thanks for so many replies in such a short time.
ArnoldC, 26? Is that how many times people have asked the same question?
I can see a lot of parts in the bottlehead kit I don't need. If sound quality is slightly less then that effectively crosses it off the list.
The Aikido looks interesting, I'll need to see what matched sets of tubes are available around here. It's tolerance of poor power supples is a big plus, power supplies can get expensive.
12B4 looks good too, nice and simple, though the added complexity of power supply is a big minus.
Poindexter's looks interesting too, the power transformer arrangement is very clever but may not be entirely safe. Generally isolation between primary windings is not of the same standard as primary-secondary.
In which ways do you think it is better than the Aikido?
ArnoldC, 26? Is that how many times people have asked the same question?
I can see a lot of parts in the bottlehead kit I don't need. If sound quality is slightly less then that effectively crosses it off the list.
The Aikido looks interesting, I'll need to see what matched sets of tubes are available around here. It's tolerance of poor power supples is a big plus, power supplies can get expensive.
12B4 looks good too, nice and simple, though the added complexity of power supply is a big minus.
Poindexter's looks interesting too, the power transformer arrangement is very clever but may not be entirely safe. Generally isolation between primary windings is not of the same standard as primary-secondary.
In which ways do you think it is better than the Aikido?
OzMikeH, the 26 is a DHT tube. I have 12AU7 (Foreplay I), 12B4, 407A, 6SN7, 5687-based preamps and the 26 is better for me.
Kevin Kennedy, Jim de Kort and others have ready circuits you can find in the web as well as in this forum.
However, based on what you posted, I don't think the 26 is for your project this time.
Kevin Kennedy, Jim de Kort and others have ready circuits you can find in the web as well as in this forum.
However, based on what you posted, I don't think the 26 is for your project this time.
I heard both good & bad about the Aikido... personally i think it is too complex. The 12B4 is really appealing, i'll probably build that. Poinz was one of the guys that seemed a god to me when i was 1st picking up tube lore on the JoeList, so anything he does (& likes) is worth a serious look. The music machine is a very good example of elegant simplicity. I'd probably look at doing his too, but i don't have any of those tubes in my "junk box"
dave
Power supply complexity: It needs to be very, very clean because of poor PSRR. Lots of filtering at a couple of hundred volts can't be cheap.
Perhaps the people who wrote about their build of it went overboard with the power supply.
Performance is important, Particularly low noise and high detail.
If performance isn't excellent then I may as well spend a few hundred bucks on super-duper op-amps. I'd rather not go down that path though.
Perhaps the people who wrote about their build of it went overboard with the power supply.
Performance is important, Particularly low noise and high detail.
If performance isn't excellent then I may as well spend a few hundred bucks on super-duper op-amps. I'd rather not go down that path though.
Performance is important, Particularly low noise and high detail>>>>
If you want the ultimate tube for a preamp, I have no doubt that it's the 10Y. It's just that bit better than the 26 and the 01A. We've done multiple shootouts over several years at the London Audiocircle and this is the current favourite. It can be run at low voltage and low current, even. Sounded wonderful at 107v and 5mA into a Lundahl LL1660/5mA. An amorphous core would be the icing on the cake. It likes an OPT.
Yes, you will need a good filament supply. I suggest a 0-12, 0-12 60VA transformer into schottky bridge into 15,000uf cap into a LM1084 voltage reg to bring voltage down to 12v, then another LM1084 as current source. This is simply a LM1084 with adj connected to output via a 1 ohm resistor, 12W, and output taken from adj pin. Needs a nice big heatsink. You should get 7.25vDC out of this - perfect.
What you will get with the above is pure magic. In fact it's almost psychodelic.
6SN7 and 12b4 preamps went out the window years ago for most of us in the London Audiocircle, though clearly they still have fans.
If you want the ultimate tube for a preamp, I have no doubt that it's the 10Y. It's just that bit better than the 26 and the 01A. We've done multiple shootouts over several years at the London Audiocircle and this is the current favourite. It can be run at low voltage and low current, even. Sounded wonderful at 107v and 5mA into a Lundahl LL1660/5mA. An amorphous core would be the icing on the cake. It likes an OPT.
Yes, you will need a good filament supply. I suggest a 0-12, 0-12 60VA transformer into schottky bridge into 15,000uf cap into a LM1084 voltage reg to bring voltage down to 12v, then another LM1084 as current source. This is simply a LM1084 with adj connected to output via a 1 ohm resistor, 12W, and output taken from adj pin. Needs a nice big heatsink. You should get 7.25vDC out of this - perfect.
What you will get with the above is pure magic. In fact it's almost psychodelic.
6SN7 and 12b4 preamps went out the window years ago for most of us in the London Audiocircle, though clearly they still have fans.
I suggest a 0-12, 0-12 60VA transformer into schottky bridge into 15,000uf cap into a LM1084 voltage reg to bring voltage down to 12v, then another LM1084 as current source. >>
I should point out that the above is ONE filament supply per TUBE - schottky bridge into 15,000uf cap into a LM1084 voltage reg to bring voltage down to 12v, then another LM1084 as current source. Two tube supplies can therefore be run off one 60VA toroid with double 12-0 secondaries.
I should point out that the above is ONE filament supply per TUBE - schottky bridge into 15,000uf cap into a LM1084 voltage reg to bring voltage down to 12v, then another LM1084 as current source. Two tube supplies can therefore be run off one 60VA toroid with double 12-0 secondaries.
Arnold,
Most people don't have the ability to build a really quiet good performing 26 line stage without the extensive use of high dollar transformers or complex battery charging circuits.
I've been working on one for a long time and still cannot get the hum out of it.
What is wrong with a 6SN7 preamp? its very neutral and most can built it without a hum problem.
Got a schematic of the 10Y?
Most people don't have the ability to build a really quiet good performing 26 line stage without the extensive use of high dollar transformers or complex battery charging circuits.>>
I don't think it's difficult at all - people seem to be put off by mythology about DHTs, i.e. that they need battery supplies, are all microphonic etc. A DHT will work perfectly well off a bench supply - I've used bench supplies to develop circuits for a while.
<<<I've been working on one for a long time and still cannot get the hum out of it.>>
Ah - you're not wrong here!!!! Once you put the filament supplies inside the preamp you can get all sorts of interactions, and I've also been plagued by hum in some one box units. But I don't get a problem when you use outboard supplies. I'm learning all the time here, like also you bypass cathode resistors with large polypropylene caps.
quote:
6SN7 and 12b4 preamps went out the window years ago for most of us in the London Audiocircle, though clearly they still have fans.
<<What is wrong with a 6SN7 preamp? its very neutral and most can built it without a hum problem.>>
What's wrong only stands out when you directly compare a 6SN7 pre against a DHT like 26, 01A or 10Y. We did this in a repeated A-B test and while the 6SN7 was smooth and pleasant it wasn't so detailed, delicate or magical in terms of the tone of intruments. Sounded a bit "thicker" while the DHTs were more quicksilver and mercurial. Aren't you hearing this extra dimension with your 26 pre?
I don't think it's difficult at all - people seem to be put off by mythology about DHTs, i.e. that they need battery supplies, are all microphonic etc. A DHT will work perfectly well off a bench supply - I've used bench supplies to develop circuits for a while.
<<<I've been working on one for a long time and still cannot get the hum out of it.>>
Ah - you're not wrong here!!!! Once you put the filament supplies inside the preamp you can get all sorts of interactions, and I've also been plagued by hum in some one box units. But I don't get a problem when you use outboard supplies. I'm learning all the time here, like also you bypass cathode resistors with large polypropylene caps.
quote:
6SN7 and 12b4 preamps went out the window years ago for most of us in the London Audiocircle, though clearly they still have fans.
<<What is wrong with a 6SN7 preamp? its very neutral and most can built it without a hum problem.>>
What's wrong only stands out when you directly compare a 6SN7 pre against a DHT like 26, 01A or 10Y. We did this in a repeated A-B test and while the 6SN7 was smooth and pleasant it wasn't so detailed, delicate or magical in terms of the tone of intruments. Sounded a bit "thicker" while the DHTs were more quicksilver and mercurial. Aren't you hearing this extra dimension with your 26 pre?
andy, I have 8 pairs of 10Y and I've been, in my mind, trying to make one. Since I saw the Electronluv, I always wanted to make one, then the 26 came along.
That's just the kick in the **** I needed! I will make a 10Y pre now!
My friend is the distributor of Lundahl here and he's got lots of 1660.
Thanks for sharing that information on the op points! Can you complete the recipe by sharing the wiring of the 1660? ALT-S perhaps?
I would agree that there's nothing wrong with a 6SN7 pre, but for me, compared to my 26... ahh no contest.
That's just the kick in the **** I needed! I will make a 10Y pre now!
