IMPROVING THE EICO HF-81, Part Two
The Story to This Point
Due to the time it has taken to finish this article, I have touched on some of these points
already in both the “May 2006” article as well as in “Loudspeakers, Listening Rooms
and Spongy Floors,” so I while I don’t want be redundant, a quick review of what has
gone on before might be helpful to the reader.
After completing the parts upgrades and checking the amp out on my oscilloscope,
the Eico went into the living room system hooked up to my JBL L110 speakers. I did
not get very good bass and worse imaging. I discovered that the JBLs had been
refoamed incorrectly (by an authorized JBL repair facility here in St. Louis, of course.) I
only discovered that I had a problem when I attempted to sell the JBLs to fund
something that would work better in my living room.
I purchased a pair of refurbished Infinity Primus 360 loudspeakers on eBay for
$353, including shipping. I thought these might be ideal for this system given both their
high efficiency and the very good review in the June 2005 Stereophile. At this point, I
also decided to replace the bias resistors in the Eico with a lower value and started to
track down the parts I needed. I hooked the 360s up to a small JVC receiver to break
them in. I did not get good sound again. The bass really boomed and the treble was
phasey in a way that I just couldn’t track down. I subsequently discovered that using
the speaker 2 connections of the JVC, without speakers attached to the speaker 1
connections, did strange things to the damping of the amp. The bass improved
considerably using the speaker 1 outputs but not completely.
I put 174-Ohm bias resistors in the Eico replacing the 189-Ohm set that had been in
it. I expected this to improve the dynamics. Since the JVC wasn’t making sound that
was particularly great, I had high hopes that reintroducing the Eico would rectify things.
It didn’t. There were glimmers of greatness but overall, I wasn’t hearing the quality of
sound I had expected. I was beginning to worry at this point about this whole project.
So I took the Primus 360s apart. A tweeter was not connected. I also tightened
down all the drivers and looked over the interiors of the speakers. (I will have an article
on the 360s done sometime fairly soon.) I feel like an idiot that I didn’t identify the
tweeter problem but it accounts for the “phasey” quality that I kept hearing. So what
actually was refurbished? Wouldn’t that involve checking things like connections?
Using both tweeters helped the sound immensely. Tightening down the drivers took
care of the remaining boom and the Infinities were finally showing signs of being able to
image. Now, though, I started getting really bad transformer hum as the Eico warmed
up. I decided to swap out the rectifier tubes and discovered that one of them was
shorted and the cause of the problem. I also found that the red switch inside the
chassis, whose function I am still unclear on, was also part of the problem. Setting the
switch to the right (facing the amp) improved the sound substantially while also
reducing transformer hum. Suddenly everything was working. Frankly, I wasn’t sure
how to react.
After two months, I could finally start evaluating the sound the Eico was actually
producing.
Some Questions Get Answered
Before proceeding further, let me touch on a number of questions/points that were
noted in Part One.
Will the amp work without the two 12AX7 phono preamp tubes? (V1 and V6 for
those of you checking your schematics at home.) The answer is yes--it works fine.
This also removes from the circuit all of the old, marginal parts attached to these two
tubes. I am not hearing any noise resulting from leaving the tube shields off the
12AU7s either.
The Eico is significantly quieter through the speakers than before the parts were
replaced. Considering the high efficiency of the Primus 360s, this is very good.
External noise from the power transformer is also definitely lower. The noise isn’t
audible unless I am changing CDs and hovering right over the amp. This is acceptable
since I see little possibility of doing anything about it. I will put in new rectifier tubes at
some point.
The balance control is now centered. This is probably due to matching the bias
resistors but it also reinforces my belief that matching parts as closely as possible,
channel to channel, is absolutely essential.
And Speaking of Parts
I decided to replace the two 30-microFarad caps in the power supply (C1 and C2) and
also the two 50-microFarad caps that parallel the bias resistors (C6 and C9.) Even
though these capacitors seemed to be working fine, they are ten years old. With these
caps installed, I ended up replacing all of the resistors and capacitors in the power
supply, line, and output stages of my amp. I also changed the bias resistors yet again
to 179-Ohms. This is the last time I am touching these resistors. I swear. Probably.
