Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > The lowest distortion way to build the output stage of a solid state > power amp is a carefully biased class AB. The trick is to come up with > the right bias as a function of current and temperature. Needless to say > this is far from being an insurmountable problem as long as you stay > away from pure class B or pure class A. As with many things in life, the > optimum is a carefully chosen mean or compromise. > > If you depart from the ideal too far in the direction of Class B you get > crossover distortion which is especially bad sounding because it affects > sound quality at all power levels. > > If you depart too far from the ideal in the direction of Class A you > have a problem with what is called gm doubling. This is a fairly deep > technical issue further elaborated on by Douglas Self in his various > well-known publications related to power amp design and also > 'Douglas-sel on SS power amps,' > (http://douglas-self.com/ampins/dipa/dipa.htm#5) as well as 'Solid State > amplifiers by teemu_kyttala_v1.0.pdf' > (http://www.thatraymond.com/downloads/solidstate_guitar_amplifiers_teemu_kyttala_v1.0.pdf). > I have personally observed and addressed this problem in my own > unpublished power amp designs. Hi Arny! Thank you for your clear response. I'm probably best off with my Class A/B Logos which at least sounds as if it's done well, and save money by avoiding the pure Class A Inpol 2. I suspect you've just saved me from falling for an expensive "down-grade"! Dave :) Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Julf wrote: > As one part of the monitoring chain, yes, but it is becoming less > common. For near-field monitoring, studios use active monitors that have > class D or A/B amps built in, and for listening room use class A amps > don't have enough power for modern, power-hungry speakers. > > IM distortion, just like HD, is caused by non-linearity. A badly > designed class A/B amp can have nonlinearity caused by the (gradual) > transfer from class A to B, and push-pull designs can have crossover > distortion. Neither are an issue with most class D architectures. Hi Julf! Thought I'd reply to your second post of the day, although I found your potted history of Bell Labs interesting as well. My own gear consists of a Class A/B hybrid (but with the twin triode valves used in the pre-amp stage & MOSFET's used in the power amp)Pathos Logos amplifier driving my 2-way minimal crossover B 805S loudspeakers. Then I have 2 B PV1 subwoofers (which each contain a 500W Class D amp) connected in true stereo from the speaker posts of the Pathos amp which very handily has banana plug sockets built into its massive metal clamps. None of this gear represents the respective manufacturers' very latest takes on the subject, but I'm happy with the sound I get in my modest room. The Logos amplifier is biased to produce its first 30W in Class A, before a hopefully well-implemented transfer to Class B offering 110W into 8 ohms, or if you'd prefer 220W into 4 ohms. This simple doubling-up does suggest that they have made a decent fist of the power supply at least. It measures well (Pathos quoted specs: 2Hz-200kHz +/- 0.5dB; <0.05% THD (unspecified frequency/power); S/N >90dB; input 100KOhm) & doesn't sound particularly "tubey", so hopefully they've got the triodes operating in the linear range alluded to by Arny. Pathos's published design rationale is "valves are best for voltage amplification, solid-state devices are best for current amplification" which seems to an extent to chime with Arny's comments about the linear/non-linear range of valves, although I suspect it's something of an over-simplification for marketing acceptance. You can't really blame them for not wanting to give all their commercial secrets away. The Mk. 2 version apparently has some subtle improvements to the pre-amp stages, and the option of an inboard DAC giving it 9 inputs (2 digital, 2 balanced XLR analogue & 5 unbalanced phono analogue) whereas mine only has the latter 7. I wouldn't swap my Mk.1 since I don't need the DAC, but I might be tempted by their 50W pure Class A hybrid Inpol 2 amplifier at the right second-hand price: 50W per channel would be quite adequate given the size of my room, & I'd still have the 1000W of combined Class D amplification in the subwoofers to back it up where the main power of the frequency range for a music signal occurs. I bought my Logos second-hand from the dealer in Oxford who had supplied it new (I presume 4 years earlier) for 50% of the then going new price. I've used it extensively for nearly 8 years now & it's only popped 1 valve (heater element) in that time which also took out an internal board-mounted 1A fuse in the pre-amp stage obviously. I was able to sort this myself although I did have to buy a small set of hex drives since my screwdriver set didn't have one small enough to get the lid off. Blew a bit of dust out for