Ha yes you're right! CT probably means they're not independant.
I'm in Taiwan right now.. I might go see James and investigate directly at the source one of these days....
if you look closely at this image : http://jianshin.myweb.hinet.net/Dscf0012.jpg , it seems that their CT's can be untied , in fact - that you need to tie windings for making CT
so - good for this purpose
so - good for this purpose
I completely agree. I read that F4 thread over and over until things sunk in.
I am really happy how the headphone amp turned out. The Jensens were such a nice touch. I need to order the ones mentioned in this thread. Nelson and Choky's suggestions are well worth considering 😉
yes, or the topology fromyou can always build Halcro
http://home.tiscali.nl/audio/FrontEndSchPcb.html
About the paper
http://home.tiscali.nl/audio/index.html
there is described an amp with such an approach to get very excellent measuring THD results.
About the paper
http://www.passdiy.com/pdf/zenamp.pdf
I read:
There are two most essential principles to audio amplifier design. The
first is simplicity. The second is linearity.
Einstein said: "Everything should be made as simple as possible, but no
simpler." Simplicity is a common element of the best and most subtle
designs. It is preferred for purely aesthetic reasons, but also because
fewer elements color the sound less, and lose less information.
Actually the opposite approach, for me the only right way in order to get good sonic results by listening tests.
Attachments
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franzm: The attached is a simplified output stage of a Threshold S/----[STASIS {R}] power amp. The highly linear NPN transistor voltage source amplifier [Nvs] controls multiple PNP transconductance amplifiers [Ptcas]. Nvs and P tcas are connected in parallel. Ditto for the complementary portion using the highly linear PNP voltage source amp [Pvs] and its affiliated NPN transconductance amplifiers [Ntcas]. Maybe your question pertained to this particular combination in the attached schematic. {1}: [Nvs] and [Ntcas], and its complement {2}: [Pvs] and [Ptcas]. Clearly each of {1} and {2} are configured like the output stage of F6 [e.g Nvs common collector loaded with a common emitter Ntcas]. Will their operation be like F6?
DIYers visiting Jensen and Lundahl websites will find schematics of their transformers driven by operational amplifiers [OAs] . The attached schematic is a "new" one to add to their collection. I will not be surprised if this was done exactly somewhere else. A year ago, I needed to simultaneously attenuate, and ground-loop isolate the generous output signal of a compact disc player. I used a stepdown transformer [to attenuate] by Xicon [published response of 300 Hz -3.5Khz]. Two OAs [a dual OPA 2134] drove its primary out of a phase. The loop feedback of the OAs gave an output [at the secondary] frequency response which was flat [30 Hz -10 KHz; as seen on the scope]. So what?
- A certain DIYer may wish to use the general topology of the attached schematic in an F6 application; despite the clear simplicity of the front end of F6.
- Summing junction of OA2 [or its non-inverting port] may be the loop feedback point from the power output stage; speculation on my part.
- A DIYer may wish to lower the power of F6 to make a headphone amp. I have 2 working prototypes [of the attached] which are great headphone [GRADO SR-80i] amps. The lows are rich and the highs are detailed. A testament to the high quality of the topology; despite the limited frequency response of the Xicon transformer.
Audio Transformers book chapter
I found a very useful book chapter on audio transformers, by Bill Whitlock of Jensen Transformers. http://www.jensen-transformers.com/an/Audio Transformers Chapter.pdf
I found a very useful book chapter on audio transformers, by Bill Whitlock of Jensen Transformers. http://www.jensen-transformers.com/an/Audio Transformers Chapter.pdf
Thanks for the info. Last time I read it, I paid particular attention to "reflected impedance". Mr. Whitlock is a bright and knowledgeable scientist. He has also written other application notes; for example Jensen AN 003. It is entitled "Interconnection of balanced and unbalanced equipment". In it he showed schematics of Jensen transformers driven by operational amplifiers.
Pure Symmetry Lost
Now I understand why 0.1% THD at 1 watt might be expected, unless there are some tricks to be discovered.
The Jenson JT-123-FLPCH has inter-winding capacitances of 18nF. When these are taken into account, "pure symmetry" is lost because the secondary for the upper FET is moving with the output signal, vs the secondary of the lower FET is at a nearly constant voltage. The result is that the capacitive coupling to the gates introduces significant 2nd harmonic.
Now I understand why 0.1% THD at 1 watt might be expected, unless there are some tricks to be discovered.
Does the lack of symmetry come from the fet phase splitter in the PLH or the load that is presented to it by the two different output fets. Sy's impasse article states that a phase splitter is symmetrical if presented with a symmetrical load. I wonder if it is possible that the use of the transformer has manipulated the output into presenting the transformer with a symmetrical load. Here is a reference for the possiblity of the idea.
6C33C-B OTL Amplifier - Background and OTL Circuits
Nelson says its a classic, but i have a feeling that his "classic" is going to have a clever spin on it. taking something old and making it "new". No student is greater than his teacher.
6C33C-B OTL Amplifier - Background and OTL Circuits
Nelson says its a classic, but i have a feeling that his "classic" is going to have a clever spin on it. taking something old and making it "new". No student is greater than his teacher.
every good teacher is streaming exactly to opposite , even if just rare ones will better him .
anyway - study of magnetic apparatus's is good thing , but do not expect that numbers will tell most important part of the story ......... which is also hard to measure
feel of continuum is probably most important nominator of said quality .
regarding symmetry - where I'm not loosing my sleep about that issue too much - off course that symmetry will be easier to maintain in F5-like circ but , as with all things in life-one must choose his compromises ;
it's relatively easy to see how many -properly made- sub-blocks are substituted with just one xformer ........
of course that amp will measure better with all that electronic sub-blocks shebang ; but - I have strong feeling that that gizmo will be lacking in one important area of sound - immediacy , comparing with xformer solution
it's relatively easy to see how many -properly made- sub-blocks are substituted with just one xformer ........
of course that amp will measure better with all that electronic sub-blocks shebang ; but - I have strong feeling that that gizmo will be lacking in one important area of sound - immediacy , comparing with xformer solution
nice word ZM!
PS
we need 3diapason.... 😉PS2
DiyAudio not sure that we need this emoticon :
What is the open loop gain of the proposed F6? Some of it needs to be sacrificed in order to lower intrinsic distortion and linearize the operation of the device.