To audio techies. Is the anything against my occasionally using a Millennia
Media HV-3B microphone preamp as a phonostage just by heading it with an
RIAA network. I hate to see it sitting lonely at quiet times ;-)
Thanks.

Mike

In article ,
Mike Gilmour wrote:
To audio techies. Is the anything against my occasionally using a
Millennia Media HV-3B microphone preamp as a phonostage just by heading
it with an RIAA network. I hate to see it sitting lonely at quiet times
;-)

Most quality mic amps will have too low an input impedance to give the
best results with a cartridge. And I'd say a passive input matching
network that also incorporated the EQ would be too lossy.

--
*The closest I ever got to a 4.0 in school was my blood alcohol content*

Dave Plowman London SW 12
RIP Acorn

In article ,
Mike Gilmour wrote:
To audio techies. Is the anything against my occasionally using a
Millennia Media HV-3B microphone preamp as a phonostage just by heading
it with an RIAA network. I hate to see it sitting lonely at quiet times
;-)

Most quality mic amps will have too low an input impedance to give the
best results with a cartridge. And I'd say a passive input matching
network that also incorporated the EQ would be too lossy.

--
*The closest I ever got to a 4.0 in school was my blood alcohol content*

Dave Plowman London SW 12
RIP Acorn

Mike Gilmour wrote:
To audio techies. Is the anything against my occasionally using a Millennia
Media HV-3B microphone preamp as a phonostage just by heading it with an
RIAA network. I hate to see it sitting lonely at quiet times ;-)
Thanks.

Mike



I guess not, but you would have to take into account the impedance of
the cartridge when calculating the RIAA, and also the effect the loading
of the network would have on the cartridge. Also take into account the
input impedance of the preamp on the network.

It may be better to have the network after the preamp, then you would
have better noise performance, and the network calculation could be
simplified. You would need to know the output impedance of the preamp,
but I guess this could be low enough to be ignored, you will also need
to know the input impedance of the amp its feeding, and also any
capacitance in the connection. This does assume the input impedance of
the amp is constant with volume, or its going to be a bit hard to
calculate the network.

May be best to do a SPICE simulation, using a inverse RIAA network
feeding the amp, and then fiddle the network after the amp (with
required loading) to obtain a flat response.

--
Nick

Nick,

Thanks, I could also try an small active 'buffer' stage to prevent loading
on the cartridge and accidental phantom damage. This stage would have to be
very quiet so SS I expect. I agree with having the network after the
preamp, loss of gain would probably not be too much of a concern. The HV-3B
Input Z = 6,200 ohms, o/p Z = 24.3 ohms. With a frequency response to -3 dB
points Sub 2 Hz to over 300 kHz -its also good for seismic or bat
measurements ;-) This is looking like another winter project to get me back
into building circuits once again :-)
I don't have spice as I've been away from circuit building for many years.
I'll do a google search to see what comes up.

Mike


"Nick Gorham" wrote in message
.. .
Mike Gilmour wrote:
To audio techies. Is the anything against my occasionally using a
Millennia
Media HV-3B microphone preamp as a phonostage just by heading it with an
RIAA network. I hate to see it sitting lonely at quiet times ;-)
Thanks.

Mike



I guess not, but you would have to take into account the impedance of
the cartridge when calculating the RIAA, and also the effect the loading
of the network would have on the cartridge. Also take into account the
input impedance of the preamp on the network.

It may be better to have the network after the preamp, then you would
have better noise performance, and the network calculation could be
simplified. You would need to know the output impedance of the preamp,
but I guess this could be low enough to be ignored, you will also need
to know the input impedance of the amp its feeding, and also any
capacitance in the connection. This does assume the input impedance of
the amp is constant with volume, or its going to be a bit hard to
calculate the network.

May be best to do a SPICE simulation, using a inverse RIAA network
feeding the amp, and then fiddle the network after the amp (with
required loading) to obtain a flat response.

--
Nick

Mike Gilmour wrote:
Nick,

Thanks, I could also try an small active 'buffer' stage to prevent loading
on the cartridge and accidental phantom damage. This stage would have to be
very quiet so SS I expect. I agree with having the network after the
preamp, loss of gain would probably not be too much of a concern. The HV-3B
Input Z = 6,200 ohms, o/p Z = 24.3 ohms. With a frequency response to -3 dB
points Sub 2 Hz to over 300 kHz -its also good for seismic or bat
measurements ;-) This is looking like another winter project to get me back
into building circuits once again :-)
I don't have spice as I've been away from circuit building for many years.
I'll do a google search to see what comes up.

I have found LTSpice to be a nice simple (free) way of messing around
with ideas, and great for fiddling about to get a flat RIAA response.

http://www.linear.com/software/

--
Nick

Mike Gilmour wrote:
Nick,

Thanks, I could also try an small active 'buffer' stage to prevent loading
on the cartridge and accidental phantom damage. This stage would have to be
very quiet so SS I expect. I agree with having the network after the
preamp, loss of gain would probably not be too much of a concern. The HV-3B
Input Z = 6,200 ohms, o/p Z = 24.3 ohms. With a frequency response to -3 dB
points Sub 2 Hz to over 300 kHz -its also good for seismic or bat
measurements ;-) This is looking like another winter project to get me back
into building circuits once again :-)
I don't have spice as I've been away from circuit building for many years.
I'll do a google search to see what comes up.

I have found LTSpice to be a nice simple (free) way of messing around
with ideas, and great for fiddling about to get a flat RIAA response.

http://www.linear.com/software/

--
Nick

In article ,
Mike Gilmour wrote:
The HV-3B Input Z = 6,200 ohms, o/p Z = 24.3 ohms.

Sure you don't mean 600 or 200 ohms for the input? 6K2 is high for a low
impedance mic, and not high enough for a high impedance type.

--
*Eat well, stay fit, die anyway

Dave Plowman London SW 12
RIP Acorn

6K2, nominal is correct according to John La Grou's general specs.
Mike


"Dave Plowman" wrote in message
...
In article ,
Mike Gilmour wrote:
The HV-3B Input Z = 6,200 ohms, o/p Z = 24.3 ohms.

Sure you don't mean 600 or 200 ohms for the input? 6K2 is high for a low
impedance mic, and not high enough for a high impedance type.

--
*Eat well, stay fit, die anyway - Jim Fixx

Dave Plowman London SW 12
RIP Acorn

In article ,
Mike Gilmour wrote:
6K2, nominal is correct according to John La Grou's general specs.

Strange. Anyone care to explain?

--
*Why do they put Braille on the drive-through bank machines?

Dave Plowman London SW 12
RIP Acorn