good measure & fitted a matched pair of new Phillips tubes from Watford Valves who supply mainly musicians with a penchant for Marshall speakers with their valve amplification: again no silly prices, think I paid about £30 a pair. Got a spare set which may need to be used for the Digit, since the tubes are the same type. Have to confess now that I did have them cryogenically treated, not because I thought it would affect the sound but because it was a cheap option which I thought -*might*- improve longevity. Anyway they're doing well so far, & as far as I could tell (accepting Arny's point about forgetting after 20 seconds, which may yet consume the rest of my perception, who knows? I'm certainly not getting any younger) but could easily have simply been down to the original Sovteks being a bit tired if it was a genuine effect. I must confess that despite the size & weight of the beast, I had expected the box to be relatively empty, governed by the size of the large heat-sinks necessary to avoid the use of noisy cooling fans. Couldn't have been more wrong, it's full of stuff - there are pictures on Google images you can't miss if you're at all interested. It took me back to the practical difficulties in achieving Peter Walker's "straight piece of wire with gain" definition of the perfect amplifier... It nearly broke my heart that I couldn't find any of the B 805S's for sale second-hand anywhere back in 2009, so I had to visit their Portsmouth dealer Audio T to negotiate a new pair. Thankfully they didn't have any in stock. The salesman enquired slightly desperately whether I wouldn't
Re: [SlimDevices: Audiophiles] Intona USB thing
darrenyeats wrote: > Arny, that's one thing Siegfried states. > Please remember that you brought this document into this discussion to apparently counter my comments about IM. That you seem to feel to do such a thing tells me that you don't understand what I'm trying to say. > > Also, he rates the drivers by HD and picks them on a combination of IM > and HD performance. Implying HD is significant and not made moot by IM. > Again, it appears that you are not understanding the core of this discussion. > > I do see your point TBH, I just think you're over-egging the pudding. You appear to be grasping at any straw to avoid the point of my comments. Let me throw a few more eggs at the problem: ;-) (1) THD and IM are not forms of distortion. The forms of distortion are linear and nonlinear distortion. Not seeing IM or THD on that short list, they must be absent for a reason and the reason is that they are irrelevant to a discussion of forms of distortion. I say so, Geddes says so, Linkwitz says so, a ton of other recognized authorities you may not have heard of say so, by gosh it could even be true! ;-) (2) Well then, what are THD and IM if they are not forms of distortion? They are means for characterizing or quantifying or measuring distortion. They are means, not the ends. Are cubic centimeters a form of automobile engine displacement? No! Cubic centimeters are a means for characterizing or quantifying or measuring engine displacement. (3) THD and IM are means for measuring nonlinear distortion, so what is nonlinear distortion? Nonlinear distortion is a something whose fundamental cause is things that take in one tone and put out more than one tone, where the additional new tone(s) have a more-or-less consistent correlation with the input. This contrasts with noise and interfering signals where that correlation is random. This contrasts with frequency response and phase distortion where the same tones that go in, come out but with their relative timings and/or sizes changed. (4) Can you estimate IM given THD or vice-versa? Yes you can. The procedure is that you estimate the underlying form of nonlinear distortion from either THD or IM measurements or better yet from a FFT analysis, and then simulate the other measurement based on what you find out about the distortion mechanism at hand. This would be more popular except for the fact that are about an infinite combinations of number of tones, tone frequencies, and tone amplitudes for measuring THD and IM, and the relationship depends on which set(s) of tones you chose to compare. My point is that if you have IM, you have THD and vice versa. They are basically equally important because they are like two sides of the same coin, and the coin is named *nonlinear distortion*. Harmonic distortion can possibly be euphonic or at least hard to detect because it is often masked by the harmonics that are already naturally in the music. IM has this nasty strong tendency to sound ugly to most people, except possibly people who like things like Punk Rock or Heavy Metal. Thing is, Deep Purple sounds better to me on a measurably clean system than a dirty one. The fact that the mainstream of audio is highly dependent on the existence of gear with vanishing or at least inaudible distortion is a matter of historical fact. Of course