The Questions Now Being Examined
I started listening critically with this tube configuration: original (God-only-knows-how-
old) RCA 6CA4 rectifiers, ten-year-old Ei 12AU7 and Sovtek 12AX7WXT+ preamp
tubes, and new JJ Tesla EL-84 output tubes. My thinking was that new output tubes
would make hearing any changes upstream easier so I went ahead and installed them
first. Regarding what noise is present, there is very low level hum audible with my ear
to the right speaker, very low-level hiss at the left speaker’s tweeter. I listened to the
Primus 360s with the grills off. The Eico tone controls are centered as perfectly as I
can center them. They may or may not actually be at their “flat” settings. But they are
close.
I am finding that it takes about ten minutes for the Eico to warm up and starting
sounding its best. There is no real change after that regardless of how long the amp
runs.
I like soundtrack albums with a variety of types of music on them for critical listening. It
simplifies things since I am not constantly changing CDs. I just got The Big Lebowski
soundtrack (Mercury 314 536 903-2) from my daughter for my birthday so I used a
number of its tracks to evaluate how the system was sounding.
The cut “Traffic Boom” exhibited good, tight, deep bass. The trumpets that mimic car
horns in each speaker attack and disappear in a way that makes the system sound
“fast.”
“Walking Song” by Meredith Monk, which consists of two a cappella female vocalists
located just inside each speaker relies on both the vocal sounds being sung and the
singers’ breaths for its effect and makes for very interesting sonics. Echoes give a
sense of the acoustic space. Very interesting music, I am going to have to look for
more of her recordings.
“Hotel California” sung in Spanish by the Gipsy Kings features three guitars, left, right,
and center, each of which sounds very fast and realistic. The soundstage is wide with
limited depth. The vocalist, a guitar, and an accordion share the center of the
soundstage and each is easy to hear and follow. A really fun song.
There are voices in the background of “Dead Flowers” sung by Townes Van Zandt that
let you know you are listening in a bar. They are easy to hear but not intelligible.
Townes is joined by a second male voice singing harmony, or at least an approximation
of it, and both male voices are clean and without boom. Again, the guitar sounds very
good. Unfortunately, there is no information as to whom the other male voice is.
Frankly, it sounds like a lot of beer was involved.
I also listened to many other CDs including Marcus Roberts’ Gershwin for Lovers,
Columbia CK 66437, which has double bass solos that were useful in evaluating bass
depth and accuracy. Cymbals had lovely sheen and realistic decay. The piano
sounded pretty good, too. I have really enjoyed this CD.
Also listened to were Diana Krall’s, The Look of Love, Verve 3145498462; Guitar Music
of Argentina, Naxos 8.555058; and portions of the Forget Paris soundtrack, Elektra
61825-2.
The Billy Holiday tracks on Forget Paris were lovely but “April in Paris” sung by Ella and
Louis was even better. This track sounded almost as good as it does on my main
system.
Regardless of what I listened to, three qualities were very consistent; the system
sounded fast, pianos sounded realistic, and percussion sounds stood out as being
especially realistic. Soundstage width was good while depth varied from adequate to
good, depending on the CD.
I now felt that I had a sense of how the Eico was sounding and was also confident that
everything was working properly. I wanted to hear what happened when I upgraded the
tubes.
Installing the 5751s and 6189s
I went ahead and put GE 5751s in for the Sovtek 12AX7WXT+s and Philips 6189s for
the Ei 12AU7s. I was going to replace each tube type individually and then listen but I
decided I really wanted to finish this article during my lifetime so I did both at once.
The results were somewhat disappointing in that there was very little discernable
change. I felt that the bass was slightly louder and deeper and that low-level sounds
like the echoes on “Walking Song” were easier to hear. It seemed like the background
noise level was also slightly lower but that was about it. What can I say? I expected a
bigger difference but it just wasn’t there.
