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<blockquote data-quote="tangmonster" data-source="post: 634043" data-attributes="member: 1581"><p>after recently spending a fair amount of time checking my d3A phono preamp RIAA curves I chose the route of chickening out and using online calculators and comparing them and using a function generator to measure real world.</p><p></p><p>http://mh-audio.nl/CalculateRIAA.asp</p><p></p><p>http://www.marignoni.it/ElettronicaHiFi/UTL/RIAA/Calcolo%20rete%20RIAA%20passivait.xls</p><p></p><p></p><p></p><p>My understanding is dat you will have to parralel your 100k and your 200k resistor so your Zin is 66k ohms (and tehcnically that 1Meg <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> )</p><p></p><p>That gives 9.7k where you have 33k</p><p></p><p>and 33nF where you have 2 x 4.7nf in parralel</p><p></p><p>And then 11nF where you have 3.3nF</p><p></p><p>Please correct me if my understanding is wrong.</p><p></p><p>I built this design a few years back:</p><p></p><p>http://www.audiodesignguide.com/Phono/pre-phono4.html</p><p></p><p>Sadly it was lacking in the bass department and it soon became clear that the 50ohm with 270uF in parralel was attenuating low frequencies too much . I have since changed to IR led cathode bias for that d3a design.</p><p></p><p>Remeasuring with signal generator and comparing voltage gains at frequencies from 20hz and up showed i was very close , at least within 1 dbv or so currently.</p></blockquote><p></p>
[QUOTE="tangmonster, post: 634043, member: 1581"] after recently spending a fair amount of time checking my d3A phono preamp RIAA curves I chose the route of chickening out and using online calculators and comparing them and using a function generator to measure real world. http://mh-audio.nl/CalculateRIAA.asp http://www.marignoni.it/ElettronicaHiFi/UTL/RIAA/Calcolo%20rete%20RIAA%20passivait.xls My understanding is dat you will have to parralel your 100k and your 200k resistor so your Zin is 66k ohms (and tehcnically that 1Meg :) ) That gives 9.7k where you have 33k and 33nF where you have 2 x 4.7nf in parralel And then 11nF where you have 3.3nF Please correct me if my understanding is wrong. I built this design a few years back: http://www.audiodesignguide.com/Phono/pre-phono4.html Sadly it was lacking in the bass department and it soon became clear that the 50ohm with 270uF in parralel was attenuating low frequencies too much . I have since changed to IR led cathode bias for that d3a design. Remeasuring with signal generator and comparing voltage gains at frequencies from 20hz and up showed i was very close , at least within 1 dbv or so currently. [/QUOTE]
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