It it's obvious. Use an output transformer in the preamp and use the ME550's balanced inputs. It is impossible for a transformer to produce DC and we all know that transformers are available with 4, 8 or 16 ohm secondaries.
It sounds to me like what is needed is a very low power "integrated amp". So take your favorite tube preamp and add a 1 watt "power section" to it If you only need low power then single ended is reasonable. You could use a 6SN7 or 12au7 to drive a small single ended transformer such as a Hammond 125*se series. You could even go "exotic" and use a 3b7 tube and then have bragging rights to a DHT preamp.
The hammond OPT when driven at 10% of it's rated power will have plenty of bass.
Also the single ended triode likely gives the best "tube sound" and I assume that is the reason for going with a tube preamp
...actually the update on this is that the 550 Type I only has unbalanced inputs @ 1K ohms. (Its the 500 that has balanced ones at 2K...)
...so, <10ohms would be optimal for pre-amp output...
...yes, it is the reason I am going with the 'tube sound'...
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I have some used 'huge' valves I purchased - taken from a local radio station transmitter - years ago when it was upgraded/demolished...I must revisit them in my shed interstate and find out what they are. Maybe I can make a 'super valve amp' with them... or something...They are quite massive...about 5" long and about 3" wide have some kind of aluminium ring setup around them
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...YES...clearly this is a good idea, ...
... you chaps know a great deal more about all this than myself, I have just viewed the tip of the iceberg -from afar- in comparison..., and am trying to understand what is underneath it..., however, know that its there....in one form or another...
So that does not change much. You are still building a "mini powered" integrated amplifier. Just a standard preamp but with a flea powered power section. You can do it exactly as I said Use an 6SN7 or 12AU7 as the power tube but now one side of the output transformer's secondary is grounded.
Why is it the unbalanced is so common with consumer electronics? I can understand it on low-end gear but but on a $200+ amp it would not add much more cost and it eliminates problems with interconnects.
and if you load it with higher impedance, its primary impedance will change to, no?
actually I thought a 600ohm balanced signal trafo qould work into 1kohm
not that I have ever really understood this stuff
and if you load it with higher impedance, its primary impedance will change to, no?
actually I thought a 600ohm balanced signal trafo qould work into 1kohm
not that I have ever really understood this stuff
Yes it would work. 600 is good enough, you really don't need 10. And yes the transformer will reflect back whatever is the actually load. But I gets if you want the tubes to see a constant load you can put a resistor across the secondary. The resistor will add in parallel with the amp and the preamp will see the sum.
I do this across the output transformer of tube power amps. I'll use a 270 or 470 power resistor. The reason is to save the amp in case the speaker is not plugged in or the cable is cut or the voice coil burns up. The 470R is huge compared to the 8R speaker but tiny compared to infinity (infinity is the impedance of a blown voice coil)
Yes, 600 might be a better design goal than 10.
I still can't believe someone build an amp with such a low input impedance. You are right
ehh, I though two resistor values in paralel would always be less than the smaller one
"Add in parallel" was maybe confusing. I should have said "combine in parallel". The load on the output transformer will be one over the sum of the reciprocals.
I like using the load resistor because, As I said, "safety". It allows you to turn on the preamp with nothing plugged in
The other method is just to give up on building an all tube pre-amp and use a solid state output section
Is there a plan/schematic (or combination of them - like a plan) that you can point me to???, as I am new to this, and it would make much more sense from a workable practical perspective..., if possible/preferrable, some kind of 'triode' optimal low-zero noise configuration...
What you need is a "headphone amp"
Your requirements are almost unique. I doubt there is already something like this that some one could just link to. Not many power amps have such low input impedance. and few people would want to drive them with a tube based preamp.
My advice: Build something else as a first project. Perhaps a small tube power amp. But then you'd need speakers that can be driven with low power. Tube headphone amps are a good first project.
Oh. man, _slap forehead_, A headphone amp is very much like the thing you are looking for. I bet any of then would work.
Build a simple valve headphone amp and figure the first one is mostly for your own education, then build another. Along the way you will acquire skills and tools. Just start SIMPLE. and make the chassis over sized.
You can still decide on a transformer or not. I like them, others see then as big heavy $50 boxes. Google will turn up any number of headphone amp schematics
Your requirements are almost unique. I doubt there is already something like this that some one could just link to. Not many power amps have such low input impedance. and few people would want to drive them with a tube based preamp.
