I just got a pair of Polk Audio Lsi9's and am considering building a tube amp (kit) for them. the speakers are rated at 88db efficiency, and they are a 4ohm nominal speaker. I've heard mixed reviews about using tubes with a low efficiency speaker so I'd like to get some expert opinions/suggestions on whether or not a tube amp is worthwhile or should I just stick with a solid state amp.
Hi Frank,
I suppose this is not for your home-cinema setup in you main living room. But rather a second setup for the bedroom/study or whatever.
Personally If I were in the market for an amp kit. I would go for the Welborne Labs DRD 300B/2A3/45 kits...
http://www.welbornelabs.com/drd.htm
With the 300b kit version being the most suited to your speakers (300b=+-8 Watt, 2a3=+-3 Watt, 45= +-1,5Watt). The 88dB sensitivity of your speakers are not neccessarily a problem. So would try to listen with a SE 300b amp first before commiting to a 300b or similar kit.
Good luck!
Cheers,
Bas
I suppose this is not for your home-cinema setup in you main living room. But rather a second setup for the bedroom/study or whatever.
Personally If I were in the market for an amp kit. I would go for the Welborne Labs DRD 300B/2A3/45 kits...
http://www.welbornelabs.com/drd.htm
With the 300b kit version being the most suited to your speakers (300b=+-8 Watt, 2a3=+-3 Watt, 45= +-1,5Watt). The 88dB sensitivity of your speakers are not neccessarily a problem. So would try to listen with a SE 300b amp first before commiting to a 300b or similar kit.
Good luck!
Cheers,
Bas
Frank Z
Not knowing what type of music you listen to or the level you desire it is difficult to predict what you would be happy with in terms of power. Not wanting to start WWIII here but I will give my opinion. With a speaker of only 88db @1W 1M I would surely want a lot more power that a 8 watt or less kit could provide. With 8 watts and the efficiency of your speakers I personally don't think you would be happy. I would recommend purchasing a Dynaco stereo 70 or something along that line that would have ample power to provide adequate listening levels. Keep in mind that these amps can be modified to provide great listening pleasure. I started out with some Quicksilver KT88 amps rated at 60 watts per mono block. These are used with some custom speakers with an efficiency of greater that 100db per watt per meter and they deliver very good sound and have a lot of headroom. I had been using solid state SAE amps such as an X25A that was rated in excess of 200 watts per channel.
The Polk is a very good speaker and I surely am not trying to put it or you down. I would certainly audition your speakers in your listening environment before purchasing any amplifier or kit. I am certain that there are a number of dealers out there that wouldn't have a problem with letting you take home a piece of equipment to try out. Just my .02
Joe
Not knowing what type of music you listen to or the level you desire it is difficult to predict what you would be happy with in terms of power. Not wanting to start WWIII here but I will give my opinion. With a speaker of only 88db @1W 1M I would surely want a lot more power that a 8 watt or less kit could provide. With 8 watts and the efficiency of your speakers I personally don't think you would be happy. I would recommend purchasing a Dynaco stereo 70 or something along that line that would have ample power to provide adequate listening levels. Keep in mind that these amps can be modified to provide great listening pleasure. I started out with some Quicksilver KT88 amps rated at 60 watts per mono block. These are used with some custom speakers with an efficiency of greater that 100db per watt per meter and they deliver very good sound and have a lot of headroom. I had been using solid state SAE amps such as an X25A that was rated in excess of 200 watts per channel.
The Polk is a very good speaker and I surely am not trying to put it or you down. I would certainly audition your speakers in your listening environment before purchasing any amplifier or kit. I am certain that there are a number of dealers out there that wouldn't have a problem with letting you take home a piece of equipment to try out. Just my .02
Joe
Basically you'd want to hear ANY SE 300B amp with your speakers since virtually all of them put out around 8Watts or so.
I have 90dB speakers mission 761 and even 1,5Watt makes them go loud enough to p*ss of the neighbours..that's why I said you don't perse need a PP amp or more powerfull amp.
I believe quite a few people are happy with the PP EL34 - Ella Kit. May also be fitted with KT88..(Would recommend Svetlana KT88)
http://www.diyhifisupply.com/diy_kits/the_ella.html then you'd have 40W. PS I think they have an American importer as well....not sure though...
Cheers,
Bas
re my planning kits.
