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About zenelectro

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  1. 6C3CC tube driven SET amplifiers

    Those Merlot amps look sweet. I recently had a pair of Lamm 2.1 monoblocks come through for service. Built like trucks inside and out. WRT 6C33C - a great tube for SET.. and you can get some decent power without requiring crazy HT voltages. I measured the Lamms at over 20 watts / channel. They use an interesting arrangement where 1 of the 6C33C is used as a series regulator. As already stated a/ they require a decent driver b/ they are all over the place WRT matching c/ The biasing can also be tricky However don't let any of that discourage you - go for it. T
  2. The end of the road

    Those amps look awesome KKK, well done. Other amps in the same league - I have a pair of Lamm 2.1 Monoblocks in for repair which I'll be keen to listen to. Same power and over double retail price (when they were made) of the Artisan so I'd say you got a bargain. PS Just to add - I know Earle winds his own transformers so there's significant value added. The Semi-Pi wind OP transformer is a really good design, I've done a few myself over the years inspired by the original Lothar Keidel Pi wind done for John Burnett of Lenard Audio. T
  3. The peaking and distortion are most likely two separate things. The peaking will almost certainly be OP transformer related. Looking at 10kHz square wave response tells the story. The rising distortion versus freq could be any number of things. If the OP transformer has limited BW then this will affect FB and for stability FB has to be rolled off at higher frequencies. T
  4. Advance in Class D amps?

    Yes I was generalizing Zaph - you know that LoL FWIW - which pres were they and did you get chance to measure them ? Z
  5. Advance in Class D amps?

    It is linear due to the internal feedback and relatively low transconductance compared to BJT (or most high gm fets used for audio) If you degenerate a fet or bjt to have similar transconductance to triode and run into similar load they end up with fairly similar distortion (at low frequencies). Where the triode wins is a/ no voltage dependent capacitances b/ no thermal junction modulation related distortions But for most SS pre amps we are talking distortion levels that are way below triodes running open loop. Quite a few SS pre's have distortion so low it gets hard to reliably measure, IOW < 0.0005% or so (at low to mid frequencies). Where tubes really win is distortion versus freq. Very flat - due to those low V modulated capacitances. I think this flat dist versus freq characteristic is subjectively good for sound. As an example my latest Mic Pre design, which for all purposes is pretty similar to a MC pre save the EQ, has distortion at 100kHz that is not much different to 1kHz and at 60dB of gain. It's a tube / SS / transformer coupled hybrid, open loop (no feedback). One feature is you can manipulate the distortion characteristics to be H2 dominant, H3 dominant or mix them - or basically not have much distortion at all. So it's like baking a cake - add your harmonic ingredients Lots of fun and very useful for recording! Purists will disagree stating that adding ANY distortion is sacrilege - but to each their own - I disagree. Z
  6. Advance in Class D amps?

    Of course not, you know me better than that. I was generalizing. As a generalization most tube preamps have more distortion than SS preamps and they also sound different - although obviously there are exceptions. If you compare something like an RTP3 to a Messenger or Audio Note, the RTP will be much cleaner and have a lower distortion profile. Z
  7. Advance in Class D amps?

    Nice tidy layout. A lot better than the rubbish (mech layout wise) that most hi-end manufacturers dish out. Most small hi-end manufacturers need to get hold of a/ A decent mech designer b/ Someone who has actually serviced electronic equipment. Some of the stuff that comes across my bench leaves me scratching my head wondering if the genius designer ever serviced a piece of gear. 8itch session over LoL Z
  8. Advance in Class D amps?

    Read my post WRT audibility of distortions. Perfect match. Class D power amp + VHQ tube preamplifier. I can almost guarantee that this same class D amplifier married with a super low distortion SS pre amp would yield entirely different and much worse subjective results. Z
  9. Advance in Class D amps?

    Generally speaking class D amps have quite a different distortion profile than class A A/B amps. Also IME on a very good two channel system, the levels of distortion you can hear are actually very low. So the answer is almost certainly yes. I know others (Zaph) don't quite agree with this but I (and a former associate) did listening tests years ago. The results were a/ eye opening b/ contrary to what you might think WRT what actually sounds better. WRT a/, the levels are at least down to 0.00x % and probably down to 0.000x%. I couldn't reliably measure the distortions at our listening levels but had to extrapolate from levels of 20V RMS. The baseline distortion at 20V RMS of amplifier voltage stage (zero FB. gain 28 dB) was around 0.0004 to 0.0006% . At that level the AP system 1's THD+N was at it's limit. Adding small amounts of H3 and H2 changed the sound and actually made it sound better. Generally with most program, H3 was preferable. Also the effect was not really blatantly 'euphonic'. It actually sounded clearer and had better 3D image and separation with small amounts of H3. This is a very very complex area that I've only just touched on. To go into it in detail would require more than a complete thread - and I don't have all the answers anyway... or time, there's work waiting for me! But suffice to say IME you can hear very low levels in a very good 2 channel system. Obviously many other peoples views are contrary to this, that's fine. T
  10. Advance in Class D amps?

    There is no transition. Class D is always working as is the linear section (they call class A) I looked at the patent. It's a very very clever system. A good (and simplified) way to visualize it is a straight zero feedback buffer, this is the so called class A bit. There is a current sense on the buffer (this could be collectors going to PS rails) which than drives the class D section. The class D section, through feedback, works to keep the 'class A' section's current constant. It's actually quite a bit more complex with actually 2 phase shifted class D sections working through auto transformers and inductors at the OP however this is conceptually what is happening. It's a bummer the Stereophile review test measurements included the digital section (internal ADC etc) and didn't just measure the amplifier in isolation. It depends how well the patent is written as to what other novel ideas like this surface. I think topologies this are the future of class D. But I'm no class D expert so who knows Z
  11. Massdrop Topping DX7s DAC

    Anyone have specs for ES9038Q2M?
  12. Advance in Class D amps?

    Q - does anyone know what freq the Devialet class D OP stage works at? T
  13. Advance in Class D amps?

    Haha - it aint Perdy!
  14. Advance in Class D amps?

    Whether 3MHz is actually necessary is subject to debate. Just because someone here says so doesn't automatically validate such a statement. Putzeys is using from memory 400kHz on Ncore and makes good points WRT problems associated with raising switching frequency. 1.5MHz is almost 4 x that of Ncore and surely has to be enough. IMV clever (possibly hybrid) topologies are more likely the answer. The Devialet is certainly a very good concept and looking at the measurements on the Stereophile test, they are showing performance superior to most class D, especially at high frequencies. I am sure this would have taken some serious R & D. It's like a linear amp that has feedback loop driving class D current. Also note JA's comments WRT absence of HF switching noise. Another very good topology is Lab Gruppens class TD where the class D basically modulates supply rails of an AB amp. It's a linear amp but the power supply rails are going up and down with signal. As such the rails only need to be quite small. Very clever design. These are very high power pro amps for concert systems offering up to total 14,000 watts in 2 rack units. Probably not something for the lounge room T
  15. Non upsampling DAC experience

    Charles and I, years ago had a pretty good dialog on a designer to designer basis. If he really felt the 1704 was better, he would have said so. A very straight shooter sometimes to a fault. These were private discussions not public forum banter. T