Post by colinf on Aug 8, 2017 20:23:36 GMT 12
It's an ac 190v 12w power supply with a digitally synthesized ac sinewave output. The frequency is adjustable from 42Hz to 72Hz in 0.1Hz steps. The frequency set can be memorised with the M button on the front.
AMR-iFi R&D
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Post by Graham on Aug 8, 2017 21:50:09 GMT 12
The requirements for the synchronous motors in Thorens, Linn and Rega etc are a little different in that although they are rated at 115 volts I have found they are smoother on only 85-90 volts while still having enough starting torque. This is the operating voltage of the Linn Valhalla and in fact my DIY Geddon Clone. They also are rated at only around 3 watts. For my own requirements I could live with only 33.3 rpm as I don't have any 45s, and if I did they could be played on the TD125. If it makes it simpler I could also do without the digital display and the memory function and be happy with just a fine tune pot. Sorry if it sounds like I am redesigning your excellent device Colin, just trying to simplify it.
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Post by Owen Y on Aug 9, 2017 9:39:47 GMT 12
Those Premotec/Airpac/Philips split phase mtrs might benefit from a smoother AC supply, but the main attraction of a PSU like Colin's IMO would be speed control (via freq fine adjust) - which these mtrs do not normally have.
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Post by guitardude on Aug 9, 2017 9:49:02 GMT 12
Are you making DAC's at all Colin ?
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Post by Graham on Aug 9, 2017 10:08:15 GMT 12
Those Premotec/Airpac/Philips split phase mtrs might benefit from a smoother AC supply, but the main attraction of a PSU like Colin's IMO would be speed control (via freq fine adjust) - which these mtrs do not normally have. That's precisely why I am interested. I'm considering replacing the overly complicated Papst DC motor on the Oracle with a simple AC synchronous motor but would like to be able to fine tune the speed rather than rely on the mains frequency. It also means that when doing the conversion I can achieve the correct platter speed electronically rather than having to very precisely calculate the drive pulley diameter. There's a method in my madness
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Post by guitardude on Aug 9, 2017 10:40:24 GMT 12
I went from the Papst AC motor on my Gyro to the DC motor. Made a huge difference to the sound, though I struggle to explain why....
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Post by colinf on Aug 9, 2017 15:36:35 GMT 12
Wow activity! Graham, it might be best to still have the display so you can see what frequency you've set it to. The cost of not having a display is only a smidge less but the inconvenience will be bigger. The output can be set for 95Vac with the appropriate output transformer. Guitardude, yes I've got some dacs in the pipeline. At the moment I'm just getting the Soekris DAM1021 resistor-ladder dac and putting it in a box with optical and coax input. When I finally figure out how to put USB on it I'll get that going too, but for now a USB to coax or I2S adapter would be needed. I've been running the Soekris here for a little while and I can say it's a natural sound. The output comes straight off the discrete resistors in the dac so there are no tubes, transformers, capacitors or opamps in the signal path to colour the sound. I've only made two units so far, one in my main system and one on the TV system with four switched optical inputs. The difference the Soekris makes to even TV sounds is huge!
AMR-iFi R&D
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Post by guitardude on Aug 9, 2017 17:36:35 GMT 12
Hi Colin,
Will talk later about DACs, but sounds like you will be busy amp finishing shortly, as the Ongaku's are nearly painted.
Anybody got a sensible reason why an AC motor driving a belt drive table sounds different to a DC motor ?
Surely if both drive the platter round at the same speed and without wow or flutter then they should sound the same ?
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Post by Owen Y on Aug 9, 2017 18:34:58 GMT 12
There are many reasons I think why AC sounds different from DC for a TT motor - whether it's an AC motor or a DC motor (eg. battery DC vs rectified AC). The reasons are not widely understood & I certainly don't fully understand them, but I remember for example testing my belt-drive Aura TT, with 12v DC mtr (mains AC feeding the DC mtr controller cct) sounded better than 12vdc direct from a big lead-acid car battery. Also as mentioned previously, why should a bigger gauge power cord make an immediately discernible sonic difference on a TT? I suspect we still under-estimate the effect of 'stylus drag' tracing the varying groove cut modulations, on platter speed - factors such as....belt material, mtr torque, mtr controller/servo design, platter rotational inertia, etc, etc.... all play a part in the recipe & the ability of a cartridge to pick up all these infinitesimal nuances.
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Post by Graham on Aug 9, 2017 19:55:20 GMT 12
My laymans understanding is that a DC motor relies on some form of feedback for rpm control. This means that there must first be some form of speed variation, no matter how slight, followed by a correction to bring the speed back to the desired rpm. There will always be this minute fluctuation back and forth with DC. The AC synchronous motor is locked to the supplied frequency and will not vary the rpm unless extremely loaded. If the supplied psu frequency is rock steady so will be the motor rpm. Put another way, if the platter slows down minutely when the stylus contacts the record or is subjected to extreme modulation, the DC system detects this and then corrects it. Cause and effect. The AC synchronous motor will ( in theory anyway ) not suffer from this speed variation but will continue to spin at the same speed.