like most avocations there are many tiny niches in audio that may defy conventional logic. arnyk's Profile: http://forums.slimdevices.com/member.php?userid=64365 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Golden Earring wrote: > Hi Darren! > > I'm most interested to hear Arny's take on solid-state Class A with > regard to IM. I know that most recording studios use Class A amplifiers > in their monitoring chain. > > The lowest distortion way to build the output stage of a solid state power amp is a carefully biased class AB. The trick is to come up with the right bias as a function of current and temperature. Needless to say this is far from being an insurmountable problem as long as you stay away from pure class B or pure class A. As with many things in life, the optimum is a carefully chosen mean or compromise. If you depart from the ideal too far in the direction of Class B you get crossover distortion which is especially bad sounding because it affects sound quality at all power levels. If you depart too far from the ideal in the direction of Class A you have a problem with what is called gm doubling. This is a fairly deep technical issue further elaborated on by Douglas Self in his various well-known publications related to power amp design and also 'Douglas-sel on SS power amps,' (http://douglas-self.com/ampins/dipa/dipa.htm#5) as well as 'Solid State amplifiers by teemu_kyttala_v1.0.pdf' (http://www.thatraymond.com/downloads/solidstate_guitar_amplifiers_teemu_kyttala_v1.0.pdf). I have personally observed and addressed this problem in my own unpublished power amp designs. arnyk's Profile: http://forums.slimdevices.com/member.php?userid=64365 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Golden Earring wrote: > I'm most interested to hear Arny's take on solid-state Class A with > regard to IM. I know that most recording studios use Class A amplifiers > in their monitoring chain. As one part of the monitoring chain, yes, but it is becoming less common. For near-field monitoring, studios use active monitors that have class D or A/B amps built in, and for listening room use class A amps don't have enough power for modern, power-hungry speakers. IM distortion, just like HD, is caused by non-linearity. A badly designed class A/B amp can have nonlinearity caused by the (gradual) transfer from class A to B, and push-pull designs can have crossover distortion. Neither are an issue with most class D architectures. "To try to judge the real from the false will always be hard. In this fast-growing art of 'high fidelity' the quackery will bear a solid gilt edge that will fool many people" - Paul W Klipsch, 1953 Julf's Profile: http://forums.slimdevices.com/member.php?userid=42050 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
Golden Earring wrote: > Still catching up here. I hear you about Bell Labs, they were a big > outfit. I believe it was 2 of their engineers who inadvertently > discovered the Cosmic Background Radiation that resulted in the general > acceptance of the Big Bang hypothesis for the origin of the universe, > although they were trying to eliminate what they initially perceived as > interference with equipment they were using for a different purpose > altogether. Part of Bell Labs remit may well have included high quality > sound reproduction, but I should imagine that in those days the focus > would primarily have been on cinema sound systems rather than domestic > ones. Please correct me if I'm wrong on this. As I recall the DIY > approach to quality home sound reproduction was much in vogue through > the 50's & 60's with many people building their own amplifiers & > loudspeakers based upon freely available designs. Times have changed. > Bell Labs in their glory days was a great place. I have had the pleasure and honour to visit a number of times, and to know and work with some of the research people there - and having grown up and worked in the technology industry in Finland, I still can't get my head around the fact that it is now "Nokia Bell Labs". There were two standard jokes about Bell Labs - one was "even the janitor has a PhD", the other, from the AT business people, "hundreds of wonderful technologies, not a single successful product". One has to remember that a lot of the research at Bell Labs was basic research, not directed at any specific product or business. So no, they didn't focus on cinema sound - they focused on things like the science of sound and hearing. Shannon's work was basic information theory. Bardeen, Brattain and Shockley's work that led to the transistor was basic semiconductor physics research. The original Bell Labs was split up, most of it becoming Lucent Technologies (and retaing the Murray Hill location), but the voice-oriented stuff (including JJ Johnston's perceptual compression research that led to mp3) ended up in AT Labs in Florham Park "To try to judge the real from the false will always be hard. In this fast-growing art of 'high fidelity' the quackery will bear a solid gilt edge that will fool many people" - Paul W Klipsch, 1953 Julf's Profile: http://forums.slimdevices.com/member.php?userid=42050 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
