Kevin, what turns ratio are you using with the 1671 in this situation? And can you estimate what output impedance this gives you? Thanks.
The LL1671 is connected 4:1 giving an output impedance of about 270 ohms and a stage gain of just over 7dB.
Whats the best lundahl transformer for 4p1l running 25-30mA???
I would go whit the LL1671 but the two LL1692A and LL1660 have higher inductance but
also higher DCR...So how does it look in the practice???
There is also a possibility of a parafeed, anyone?
Thanks...
I would go whit the LL1671 but the two LL1692A and LL1660 have higher inductance but
also higher DCR...So how does it look in the practice???
There is also a possibility of a parafeed, anyone?
Thanks...
Thomas has experience of Lundahls and so does Ale. My own experience is using them in pretty much 1:1, as the first stage in my PSE 2-stage all 4P1L amp. In 1:1 I prefer the sound of the LL1660 to the 1692A, but Thomas I think finds the opposite in stepdown.
I'm sure he can give you a lot more information than I can. I've just ended my search with the LL1660, which is fine for me. Thomas has tried a lot of others like Tango.
I'm sure he can give you a lot more information than I can. I've just ended my search with the LL1660, which is fine for me. Thomas has tried a lot of others like Tango.
The LL1671/30mA has more than enough primary inductance for the 4P1L to be able to cover the lowest audio frequencies. I have tried the LL1692A and the LL1671, and prefer the LL1671 by a large margin.
Thank you guys for your opinion!
I never used lundahl but the LL1671 is the most promising to me...Need to try!
Interesting that no one has tried a parafeed topology yet!
Lundahl has a nice transformer for that purpose and its the LL1930 or
the LL1660 parafeed....I think in the bass region the parafeed outperforms any air gaped transformer,
but this is only my experience.
I never used lundahl but the LL1671 is the most promising to me...Need to try!
Interesting that no one has tried a parafeed topology yet!
Lundahl has a nice transformer for that purpose and its the LL1930 or
the LL1660 parafeed....I think in the bass region the parafeed outperforms any air gaped transformer,
but this is only my experience.
Dear all,
it may not be exactly the right place, but if it come to bass reproduction and 4P1L as a triode then I would like to add, that the way the grids are attached to the anode may play a role:
My experience (it my well be that this only holds for me, but... give it a try) is that I should not connect G2 & G3 via a resistor to the anode.
I got more bass while still enjoying the excellent mids and treble (? right word) performance when I connect G3 to the cathode and G2 via a schottky diode (anode to anode; diode bypassed with a good electrolytic (nichicon muse or comparable) and a foil and a silver mica) to the anode.
Try and (hopefully) enjoy,
Ulrich
Interesting experiments....... all adds to the knowledge.
I connect Grids 2+3 to the anode, and filaments in parallel. What am I missing here - much or very little? Is the total output - theoretically 9W - the same in your setup?
I connect Grids 2+3 to the anode, and filaments in parallel. What am I missing here - much or very little? Is the total output - theoretically 9W - the same in your setup?
Dear Andy,
yes I also connect the filaments in parallel & via something like the Coleman board.
This idea to use diodes (either zener oder other diodes) is not really new:
Pentodes & Tedrodes to Triodes
but it took a while until I came across.
Initially I tried this method on the 6e5p (but using only one schottky (and other types of) diode, no resistors and the bypassing capacitors, see also the Midlife Crisis thread here) but now found it's also working for the 4P1L.
I'm running my 4P1L as a RC coupled driver for a static induction transistor (2SK82; having really triode like curves (no joke)) working into a 7:1 OPT.
My experience is limited, so the amount you are missing is difficult to quantify for me.
For me, the acoustic situation was, that the mids & treble performance of the 4P1L was outstanding, but my previous amp was more realistic regarding the bass reproduction in comparison #2 using the 4P1L & G2 & G3 connected to the anode. I was thinking, that I would need a blend of both amps performances (ok, no idea how to obtain that, but just to give you the flavor).
With the other connection method applied the bass reproduction "deficit" is gone. As mentioned before: for me & in my set-up. I'm convinced this experience is transposable, but I don't want to be a missionary.
Does this answer your question?
Cheers,
Ulrich
yes I also connect the filaments in parallel & via something like the Coleman board.
This idea to use diodes (either zener oder other diodes) is not really new:
Pentodes & Tedrodes to Triodes
but it took a while until I came across.
Initially I tried this method on the 6e5p (but using only one schottky (and other types of) diode, no resistors and the bypassing capacitors, see also the Midlife Crisis thread here) but now found it's also working for the 4P1L.
I'm running my 4P1L as a RC coupled driver for a static induction transistor (2SK82; having really triode like curves (no joke)) working into a 7:1 OPT.
My experience is limited, so the amount you are missing is difficult to quantify for me.
For me, the acoustic situation was, that the mids & treble performance of the 4P1L was outstanding, but my previous amp was more realistic regarding the bass reproduction in comparison #2 using the 4P1L & G2 & G3 connected to the anode. I was thinking, that I would need a blend of both amps performances (ok, no idea how to obtain that, but just to give you the flavor).
With the other connection method applied the bass reproduction "deficit" is gone. As mentioned before: for me & in my set-up. I'm convinced this experience is transposable, but I don't want to be a missionary.
Does this answer your question?
Cheers,
Ulrich
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This is also something I want to do for my 4p1l pre amp. I also tried it on 6e5p whit normal diode and the results where absolute amazing in regards of high/mid reproduction. Way more realistic!!! This is a good tweak!!! Try it out.....
Finished my test version of the amp. The first impression - very good soundstage. There are, of course, problems to solve.
All kinds of noise to handle: hum, some strange pulse (140 times per minute) noise. The rig: CRC stage (20000uF) for heaters will definitely be changed for (c)LC and more attention will be paid to this part, HT will be tuned, 50W 15 Ohm Mills resistors don't need that big heatsink, and that wire chaos will be handled properly during noise cleanup procedure. There will be separate enclosures for power supply and the pre-amp definitely. Too much gain - not sure how to handle it so far.
All kinds of noise to handle: hum, some strange pulse (140 times per minute) noise. The rig: CRC stage (20000uF) for heaters will definitely be changed for (c)LC and more attention will be paid to this part, HT will be tuned, 50W 15 Ohm Mills resistors don't need that big heatsink, and that wire chaos will be handled properly during noise cleanup procedure. There will be separate enclosures for power supply and the pre-amp definitely. Too much gain - not sure how to handle it so far.
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Answering about numbers from memory can be hazardous. While the gain was correct, the output impedance with that connection is 160ohms.
Hi. I am collecting the parts for this preamp. Rod Colemans kit seems the best filaments approach. For the shunt regulator I am not sure yet. One of the K&K kits maybe but which one. Will there be large differences?
Also for the 15 ohm resistor I need a 10 watt version?
Also for the 15 ohm resistor I need a 10 watt version?
The 100-350V Shunt Regulator Kit does nicely in my 4P1L preamp. If you wish to run the tubes at greater than 25mA/ch, you would want one per channel.