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Post by Graham on Aug 9, 2017 20:38:31 GMT 12
Another question for Colin. I would like to use the Thorens motor because it has proven to be much smoother than others in my experience, plus it is brand new. However at this stage I don't have an original pulley but do have a machined alloy one of slightly larger diameter. This means that to achieve the same platter rpm via the belt drive the motor would only be spinning at approx. 245 - 250 rpm as apposed to 375 rpm on a Thorens turntable set up. According to my quick calculation being 16 poles the motor spins at this 375 rpm with 50 Hz. But to drop down to only 254 - 250 rpm it would be supplied with only around 32 Hz. Is this lower Hz figure a problem or complication for your unit. ??
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Post by Owen Y on Aug 9, 2017 21:23:14 GMT 12
My laymans understanding is that a DC motor relies on some form of feedback for rpm control. This means that there must first be some form of speed variation, no matter how slight, followed by a correction to bring the speed back to the desired rpm. There will always be this minute fluctuation back and forth with DC. Which is why some TT designers say eschew feedback/servo mtr control ccts - just accept electrical variations, it sounds better. Then use other (mechanical) techniques to minimise speed variation, eg. increase rotational inertia, stiffer belts, multiple belts, flywheels, rim/idler drive, etc etc
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Post by colinf on Aug 10, 2017 7:44:49 GMT 12
IME it's all down to the ultimate flutter the motor produces. DC motors by design can't synchronize to their DC power input so some form of speed governance is required. That would most likely be by negative feedback in a servo loop arrangement. This system is subject to characteristic NFB control limitations, and a rotational velocity bode magnitude plot would indicate how well the NFB system is working. Some systems would be set up better than others and each specific setup will have its own influence on the flutter and thus the sound. I had a great chat to Mark Dohmann at the Hifi show in Melbs last year talking about how he thought typical direct drive TTs sound brighter due to the servo systems used. He also thought the higher the feedback frequency on the servo system the feedback pulses would be high enough to filter out effectively enough mechanically. My thoughts are that a synchronous AC no-NFB/servo setup could theoretically have lower flutter, apart from the slight pulses of rotational torque from the power frequency used, and that they could be filtered out mechanically too. The bode plot would be naturally smooth with no need to control any resonant peak as with a servo setup. Which brings me to Graham's idea of running the Thorens motor at approx. 32Hz. The motor will run warmer at the same voltage input as the coil inductance at that frequency would be lower and more prone to saturation. So the ac voltage to it might need to be reduced with consequent reduction in torque output. If I could, I would run it at the normal 50Hz for which it was designed, and use a smaller diameter pulley. Otherwise I can re-program the micro in my generator to run at 32Hz, just that the output transformer would need to be larger as its input impedance at that frequency would be lower. By making it larger the core wouldn't saturate magnetically.
AMR-iFi R&D
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Post by Deleted on Sept 29, 2017 16:15:12 GMT 12
Just saw a really good plug for our friend Colin F on another forum, one very high end geek excitedly telling another very high end geek that Colin F 'the tech you can trust' would be in Australia at the end of October... The man has his fans! Pleasing indeed to hear, knowing my humble MF is currently taking up space in his workshop...
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Post by colinf on Oct 3, 2017 8:01:53 GMT 12
Thanks! Stereonet?
AMR-iFi R&D
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Post by Deleted on Oct 3, 2017 9:13:25 GMT 12
Yes. Can't remember what thread or who, or even the gear mentioned suffice to say it was probably worth more than I earn in a year... 😬
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Post by colinf on Feb 17, 2018 6:26:51 GMT 12
Well after a while in NZ my family and I have decided as a unit to shift back to England, to north Devon. For family reasons. I'll most likely still be doing what I do best...making amplifiers out of any technology that sounds good! After setting up there, most likely near Barnstaple, my next project is likely to be a medium-powered Vfet amp of about 50w. After hearing Rocl's classic Sony TA-4650 I was inspired by the fluid and clear sound. I'd like it to be an affordable amp to go with my other units...the passive line stage and phono preamps. As well as the Soekris Dac. Hopefully I'll report back on the Bristol hifi show, and later in the year, the Munich high end show!
AMR-iFi R&D
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Pundit
Post by rocl on Feb 17, 2018 9:26:01 GMT 12
Well after a while in NZ my family and I have decided as a unit to shift back to England, to north Devon. For family reasons. I'll most likely still be doing what I do best...making amplifiers out of any technology that sounds good! After setting up there, most likely near Barnstaple, my next project is likely to be a medium-powered Vfet amp of about 50w. After hearing Rocl's classic Sony TA-4650 I was inspired by the fluid and clear sound. I'd like it to be an affordable amp to go with my other units...the passive line stage and phono preamps. As well as the Soekris Dac. Hopefully I'll report back on the Bristol hifi show, and later in the year, the Munich high end show! bummer - i shall really miss your expertise but wish you all the best with the move back. interested in more about the v-fets. how about a pair of v-fet monoblocks to go with 4650? i'm sure the sony will outlast me but hope i won't need your skills on the AMR again!