darrenyeats wrote: > Army, that's one thing Siegfried states. > > Also, he rates the drivers by HD and picks them on a combination of IM > and HD performance. Implying HD is significant and not made moot by IM. > > I do see your point TBH, I just think you're over-egging the pudding. Hi Darren! It's always difficult to make a complicated point by simplifying to the maximum extent without oversimplifying it. I think that Arny is doing his best to make his clearly expert understanding accessible to us, & that both of you are raising valid points. IM is truly horrible & I am currently enjoying a 1st rate live recording of The Allman Brothers Band playing the Fillmore East shortly before it closed for good in 1971. To have my subwoofers roaring away whilst enjoying crystal-clear percussion is immensely enjoyable: whether my neighbours agree remains a moot point. I'm most interested to hear Arny's take on solid-state Class A with regard to IM. I know that most recording studios use Class A amplifiers in their monitoring chain. Dave :) Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > That Linkwitz Lab page seems to support my claim: "The distortion > spectrum of this test signal is very discriminating and robust. It > contains not only harmonics, but also *the more serious intermodulation > components, which are of higher amplitude*. " Army, that's one thing Siegfried states. Also, he rates the drivers by HD and picks them on a combination of IM and HD performance. Implying HD is significant and not made moot by IM. I do see your point TBH, I just think you're over-egging the pudding. Check it, add to it! http://www.dr.loudness-war.info/ SB Touch darrenyeats's Profile: http://forums.slimdevices.com/member.php?userid=10799 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > Bell Labs (who no longer exist) concerned themselves with far more than > mere telephone conversations. Given your probable age you should > remember when about half of all movies featured "Western Electric Sound > System" in their credits. If you are familiar with large corporate > arrangements of the day, Western Electric was the manufacturing division > of American Telephone and Telegraph (AT) and their research devision > was called "Bell Labs" IOW, high quality sound was part of their agenda. > > There is a principle called extensibility or scaling. Basically, in very > many cases high performance is obtained using the same basic principles > as is used to achieve lower level performance, they are just logically > extended by carrying them a little further. This is abundantly true for > audio. If modest frequency response and distortion yields good speech > performance, extending the relevant technology along existing clear > paths yields far better performance, and excellent high fidelity will > result. This is particularly true of audio, and even more true of > digital audio. It shows up in the development of digital audio in that > many of the same research organizations as developed digital > switchboards extended the same basic technology and within 10 years > their digital hardware were producing commercial digital recordings that > sound excellent to this day. > > > > That is a pretty brave dare because if you actually do it, the resulting > sound is actually pretty good, and it gets even better when leave a > component that is superfluous for recording and playback namely Skype, > out of the system. OTOH, even the sonic and visible performance of Skype > continues to improve. > > The technical performance of modern PC sound systems is in the same or > better than best audio CDs, and in fact millions of audiophiles use > their computers or cell phones (whose basic audio systems aside from the > cell phone system) is comparable or better than the best audio recording > and playback systems that were in use for the most critical professional > work not that many years ago. In fact most technical advances beyond > current cell phones and PC's have no scientifically demonstrable audible > advantages. > > > > What a wad of Poorly informed falsehoods! Hi yet again Arny! Still catching up here. I hear you about Bell Labs, they were a big outfit. I believe it was 2 of their engineers who inadvertently discovered the Cosmic Background Radiation that resulted in the general acceptance of the Big Bang hypothesis for the origin of the universe, although they were trying to eliminate what they initially perceived as interference with equipment they were using for a different purpose altogether. Part of Bell Labs remit may well have included high quality sound reproduction, but I should imagine that in those days the focus would primarily have been on cinema sound systems