I listened again to the CDs I had been using and heard only small differences but felt
that those differences were all improvements.
A CD that has become a reference is Yo-Yo Ma Japanese Melodies, CBS MK 39703.”
It sounded very good on the Eico system. Wood blocks, bells, and cymbals all appear
with startling suddenness within a fairly wide and deep soundstage. A flute appears
whose sound indicates that it must be wood or bamboo as it is clearly not metal. The
cello is rich and woody and sits solidly in the center between the speakers. The Eico
had no trouble reproducing its lowest notes with a firmness that could be felt as well as
heard.
Emiliana Torrini’s album, Fisherman’s Woman, Rough Trade RTA 30055-2, features
her breathy, very upfront vocals. This also sounded very good. On track four,
“Lifesaver” a wooden ship creaks and groans and the wind rises and falls very
realistically in a three-dimensional soundstage behind her voice.
The new Johnny Cash, Personal File, Columbia/Legacy 82769 94265 2, was recorded
in the House of Cash, Johnny’s home recording studio, over a period of about nine
years. Different recording dates are different sonically, however, and this difference is
easily discernible via the Eico system. Johnny’s voice is deep without any boom or
exaggeration.
I was going to listen to the new Dixie Chicks CD but my daughter appropriated it before
I had the chance.
While these CDs sounded quite good, they also highlighted the differences between
this system and my main system. The living room system does not have the same
black background my main system does; the bass does not go as low; the highs are not
as pristine; and the soundstaging is not as good. No surprise here. Still, I think this
system easily delivers 80% of the sound quality of my main system, which is pretty
amazing. I can not only enjoy the music I hear on it, I can also listen critically to it and
feel confident of any judgments that I make. I now have better sound in my living room
than I have ever had before by a very large margin.
I rechecked noise levels at the tweeters with the new tubes and the system well warmed
up and I can now hear only very low-level white noise. I guess the hum and hiss were
related to the older tubes. The Eico does get very warm. It was reassuring to read in
the June 2006 Stereophile article on the Eico HF-81 that mine is not the only amp that
runs this hot. I can’t really detect any difference that changing the bias resistance has
made in the heat output. Still, I would run it (or any Eico HF-81) with bias resistors
higher than 165-Ohms in value to just to give the power transformer some breathing
space. Ultimately, the bias resistors had nothing to do with the amp’s dynamics. The
dynamics are excellent. I’m also not sorry I added some higher feet and some
additional ventilation to the chassis bottom.
In Conclusion
Despite the detours and the time it has taken, I ended up getting what I had hoped for:
a living room system with the best qualifies of my main system, just scaled-down.
Combined with the Infinity Primus 360s, Philips DVD963SA, and an Eichmann
terminated DH Labs interconnect, I would list the following as virtues of this system:
· Satisfyingly (and measurably*) deep, well-articulated bass that still does male
vocalists, such as Johnny Cash, without boom or distortion.
· Clean highs—nothing exceptional about them but then nothing negative either.
· Accurate midrange
· Very, very little system noise. What there is can only be heard right at the
tweeters or within a couple of feet of the Eico’s forty-six year old power transformer.
· Very satisfying soundstage width with decent depth. Hey, these aren’t
Magneplanars but I’m very pleased by what they do.
· The ability to play as loudly as I will ever need without fear of running out of
power thanks to the high efficiency of the Primus 360s.
Overall, the results have exceeded my expectations but happily not my hopes. I have a
very good sounding living room system for right at $1,000. And that total includes
everything--from all the parts that have ever been put into the Eico since I bought it to
the cones under the speakers. I have satisfied my desire for a good sounding system
with my pathological need to get a good deal in the process. I am happy. I also
learned a lot in the process. (Click here for a photo of the system.)
The most difficult thing about evaluating this system has been to keep in mind its very
low cost. It sounds good enough that making direct comparisons with my main system
is unavoidable and, frankly, unfair. I don’t think I can give it higher praise than that.
Kent Johnson
June 25, 2006
*See the Primus 360 article for the actual measurements.
The Story to This Point
Due to the time it has taken to finish this article, I have touched on some of these points
already in both the “May 2006” article as well as in “Loudspeakers, Listening Rooms
and Spongy Floors,” so I while I don’t want be redundant, a quick review of what has
gone on before might be helpful to the reader.
After completing the parts upgrades and checking the amp out on my oscilloscope,
the Eico went into the living room system hooked up to my JBL L110 speakers. I did
not get very good bass and worse imaging. I discovered that the JBLs had been
refoamed incorrectly (by an authorized JBL repair facility here in St. Louis, of course.) I
only discovered that I had a problem when I attempted to sell the JBLs to fund
something that would work better in my living room.
I purchased a pair of refurbished Infinity Primus 360 loudspeakers on eBay for
$353, including shipping. I thought these might be ideal for this system given both their
high efficiency and the very good review in the June 2005 Stereophile. At this point, I
also decided to replace the bias resistors in the Eico with a lower value and started to
track down the parts I needed. I hooked the 360s up to a small JVC receiver to break
them in. I did not get good sound again. The bass really boomed and the treble was
phasey in a way that I just couldn’t track down. I subsequently discovered that using
the speaker 2 connections of the JVC, without speakers attached to the speaker 1
connections, did strange things to the damping of the amp. The bass improved
considerably using the speaker 1 outputs but not completely.
I put 174-Ohm bias resistors in the Eico replacing the 189-Ohm set that had been in
it. I expected this to improve the dynamics. Since the JVC wasn’t making sound that
was particularly great, I had high hopes that reintroducing the Eico would rectify things.
It didn’t. There were glimmers of greatness but overall, I wasn’t hearing the quality of
sound I had expected. I was beginning to worry at this point about this whole project.
So I took the Primus 360s apart. A tweeter was not connected. I also tightened
down all the drivers and looked over the interiors of the speakers. (I will have an article
on the 360s done sometime fairly soon.) I feel like an idiot that I didn’t identify the
tweeter problem but it accounts for the “phasey” quality that I kept hearing. So what
actually was refurbished? Wouldn’t that involve checking things like connections?
Using both tweeters helped the sound immensely. Tightening down the drivers took
care of the remaining boom and the Infinities were finally showing signs of being able to
image. Now, though, I started getting really bad transformer hum as the Eico warmed
up. I decided to swap out the rectifier tubes and discovered that one of them was
shorted and the cause of the problem. I also found that the red switch inside the
chassis, whose function I am still unclear on, was also part of the problem. Setting the
switch to the right (facing the amp) improved the sound substantially while also
reducing transformer hum. Suddenly everything was working. Frankly, I wasn’t sure
how to react.
After two months, I could finally start evaluating the sound the Eico was actually
producing.
Some Questions Get Answered
Before proceeding further, let me touch on a number of questions/points that were
noted in Part One.
Will the amp work without the two 12AX7 phono preamp tubes? (V1 and V6 for
those of you checking your schematics at home.) The answer is yes--it works fine.
This also removes from the circuit all of the old, marginal parts attached to these two
tubes. I am not hearing any noise resulting from leaving the tube shields off the
12AU7s either.
The Eico is significantly quieter through the speakers than before the parts were
replaced. Considering the high efficiency of the Primus 360s, this is very good.
External noise from the power transformer is also definitely lower. The noise isn’t
audible unless I am changing CDs and hovering right over the amp. This is acceptable
since I see little possibility of doing anything about it. I will put in new rectifier tubes at
some point.
The balance control is now centered. This is probably due to matching the bias
resistors but it also reinforces my belief that matching parts as closely as possible,
channel to channel, is absolutely essential.
And Speaking of Parts
I decided to replace the two 30-microFarad caps in the power supply (C1 and C2) and
also the two 50-microFarad caps that parallel the bias resistors (C6 and C9.) Even
though these capacitors seemed to be working fine, they are ten years old. With these
caps installed, I ended up replacing all of the resistors and capacitors in the power
supply, line, and output stages of my amp. I also changed the bias resistors yet again
to 179-Ohms. This is the last time I am touching these resistors. I swear. Probably.
