Amp/Preamp Asylum: REVIEW: EICO HF-85 Amplifier (Tube) by Richard CWY

Model:	HF-85
Category:	Amplifier (Tube)
Suggested Retail Price:	$100
Description:	EICO HF-85 tube stereo pre-amp
Manufacturer URL:	EICO
Model Picture:	View

Review by Richard CWY ( A ) on May 08, 2003 at 11:13:09
IP Address: 218.188.131.46

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for the HF-85

Further to my first review and report on the floating potential (FP) modification, here is my follow-up tests on the sounding of a FP modified EICO HF-85 vis-a-vis a perfectly stock HF-85.
People are welcome to join the discussions at the EICO Tube-Amp Fans Club at Yahoo eGroups.
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Subject: EICO HF-85 Pre-amps Party - FP Modded vs Stock

Thanks for Dr. John, John Keung, Brother Hoi, Mr. Ho, and Ah So
coming for the Vintage Pre-amps Party held today (8 May 2003) between 3:30 p.m. to 6:30 p.m. at my flat.
Set-up
The following vintage pre-amps played in that order:
a) HH Scott LC-21
b) EICO ST-84
c) EICO HF-85 (I) - perfectly stock
d) EICO HF-85 (II) - FP modified
Source was 5 CDs played by a Denon transport + Xindak DAC. Power amp
was a pair EICO HF-30 monoblocs, driving a pair single-wired Harbeth
BBC LS3/5A speakers sitting on a pair SolidSteel stands.
Audience warm-up
LC-21 was for the warming up of the audience. ST-84 was the second
played but it did not appear in the right condition. Dr John has a
very sharp hearing that he pointed point straightaway that its power
transformer might have been touched. He is right indeed! (The stock
transformer has been taken out for repair.) While it still scored
very high marks, audience agreed to excluded it from the test.
Tests
The tests was on a pair of EICO HF-85s - one is perfectly stock and
the other has been FP modified (see relevant report at:
http://groups.yahoo.com/group/eico/message/378 ).
Before the tests was completed and before they had given marks on a
piece printed form, NONE of the audience was given to know which one
was which. 4 of the 6 (excluding John Keung and myself) took part
in giving markings according to their uncommunicated SUBJECTIVE
preference in a continuum from 'totally dislike' (0 marks) and 'die-
for' (10 marks) on a piece of paper in 8 aspects (a) to (h) from 5
CDs played by each pre-amp:
1) Belafonte at Carnegie Hall (1959) track #15
a) male vocal/whistling
b) stereo soundstaging
2) Carol Kidd - Fly me to the moon
c) female vocal
d) guitar strings
3) Chan Kit-lai - I believe (Putonghua)
e) young female vocal
4) Yo-yo Ma - Playing the music of John Williams track #3
f) dyanamic
g) bass/lower rang performance
5) Danny Summer & So Yui(?) - Station (Cantonese)
h) expression of sentiments in male/female vocals
Our panel was rather strict in giving marks! The marks given for one
aspect was, at best, 32 marks, i.e. 80%, out from 10 x 4 = 40, a
hypothetical value. The scores are as follows:
HF-85 (I) - perfectly stock: 206 marks, i.e. 64%
HF-85 (II) - FP modified: 234 marks, i.e. 73%
(At that point in time, the 5 audience were then allowed to see the
piece of paper showing which one is which!)
In fact, the two pre-amps scored fairly equally in virtuall all
aspects but HF-85(II), the FP modded one, had shown particular
advantages in following aspects by a biger margin:
c) female vocal (32 marks)
e) young female vocal (32 marks)
g) bass/lower rang performance (28 marks)
h) expression of sentiments in male/female vocals (32 marks)
Details of the marks scored by each pre-amps will be uploaded to
the "file section".
Conclusions of the audience panel
The auidence discussed actively and agreed with the following in
general:
a) The perfectly stock HF-85(I) sounded so much better compared to
other non-modifed HF-85 that they have heard before (if they had)!
The audience believed that a perfectly stock (and NORMAL working) HF-
85 can sound superb without any modification!
(Note: Dr. John himself owns a stock HF-85 but complained about its
lack of clarity in high range and blurred in soundstaging. I also
complained my HF-85(II) being dull when it was stock.)
b) The difference in sounding between the two HF-85s was not too
obvious though in general the FP modified was slight better in all
kinds of vocals presentation.
Hypothesis
After the discussion, I have the following hypothesis as a brick
thrown out to attract jade (further discussions):
A perfectly stock HF-85 can sound superb if all the original ceramic
disc caps plus vintage resistors (mostly A&B carbon composites) are
working NORMALLY. But these components are easily tired and
replacements by other components (even the much more expensive
ones!) void the superb balance and hence the sound. Undetected off-
spec. components would cause bad sound without saying.
FP modification lowers the demand on a superbly balanced system
inside the HF-85 maintained by ALL the components, a synergy! In
other words, FP modification 'rejuvenate' a tired system of HF-85.
Hence, if one's HF-85 is perfectly normal working and sounds superb,
it is no use and NOT necessary to perform the FP modification.
Doing so would likely cause imbalance and affect the sound.
By the same token, if a HF-85 become blurred in sounding (after
retubing and all necessary repairs done!), it is time to consider FP
modification.
Any views are welcome.. :)

Richard
Moderator of EICO Tube-Amp Fans Club
http://groups.yahoo.com/group/eico/

Product Weakness: See the above follow-up report.
Product Strengths: See the above follow-up report.

Associated Equipment for this Review:
Amplifier:	Power amp: EICO HF-30 monoblocs
Preamplifier (or None if Integrated):	EICO HF-85 x2
Sources (CDP/Turntable):	CDs
Speakers:	Harbeth BBC LS3/5A
Cables/Interconnects:	Esscos Reference
Music Used (Genre/Selections):	See the report above.
Other (Power Conditioner etc.):	-
Type of Audition/Review:	Home Audition

Product Weakness:	See the above follow-up report.
Product Strengths:	See the above follow-up report.