How do I know tubes are getting old?

Archived from groups: rec.audio.high-end (More info?)

"MD" <imispgh@adelphia.net> wrote in message
newsaoqm702nf1@news3.newsguy.com...
> My high freqs are dropping off
> 10k -2db
> 12k -4db etc
>
Determined by what method?
I've seen (heard) this in old men but not in old tubes. Women however do
have tubes and I bet they drop off when they get old. :-)




> Happens on both channels though (maybe this is how the amp works normally?
> I checked the Stereophile specs and it should be much better than this.
> Also - I have checked on 3 different speakers)

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"MD" <imispgh@adelphia.net> wrote in message
newsaoqm702nf1@news3.newsguy.com...
> My high freqs are dropping off
> 10k -2db
> 12k -4db etc
>
> Happens on both channels though (maybe this is how the amp works normally?
> I checked the Stereophile specs and it should be much better than this.
> Also - I have checked on 3 different speakers)

What amp are you talking about?

Archived from groups: rec.audio.high-end (More info?)

"MD" <imispgh@adelphia.net> wrote in message newsaoqm702nf1@news3.newsguy.com...

> My high freqs are dropping off
> 10k -2db
> 12k -4db etc

..... if you are over 50 years old, your hearing loss is about normal ...

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MD has posted this question on several NGs and has never revealed the type
of amp or other specifics, despite repeated requests. Agenda?
west

"Harry Lavo" <hlavo@comcast.net> wrote in message
newsaov5001n3o@news4.newsguy.com...
> "MD" <imispgh@adelphia.net> wrote in message
> newsaoqm702nf1@news3.newsguy.com...
> > My high freqs are dropping off
> > 10k -2db
> > 12k -4db etc
> >
> > Happens on both channels though (maybe this is how the amp works
normally?
> > I checked the Stereophile specs and it should be much better than this.
> > Also - I have checked on 3 different speakers)
>
> What amp are you talking about?
>

Archived from groups: rec.audio.high-end (More info?)

Gene Poon wrote:
> MD wrote:
>
>> My high freqs are dropping off
>> 10k -2db
>> 12k -4db etc
>>
>> Happens on both channels though (maybe this is how the amp works
>> normally? I checked the Stereophile specs and it should be much
>> better than this. Also - I have checked on 3 different speakers)
>
>
>
>
> What kind of amp, what kind of speakers? Also it sounds like you are
> trying to determine the HF rolloff with your EARS!! How do you know
> your EARS aren't getting old?
Not using my ears - using a sound meter

AMC CVT-3030

On 3 different speakers - Mirage, PAradigm and Magepan

Bias is good

Tubes are about 6 years old but less than 1000hrs

I figure it can't be the tubes if the channels match?

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"MD" <imispgh@adelphia.net> wrote in message
newsbdt2a0ose@news3.newsguy.com...
> Gene Poon wrote:
>> MD wrote:
>>
>>> My high freqs are dropping off
>>> 10k -2db
>>> 12k -4db etc
>>>
>>> Happens on both channels though (maybe this is how the amp works
>>> normally? I checked the Stereophile specs and it should be much better
>>> than this. Also - I have checked on 3 different speakers)
>>
>>
>>
>>
>> What kind of amp, what kind of speakers? Also it sounds like you are
>> trying to determine the HF rolloff with your EARS!! How do you know your
>> EARS aren't getting old?
> Not using my ears - using a sound meter
>
> AMC CVT-3030
>
> On 3 different speakers - Mirage, PAradigm and Magepan
>
> Bias is good
>
> Tubes are about 6 years old but less than 1000hrs
>
> I figure it can't be the tubes if the channels match?

It must have occurred to you that if the tubes are not at fault, it's one of
your components?

Archived from groups: rec.audio.high-end (More info?)