rather than domestic ones. Please correct me if I'm wrong on this. As I recall the DIY approach to quality home sound reproduction was much in vogue through the 50's & 60's with many people building their own amplifiers & loudspeakers based upon freely available designs. Times have changed. The reason that I suggested using Skype was precisely because its main design priority must have been to get acceptable results given hardware limitations. I accept that as these hardware constraints relax, better & better performance will be easier to achieve. You would have a similar constriction if you interposed a telephone landline or indeed a mobile phone call but it would be more difficult to use an external microphone which would feed a decent signal into either of those communication systems, which is why I suggested Skype. The only reason that I raised this point was to reference the kind of real world applications Nyquist in the 20's & Shannon et al in the 40's/50's were directly concerned with. I take your point about extensibility, & this is great because we don't have to keep we inventing the wheel. There must be some additional design input in coming up with something that works well in a new area though, surely? I expect you'll tell me that this is a poor analogy, but an ox-cart (which is designed for neither comfort nor speed) does not need pneumatic tyres on its wheels even though they are round (basic principle ready to be extended). A stretch limo (which favours comfort, but would not corner well at speed) will definitely want pneumatic tyres on its still-round wheels. Finally my sports car (which has a firm ride some of my passengers have found to be lacking in comfort - shame, but which will wriggle its way around Goodwood at speed) has low-profile pneumatic tyres on wider than standard but still round wheels, which incidentally are lightweight to boot to reduce the "unsprung" weight on the outside of the firmed-up suspension system. I think that there has to be a limit on this "convergence" thingy
Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > That Linkwitz Lab page seems to support my claim: "The distortion > spectrum of this test signal is very discriminating and robust. It > contains not only harmonics, but also *the more serious intermodulation > components, which are of higher amplitude*. " > > If you listen to anything but simple test tones over a system with > nonlinear distortion, you will hear IM. It is probable that the IM will > predominate because of its nature. (explained by means of a simple > example, below)" > > The only way to have the HD profile be a greater factor than the IM is > to listen to pure test tones. As soon as you start listening to music, > the IM will overwhelm the harmonic distortion. > > Let's say that you have an amp that has only a second order nonlinearity > that is as large as possible. > > If you put in 1KHz, you will get out a 2 KHz tone half the amplitude of > the input wave, plus a DC signal that is also half the amplitude of the > input, but since your speakers and ears dont' respond to DC, it will be > inaudible. > > If you put in a 1 KHz tone and a 1.5 KHz tone that are together the > same amplitude, you will make each half the maximum amplitude so they > don't clip when you sum them. > > Due to the *same nonlinearity *you will get a 500 Hz tone, a 2 KHz tone, > a 2500 Hz. tone and a 3 KHz tone. * Right off you get about four times > as many audible distortion-related spurious responses.* The 500 and > 2500 Hz tones are about half the size of each input wave, and the 2 KHz > and 3 KHz tones are about half as large as them. So, the spurious > responses from the IM are all audible and when added together have a > about double the percentage as the one audible tone from the harmonic > distortion. > > Thus the IM will overwhelm the harmonic distortion. Furthermore the > harmonic distortion is likely to be masked by the natural harmonic > structure of musical sounds, while the IM distortion as you can see, is > about half tones that are not harmonically related to the source, and > won't have anything to mask them in the music. They will blare in your > ear! Hi again Arny! You've been busy posting since I sloped off last night so I'm still catching up. Thank you for this clear & informative post on IM. Would you think that your remarks in any way justify my preference for Class A amplification since it seems to me to produce a output remarkably free from IM at least in the case of my Pathos amp (ok, it's only strictly Class A up to 30W per channel into 8 ohm but that goes a long way in my modest room). Or am I misguidedly suffering from yet another audiophile myth here, in your opinion? Dave :) Golden Earring's Profile: http://forums.slimdevices.com/member.php?userid=66646 View this thread: http://forums.slimdevices.com/showthread.php?t=106914 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] Intona USB thing