The Questions Now Being Examined
I started listening critically with this tube configuration: original (God-only-knows-how-
old) RCA 6CA4 rectifiers, ten-year-old Ei 12AU7 and Sovtek 12AX7WXT+ preamp
tubes, and new JJ Tesla EL-84 output tubes. My thinking was that new output tubes
would make hearing any changes upstream easier so I went ahead and installed them
first. Regarding what noise is present, there is very low level hum audible with my ear
to the right speaker, very low-level hiss at the left speaker’s tweeter. I listened to the
Primus 360s with the grills off. The Eico tone controls are centered as perfectly as I
can center them. They may or may not actually be at their “flat” settings. But they are
close.
I am finding that it takes about ten minutes for the Eico to warm up and starting
sounding its best. There is no real change after that regardless of how long the amp
runs.
I like soundtrack albums with a variety of types of music on them for critical listening. It
simplifies things since I am not constantly changing CDs. I just got The Big Lebowski
soundtrack (Mercury 314 536 903-2) from my daughter for my birthday so I used a
number of its tracks to evaluate how the system was sounding.
The cut “Traffic Boom” exhibited good, tight, deep bass. The trumpets that mimic car
horns in each speaker attack and disappear in a way that makes the system sound
“fast.”
“Walking Song” by Meredith Monk, which consists of two a cappella female vocalists
located just inside each speaker relies on both the vocal sounds being sung and the
singers’ breaths for its effect and makes for very interesting sonics. Echoes give a
sense of the acoustic space. Very interesting music, I am going to have to look for
more of her recordings.
“Hotel California” sung in Spanish by the Gipsy Kings features three guitars, left, right,
and center, each of which sounds very fast and realistic. The soundstage is wide with
limited depth. The vocalist, a guitar, and an accordion share the center of the
soundstage and each is easy to hear and follow. A really fun song.
There are voices in the background of “Dead Flowers” sung by Townes Van Zandt that
let you know you are listening in a bar. They are easy to hear but not intelligible.
Townes is joined by a second male voice singing harmony, or at least an approximation
of it, and both male voices are clean and without boom. Again, the guitar sounds very
good. Unfortunately, there is no information as to whom the other male voice is.
Frankly, it sounds like a lot of beer was involved.
I also listened to many other CDs including Marcus Roberts’ Gershwin for Lovers,
Columbia CK 66437, which has double bass solos that were useful in evaluating bass
depth and accuracy. Cymbals had lovely sheen and realistic decay. The piano
sounded pretty good, too. I have really enjoyed this CD.
Also listened to were Diana Krall’s, The Look of Love, Verve 3145498462; Guitar Music
of Argentina, Naxos 8.555058; and portions of the Forget Paris soundtrack, Elektra
61825-2.
The Billy Holiday tracks on Forget Paris were lovely but “April in Paris” sung by Ella and
Louis was even better. This track sounded almost as good as it does on my main
system.
Regardless of what I listened to, three qualities were very consistent; the system
sounded fast, pianos sounded realistic, and percussion sounds stood out as being
especially realistic. Soundstage width was good while depth varied from adequate to
good, depending on the CD.
I now felt that I had a sense of how the Eico was sounding and was also confident that
everything was working properly. I wanted to hear what happened when I upgraded the
tubes.
Installing the 5751s and 6189s
I went ahead and put GE 5751s in for the Sovtek 12AX7WXT+s and Philips 6189s for
the Ei 12AU7s. I was going to replace each tube type individually and then listen but I
decided I really wanted to finish this article during my lifetime so I did both at once.
The results were somewhat disappointing in that there was very little discernable
change. I felt that the bass was slightly louder and deeper and that low-level sounds
like the echoes on “Walking Song” were easier to hear. It seemed like the background
noise level was also slightly lower but that was about it. What can I say? I expected a
bigger difference but it just wasn’t there.