My advice: Build something else as a first project. Perhaps a small tube power amp. But then you'd need speakers that can be driven with low power. Tube headphone amps are a good first project.
Oh. man, _slap forehead_, A headphone amp is very much like the thing you are looking for. I bet any of then would work.
Build a simple valve headphone amp and figure the first one is mostly for your own education, then build another. Along the way you will acquire skills and tools. Just start SIMPLE. and make the chassis over sized.
You can still decide on a transformer or not. I like them, others see then as big heavy $50 boxes. Google will turn up any number of headphone amp schematics
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...what about a phono valve pre-amp?...or a combination of phono/headphone ideas for one?
hmmmm, this looks interesting...I wonder what the output impedence would be???
TUBE RECTIFIED STEREO PRE-AMPLIFIER KIT
TUBE RECTIFIED STEREO PRE-AMPLIFIER KIT
It's not all that special really..
The me-550 had a pretty usual input topography - the unusual low input impedance was set with a couple of resistors plugged into small sockets on the boards inside. Some people just cut or lifted a leg to give a more normal 50k unbalanced input that most things can drive. He used to have an info sheet he sent out regarding that.. Peter Stein's pre's were as powerful as little headphone amps (I used to drive my High impedance Sennheisers with them pretty happily.) but an all ME system, while about as dynamic as it gets, can be short on tubey warmth and depth of soundstage and plain listenability. A tube pre can be just the ticket to make low volume listening more satisfying and flesh out the acoustic guitar and vocals. I'm surprised Mr Stein didn't tell you though perhaps, like a lot of good engineers, he's better at answering the question you actually asked and not the one you *wanted* to ask. 8) I like ME stuff.. nicely made and great dynamics - very accurate, a lot like later Krell or Spectral. The 850 was pretty special with Apogees. A lot of them (all models) blew up for various reasons though.. they're not the simplest of animals and I guess that can be bad news for durability. Australia is also pretty harsh on high-bias power amps.. hell, it's not that habitable for humans a lot of the time!
The me-550 had a pretty usual input topography - the unusual low input impedance was set with a couple of resistors plugged into small sockets on the boards inside. Some people just cut or lifted a leg to give a more normal 50k unbalanced input that most things can drive. He used to have an info sheet he sent out regarding that.. Peter Stein's pre's were as powerful as little headphone amps (I used to drive my High impedance Sennheisers with them pretty happily.) but an all ME system, while about as dynamic as it gets, can be short on tubey warmth and depth of soundstage and plain listenability. A tube pre can be just the ticket to make low volume listening more satisfying and flesh out the acoustic guitar and vocals. I'm surprised Mr Stein didn't tell you though perhaps, like a lot of good engineers, he's better at answering the question you actually asked and not the one you *wanted* to ask. 8) I like ME stuff.. nicely made and great dynamics - very accurate, a lot like later Krell or Spectral. The 850 was pretty special with Apogees. A lot of them (all models) blew up for various reasons though.. they're not the simplest of animals and I guess that can be bad news for durability. Australia is also pretty harsh on high-bias power amps.. hell, it's not that habitable for humans a lot of the time!
Hey, thanks for that - that is what I figured. A tube-pre would be just the ticket.
Do you suggest I remove the resistors? Would sound quality be affected? (where are they lol )
Or just find a very low impedance (ie: 400ohm) tube pre, such as this one: 12AU7 Balance Tube Valve Preamplifier Amplifier DIY Kit ref AR (No Tube) | eBay
Do you suggest I remove the resistors? Would sound quality be affected? (where are they lol )
Or just find a very low impedance (ie: 400ohm) tube pre, such as this one: 12AU7 Balance Tube Valve Preamplifier Amplifier DIY Kit ref AR (No Tube) | eBay
Sound quality is not affected though the unit may be more susceptible to hum and noise if you have very high efficiency speakers. See if you can't get rage audio or Peter Stein to send you a diagram. They ought to have them somewhere. Or you can post a high res picture and we can point them out.. I'm going to guess that they will be 820 or 620 ohm resistors in single leg socketed pins. (It was a while ago regarding the value but I'm almost certain they were between 620ohm and 1k)
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This one looks like it could be a good one; not sure about the impedance tho: http://www.ebay.com.au/itm/JP-200-J...mplifier_Parts_Components&hash=item4ab888e981
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