Support Head-Fi.org by
starting all of your
Amazon.com shopping by
clicking here.
____________________________________________________________________
Today's Featured Head-Fi Blog: Jude's Blog
____________________________________________________________________
Please help
support Head-Fi by becoming a Contributing Member
CLICK
HERE -- Contributing Members, thank you
for your generous support! --
__________________
************************************************* "The only difference between me and a madman is that I am not mad."
- Salvador Dali
"We all agree that your theory is crazy, but is it crazy enough?"
- Niels Bohr
TEAM MILLETT MAX - TEAM BIJOU
TEAM HEADROOM - TEAM β22
Wait... you owe me beer too, don't you? I sense a conflict of interest...
Pete
Truth be told, and in a perfect world, half the DIY board owes you (more than) a beer... I'm sure my tab is at five or six, just based on your designs I have enjoyed / built.
__________________
Starters: Cambridge 840c -> ApureSound Balanced IC -> Blue Hawaii -> (Stax reterminated) HE60
Office: Sony DVP - NS775V -> OPUS DAC -> Millett Maximus Balanced -> APS v3 Balanced HD600 OR Enigma Oracle Balanced HD650
One answer is that I think the Amveco toroids actually sound better for less money. Or, the Lundahl LL1930's also sound better for about $40 extra (these use mu metal rather than amorphous cores and lack the shielding of the other Lundahls which is why they are less expensive. They are still quite good, and probably the best deal in the Lundahl line.) If you have the Hammonds, use them, but otherwise they probably aren't the best deal in the price range.
The other answer is that the Bijou is not really the ideal platform for transformer coupling. It will work, but the amp uses various features to obtain a low Z out, and my sense is that using those features is an either or with transformers. That is, transformers allow you to build much simpler circuits that use many less components -- less tubes, less capacitors, etc. The trade off, of course, is that you have to spend the extra money on the transformer. But, doing both in the same amp is probably not the best idea from a design perspective as I think it probably compromises both designs. That is to say, I don't think adding a pair of OPTs is going to bring much to the table.
I like to joke about the original L'espressivo being so cheap to build, but honestly, the only reason it ever becomes expensive is if you start adding expensive parts -- the parts list remains pretty constant.
Ok, the only reason I brought that up was Lo Z phones(K701) and NFB removed. The lower the impedance load, the closer to a shorted output. Just too large of a current demand that might be tamed with a matched OPT. Nates design here looks good. The Native Menace.
__________________
************************************************* "The only difference between me and a madman is that I am not mad."
- Salvador Dali
"We all agree that your theory is crazy, but is it crazy enough?"
- Niels Bohr
TEAM MILLETT MAX - TEAM BIJOU
TEAM HEADROOM - TEAM β22
__________________
************************************************* "The only difference between me and a madman is that I am not mad."
- Salvador Dali
"We all agree that your theory is crazy, but is it crazy enough?"
- Niels Bohr
TEAM MILLETT MAX - TEAM BIJOU
TEAM HEADROOM - TEAM β22
i was looking at the less-pressivo thread over at headwize, and that amp looks sweet. I like original design too, but too much money
i was curious with the balanced schematic why you put the cap between the halves of the transformer with no ground connection rather than at both ends with the centers grounded. it is still parafeed, and no current flows in the primary, but why drop the safety feature of having the transformer grounded?
__________________
Originally Posted by mkmelt
ACHTUNG - ALLES KOPFPHONERLISTENERS
Alles kopfphonerlisteners non-technischens! Das tubenmachine is nicht for gefengerpoken und mittengrabben. Oderwise is easy schnappen der springenverk, blowenfus, und poppencap, mit spitzensparken, und smokentubes. Geverken inside der tubenmachine is fur der experten only. Is nicht fur geverken inside by das dumpkopfen. Das rubbernecken amateuren keepen das cotton-picken hands in das pockets. Just relaxen, enjoyen der musik, und vatchen das pretty glowentubes.
i was curious with the balanced schematic why you put the cap between the halves of the transformer with no ground connection rather than at both ends with the centers grounded. it is still parafeed, and no current flows in the primary, but why drop the safety feature of having the transformer grounded?
So, two issues. The first is what it means to be balanced, and the second is the parafeed part. For my own personal safety, I don't believe in using balanced phones that have no connection to ground, especially with high voltage amplifiers. OPTs are inherently going to give out a balanced signal, but I always ground one side of the secondary. So, when I say balanced, I really mean that the amp is balanced throughout, but not on the output necessarily. If you really want to do balanced phones, I'd connect another wire to ground the body of the phones.
For the parafeed part, any high voltage amp (for dynamic phones) is going to have something between you and the high voltage. With OTL and most single ended parafeed, it is a capacitor -- parafeed (though not the original Espressivo) having a transformer too. With single feed designs, the primary of the transformer sits at a high voltage with the secondary grounded. With the balanced design, like the single feed design, the transformer acts as the block.
Your suggestion essentially puts a secondary safety measure in place. The down side is that, as drawn, the signal path includes 2 tubes, 1 transformer, and one cap. Your suggestion would add a second cap plus the biasing mechanism which would need to be bypassed with a cap (or LED) which would impact in the sound quality. But, being aware of these issues and knowing what stands behind you and oblivion, is important. I happen to trust transformers more than caps to block voltage.
Linear Mode
