I have a pair of Lundahl LL1682PP output transformers.
I'm wondering if these would be suitable for a PP amplifier using 300B's or JJ2A3-40's running at 300B operating point.
Anyone here used these transformers for 300B PP?
I also have a pair of LL11660 PP AM I plan to use as an interstage with 4P1L drivers.
I'm wondering if these would be suitable for a PP amplifier using 300B's or JJ2A3-40's running at 300B operating point.
Anyone here used these transformers for 300B PP?
I also have a pair of LL11660 PP AM I plan to use as an interstage with 4P1L drivers.
I haven't used the PP version of the LL1682, but I use the LL1682/70mA SE with a single 4P1L in the output stage. It's a very nice sounding OPT, like its brothers the 1664 and 1663.
4P1L goes well into 1660. Good driver. For the stage before that, if SE is OK, try the 01A Gen 2 preamp with gyrator on the Bartola Valves site. That's perfect into a 4P1L.
4P1L goes well into 1660. Good driver. For the stage before that, if SE is OK, try the 01A Gen 2 preamp with gyrator on the Bartola Valves site. That's perfect into a 4P1L.
Thanks for your thoughts. The LL1682PP has the smaller core, it's a 1.35Kg transformer. It's rated as a 40W maximum as opposed to the larger 2.5Kg LL1620 series.
That's why I was asking about the suitability of these for 300B push pull and low frequency performance.
I'm not sure that Allen Wright used the LL1682 in his 300B differential amplifier. It looks like he used the larger LL1620 series in the pictures I found.
300b output transformer
i´m 100% that the 1682 is used. the 5k-5,5 ohm gives a good dampingfaktor with the selected operating points and the current source on the cathodes.
power output is more in the 15W region and Allen prefered the simpler cores from lundahl due to the easier winding arrengements that does a smooth hf rollof (all of this was personal info from Allen himself)
i´m 100% that the 1682 is used. the 5k-5,5 ohm gives a good dampingfaktor with the selected operating points and the current source on the cathodes.
power output is more in the 15W region and Allen prefered the simpler cores from lundahl due to the easier winding arrengements that does a smooth hf rollof (all of this was personal info from Allen himself)
http://www.lundahl.se/wp-content/uploads/datasheets/1682.pdf
At 20Hz it will be little less W
data says 300b pp is max 20w @4k... (you may go >>350V AB1 instead..squeeze more)
Or go to expensive ll1620 300 H (overkill)
Actually....what is your speakers eff?
32:1 => sec 14vrms (24,5W@8R)
At 20Hz it will be little less W
data says 300b pp is max 20w @4k... (you may go >>350V AB1 instead..squeeze more)
Or go to expensive ll1620 300 H (overkill)
Actually....what is your speakers eff?
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Better in treble, mids i suppose. Smaller trafo, shorter turns--less parasitic elements.
Bigger iron, more henries, better bass..
Can´t have both
http://www.lundahl.se/wp-content/uploads/datasheets/1620_3_7_9202.pdf
This time how about 11k mode, higher Ua, colder biased.
This time how about 11k mode, higher Ua, colder biased.
I use 2x4P1L as outputs, and 250v a-k is the max. I'm not far off that whatever bias I go for! I do intend to try the LL1682/50mA at 25mA per 4P1L. That's around 8K into 8 ohms. I do really need 2x4P1L. Running them at 35mA each sounds fine with my LL1664. At least two of them at 25mA each would give me more output than a single one at 35mA.
Better in treble, mids i suppose. Smaller trafo, shorter turns--less parasitic elements.
Bigger iron, more henries, better bass..
Can´t have both
Well - I tried 2x4P1L into the LL1682/50mA, which is 8K into 8 ohms. Sound is exceptionally clear - can hear all kinds of words in vocals that were a little more unclear before.
It's a little bass light. Is this because of the high primary impedance?
High primary impedance cleans up the sound, but a real 8k transformer should have about double the primary inductance of the LL1682/50mA. What source impedance would your parallelled 4P1L's provide?
According to web, el34 needs 20H for 15Hz -3dB.
Pse 4p1l has twice gm; half ra.
So, 35H should not be any problem.
Your LL1682 DF with 8r spk, is about ~12, higher than "standard" 300B..(~5)
I don´t know, maybe such DF is common in the PP territory
Well, now your boomy bass has gone bye bye
LL1664 /8 DF ~4,3
Pse 4p1l has twice gm; half ra.
So, 35H should not be any problem.
Your LL1682 DF with 8r spk, is about ~12, higher than "standard" 300B..(~5)
I don´t know, maybe such DF is common in the PP territory
Well, now your boomy bass has gone bye bye
LL1664 /8 DF ~4,3
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