An ode to the EL84

By mrgoodsound

A friend recently asked me about my experience with EL-84 amps and I decided now was as good as time as any to document them in an article.

The ubiquitous EL84 (American designation 6BQ5) was developed by Philips in 1953 and introduced to market by Mullard by 1954. The latest in a series of miniature output pentodes developed by Philips, its lineage stems from the superb EL11 and EL3N tubes of the pre-war period. Indeed, at that time Philips was the largest patent holder in Europe, and their engineers were on the bleeding edge of advancing vacuum tube technology. We still see plenty of the EL84 today, likely due to its introduction at the beginning of the 'golden era' of hi-fi, as well as its popularity in guitar amps dating back to the 'British Invasion' of the 1960s.

Readers can enjoy an entertaining although politically incorrect commercial from Telefunken below, where the pre-war output pentodes are depicted as sickly and distorting the sound, while the brand new miniature finger lamps such as the EL84 and its cousin EL95 make sweet music.

My own experience

I can safely say I have never heard an EL84 amp I didn't like (at the least). Within its power envelope it bridges the gap nicely between flea power triodes and beefier output pentodes such as the EL34 and 6L6. A pair of original Telefunken EL84s reside in my 1956 Opus 6 radio. In general, this tube can be characterized as having a sweet and honest tone, plenty of 'snap', and pretty good bandwidth. It does not sound as 'big' in scale or dynamics as larger envelope pentodes such as the EL34, but with efficient enough speakers it certainly gets close.

Speaking of power envelope, here are some examples of what this tube can do in common configurations:

• Class A SE (triode-connected): ~2 watts
• Class A SE (pentode-connected): ~4 watts
• Class AB PP (pentode-connected pair): ~10 watts
• Class AB PP (ultralinear connected pair): ~8 watts

Eico HF-81

One of the first EL84 amps I owned was the integrated HF-81 by the American firm Eico. This amp was a sleeper in the early 2000s as collectors and vintage audio enthusiasts would often overlook Eico in favour of more prestigious American brands such as McIntosh, Fisher or Marantz. The fact is this amplifier simply sounds excellent, thanks in large part to the Heyboer manufactured output transformers. Prices have steadily risen since a review of it was published in Stereophile a few years ago, and now even so-so unrestored examples can be priced sharply.

I have actually owned two HF81s, the first one I kept original but it always had some sort of hum or noise issue so I eventually sold it. The second time around, I decided to go 'all-out' and send the unit in for a 'restoration'. This was a painful lesson learned as after I got it back it never quite sounded the same, most of the magic was gone.

Pros of the Eico include an excellent line and phono section. Cons include a poorly implemented balance control and flimsy RCA input jacks. Build quality will vary depending on if the unit was factory-assembled or made from a kit. With 4 EL84s, 4 12AX7s, 2 12AU7s and 2 EZ81s, the unit is also very costly to refit with tubes. The original Eico labelled Mullards are sublime but difficult to come by. I mostly agree with the rave reviews this amplifier receives, it has presence and tone in spades.

Grundig NF-20

This is (was?) another sleeper amp found in Grundig stereo consoles of the 1960s. It is a simple circuit with high quality parts, including German-made transformers of outstanding quality. More information can be found on the Tube-Classics site here. 

Grundig NF20 sits atop EMI 319 speakers

It will require at the minimum some work to incorporate into a modern system. I have seen some add RCAs and binding posts, while others made pigtail adapters to use the existing German DIN connections for signal in & out. Restorations should be conducted with careful selection of parts to not disturb the sound character of the amp. 

I managed to find one of these that had already been restored at a very good price, including a contingent of original Valvo EL84s and 12AX7s. While it was modified to include a volume control, I find it sounds best with an active pre-amp to provide more drive. This amplifier does sound a little better than the Eico, but it is an apples to oranges comparison.

Chapman Model 305

Chapman 305 Stereo Amp

Chapman is a little lesser known British manufacturer of hi-fi electronics from the 1950s and 60s. The model 305 amplifier and pre-amp work as a pair, as mains input and signal are passed to the amplifier through an umbilical cord.

The 305 employs the EL84s in an ultralinear configuration, using transformers from the British firm Partridge. I was very lucky to find an export version of this amplifier that has a 120V mains transformer, as the very few I located through online searches always showed a 240V primary. 

This is, overall, the 'finest' amplifier I have yet owned. The Partridge transformers deserve their reputation as this amp delivers a very open and honest presentation of music. Because of how rare it is, I am not sure how much good it will do to heap sonic praise upon it. I will just say that the gentleman I purchased the amp from said this: "Leak had the name, but Chapman had the sound".

Other choices

A very cute RH-84 build

This is just a small sampling of EL84 amps I have owned. There are of course many excellent vintage choices including but not limited to: Acrosound 20/20, Pilot 232, Leak Stereo 20, Fisher SA-100, Fisher X-100, Eico HF-14, Dynaco Stereo 35, the list goes on.

There are a few more modern examples, such as the Music Reference RM-10, Quicksilver Audio Integrated and Leben CS-300, though my gut tells me they won't hold a candle to the vintage amps. I also had the opportunity to hear a Beard P-35 which can still be found second-hand in the UK/EU sometimes. The Beard is nicely made and has multiple push-pull pairs of EL84s for less efficient speakers.

People also discovered the EL84 amplifier circuits from Akai and Sony reel-to-reel machines. While the transformers from these machines are often harvested for other SET builds, many have found success creating modern SEP amps around them, such as the RH-84. Other single-ended examples include the Decware SE84 and Almarro A205A. I know doctorjohn has a lot of EL84 experience so hopefully he can chime in with some models I missed.

In terms of the tubes themselves, the answer of the 'best' is quite simple, West European made in the 50s: Mullard, Telefunken, Siemens, Valvo, Philips Miniwatt. Perhaps not worth splurging on these for a Magnavox console amp, but something to consider if you have one of the amplifiers listed above.