I listened again to the CDs I had been using and heard only small differences but felt
that those differences were all improvements.
A CD that has become a reference is Yo-Yo Ma Japanese Melodies, CBS MK 39703.”
It sounded very good on the Eico system. Wood blocks, bells, and cymbals all appear
with startling suddenness within a fairly wide and deep soundstage. A flute appears
whose sound indicates that it must be wood or bamboo as it is clearly not metal. The
cello is rich and woody and sits solidly in the center between the speakers. The Eico
had no trouble reproducing its lowest notes with a firmness that could be felt as well as
heard.
Emiliana Torrini’s album, Fisherman’s Woman, Rough Trade RTA 30055-2, features
her breathy, very upfront vocals. This also sounded very good. On track four,
“Lifesaver” a wooden ship creaks and groans and the wind rises and falls very
realistically in a three-dimensional soundstage behind her voice.
The new Johnny Cash, Personal File, Columbia/Legacy 82769 94265 2, was recorded
in the House of Cash, Johnny’s home recording studio, over a period of about nine
years. Different recording dates are different sonically, however, and this difference is
easily discernible via the Eico system. Johnny’s voice is deep without any boom or
exaggeration.
I was going to listen to the new Dixie Chicks CD but my daughter appropriated it before
I had the chance.
While these CDs sounded quite good, they also highlighted the differences between
this system and my main system. The living room system does not have the same
black background my main system does; the bass does not go as low; the highs are not
as pristine; and the soundstaging is not as good. No surprise here. Still, I think this
system easily delivers 80% of the sound quality of my main system, which is pretty
amazing. I can not only enjoy the music I hear on it, I can also listen critically to it and
feel confident of any judgments that I make. I now have better sound in my living room
than I have ever had before by a very large margin.
I rechecked noise levels at the tweeters with the new tubes and the system well warmed
up and I can now hear only very low-level white noise. I guess the hum and hiss were
related to the older tubes. The Eico does get very warm. It was reassuring to read in
the June 2006 Stereophile article on the Eico HF-81 that mine is not the only amp that
runs this hot. I can’t really detect any difference that changing the bias resistance has
made in the heat output. Still, I would run it (or any Eico HF-81) with bias resistors
higher than 165-Ohms in value to just to give the power transformer some breathing
space. Ultimately, the bias resistors had nothing to do with the amp’s dynamics. The
dynamics are excellent. I’m also not sorry I added some higher feet and some
additional ventilation to the chassis bottom.
In Conclusion
Despite the detours and the time it has taken, I ended up getting what I had hoped for:
a living room system with the best qualifies of my main system, just scaled-down.
Combined with the Infinity Primus 360s, Philips DVD963SA, and an Eichmann
terminated DH Labs interconnect, I would list the following as virtues of this system:
· Satisfyingly (and measurably*) deep, well-articulated bass that still does male
vocalists, such as Johnny Cash, without boom or distortion.
· Clean highs—nothing exceptional about them but then nothing negative either.
· Accurate midrange
· Very, very little system noise. What there is can only be heard right at the
tweeters or within a couple of feet of the Eico’s forty-six year old power transformer.
· Very satisfying soundstage width with decent depth. Hey, these aren’t
Magneplanars but I’m very pleased by what they do.
· The ability to play as loudly as I will ever need without fear of running out of
power thanks to the high efficiency of the Primus 360s.
Overall, the results have exceeded my expectations but happily not my hopes. I have a
very good sounding living room system for right at $1,000. And that total includes
everything--from all the parts that have ever been put into the Eico since I bought it to
the cones under the speakers. I have satisfied my desire for a good sounding system
with my pathological need to get a good deal in the process. I am happy. I also
learned a lot in the process. (Click here for a photo of the system.)
The most difficult thing about evaluating this system has been to keep in mind its very
low cost. It sounds good enough that making direct comparisons with my main system
is unavoidable and, frankly, unfair. I don’t think I can give it higher praise than that.
Kent Johnson
June 25, 2006
*See the Primus 360 article for the actual measurements.
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