Check this Beast out !!

[NOSValves]

Loks interesting !!

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=802884182

[Guy Landau]

Very intersting.

It really makes me wanna bid,even though I don't need it.

[Tom Mobley]

jeez. and that Mac pre-amp, must have been a killer setup. Wish I had some money laying around.

[Clipped and Shorn]

Looks very interesting and tempting.

I seem to recall some tubephiles not being enamored of 6L6 (5881) output tubes compared to all the others. I am about to upgrade some Eico HF-22 which use this same output tube. I am curious about these reservations regarding this output tube which from my recollection is one of the standards and one that you see in many vintage amps as well as guitar amps and organ amps etc. What is the skinny on the 5881. I will be using the Tung Sols since I heard those were some of the best.

-c7s

[mike stehr]

I would imagine that it wouldn't better your EL-34 amplifier, but it will have it's own sound from the type tube used, and circuit, parts, etc....

I have a Bell Carillon 35 watt mono P.A. amp that uses 6L6 output tubes (RCA.)

But I only used it for a subwoofer.

Compared to SS, it was kinda flabby. But I had more control if that makes any sense.

I liked the sound, though.

But the Bell has a few out of spec coffin resistors and I shut it down. (Another #@$%&*& project!)

[Clipped and Shorn]

I have run across positive recommendations for the Eico HF-22 and I will proceed on that upgrade. This will be for a second system. The Eico HF-35 will be the ones used here in the house system and those will receive the upgrades as well, that amp does employ the EL-34.

Here is another question. In my proposed tri-amp set up I will have at my disposal two tube amps using EL34, one a Triode Dynaco 70 mod, and the other a stock upgraded Eico HF-35. One can be used for the mids ala an Altec 515C, and the other for the higher frequencies 511B (802 driver) + Tweeter. I am wondering which is best for each of these applications.

Maybe the Dynaco triode mod for the 515, and the Eico {with "better" iron) on the high frequencies. The bass will be handled by an SS amp. The use of an electronic crossover elimates some of the complications of designing the system with passive crossovers all around, I am told. The active crossover makes it relatively simple to tweak and experiment with slight alterations of crossover points etc. and also makes it possible to compensate for the phase shift due to the horn driver being at a longer distance behind.

-c7s

[mike stehr]

I dunno,

Your best bet is to experiment and see which amp is suited best for each driver.

Same with the Active crossover, you won't really tell until you set it up in your listening area.

Have you hit Mark Deneen up with these ideas yet?

Craig,

That amp does look interesting!

[Deang]

Several here on the forum, including me -- are worried about Mark. Is he O.K.?

[Clipped and Shorn]

Yes, most of what I am doing has been with Mark's help, insights, example, and recommendations.

He is well and at this very moment is in the process of moving to a home further north in California. In that regard he is not currently active in the hobby and may not be for some time given the various demands on his time and other interests. We all miss his involvement and expertise here.

-c7s

[Clipped and Shorn]

Back to the amp that started this thread. Anyone seriously feel that this 6L6 amp could be a real winner? At this point it is not much more $ than a good Dynaco 70.

-c7s

[NOSValves]

Clipped and Others,

Where did you get the Idea this was a 6L6 based amp ? I believe its a 5881 based amp and if so could be rewired to run a bunch of different tubes with are missed dearly buddy Marks great audio Knowledge. I think this amp would be a winner !! It has all the important parts good Iron a choke the works and some great driver tubes !!

Craig

[Clipped and Shorn]

I was not making any distinction between the 6L6 and 5881 which are the same for all practical purposes. I just recall a few people saying they were not really thrilled with this tube (6L6 and/or 5881 ). If I were to think about acquiring the amp, I would just leave it with the 5881 myself, which as I mentioned was a classic vintage tube used by many reputable makers. I was just wondering why some seem to have reservations about this output tube sonically compared to others.

c7s

[Allan Songer]

Hey now!

Whoever says that there are no GREAT beam power tubes in the 6L6 family does NOT know what they are talking about! Three of the ALL TIME GREAT power tubes are 6L6 types.

#1 The Western Electic 350B. The holy grail of 6L6 tubes.

NOS quads go for $1500 or more. I was lucky

enough to hear them in a MC-30 MAC once and actually

auditioned a pair of movie-theatre amps from the early

1950's that had these babies. I've been actively

looking for a quad for my 30s ever since. I just can't

pony that much cash--it's not in me. But if I come

across some one day for a good price . . . .

