John, Milan, my intent was to add a different perspective (but one based on real-world experience rather than conjecture) on some of the specific issues that have been raised in this thread. Outside of providing the basis for my hands-on observations, I don't think it is appropriate to talk about the Lyra preamps per se in this thread, as this rightfully belongs to the Blowtorch and John.
Besides, I think that somewhere on diyAudio there already is a thread or two about the Lyra preamp.
regards, jonathan carr
Besides, I think that somewhere on diyAudio there already is a thread or two about the Lyra preamp.
regards, jonathan carr
moamps said:
Stuart, it's easy to make such a 'mistake' with the BT. 😉 The power of advertising, eh?
No, for me it was more a matter of it not having tubes in it.
😉
John,
Jonathan,
I started a thread about the Lyra 4-2L SE which you can find at
http://www.diyaudio.com/forums/showthread.php?s=&threadid=62998&highlight=
Jonathan gave us some bread crumbs, and I tried to make a cake out of those crumbs, but I did not succeed.
I will post some news in that thread.
Sigurd
Jonathan,
I started a thread about the Lyra 4-2L SE which you can find at
http://www.diyaudio.com/forums/showthread.php?s=&threadid=62998&highlight=
Jonathan gave us some bread crumbs, and I tried to make a cake out of those crumbs, but I did not succeed.
I will post some news in that thread.
Sigurd
jcarr said:
Thank you, John. I know that you have high standards, so a compliment from you means something! I am honored. 
regards, jonathan carr
regards, jonathan carr
Hi Jonathon. From the pictures in Sigurd's link it appears the 4-2LSE audio section is shielded five of six sides, assuming those side panels are metal (hard to tell from the shots.) Is the front panel wood treated in any way for RF rejection? It's an interesting contrast to the Blowtorch chassis.
rdf, with apologies, but since I consider this to be John's thread, I'm trying to avoid talking overly much about the L-C here. 
regards, jonathan carr
regards, jonathan carr
Originally posted by jcarr
rdf, with apologies, but since I consider this to be John's thread, I'm trying to avoid talking overly much about the L-C here.
regards,
jonathan carr
111111111111111111111111111111111111111111111111111
at least 2 of the forum members here would like to see you start an L-C thread .
rdf, with apologies, but since I consider this to be John's thread, I'm trying to avoid talking overly much about the L-C here.
regards,
jonathan carr
111111111111111111111111111111111111111111111111111
at least 2 of the forum members here would like to see you start an L-C thread .
jcarr said:rdf, with apologies, but since I consider this to be John's thread, I'm trying to avoid talking overly much about the L-C here.
regards, jonathan carr
Can't fault a guy for trying. 🙂
Who started this madness?
Neither JC started this thread. I doubt if JCarr wants to discuss his linestage.
I may cop his regs on top of the circuit idea though. Putting those discrete regs so close has be help some.
I bought a 12.00 copy of HIFI+ just to drool on the pics of the L-C. Guess another 19,988.00 and I could buy the real thing.
Poor relative George
Neither JC started this thread. I doubt if JCarr wants to discuss his linestage.
I may cop his regs on top of the circuit idea though. Putting those discrete regs so close has be help some.
I bought a 12.00 copy of HIFI+ just to drool on the pics of the L-C. Guess another 19,988.00 and I could buy the real thing.
Poor relative George
volume pot
Sorry if this is covered before, but what is the impedance of BT vol pot? 10k to keep impedances low?
Sorry if this is covered before, but what is the impedance of BT vol pot? 10k to keep impedances low?
Bob Crump preferred 10K, but we could have used a 1 Meg pot, if we wanted to. This is because the fet input doesn't leak much or get noisy with changes of input impedance.
Most of us chose 25K, because we had tube equipment as sources as well. My unit has a buffered input that is about 50K on one switch selection. I plug my vacuum tube tuner there. Generally speaking, lower impedance pots sounded better to Bob, and he was our guru, when it came to parts selection.
Most of us chose 25K, because we had tube equipment as sources as well. My unit has a buffered input that is about 50K on one switch selection. I plug my vacuum tube tuner there. Generally speaking, lower impedance pots sounded better to Bob, and he was our guru, when it came to parts selection.
John -
I have almost always heard better sound with low value pot, like 10k. My explanation is that it reduces effect of non-linear input capacitance of the input stage. What is your opinion?
Regards,
Pavel
I have almost always heard better sound with low value pot, like 10k. My explanation is that it reduces effect of non-linear input capacitance of the input stage. What is your opinion?
Regards,
Pavel
If I had to guess, I would think that is is the material that creates the resistance that would be most important.
Johnson noise would always an issue and would benefit from a lower Zin. Also, noise currents induced in the inputs via interconnects etc... will be swamped by higher signal currents demanded by a lower Zin.
😉
😉
active / passive
If one has fet input PowAmp with sufficient gain, does he/she need a gain stage between Vol Pot and PowAmp input ?john curl said:
PMA said:
For what it is worth (i.e. almost nothing, I'm affraid), simulation gives 30 times more distortion (0.2%) at the gates of the fets with a 500K source impedance compared with 5k source impedance.
regards.
Philippe.
That might be possible, fets are fets, even cascoded. Tubes are better with 500K pots. Also, a 500K pot would be very noisy, compared to the input circuit.
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