amp from BorderPatrol, an $8,995 SE300b with a big-sounding 9 wpc. With this as my barometer, the 45 CU was clearly softer, warmer, less detailed and less impactful. More “SET-like”. The only thing I could put my ear on, was, interestingly the speaker. That is, the tweeter, mid and bass horns — the Electra Fidelity amp was quieter. I had to go back to trim the “hum pot” on the big BorderPatrol to bring it in line with the 45 Cu. As for noise, of course that latter amp uses a choke-regulatued, tube-rectified external power supply, so we’re not apples to apples anymore. The external PSU on the BorderPatrol unit is itself almost as big as the entire Electra-Fidelity amp — and as result of it’s size and design, the power feeding into the SE300b is going to be a lot more robust. Taken together, the Electra-Fidelity cleaves more to the stereotype of an SET, with all the positives and negatives that so apply, where the BorderPatrol unit is simply more transparent — and as it’s more than 3x the price, that’s probably not inappropriate.

I don’t have another low-power SET amp to compare the 45-cu to, other than a Miniwatt N3 (and no, it wasn’t close). However, in an interesting twist, a Yamamoto A-08s does happen to be en route. I say “interesting”, because this note was included with the setup instructions:

One of our customers compared the Silver 45-SE to the Yamamoto 45. He found overall the Silver 45-SE to be faster, more transparent, and detailed. However, he did like the sound of the Yamamoto for some specific types of music and set out on a quest to try and duplicate that sound with the Silver 45-SE by tube rolling the driver tubes. Here is his final observation (NOTE: the 45 tube used in each amp was the EML 45): “So far, the tube that can faithfully recreate the sound of the Yamamoto in the Silver 45-SE is the RCA 6SN7GT Grey glass tube with parallel plates. The sound was pretty much the same as the Yamamoto, with similar bloom, sweetness and relaxation, but with slightly better clarity, tighter mid range, and more punch in the bass, which made it an even better choice.”

Wrap up

Did I mention that I love integrated amps? I do! And the Electra Fidelity 45-Cu is a delightful case in point. Compact. Elegant. Full featured. Retro. A little bit country. A little bit rock and roll. I’m lovin’ it.

Look, if you’re a tube guy and a high-sensitivity loudspeaker isn’t a sacrifice for you, you owe it to yourself to check these amps out. They’re fun. The sound is terrifically sexy. Yes, I’ve heard sound that was technically a bit more of this or that, but none of that took anything away from the music I was enjoying.

To be honest, I’m not entirely sure what to do with a little tube amp like this. It works great as a near-field amp for those of you with such setups, and that arrangement would probably let you back off the sensitivity thing — from crazy-sensitive 100db+ horns to something more reasonable, like a 92dB Reference 3a MM de Capo I. Anything with a Lowther is always an option, of course. But if I had a large room, and Lowthers or horns weren’t my thing, I’d look hard at Zu Audio. The Yamamoto A-08S amp is an acclaimed match for that brand, whose sensitivities tend to float in the 100dB range. Sonist might be another good choice for near full-range; designer Randy Bankert used to demo quite routinely with a Glow Audio amp, putting out flea-watted power — a 45-based amp would be a fine fit for the 97dB Concerto 4.

So, yeah, aside from that … well, things are limited. Of course, things are always limited with micro-powered amps, but then, what else is new?

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