Try 8AL9. 10W dissipation, 30 mA/V framegrid pentode with a triode in the bottle with 56 mu.
Wavebourn - Testing the preamp. I am pleased, the result... | Facebook
Wavebourn - Testing the preamp. I am pleased, the result... | Facebook
So, I tried an input transformer 1:4 after my DAP, and it gives me more volume, but there is some serious ringing/harshness to the sound (miller capacitance?). I am currently using a 100k put on the input of the amp, is this adequate? Maybe I should hook up the DAP to my 26 preamp (4:1 transformer coupled) then to the step up transformer then to the 6SN7 amp?
Would an input buffer be good in my situation? I realize what I really need is a gain in current and not voltage. Maybe I can add a 12au7 and take the output from the cathode- would this be of any use?
On a side note, I tried the amp at work and for some reason I was getting a little bit better volume than what I was getting at home. I will check the voltage at the socket at home and see if there is a difference in voltage.
On a side note, I tried the amp at work and for some reason I was getting a little bit better volume than what I was getting at home. I will check the voltage at the socket at home and see if there is a difference in voltage.
I cant believe how good this amp sounds with the planars with the NFB removed! I wish I could try it with regular speakers, but my OPT wont reflect the correct load to the 6SN7s. I suspect that removing the NFB would not sound as good with dynamic speakers and I would have to add some back in.
I recently put my flea amp back into daily use to save on heat (was running the 6CW5 amp) and forgot how lovely it sounds. I forget, which schematic did you build off of?
I may pull the NFB off of mine to see how I like it, but running a lower than ideal load impedance like I am I'm not sure how it will do, as the NFB can help to iron out non-ideal operating points to some extent. I know from past experimentation it doesn't effect the volume much, so I doubt it's running very much NFB as built anyway. I also may try LED bias for more gain on the input tubes, followed by an increase in NFB as well, to test possible features for the PCBs when I make some revisions.
One of the first things I noticed when putting this amp back in after running the larger one was how huuuuge it sounds soundstage wise- I am thinking this is due to the low overall feedback implemented. I'm curious if it will still retain that character after increasing overall gain and feedback.
I may pull the NFB off of mine to see how I like it, but running a lower than ideal load impedance like I am I'm not sure how it will do, as the NFB can help to iron out non-ideal operating points to some extent. I know from past experimentation it doesn't effect the volume much, so I doubt it's running very much NFB as built anyway. I also may try LED bias for more gain on the input tubes, followed by an increase in NFB as well, to test possible features for the PCBs when I make some revisions.
One of the first things I noticed when putting this amp back in after running the larger one was how huuuuge it sounds soundstage wise- I am thinking this is due to the low overall feedback implemented. I'm curious if it will still retain that character after increasing overall gain and feedback.
My understanding is that planar magnetic headphones (e.g., Fostex T50RP) have practically flat, unvarying impedance across the frequency band. That means an amplifier with low damping factor (such as a triode amp with no added NFB) won't vary its frequency response into that load. However, the bass sound *quality* might still be kind of loose, boomy, or the mids might have some more 'resonance' to them (more expansive soundstage?). That's a matter of taste, preference. FWIW, I enjoy that kind of sound too, especially for classic small group jazz recordings (Blue Note, Prestige, Riverside, Impulse!, etc.).
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