Attention: Many of these amplifiers need a constant impedance variable attenuator at the output to protect ears from irreversible damage. At your own risk.
The excellent Sennheiser HD580 have each moving coil at 300Ω which is very nearly to the 600Ω or 200Ω pro audio protocol. So there is impedance match and an amazing sound comes from these world class pre amplifiers.
As of writing this post Insensatez - Antonio Carlos Jobim plays on the Sennheiser HD580 headphones at pristine quality. Each voice coil is driven by just one Pleiades 2N3053. One 2N3053 transistor is used for each channel from CD player to each headphone voice coil. So 2 transistors, 2 biasing resistors, 2 rheostat resistors connected to the base for volume control. And just a 1.3V battery for power supply. And it sounds amazing. Why should it not? It is such a simple and pure signal path.
All the amplifiers on the title of this post have given world class sound quality on the HD580 headphones on various Pleiades experiments.
Exceptional sound for example was from 2 hand built Altec 436C with Sowter octal base transformers for both inputs and output. On those Pleiades versions the modifictaion consulting the Kurt Singer US 2357696 patent was done with fabulous results. (If memory is correct there is description on a previous euroelectron post on this brilliant dynamic patent of supplying side chain feedback from the second stage cathode to the first stage cathode?). 600Ω constant impedance attenuators were connected between the each Altec channel and headphone voice coil. There is an amazing bass sound on this setup. And everything else sounds big too.
As this post is being written track 15 plays on the Jobim CD and the bass is breath taking and smooth. And everything else big too and natural. With just one 1.3V battery and 2 power transistors. There may be some instanteniously peak limiting by the gentle non linearity of the transistors at higher signal level. This is non linearity peak limiting not to be confused with side chain automatic gain control. In the classic electron tube limiters both effects may be taking place at high levels.
At very high level of audio engineering compressors or limiters are normally not needed. See for example Bruce Swedien, Al Schmitt interviews.
So we may be left with EMI RS61, Telefunken V72. On Pleiades experiments many other world class circuits have been built like the classic U47 head amp. It cannot remembered if this was used to drive headphones too. By the way another excellent circuit is the RCA BA-2C microphone booster amplifier. This circuit was not built. Live mic, headphone experiments with RS61 driving the HD580 for example were written up on previous electron posts.
Also on earlier Pleiades expeeiments a E88CC 2 stage log tailed pair for each channel was built. Both input and output transformers were Sowter. It can drive hi impedance headphones to exceptional quality when microphones are connected to its input. At the time only a Shure Unidyne B was available and a no name directional moving coil mic. They were used at about 1ft to minimize some proximity effect. The sound quality by the headphones in real time is so good. A very natural voice in almost binaural. Amazing sound. It was also tested with a direct speaking person and a different listener. Why should it not sound great? Just 2 double section electron tubes for each channel from production to reproduction in real time. The Grampian GR1/L ribbon microphones could not be tested in this way because of the proximity effect. For ways to make them sing at small distance too see other euroelectron posts.
Where might this lead too?
Can the signal path be even more simplified with still better sound and even lower possible noise?
The Pleiades V6 can be thought of as the child of the Neumann U47 amplifier and the BA-2C microphone booster amplifier. See the relevant euroelectron post.
Note: the headphones have been removed. Sound may be too loud for safety. Still on the Jobim CD. All instruments can be greatly heard while the headphones lie on a nearby pillow. How can this tiny Pleiades 2N3053 amplifier sound so big with just a 1.3V battery? Tubes vs transistors (vs op amps) - Russel O. Hamm may be part of the answer.
Back to the Pleiades V6 microphone booster amplifier. It sounds amazing, the electron tube is powered by just a 4V battery. It may even drive the HD589 headphones but not to a high level. Unless it is supplied by 12V to the anode of its electron tube, the triode connected EF183. And at least one driving stage is needed if a mic is connected up.
The Pleiades 2N3053, just one transistor per channel and no input or output transformer can drive the HD580 headphones to a presumably safe loud sound and pristine sound quality. It has also very interesting gentle overload characteristics. In the same game level as the Pleiades Electra II. At the moment the Electra II sound can presumably go to higher level as the 12K5 electron tubes are powered by 9 volts. The circuits are very similar as just one device is OTL or direct connected with no output transformer to the headphone voice coil. Everything in class A (electrons flowing all the time and this also includes the headphone coil themselves). They are single ended amplifiers.
So how about connecting a Pleiads V6 or V5 directly to the Pleiades 2N3053? This should be a world class setup from producer's to listener's brain (in the same room at least) with just 3 amplifing stages at max. For distribution of sound of course the V6 can be used on the mic side and any known channel can be used, and the listener's brain can hopefully enjoy a simple to build Pleiades 2N3053 amplifier.
Advantages of such input (producer's side) or output (listener's side) amplifiers are: Lightweightnesss, portability, power by battery, minimum number of components for the purest possible sound. Class A operation. Everything operating in pure class A.
For example the Pleiades V6 can be driven by a world class omnidirectional moving coil mic such as DP4/L DP4, MD21, MD211 etc.
The Pleiades amplifiers are open source. Relatively easy to built. Even the electron tube versions are portable using battery and can be taken to field. Forest. Beach. Why should someone do this? The sound of nature is already there and so beautiful (acoustics are great).
Other relevant to this post Pleiades experiments not done yet are a mic feeding V6 feeding 2N3053 feeding the PHILIPS AD5046N 800Ω loudspeaker live, in real time. Or an amplifier such as the world class EMI RS61 or Telefunken V72 etc feeding directly this amazing loudspeaker. Each driven be the Pleiades V6 microphone head amplifier.
No comments:
Post a Comment