This is a offshoot from my "EL34 Schematic confusion" thread.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=69042&perpage=10&pagenumber=8
so far we have an ECC88 based crossover and 2 x ECC88-6SN7-EL34 based power amps.
Crossover: 2 x ECC88 (Steve Bench ckt)
Line Stage: 4 x ???
Power amp: 1x ECC 88 AF, 2 x 6SN7 Phase Splitter, 4 x EL34.
octal: ECC88 (4), EL34 (8)
nonal: 6SN7 (4)
However since my power amps will be about 10m away from my preamp (no space near the pre amp) but I can hide the power amps behind the speakers (push - push).
what line drive will do. I was looking at the 6SN7 shown below
http://www.tubebuilder.com/images/schematics/preamps/6sn7_sig.gif
http://www.diyaudio.com/forums/showthread.php?s=&threadid=69042&perpage=10&pagenumber=8
so far we have an ECC88 based crossover and 2 x ECC88-6SN7-EL34 based power amps.
Crossover: 2 x ECC88 (Steve Bench ckt)
Line Stage: 4 x ???
Power amp: 1x ECC 88 AF, 2 x 6SN7 Phase Splitter, 4 x EL34.
octal: ECC88 (4), EL34 (8)
nonal: 6SN7 (4)
However since my power amps will be about 10m away from my preamp (no space near the pre amp) but I can hide the power amps behind the speakers (push - push).
what line drive will do. I was looking at the 6SN7 shown below
http://www.tubebuilder.com/images/schematics/preamps/6sn7_sig.gif
Hi navin,
You need to get the lowest impedance output with the lowest distortion possible. Balanced lines wouldn't hurt depending on how much electrical noise there is in the area.
You may be further ahead to drive a transformer coupled balanced line. Everything is a trade off. The answer depends on what your biggest problems are in your house. You may not know this until everything is built and you switch it on.
-Chris
You need to get the lowest impedance output with the lowest distortion possible. Balanced lines wouldn't hurt depending on how much electrical noise there is in the area.
You may be further ahead to drive a transformer coupled balanced line. Everything is a trade off. The answer depends on what your biggest problems are in your house. You may not know this until everything is built and you switch it on.
-Chris
My Heretical article (http://www.diyaudio.com/forums/showthread.php?s=&threadid=58757) is a reasonable tutorial on CF design. You don't necessarily need the bells, whistles, transformers, and servos I threw in, but a high gm triode and a current source can do wonders.
Whoa! I take that back. I was thinking that you have 30' cables, not 30 meter. That's about 100 feet. At 100pF/meter as a typical value for shielded cable, that's 3000 pF. You'd need a much bigger, heftier cathode follower than I think is reasonable For a line that long, I'm with Chris, transformers and 600 ohm balanced line.
SY said:
i did consider the Ecc81 and 82 but feared their reputation for stridency.
BTW I know you have answered this before but since m sources are all line level high impedance why the input transformers. OPTs in understand as tube impedances are 1000 time higher that of my speaker but the output impedance of my source is on the order of 10K and so is the input impedance of the ECC88.
Hi navin,
One of the things about the preamp to amplifier link are the very low levels that are present. This connection is almost as delicate a signal as your phono to preamp link. I vote for balanced, using transformers. I don't like transformers, but if you are going to run the signal that far, treat it as a studio mic signal.
This is the reason I speak out when I hear people placing the amplifiers near the speakers to reduce the speaker cable run. It's the opposite thing you want to do. You don't have a choice, so do it the best you can. Read SY's article and build something to drive the transformer. Use a transformer at the other end too. CMRR is important here (it's the whole point really).
-Chris
One of the things about the preamp to amplifier link are the very low levels that are present. This connection is almost as delicate a signal as your phono to preamp link. I vote for balanced, using transformers. I don't like transformers, but if you are going to run the signal that far, treat it as a studio mic signal.
This is the reason I speak out when I hear people placing the amplifiers near the speakers to reduce the speaker cable run. It's the opposite thing you want to do. You don't have a choice, so do it the best you can. Read SY's article and build something to drive the transformer. Use a transformer at the other end too. CMRR is important here (it's the whole point really).
-Chris
SY said:
Though some would argue that the increasing input impedance and decreasing output impedance as you step down is a plus. In fact, the primary reason for using a TVC.
But in my experience, I've found transformers sound their best when they're working into their ideal load. With TVCs and autoformers, you effectively have x number of transformers, which means that only a few positions can possibly have their ideal load.
A good example of this is the review of the Sonic Euphoria autoformer volume control in the January issue of Stereophile.
Depending on where you have it set and what the load impedance is, it can have as much as a 13dB resonant peak at about 50kHz which will give you some very nasty group delay in the upper portion of the audio band.
Personally I've always felt that the biggest advantage of the TVC was really just the "T" part. And I've always had excellent results using a fixed, 1:1 input transformer coupled to a passive attenuator of the value of the transformer's ideal load.
se
anatech said:
so a nice choice would be to hide the the power amps somewhere close to the crossover/line stage.
Q: How long a cable can a transformerless line stage drive? and what tube is normally used for such line stages. 3m?
my present system is SS (live level preamp suing relay switching and a OP275 driving a power amp using 3 pairs (per channel) of 2 SJ50, 2SK 135 (1200VA trannry). It is clean and clinical and can provide goosbumps at times but I am hoping to take things to the next level by using tubes and going active (no passive crossovers).
navin said:
octal:6SN7, EL34
noval: ECC88
It depends of the preamp, the cable and the amp characteristics.
However, the ground loop is the biggest problem in a long unbalanced connection, IMO.
Transformerless? 6C33.
My vote goes to the balanced output with the output transformer.
Regards,
Milan
moamps said:
octal:6SN7, EL34
noval: ECC88
It depends of the preamp, the cable and the amp characteristics.
However, the ground loop is the biggest problem in a long unbalanced connection, IMO.
Transformerless? 6C33.
My vote goes to the balanced output with the output transformer.
yes the ECC88 is noval and the 6Sn7 is octal. sorry.
how long is long? 1.5m? 3m? 5m?
i dont want to add any more transformers than absoltely nesscary. i'd rather find a location for the power amps that is closer.
I was thinking of a 6SN7 line drive.
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