My friend is the distributor of Lundahl here and he's got lots of 1660.Thanks for sharing that information on the op points! Can you complete the recipe by sharing the wiring of the 1660? ALT-S perhaps?
I would agree that there's nothing wrong with a 6SN7 pre, but for me, compared to my 26... ahh no contest.
http://www.lundahl.se/pdfs/datash/1660.pdf
Wiring is indeed ALT-S as you say. I was astonished that the 10Y worked so well at such a low current, but this does enable you to use the 5mA SE version which means more inductance. With a plate resistance of 5k the 10Y probably likes to see this higher inductance. I haven't tried the 10mA version - that should work too.
I made a circuit diagram but don't know how to post it - also it's in .bmp right now. I'm not a wizard with computing. Andy
Wiring is indeed ALT-S as you say. I was astonished that the 10Y worked so well at such a low current, but this does enable you to use the 5mA SE version which means more inductance. With a plate resistance of 5k the 10Y probably likes to see this higher inductance. I haven't tried the 10mA version - that should work too.
I made a circuit diagram but don't know how to post it - also it's in .bmp right now. I'm not a wizard with computing. Andy
Mike, I have that transformer in service in the dozens, have never encountered a failure. Buck and boost windings are a grand tradition among small builders who can't finance specialty transformers; the only thing unusual here is the use of one primary as a secondary. A winding doesn't know if it's a primary or secondary, it's just a winding, on the core with all the other windings. Of course, using one half the primary effectively halves the VA of the transformer, which is why I use a 20VA part for a 6 watt application. For EU clients, I use the Hammond 182E117; use it if you're nervous. You'll want to drop the cathode resistors a value (to 75 and 68Ω ) to keep the current up. All it costs is about 16 volts on the B+; the circuit still has plenty of input and output swing.
I built both the Aikido and Bruce's grounded grid (which is actually a singly-driven diff-amp, a circuit of which I'm very fond), and honestly preferred this one; it's quieter and has higher rez. Of course, I would say that, hm?
:^)
Poinz
I built both the Aikido and Bruce's grounded grid (which is actually a singly-driven diff-amp, a circuit of which I'm very fond), and honestly preferred this one; it's quieter and has higher rez. Of course, I would say that, hm?
:^)
Poinz
The PSRR of the 12B4 is no different to the 6SN7 or the 26 or any other triode. It's not hard, nor is it that expensive. If you can deal with the extra gain use a CCS load and/or a Maida reg. CCS and shunt reg is best, but that is more complex.OzMikeH said:
I didn't read much of the linked 12B4 thread as there were a bajillion posts for something that is incredibly simple.
I'm posting this on behalf of andyjevans
Geez, I'm tempted to use my VR105 on the plate
An externally hosted image should be here but it was not working when we last tested it.
Geez, I'm tempted to use my VR105 on the plate
Thanks for posting that!
I should point out that the 107v B+ just happened to be from a transformer I had handy - I used this voltage for testing a whole heap of DHTs, some of which were 90v max plate voltage.
For the 10Y you could take up the voltage over 300vDC. The current stayed low because of the LL1660/5mA which I happened to have. Again, you could swap that for a LL1660/10mA for instance.
The schematic isn't optimised - it just works and sounds very nice indeed.
I should point out that the 107v B+ just happened to be from a transformer I had handy - I used this voltage for testing a whole heap of DHTs, some of which were 90v max plate voltage.
For the 10Y you could take up the voltage over 300vDC. The current stayed low because of the LL1660/5mA which I happened to have. Again, you could swap that for a LL1660/10mA for instance.
The schematic isn't optimised - it just works and sounds very nice indeed.
Excellent guys, I'll start collecting and building some external power supplies. Meanwhile I'll ponder some more. Had another look at the Tek 845b, Seems a shame to trash it but there's a million of them out there and mine has had mice living in it. SHould be able to run all sorts of stuff off such a big supply.
Just spotted that Heretical line stage this morning. Steep learning curve at the moment. This High voltage low current thing is still too new to me to be a seat of the pants thing.
I appreciate the advice and tolerance of stupid questions.
Poindexter, I'll definitely remember the trick with the double primaries.
Just spotted that Heretical line stage this morning. Steep learning curve at the moment. This High voltage low current thing is still too new to me to be a seat of the pants thing.
I appreciate the advice and tolerance of stupid questions.
Poindexter, I'll definitely remember the trick with the double primaries.
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