Valve Itch phono

diyAudio Chief Moderator
Joined 2002
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Better subjectively to both of us than the amorphous Lundahl we used in the first one. No one gave its nominal ratio when 47k loaded mind you. Could give about 9.5X when measured with the DVM (very high impedance) but dropped 30-40% in real use. When the naked input gave 43dB exactly as modelled when I measured it, the SUT got it up to 58dB total. It also rose THD significantly when we downloaded it at 18K. So we went to 47K as recommended in spec.
 
Member
Joined 2006
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Better subjectively to both of us than the amorphous Lundahl we used in the first one. No one gave its nominal ratio when 47k loaded mind you. Could give about 9.5X when measured with the DVM (very high impedance) but dropped 30-40% in real use. When the naked input gave 43dB exactly as modelled when I measured it, the SUT got it up to 58dB total. It also rose THD significantly when we downloaded it at 18K. So we went to 47K as recommended in spec.

So you mean the setup ratio is dependent of the load and amplification right ?

I am seriously considering "stepping up" my 48dB riaa with a 10x lundahl for use with a 0.15mV cart but the more I read the more I am convinced this is not an easy process.
 
diyAudio Chief Moderator
Joined 2002
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I don't know, its a quirk that I did not have time to investigate enough. Maybe its individual to those tube phono matching that I had seen it. I am sure I got less than nominal ratio when in circuit in 3 cases and 2 types. Maybe its because the primary was floating, grid current, can't say as for now. There is also 1:5 and 1:20 configuration option in Lundhal.
 
diyAudio Chief Moderator
Joined 2002
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But, wait a minute... if primary is floating and cart was surely not grounded, that is balanced transfer. The secondary sees a single ended circuit that has a signal ground. Mustn't we lose dB if it is magnetically analogous to converting from balanced to SE?:scratch: