I was looking around trying to find a nice preamp for my turntable to pair it with my newly completed S5 K-12 kit, when I came across this recent article on the Oatley K282:
6418 Tube RIAA Phono Preamplifier Kit (Oatley Electronics K282)
This seems ideal as its reasonably priced (~$41ish USD), compact, and completely tube based. I was just posting here to find out if anyone has completed one of these kits and if so, their thoughts on the preamp. If anyone has built a project with these tubes and has any information on them, that'd be appreciated too, thanks!
6418 Tube RIAA Phono Preamplifier Kit (Oatley Electronics K282)
This seems ideal as its reasonably priced (~$41ish USD), compact, and completely tube based. I was just posting here to find out if anyone has completed one of these kits and if so, their thoughts on the preamp. If anyone has built a project with these tubes and has any information on them, that'd be appreciated too, thanks!
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yeah, had me worried too
ecpecially when I read they wrote them tubes ring like a bell without rubbers
maybe its microfonic, and related to smps
But I wouldnt want to ruin a possibly good cheap project, so I didnt post
But I also thought that playing vinyl, a phono pre is the most important part of a setup
and it should match the pickup
and many other gain matching through the setup should be considered
Broskies new Tetra with onboard supply looks good, and cost more
But the higher voltage is more dangerous, and so a lot more problematic
ecpecially when I read they wrote them tubes ring like a bell without rubbers
maybe its microfonic, and related to smps
But I wouldnt want to ruin a possibly good cheap project, so I didnt post
But I also thought that playing vinyl, a phono pre is the most important part of a setup
and it should match the pickup
and many other gain matching through the setup should be considered
Broskies new Tetra with onboard supply looks good, and cost more
But the higher voltage is more dangerous, and so a lot more problematic
I wonder about preamps like this:
HIFI Buffer Audio preamplifier 6N3 Tube PRE-AMP NEW-B1 - eBay (item 120595904218 end time Sep-12-10 03:58:45 PDT)
Of course, you can never find out any information about them online, which is why I don't think I'd ever spend any money on something that others haven't at least mentioned online in forums, reviews, or otherwise.
HIFI Buffer Audio preamplifier 6N3 Tube PRE-AMP NEW-B1 - eBay (item 120595904218 end time Sep-12-10 03:58:45 PDT)
Of course, you can never find out any information about them online, which is why I don't think I'd ever spend any money on something that others haven't at least mentioned online in forums, reviews, or otherwise.
Oatley kits based on 6418
Hallo guys,
The Oatley kit schematics raised the same doubts in my mind as in yours. However, one of your comments is not quite correct. It is true that the 6418 has virtually zero drive capability, but in the K282 kit, each tube is followed by a MOSFET source follower. Gain is provided by the tube and output impedance matching by the MOSFET.
I gave Oatley the benefit of the doubt and have bought both the K272A and K282 kits. My K272A (portable headphone amplifier) is finished and it sounds surprisingly good. VERY good when driving Grado SR125 headphones. For 30 AUS$, I consider the K272A a real winner. The K282 (RIAA phono preamplifier) is not yet finished. By the end of September, I'll (hopefully) know what it sounds like. Will keep you informed. Rumor has it that it sounds much better than one would expect. Keep your fingers crossed...
If you have doubts about the (dual!) switched-mode power supply of the K282 you may consider replacing this by a good quality series or shunt regulator providing 30V output. Or even by 20 AA cells wired in series....
Greetings,
Aren van Waarde
aka arensattic
Hallo guys,
The Oatley kit schematics raised the same doubts in my mind as in yours. However, one of your comments is not quite correct. It is true that the 6418 has virtually zero drive capability, but in the K282 kit, each tube is followed by a MOSFET source follower. Gain is provided by the tube and output impedance matching by the MOSFET.
I gave Oatley the benefit of the doubt and have bought both the K272A and K282 kits. My K272A (portable headphone amplifier) is finished and it sounds surprisingly good. VERY good when driving Grado SR125 headphones. For 30 AUS$, I consider the K272A a real winner. The K282 (RIAA phono preamplifier) is not yet finished. By the end of September, I'll (hopefully) know what it sounds like. Will keep you informed. Rumor has it that it sounds much better than one would expect. Keep your fingers crossed...
If you have doubts about the (dual!) switched-mode power supply of the K282 you may consider replacing this by a good quality series or shunt regulator providing 30V output. Or even by 20 AA cells wired in series....