Hi,
this is my palnning kits.
pls give me any advise.
2a3SE
thanks
thomas
www.diyaudiocraft.com
http://www.diyaudiocraft.com/bb/viewtopic.php?t=125
Hi,
this is my palnning kits.
pls give me any advise.
2a3SE
thanks
thomas
www.diyaudiocraft.com
http://www.diyaudiocraft.com/bb/viewtopic.php?t=125
Attachments
I'm with Joe: single-ended, low-power, high source Z, high distortion amps are completely unsuitable for your speakers. If you want tubes, think push-pull. An ST-70 is a fine base for a project, and there's lots of kits out there for rebuilds that will give you an amp that will be happy driving your speakers. My personal favorite is the ST-70 input boards and power supply/regulator from Joe Curcio.
SY said:
Sy, I did this mod to a cousin's ST70 a number of years ago. I had one major problem, that is that the bias resistor kept burning out until I put in a 5W sandcast. According to Curcio there should have only been a couple of milliwatts dissipation there, but nothing else seemed to work. The amp ran smoothly for a few years, but then my cousin complained that he couldn't get the bias up on the unit. I tested with new output tubes, no change. So I started to poke around inside. Vref measured fine, but the high voltage regulators weren't working. I replaced all of the transistors/opamps, even though they tested fine. Still no change. The amp has been sitting on my shelf for almost a year, unusable. Curcio didn't have any suggestions beyond shipping him the amp (expensive, I'm in Canada). Would you have any suggestions?
Sorry to hijack this thread.
FrankZ, I have the makings of an Assemblage ST40 kit. This is the same amp as an Anthem Amp1, a push pull EL34 amp. I've got the power and output transformers for the Anthem, plus the PCB for either the Anthem or the Assemblage, your choice. Also the large reservoir caps and the manual with schematic and parts list. Everything is brand new, you'd have to build a chassis. I bought this from a friend who was the designer of the amp. Search the net and you'll find more info/reviews. If you're interested, email me at ron.steinberg at sympatico.ca replacing "at" with "@".
Cheers,
RonS
Hi,
If this amp is to serve in a dual channel system in a reasonably sized room I'd heartily recommend a PP 2A3 amp.
With attention paid to PS design and driver stage you'd be amazed about the amount of power you can squeeze out of them.
There's something about those DHT triodes that just defies logic...
In the smallish studio I usually work from I have a simple two way speakersystem with a 2A3 PP and a Plextor CD-Rom, software controlled.
This stuff rocks, is detailed and throws a stereo image to make quite a few big boys envious.
Moreover, for a CD based system, this is actually one I can listen to for hours.
Spot the Ultranalog analogy and I'll consider you a smart person...
Cheers,
If this amp is to serve in a dual channel system in a reasonably sized room I'd heartily recommend a PP 2A3 amp.
With attention paid to PS design and driver stage you'd be amazed about the amount of power you can squeeze out of them.
There's something about those DHT triodes that just defies logic...
In the smallish studio I usually work from I have a simple two way speakersystem with a 2A3 PP and a Plextor CD-Rom, software controlled.
This stuff rocks, is detailed and throws a stereo image to make quite a few big boys envious.
Moreover, for a CD based system, this is actually one I can listen to for hours.
Spot the Ultranalog analogy and I'll consider you a smart person...
Cheers,
<hijack>
Transducer, I'd suspect the power supply electrolytics. Poke around the input and output rails with a meter and a scope to see if the B+ voltage is the required 390V and that the input is more or less 450V, with low ripple. FWIW, that's the only part I've lost on mine in about 10 years of service and some pretty terrifying modifications.
Make sure you observe appropriate safety precations when poking around high voltages like this. It's WAY too easy to brush up against something you shouldn't, and we don't have so many members at diyAudio that we can afford to lose any.
</hijack>
Transducer, I'd suspect the power supply electrolytics. Poke around the input and output rails with a meter and a scope to see if the B+ voltage is the required 390V and that the input is more or less 450V, with low ripple. FWIW, that's the only part I've lost on mine in about 10 years of service and some pretty terrifying modifications.
Make sure you observe appropriate safety precations when poking around high voltages like this. It's WAY too easy to brush up against something you shouldn't, and we don't have so many members at diyAudio that we can afford to lose any. </hijack>
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