MD wrote:

> Gene Poon wrote:
>
>> MD wrote:
>>
>>> My high freqs are dropping off
>>> 10k -2db
>>> 12k -4db etc
>>>
>>> Happens on both channels though (maybe this is how the amp works
>>> normally? I checked the Stereophile specs and it should be much
>>> better than this. Also - I have checked on 3 different speakers)


> Not using my ears - using a sound meter

===========================

Okay, are you testing at nearfield, or distant?

Also, at what level? This could be the normal rolloff in power response
of ANY tweeter, if tested at too high a level.

Archived from groups: rec.audio.high-end (More info?)

Norman M. Schwartz wrote:
> "Chung" <chunglau@covad.net> wrote in message
> newsbehsj01h0k@news3.newsguy.com...
>
>>It is very difficult to measure your amp's frequency response using a
>>sound level meter. You would be measuring the room's response and the
>>speaker's response, at the meter's position, instead of the amp's
>>response.
>
>
> Indeed, but he said it rolled off as compared to previous measurements,
> which we can assume were carried out under similar circumstances.


In my old VTL Compact 100 mono amps, the sure sign that the tubes were
getting old was that it would blow out a bias resistor, blow the tube,
and shoot a flame a few feet above the unit. My silly wife determined
that this also signalled that tube audio wasn't compatible with our
toddlers and I've since "downgraded" to a solid state amp. Sigh...

Oh, and there are also tube testers available. Back in the day, I had a
Hickock tester, but sold it on Ebay a few years ago.

Cheers,

Archived from groups: rec.audio.high-end (More info?)

"MD" <imispgh@adelphia.net> wrote in message
newsbdt2a0ose@news3.newsguy.com...
> Gene Poon wrote:
>> MD wrote:
>>
>>> My high freqs are dropping off
>>> 10k -2db
>>> 12k -4db etc
>>>
>>> Happens on both channels though (maybe this is how the amp works
>>> normally? I checked the Stereophile specs and it should be much better
>>> than this. Also - I have checked on 3 different speakers)
>>
>>
>>
>>
>> What kind of amp, what kind of speakers? Also it sounds like you are
>> trying to determine the HF rolloff with your EARS!! How do you know your
>> EARS aren't getting old?
> Not using my ears - using a sound meter
>
> AMC CVT-3030
>
> On 3 different speakers - Mirage, PAradigm and Magepan
>
> Bias is good
>
> Tubes are about 6 years old but less than 1000hrs
>
> I figure it can't be the tubes if the channels match?


Just as well, as its not so easy on the CVT-3030 to straight swop output
tubes. The EL34's are soldered to daughter boards, fine if you have matched
pairs and are handy with a soldering iron otherwise its a dealer or factory
job. When you say 'bias is good' I trust you mean that all bias measurements
readings were in spec and didn't need to adjust any of the bias
potentiometers?

-=Mike=-

Archived from groups: rec.audio.high-end (More info?)

In article <dc5u0n01j1o@news4.newsguy.com>,
Norman M. Schwartz <nmsz@optonline.net> wrote:

>Those amps failed when it came to driving speakers with impedance less than
>8 ohms, and since those were the only speakers which I was attracted to,
>they proved to be useless. I understand that modern tubes amps can drive
>such loads effortlessly, but their maintenance is too much of a PIA for me.

Curious; never had problems driving a double pair of KLH Nines with 4
slightly modified Dyna MK III's, and if my old GR 650A was to be believed
the Nines had an impedance of about 1/2 ohm, almost all capacitative, at
20Khz.

I much preferred the D75N to the D76, but never took the time to figure
out why.

On the other hand the Nines did sound much better being driven with the
dB Systems DB-6, and long-term operation was a lot cheaper since even then
matched pairs of 6550A's were not cheap.

Mike Squires
--

Mike Squires (mikes at cs.indiana.edu) 317 233 9456 (w) 812 333 6564 (h)
mikes at siralan.org 546 N Park Ridge Rd., Bloomington, IN 47408