Wirewound linear 25 ohm of any sort a few watts. Look for that on pots or rheostats in your favourite shop.
Hi,
According to Kevin Carter, the US Lundahl importer:
"a triode connected 6V6GT used at the operating points given has an Rp of about 2000ohms, so the LL1671/20mA is the best choice."
Depending on what country you are in, I'd check with Kevin Carter or Per Lundahl as to how well the LL5402 will work.
According to Kevin Carter, the US Lundahl importer:
"a triode connected 6V6GT used at the operating points given has an Rp of about 2000ohms, so the LL1671/20mA is the best choice."
Depending on what country you are in, I'd check with Kevin Carter or Per Lundahl as to how well the LL5402 will work.
Greetings All. I am about to build Salas' 6V6 Line Preamp using anode chokes. I have a dozen good quality anode chokes (all the same model, 1850 DCR/225H/15ma) in my parts box and would use them except that their current handling capacity (15ma) is somewhat less than the 22-23ma that the choke will need to pass using Salas' design. I suppose two chokes could be used in parallel to raise their current handling ability to 30ma but paralleling them would halve their inductance - something I don't want to do. The reduced inductance could be overcome by adding another paralleled pair in series with the first paralleled pair to bring their inductance back up to the original 225H spec. Essentially, two paralleled pair of these chokes in series would provide the inductance spec of a single choke but double the current handling capacity. Any thoughts or comments at this point would be appreciated. Many thanks. -Edward
Don't go to such lengths. You can use just one at 14mA bias. Because of the very high apparent anode load provided by such a choke the THD is predicted to about -85dB anyway. I don't know if you have use of the elevated to 19.3dB voltage gain though. Or how microphonic will such gain emerge out of such a tube type. Build it as a test fixture first to evaluate better before investing in any good parts and a box I would recommend. The tube is going to have about 275V on its anode and about 21V at its cathode with your choke data and 300V B+ so it will dissipate about 3.55W. Use a 2W cathode resistor. R1 is for the simulation. Use 1Meg or skip it when having a pot. 20-50K log pot is fine.
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Thank you, Salas, for your prompt and informative reply. Much appreciated. Regarding the 19.3dB voltage gain ... I really have no need for that much voltage amplification. Even the 15dB voltage gain of the original design was more than I could use. I considered using anode chokes in this design with view to bettering the already remarkable sonics of the original design. Gilding the Lily projects rarely go as planned. Again, Salas, many thanks for your help with this. -Edward
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You are welcome. There is always the cathode follower alternative too. There your choke can push THD to super low levels even when handling large input signals. 300V B+ 14mA bias again.
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My intention now is to make both versions. Whether they will exist simultaneously or not, I don't know. Having both on hand would be optimum for comparisons though. I'll build the unity gain version first and see how it performs in the system. Thank you for helping with this, Salas, it's made a big difference. As mentioned previously, pics and comments will be posted soon after it's built. -Edward
What design has higher output the standard version or the cathode follower? Has anyone up'd the gain of the standard version with good results. (different operating point)
I need lots of gain! I'm in the layout design of this 6V6 Preamp to match my 2A3/45 x 6SN7 amp I built based on DHTRob's design (Thanks Rob!) The amp is remarkable. I drove it with a preamp that had an amplification factor of 34 but feel I could take even more input to take it to the next level. I'm hoping this 6V6 design will do the trick.
I need lots of gain! I'm in the layout design of this 6V6 Preamp to match my 2A3/45 x 6SN7 amp I built based on DHTRob's design (Thanks Rob!) The amp is remarkable. I drove it with a preamp that had an amplification factor of 34 but feel I could take even more input to take it to the next level. I'm hoping this 6V6 design will do the trick.
