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From: Paul on 12 May 2010 21:03
jw(a)eldorado.com wrote:
> On Wed, 12 May 2010 15:20:58 -0400, kony <spam(a)spam.com> wrote:
>
>> On Tue, 11 May 2010 14:55:41 -0400, jw(a)eldorado.com wrote:
>>
>>> I haven't used sound input on my computer for a long while. It used
>>> to work, Now, despite the fact that I get sound fine when playing a
>>> video DVD, I get no sound when I use my microphone . As a simple
>>> test, I executed MS's 'sound recorder' and tried to record my voice.
>>> Nothing, I checked the mobo manual to assure that my microphone was
>>> connected right, and it is. I checked sounds in Control
>>> Panel>Sounds, and I get sounds fine.
>>>
>>> I must have forgotten something crucial to this operation, Anyone
>>> suggest what I missed?
>>>
>>> Duke
>>
>> Try checking the Windows Control Panel "Sounds and Audio
>> Devices" controls, aka Windows Mixer controls. Where you
>> have the "Mic Volume" slider, see if there is an "Advanced"
>> button at the bottom and if so, click on it.
>>
>> Doing so should bring up a window with an "Other Controls"
>> category at the bottom and a box you should (for the time
>> being at least) checkmark for "Mic Boost".
>
> I never found Mic Boost.
>> Also do as Paul suggested and per your reply, hook up
>> another audio source like the VCR and play any tape you have
>> with audio on it, which I would think is most of them.
>
> Did this, and the sound track from 'Top Gun' sounds great!
> Connecting the phono player to the preamp and the latter's output to
> same 'line in' on computer produced nothing,
> Now what?
> Duke

You could always record "Top Gun" :-)

I would say the results you got, are great progress. It means
the computer end is working. Now, all you have to do, if figure
out whether the phono cartridge wiring is disconnected, some switch
on the turntable is in the wrong position, and so on. Or whether
the preamp has a bad power source, is muted, or has a blown fuse
inside.

The phono amp is not strong enough to drive magnetic headphones
(like 32 ohm ones). It has an output impedance of 1000 ohms, which
is suitable for driving the computer Line In, or the line level
input of your stereo system. But that isn't enough to drive headphones.

How is the cartridge connected to the cabling in the tone arm
of the phono gadget ? Is is soldered, or is a connector involved ?
Have you checked that everything is still intact ? All
wires secure ?

You need to debug, stage by stage.

For sensitive equipment, I might use the 60Hz hum from my
fingertip, as a test stimulus. If you disconnect the phonograph
from the preamp, then touch one of the input terminals on the
preamp, the 60Hz hum should be heard on the computer (output)
side. Always turn down the volume control, on the computer,
so you don't blow out any speakers. Then turn it up slowly and see
if your fingertip applies enough noise to make the preamp work.
With the RCA-style jacks, you'd need to touch the "center pin"
contact on each channel as a test.

The TC750LC has a level knob on the front, which you have to
turn up to get sound on the output. If the front level knob is
set to zero, you get no output.

http://www.phonopreamps.com/tc750lcpp.html

Paul
From: jw on 13 May 2010 06:01
On Wed, 12 May 2010 21:03:57 -0400, Paul <nospam(a)needed.com> wrote:

>You could always record "Top Gun" :-)
Yeh
>
>I would say the results you got, are great progress. It means
>the computer end is working. Now, all you have to do, if figure
>out whether the phono cartridge wiring is disconnected, some switch
>on the turntable is in the wrong position, and so on. Or whether
>the preamp has a bad power source, is muted, or has a blown fuse
>inside.
>
>The phono amp is not strong enough to drive magnetic headphones
>(like 32 ohm ones). It has an output impedance of 1000 ohms, which
>is suitable for driving the computer Line In, or the line level
>input of your stereo system. But that isn't enough to drive headphones.
>
>How is the cartridge connected to the cabling in the tone arm
>of the phono gadget ? Is is soldered, or is a connector involved ?
>Have you checked that everything is still intact ? All
>wires secure ?
>
>You need to debug, stage by stage.
>
>For sensitive equipment, I might use the 60Hz hum from my
>fingertip, as a test stimulus. If you disconnect the phonograph
>from the preamp, then touch one of the input terminals on the
>preamp, the 60Hz hum should be heard on the computer (output)
>side. Always turn down the volume control, on the computer,
>so you don't blow out any speakers. Then turn it up slowly and see
>if your fingertip applies enough noise to make the preamp work.
>With the RCA-style jacks, you'd need to touch the "center pin"
>contact on each channel as a test.
>
>The TC750LC has a level knob on the front, which you have to
>turn up to get sound on the output. If the front level knob is
>set to zero, you get no output.
>
>http://www.phonopreamps.com/tc750lcpp.html
>
> Paul

In an effort to determine if the preamp is working, I connected the
VCR to the preamp and the preamp to my computer. When I play TOP GUN,
I get unintelligible scratchy sounds for audio on the VCR tape. So, I
figure that means the preamp is working?

Duke
From: jw on 13 May 2010 07:15
On Wed, 12 May 2010 21:03:57 -0400, Paul <nospam(a)needed.com> wrote:


>> Did this, and the sound track from 'Top Gun' sounds great!
>> Connecting the phono player to the preamp and the latter's output to
>> same 'line in' on computer produced nothing,
>> Now what?
>> Duke
>
>You could always record "Top Gun" :-)
>
>I would say the results you got, are great progress. It means
>the computer end is working. Now, all you have to do, if figure
>out whether the phono cartridge wiring is disconnected, some switch
>on the turntable is in the wrong position, and so on. Or whether
>the preamp has a bad power source, is muted, or has a blown fuse
>inside.
>
>The phono amp is not strong enough to drive magnetic headphones
>(like 32 ohm ones). It has an output impedance of 1000 ohms, which
>is suitable for driving the computer Line In, or the line level
>input of your stereo system. But that isn't enough to drive headphones.
>
>How is the cartridge connected to the cabling in the tone arm
>of the phono gadget ? Is is soldered, or is a connector involved ?
>Have you checked that everything is still intact ? All
>wires secure ?
>
>You need to debug, stage by stage.
>
>For sensitive equipment, I might use the 60Hz hum from my
>fingertip, as a test stimulus. If you disconnect the phonograph
>from the preamp, then touch one of the input terminals on the
>preamp, the 60Hz hum should be heard on the computer (output)
>side. Always turn down the volume control, on the computer,
>so you don't blow out any speakers. Then turn it up slowly and see
>if your fingertip applies enough noise to make the preamp work.
>With the RCA-style jacks, you'd need to touch the "center pin"
>contact on each channel as a test.
>
>The TC750LC has a level knob on the front, which you have to
>turn up to get sound on the output. If the front level knob is
>set to zero, you get no output.
>
>http://www.phonopreamps.com/tc750lcpp.html
>
> Paul

I tried connecting the phono player to the computer via the preamp.
As I plug the RCA connectors together, I get a decided hum, which
disappears once the plugs are fully connected. The audio from the
phono vinyl record is still completely silent however.

Duke
From: Paul on 13 May 2010 10:38
jw(a)eldorado.com wrote:
> On Wed, 12 May 2010 21:03:57 -0400, Paul <nospam(a)needed.com> wrote:
>
>
>>> Did this, and the sound track from 'Top Gun' sounds great!
>>> Connecting the phono player to the preamp and the latter's output to
>>> same 'line in' on computer produced nothing,
>>> Now what?
>>> Duke
>> You could always record "Top Gun" :-)
>>
>> I would say the results you got, are great progress. It means
>> the computer end is working. Now, all you have to do, if figure
>> out whether the phono cartridge wiring is disconnected, some switch
>> on the turntable is in the wrong position, and so on. Or whether
>> the preamp has a bad power source, is muted, or has a blown fuse
>> inside.
>>
>> The phono amp is not strong enough to drive magnetic headphones
>> (like 32 ohm ones). It has an output impedance of 1000 ohms, which
>> is suitable for driving the computer Line In, or the line level
>> input of your stereo system. But that isn't enough to drive headphones.
>>
>> How is the cartridge connected to the cabling in the tone arm
>> of the phono gadget ? Is is soldered, or is a connector involved ?
>> Have you checked that everything is still intact ? All
>> wires secure ?
>>
>> You need to debug, stage by stage.
>>
>> For sensitive equipment, I might use the 60Hz hum from my
>> fingertip, as a test stimulus. If you disconnect the phonograph
>>from the preamp, then touch one of the input terminals on the
>> preamp, the 60Hz hum should be heard on the computer (output)
>> side. Always turn down the volume control, on the computer,
>> so you don't blow out any speakers. Then turn it up slowly and see
>> if your fingertip applies enough noise to make the preamp work.
>> With the RCA-style jacks, you'd need to touch the "center pin"
>> contact on each channel as a test.
>>
>> The TC750LC has a level knob on the front, which you have to
>> turn up to get sound on the output. If the front level knob is
>> set to zero, you get no output.
>>
>> http://www.phonopreamps.com/tc750lcpp.html
>>
>> Paul
>
> I tried connecting the phono player to the computer via the preamp.
> As I plug the RCA connectors together, I get a decided hum, which
> disappears once the plugs are fully connected. The audio from the
> phono vinyl record is still completely silent however.
>
> Duke

I could be wrong, but it seems like the preamp has a problem.

(You really shouldn't have connected the VCR to the input of the
preamp, as that is about 500x more signal than it needs.)

If you have RCA cabling for this setup, you should be able to touch
the center pin of the RCA cable. Plug the RCA cable into the
preamp, and touch the exposed pin on the other end of the cable
_ _
_____ cable cable
Hum <_____ ********** Preamp ********* Computer
_ _

The claimed input impedance of the preamp, is 47K and 220pF.
The 47K is a relatively high input impedance, so the hum
test should work.

If the hum isn't coming through, and the gain control on the
front of the preamp is at max, then the preamp must be
broken in some way. (Not getting power internally.)

It is pretty hard to determine if any signal (2-3mV level)
is coming from the phono cartridge itself. You'd have to
rip the needle off the thing, to quiet the cartridge. And
you'd probably have noticed by now, if the cartridge isn't
quite right (physically damaged). Using a (working) preamp,
is about the only thing I can suggest, to monitor the cartridge.
It is pretty hard to get instruments to do that.

I have had access to equipment, that could amplify the signal
enough. I had an oscilloscope in university, with a diff amp
on the front end, that was sensitive enough to pick up a
human heartbeat. We used to hold the test leads, one in each
hand, and the oscilloscope could display the heartbeat. So
they do make instruments with the required sensitivity, but
they're not common garden variety devices. At work, we never
had a setup quite as nice as that one at the university.

Paul
From: jw on 13 May 2010 14:14
On Thu, 13 May 2010 10:38:40 -0400, Paul <nospam(a)needed.com> wrote:

>jw(a)eldorado.com wrote:
>> On Wed, 12 May 2010 21:03:57 -0400, Paul <nospam(a)needed.com> wrote:
>>
>>
>>>> Did this, and the sound track from 'Top Gun' sounds great!
>>>> Connecting the phono player to the preamp and the latter's output to
>>>> same 'line in' on computer produced nothing,
>>>> Now what?
>>>> Duke
>>> You could always record "Top Gun" :-)
>>>
>>> I would say the results you got, are great progress. It means
>>> the computer end is working. Now, all you have to do, if figure
>>> out whether the phono cartridge wiring is disconnected, some switch
>>> on the turntable is in the wrong position, and so on. Or whether
>>> the preamp has a bad power source, is muted, or has a blown fuse
>>> inside.
>>>
>>> The phono amp is not strong enough to drive magnetic headphones
>>> (like 32 ohm ones). It has an output impedance of 1000 ohms, which
>>> is suitable for driving the computer Line In, or the line level
>>> input of your stereo system. But that isn't enough to drive headphones.
>>>
>>> How is the cartridge connected to the cabling in the tone arm
>>> of the phono gadget ? Is is soldered, or is a connector involved ?
>>> Have you checked that everything is still intact ? All
>>> wires secure ?
>>>
>>> You need to debug, stage by stage.
>>>
>>> For sensitive equipment, I might use the 60Hz hum from my
>>> fingertip, as a test stimulus. If you disconnect the phonograph
>>>from the preamp, then touch one of the input terminals on the
>>> preamp, the 60Hz hum should be heard on the computer (output)
>>> side. Always turn down the volume control, on the computer,
>>> so you don't blow out any speakers. Then turn it up slowly and see
>>> if your fingertip applies enough noise to make the preamp work.
>>> With the RCA-style jacks, you'd need to touch the "center pin"
>>> contact on each channel as a test.
>>>
>>> The TC750LC has a level knob on the front, which you have to
>>> turn up to get sound on the output. If the front level knob is
>>> set to zero, you get no output.
>>>
>>> http://www.phonopreamps.com/tc750lcpp.html
>>>
>>> Paul
>>
>> I tried connecting the phono player to the computer via the preamp.
>> As I plug the RCA connectors together, I get a decided hum, which
>> disappears once the plugs are fully connected. The audio from the
>> phono vinyl record is still completely silent however.
>>
>> Duke
>
>I could be wrong, but it seems like the preamp has a problem.

That is my thinking, and I fear that this might be the case. It seems
unlikely since it is relatively new and used little and always worked
fine.
I know S... happens!
>
>(You really shouldn't have connected the VCR to the input of the
>preamp, as that is about 500x more signal than it needs.)

I only did that because (a) I got sound when I hooked the VCR directly
up the computer's 'line in' and (b) it put the preamp in the circuit,
I thought that this could indicate that the preamp indeed is bad, and
it may have.
>
>If you have RCA cabling for this setup, you should be able to touch
>the center pin of the RCA cable. Plug the RCA cable into the
>preamp, and touch the exposed pin on the other end of the cable
> _ _
> _____ cable cable
> Hum <_____ ********** Preamp ********* Computer
> _ _

The above diagram came through all messed up. Maybe you could say the
diagram in words? I would appreciate it. My guess as to what you
say is cable to preamp in---preamp out to computer in ---computer out
to speaker.
>
>The claimed input impedance of the preamp, is 47K and 220pF.
>The 47K is a relatively high input impedance, so the hum
>test should work.
>
>If the hum isn't coming through, and the gain control on the
>front of the preamp is at max, then the preamp must be
>broken in some way. (Not getting power internally.)
>
>It is pretty hard to determine if any signal (2-3mV level)
>is coming from the phono cartridge itself. You'd have to
>rip the needle off the thing, to quiet the cartridge. And
>you'd probably have noticed by now, if the cartridge isn't
>quite right (physically damaged). Using a (working) preamp,
>is about the only thing I can suggest, to monitor the cartridge.
>It is pretty hard to get instruments to do that.
>
>I have had access to equipment, that could amplify the signal
>enough. I had an oscilloscope in university, with a diff amp
>on the front end, that was sensitive enough to pick up a
>human heartbeat. We used to hold the test leads, one in each
>hand, and the oscilloscope could display the heartbeat. So
>they do make instruments with the required sensitivity, but
>they're not common garden variety devices. At work, we never
>had a setup quite as nice as that one at the university.
>
> Paul
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