Greetings,
Aren van Waarde
aka arensattic
I think the K272 preamp/headphone amp is excellent. It is the primary pre-amp in my system and sounds great when run off batteries. (12V car battery in my case). The tiny tubes may turn people off. They add no warmth, but instead expand the soundstage of the music.
If I had a turntable, I'd not think twice about the K282A.
To overcome tube ringing - use rubber grommets and damp your enclosure well with bitumen pads etc. My tubes only ring when I whack the enclosure very hard.
If I had a turntable, I'd not think twice about the K282A.
To overcome tube ringing - use rubber grommets and damp your enclosure well with bitumen pads etc. My tubes only ring when I whack the enclosure very hard.
Running K272 (or K272A) from a car battery
Dear Chlorophille,
Thanks for your post. I am interested in your statement that you run the K272A from a car battery. Can this be done without any modification? (normally, the PCB runs at 9V). The valves can of course handle 12V easily, but what about the L4949 chip? (it can handle voltages up to 28V but it will dissipate more when run at 12V).
I have noticed that the sound which the K272A produces is excellent when run from a new 9V battery. However, when battery voltage drops far below 8V (to 7.5V or so), the sound detoriates, probably because the triode input stage is then more easily overloaded. Thus, your selection of a car battery may be a wise choice.
I agree also with your statement that the valves produce a wide and detailed soundstage and do not produce any artificial warmth. But in my opinion the K272A sounds very sweet (in the good sense, lifelike, non-electronic) when run from a full battery.
Regards,
Aren
Dear Chlorophille,
Thanks for your post. I am interested in your statement that you run the K272A from a car battery. Can this be done without any modification? (normally, the PCB runs at 9V). The valves can of course handle 12V easily, but what about the L4949 chip? (it can handle voltages up to 28V but it will dissipate more when run at 12V).
I have noticed that the sound which the K272A produces is excellent when run from a new 9V battery. However, when battery voltage drops far below 8V (to 7.5V or so), the sound detoriates, probably because the triode input stage is then more easily overloaded. Thus, your selection of a car battery may be a wise choice.
I agree also with your statement that the valves produce a wide and detailed soundstage and do not produce any artificial warmth. But in my opinion the K272A sounds very sweet (in the good sense, lifelike, non-electronic) when run from a full battery.
Regards,
Aren
I also built the K272 and found it to be a great little device. I don't know why something so cheap gets such a negative reaction. The problem I have with it is that it picks up all kinds of RFI noise, but I don't have mine in any kind of case, just a bare board. It certainly improves the sound of an iPod, but I wouldn't necessarily replace my $$$$ pre-amp with it. And how many people can say they listen to their tube amps on the subway?
For the money the phono pre is worth a try. It'll be a quick project. My son has been buying vinyl from all his favorite bands and complaining that he can't play them. Maybe he needs his own TT and this can be his pre????? I've already built him a T-amp (diy paradise) and speakers (murphyblasters). He'll go to college next year and be the only kid with a real stereo. Everyone else uses their computers/ipods/headphones/docks these days.
For the money the phono pre is worth a try. It'll be a quick project. My son has been buying vinyl from all his favorite bands and complaining that he can't play them. Maybe he needs his own TT and this can be his pre????? I've already built him a T-amp (diy paradise) and speakers (murphyblasters). He'll go to college next year and be the only kid with a real stereo. Everyone else uses their computers/ipods/headphones/docks these days.
I have connected 2 pp3 9v batteries in parallel inside my Oatley K272 headphone amp, this gives the advantage of a greater life. I am also considering adding a socket and associated wiring to it can be run off an external source. I have also just ordered their valve buffer amp based on the same valve
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I ordered and built a 6n3p 1 tube buffer preamp kit from this same seller. I had no problems with the kit build. I wanted to use it between a Stanton ST-100 turntable, I bought many for 78rpm play. The Stanton has a built in preamp and thought maybe this would sweeten the sound of the onboard preamp. I did exactly that, improving the sound greatly. I have looked at building the kit you have shown for a DIY preamp kit I'm working on, but I was unable determine by the description if this a just another buffer preamp or a gain preamp. So now I'm looking at building a P-P 12au7 preamp instead.
...gap filler would be 'too solid' I would think, some 'soft cushioning' internally...I am considering...
...what about trying other damping, even 'rubber band' suspension methods, with thin wires soldered to the tube pins while suspended, ie: like the motor on a older Rega Planer TT...
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