Forums
New posts
Search forums
What's new
New posts
Latest activity
Members
Registered members
Current visitors
Log in
Register
What's new
Search
Search
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Commercial Members
Commercial Members - News & Discussion
Tube phono preamps
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Help Support AVForums:
This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Message
<blockquote data-quote="handsome" data-source="post: 634159" data-attributes="member: 772"><p>riaa eq should be at least accurate to 0.2dB or so. I have an analogue scope at best it is probably only 5% accurate plus you have to infer the value off the screen - that is work out were the green line is sitting not exactly accurate by any means. a digital scope could be better but if you are measuring directly you still have to cope witha 40dB dynamic range and a digital scope will only be 8 bits (unless you are lucky enough to have one of them real funky machines) that is dynamic range of only 56dB..... with an inverse eq all you are doing is measuring (ostensibly) the same value: set your function generator's level to give you an output from the preamp of 1V then measure at different spot frequencies - you are just measuring the deviation from 1V. Makes things far easier allows for any wide bandwidth meter (most DVMs dont have the bandwidth) to be accurate on the measuring device side. the other problem with measuring riaa accuracy is because of the complexity of the filter, your response variations can and will wiggle all over the show - so you need to measure most of those frequencies and not just (say) 100Hz, 1kHz and 10kHz. with amplifiers on the other hand you pretty much can be sure the response is flat and you will be just looking for where the response starts to drop at the low and high end.</p></blockquote><p></p>
[QUOTE="handsome, post: 634159, member: 772"] riaa eq should be at least accurate to 0.2dB or so. I have an analogue scope at best it is probably only 5% accurate plus you have to infer the value off the screen - that is work out were the green line is sitting not exactly accurate by any means. a digital scope could be better but if you are measuring directly you still have to cope witha 40dB dynamic range and a digital scope will only be 8 bits (unless you are lucky enough to have one of them real funky machines) that is dynamic range of only 56dB..... with an inverse eq all you are doing is measuring (ostensibly) the same value: set your function generator's level to give you an output from the preamp of 1V then measure at different spot frequencies - you are just measuring the deviation from 1V. Makes things far easier allows for any wide bandwidth meter (most DVMs dont have the bandwidth) to be accurate on the measuring device side. the other problem with measuring riaa accuracy is because of the complexity of the filter, your response variations can and will wiggle all over the show - so you need to measure most of those frequencies and not just (say) 100Hz, 1kHz and 10kHz. with amplifiers on the other hand you pretty much can be sure the response is flat and you will be just looking for where the response starts to drop at the low and high end. [/QUOTE]
Insert quotes…
Verification
Post reply
Commercial Members
Commercial Members - News & Discussion
Tube phono preamps
Top