#2 The GEC KT-66. This has been my favorite tube for

many, many years. Works great wired in triode too,

unlike most beam tubes.

#3 The Mullrd EL37. This was Mullard's answer to the

KT-66. Just as rare and expensive. An awesome tube,

but for me it lacks the clarity of the KT-66 in my

current application.

[Radiohead]

Er

[NOSValves]

Clipped,

Actually I didn't know the 5881 and the 6L6 were basically the same tube. I have some 6L6 Scott mono intergrates haven't really given them a real good listen. Just can't deal having to mess with 2 volume pots !!

Craig

[Clipped and Shorn]

I was only discussing the 6L6WGB=5881 specifically. Everyone knows about the other good tubes in the general family. I never used the word "family".

I haven't heard any sonic raves lately about 5881 or other tubes called "6L6" compared to say EL34 etc. and the other desirable output tubes in this general power rating.

Yes, I know, guitar amp people like them.

I did once find a couple of reviews which mentioned positive things about the Eico HF-22 :

"I give these speakers 5 stars. The soundstage from these speakers is huge. When people first hear these speakers, it seems everyone automatically says, "Wow." The sound coming from the speakers is very open. It feels like I can look into the speaker and know the location of the sound coming out. It's quite a convincing illusion. I would give it a 10 out of ten in the soundstage department.

These speakers require complementary equipment to perform well. Currently, I have two monoblock Eico HF-22 tube amps with a quad of RCA 6L6 output tubes (22 W/Ch RMS) and an audiophile AGI-511 solid state preamp running the Cornwalls. The sound is quite nice. It is moderately warm sounding, with very accurate detail. The tonal quality is also quite nice, really without fault. There is no harsh bell ring or harsh high-frequency output. I have found that a very good solid-state pre-amp and tube power amps give the type of sound that I like: sound that is well balanced and accentuates all the positives of the horn speakers while negating most of its negative tendancies.

The first set-up I tried initially was using a black-plastic, piece-of-crap, Yamaha receiver built in 1997 (total weight, about 7 pounds). That lousy bucket of bolts produced one of the worst sounds I've ever heard from a speaker. Next, I tried an Eico tube pre-amp driving the Eico HF-22's, but the sound was so incredibly warm and fuzzy that it was a little unbelievable. I also think accuracy suffered. Next, I powered the speakers with a Pioneer SX-1050 receiver (The Pionner SX-10xx and SX-12xx receivers are some of my favorite. Simply outstanding receivers.) with 120W/Ch RMS of very accurate, pure power. I think that the 120W RMS was plenty of power for these efficient speakers and accuracy was outstanding. However, the shrill effect of the ringing horns was very evident. Snare drums or trumpets would send a continuous high-frequency assault into the room and you actually had to get out of the way of the speaker. That set-up wasn't completely desirable.

Overall, I am completely satisfied with the Cornwalls. They are not perfect speakers, but I don't think that any are perfect. To rate the pure sonics and specs (frequency response, efficiency), I give them an 8.5 out of 10. If paired with correct, quality components, the speakers' Tone gets a 9.5 out of 10.

There are some completely minor faults that need mentioning. I have two pair of favorite speakers, the AR-3s and Cornwalls. The AR-3s are slightly more accurate, and the frequency extremes of the low bass and the high tweeters reach farther than the Cornwalls do. Drums sound great on Klipsch, however they sound perfect on the AR-3. Wind instruments have a more rich and warm sound on the Klipsch. The AR-3s, however, cannot match the Cornwall's huge soundstage. It's hard to describe what it's like listening to sound that big, but it's very impressive.

Strengths:

HUGE soundstage. Really big sound with lots of 'air' around it. Accuracy is quite nice. Woofers made of long-lasting, durable paper (believe it or not).

Weaknesses:

These must be matched correctly with your other components to sound right, "

"EICO has been considered by the experts as a "middle of the road" purveyor of tube kits. In general, I would agree with  that assessment, but I would single out the EICO HF-22 monaural power amp as a component of exceptional merit. This is a basic power amp rated at 22 watts continuous and 44 watts peak and uses a pair of 6L6GB beam power tubes.  The basic circuit is described as a variant of the British Mullard type and incorporates a Ultra-Linear output stage. The output transformer is of excellent quality and there are some neat technical features:

a EF86 pentode is used at the input as a voltage amplifier,

the voltage gain stage is direct-coupled to the phase splitter for increased speed,

a 6SN7GTB dual triode is used as a cathode-coupled phase splitter,

a 5U4GB tube rectifier is used in the power supply.