arnyk wrote: > Our hearing systems have evolved to maximize sensitivity to potential > existential threats such as large bloodthirsty predators given that our > brains and nervous systems which have relatively slow (but in the case > of the brain quite subtle) processing speeds and therefore are optimized > when data rates are lowered in optimal ways. Our sensory arguments > particularly our ears incorporate many mechanisms that reduce the data > rate of the information they transmit to the brain. Morning Arny! Apologies for delay in responding, yet again I had visitors last night. I'm doing my little bit to give the lie to Alan Bennett's droll observation: "Television is more interesting than people - if it were not, we would have people standing in the corner of our rooms". (He said that a long time ago now, 50's/60's I would guess!) I'm pretty sure that this mission will be another one of my legendary heroic failures, but such principles are important to me. Am I now correct in my interpretation of what you saying is that we needed to keep our sensitivity to quiet sounds maximised at all times because that is all we'd get (if we were lucky) from such a hungry carnivore which would probably have adopted a stalking approach, & also possessed the ability to outpace us once it finally broke cover? Life must really have been a very precarious thing back in those days. Baby boomers like ourselves have in particular lived in charmed circumstances once we finally developed the ability to "double-think" away the true significance of both the awesomely destructive "beauty of our weapons" (to borrow from Leonard Cohen "First we take Manhattan") and the effect of our increasingly materialistic lifestyles on the global ecosystems which support us. I do not think this bubble will survive long enough to protect my children, & I am not relishing the prospect of ending my days in an under-staffed retirement hovel which is all I'm now likely to get if I live long enough. Even being a curmudgeon (which I am in training for) wouldn't help much in those circumstances, they'd just jab you up with anti-psychotics to make you more "manageable", while continuing to ignore the necessary procedures required to maintain any semblance of human dignity. I have now taken up smoking cigars in sheer desperation (after an 18 month long genuine "cold turkey" break from nicotine) although I have managed to completely avoid cigarettes: my blood pressure however is remaining stubbornly normal. Ce sera, sera I suppose. At least I'm not so bored as I was when living vice-free (software stubbornly refusing to insert emoticon to indicate a trace of "gallows humour" in this last bit, sorry). In fact, assuming that we do not all fall victim to the cumulative consequences of our stupidity first, the most significant threat to our individual continued existence these days comes from one particular aspect of our technology: the most dangerous activity that most of us undertake on a regular basis is to drive a motor vehicle on the public highway. I am in the most fortunate situation of not actually needing to drive at all, so that when I do I can pick & choose the time of day & the route that I take. I have a 14.5 year old open top sports car which provides a most satisfying driving experience whilst obeying all relevant speed limits, & is capable enough in terms of grip, braking, handling & (least importantly) performance to give me a better chance of avoiding hurting anyone else (& myself) should a genuine emergency develop. Practically every time I take it out however I witness substandard driving behaviour perpetrated by motorists seemingly unaware that they have been granted a licence to operate a lethal weapon that cannot be disarmed & which does not have a safety catch (other than parking it up & taking the keys out). Frankly, it is surprising that there are not more RTA's in the UK where our roads are very busy. When I really feel the urge, I book myself into a Track Day at my local circuit (Goodwood): it's a challenging circuit even with a relatively low-powered vehicle as my 2002 Mazda MX-5 (Miata), but there is a great sense of satisfaction when you get the weight transfer and line right on its tricky corners. Top speed - don't know, I was too busy sighting my braking point & the correct line for Woodcote, but I know I hit the rev limiter in 4th (which translates to 115mph) on the Lavant straight, changed up to 5th & continued to accelerate as per racing manual instructions (if you're not braking, you should be accelerating!) until reaching the approach to Woodcote, so I think we're comfortably talking low to mid 120's. It's not cheap (c. £400 for the day) & it annihilates your fuel consumption (you're lucky to get 12mpg) but it's fantastic fun & allows you to explore the true capabilities of your car in a way that would be both illegal & grossly irresponsible on public roads. They only allow 12 cars on the circuit at any 1 time