Last year I bought a pair of HF-22s from a local hobbyist (for $150/pr) who had built them from kits as a teenager in the 50s. He  even kept a copy of the original sales receipt -- on the order of $35 ea.! The sound of these is absolutely captivating. If you're after vintage tube sound, look no further. The tube rectifier helps flesh out the lower mids  with a rich harmonic tapestry. Plenty of detail and resolution with revealing speakers such as the Samadhi Acoustics Magic Cubes. While so many collectors, clamor after anything with the McIntosh logo on it, I'm unimpressed  with the MC40 relative to the EICO HF-22. The MC40 costs much more, offers a comparable power output, but sounds congested and muddled in comparison. "

-c7s

[Allan Songer]

The only Eico gear I ever lived with for any length of time were a pair of

HF-22 monos. Had them hooked up to a pair of Quads and a McIntosh MX-110 back in the late 70's or early 80's (so far back I don't rememeber EXACTLY what year!). They were pretty fabulous--I sold or traded them for something, don't remember what. I ran them with Mullard EL37s. Wish I still had them.

[Clipped and Shorn]

Was it necessary to do any bias tweaking or other adjustments to run the EL37 in the HF-22? My tube data indicates that the EL37 is not strictly speaking an exact sub for a 6L6WGC the same way that a 5881 is. Not to say you cannot just stick them in there and they will work, maybe even better, but it is good to check these things in case you put stress on other components especially transformers.

The EL37 is usually referred to as a substitute for the KT66 not the 6L6WGB/5881. I am not so sure it is advisable to just plug in the EL37 where the 5881 is called for without making other adjustments. I am sure they work because the pin out is the same, but I think there are other ratings which are different.

It is difficult to find online definitive information about all of this. People talk about tube substitutions assuming others just know that adjustments may have to be made to other components under the chassis, but I would like to know exactly what needs to be done to make these substitutions, if anything.

Here is some of that precise data:

Subs for EL37:

Close or identical : CV586

Different rating or performance: 6L6, 6L6G, 6L6GA, 6L6GB, 6L6GC, 6L6GT, 6L6WGA, 6L6WGB, 6L6WGC, CV1286, CV1947, CV1948, CV2796, CV2817, CV3618, STR387, STR415, SV6L6GC, VT115, VT115A

Different pinout: 5B245M, 6BG6, 6BG6G, 6BG6GA, 807, 807W, ATS25, ATS25A, CV1060, CV124, CV1364, CV1374, CV1572, CV3809, CV428, QV0525, VT100, VT100A, VT60(RAF), VT60A(RAF)

Different filament voltage 19BG6G, 19BG6GA

c7s

5881/6L6WGB

This tube was first developed by TungSol for the US Military.  They are in short stubby glass envelopes.  There is no difference between the 6L6WGB or the 5881, they are the same tube.  The 5881 has a maximum plate rating of 360 volts at 23 watts and a maximum screen rating of 270 volts at 3 watts.   DO NOT USE IN AMPS CALLING FOR 6L6GC's.  They will likely melt down and damage your amp.

[Allan Songer]

I got these from a "tweaker" down in San Jose--I'm sure they must have been modified to run the EL 37s in place of the 6L6GWB. The EL37 has the highest plate voltage of any 6L6 I've come across--think it's 850v and a filamnet current of 1.4. You'd have to be careful with those Eicos--wouldn't want a melt-down. I know that SOME 6L6 amps (lots of Guitar amps and the McIntosh MC_30 for sure) can use just about anything with no mods, but not sure about the Eico.

[Clipped and Shorn]

Actually I am curious to see if I like the 5881 tube which was so popular in so many vintage amps. They are relatively plentiful and inexpensive in NOS, and I happen to have a stash of Tung Sols on hand.

I would be inclined to substitute some EL37 in the Heathkit W5M (KT66) amps when I get those upgraded since that sub is closer to begin with. I would be curious about the difference, although the vintage KT66 is also a great tube and both are kind of expensive now so maybe I won't bother. I read that the EL37 was rendered obsolete when Mullard came out with the EL34.

-c7s