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Post by Owen Y on Feb 17, 2018 11:33:46 GMT 12
Greetings colinf - best wishes from us for your new relocation & plans & hopefully you'll find time to report some news for us from that side of the world. PS. Are V-FETs still manufactured and/or still available?
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Post by deano1974 on Feb 17, 2018 12:14:45 GMT 12
Best wishes brother, hope you enjoy blighty and dont eat to much devonshire custard and the awesome ice cream clotted cream 😀
Manager & Product specialist at Rapallo AV & HI-FI
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Post by colinf on Feb 18, 2018 7:38:59 GMT 12
Thankyou for the kind wishes! I will definitely keep an eye out for clotted cream and devilish Devonshire custard events :-) Also Devonshire cream tea with scones with jam and cream on top, and avoid those pesky ones with cream put on first, ugh! Although I'd better watch how I do it as some of my family is from Cornwall. Perhaps just have them plain? Vfets haven't been in production since the 80s and as far as I know only Sony and Yamaha used them. I bought some Nos Sony Vfets 2sk60 and 2sj18 and am yet to use them, but when I get set up I'll start fiddling with them. They are a short circuit at low voltages and in the Sony circuit there is a boosted power supply which ensures the Vfets are out of their short circuit saturated range just after switching the amp on. Modern Vfets are just called depletion-mode mosfets and weren't designed for audio, mostly switching applications in switching power supplies. There isn't a modern equivalent replacement for the p-channel 2sj18. I'm most likely going to try the popular modern N-channel DN2540 paralled in a quasi-complementary output stage.
AMR-iFi R&D
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Post by colinf on Jun 24, 2018 21:59:00 GMT 12
Hi Everyone, I decided to remame my audio projects Braunton Audio (formerly Clear Image Audio NZ) as I am now in Braunton, North Devon, UK. First project...a usb dac using the Soekris dac module. It is well under way and I hope to have it finished shortly! Colin.
AMR-iFi R&D
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Post by colinf on Jan 23, 2019 7:07:31 GMT 12
Well it’s been quite a while since I wrote about my stuff but now that I’m set up here in Devon I thought I’d let you know about my new bits and pieces. I’ve been fiddling quite extensively with headphone amps and come up with some refined boxes. Also the Soekris Dac with USB input. From left to right: my two D-A converters DHP-1 and Dac-SK1usb. The DHP-1 is the lowest distortion Soekris dac with USB input coupled with the Sonic Imagery Labs (SIL) discrete opamp-based headphone amp. It’s a high end unit and I listen to it on my Focal Utopias. The Dac-SK-1usb is just the Soekris with USB input and line output straight off the dac resistors, so no output stage is needed. The units in the middle are my two headphone amps. The HP-Ge uses germanium transistors in the input stage and silicon transistor class A output stage. The Russian nos germaniums sound warm and do a good job of alleviating the harshness of some recordings without sounding weird. It has great soundstaging and natural ambience, and I love listening to it. The other headphone amp is my LHP-1, which has been the subject of considerable listening and refining to make it as clear as possible. There are no capacitors in the signal path and the power supply forgoes the use of regulation as that made the sound too dry. Without regulation the sound comes alive! It’s a very simple circuit that uses high end surface mount resistors. The Utopias don’t lie and you can hear every little change in parts quality. I chose the SIL jfet opamps as they are fabulously transparent and hide nothing. Your recordings are exposed and you’ll hear every little cable change and how many microphones are used, and the addition in some cases of artificial ambience. I was listening to Joe Jackson on the LHP-1 the other day and I’ve listened to Night and Day quite a bit in the past. I didn’t realise that there are actually three different microphones and positions of his voice on some of the tracks, something I’ve not heard before! The unit on the right is the SV-1 passive preamp. It has a TKD volume pot and 4 inputs going to one-of-two outputs. The volume control can be bypassed if you need to use a poweramp that has its own volume control. It’s proven to be a very popular little box. Here is a pic of the Sonic Imagery Labs studio grade discrete op amps.
AMR-iFi R&D
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Post by cartridgeguyonline on Jan 23, 2019 7:16:16 GMT 12
I dont see our mutual friends phono stage in those pictures ?
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Post by colinf on Jan 23, 2019 8:15:29 GMT 12
I just ordered the capacitors for it! Soon.... He is talking about my high end valve phono preamps. The parts have been sitting in boxes this year while I set up here in Devon. But it is in progress now. Good things take time! Not too long now though.
AMR-iFi R&D
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Post by colinf on Feb 1, 2019 18:06:19 GMT 12
Just been fiddling with streaming a bit more at last. I set up an Amazon account on the iPad. Although that was good in itself to be able to access so much music for a monthly fee, I was stuck with listening to it on the iPad's own headphone output, or use my big Windows 10 computer via my Dac-SK1 usb DA converter. The latter is what I use in the main stereo. But the iPad is far more convenient and portable to use for most things than the Win10 computer (except for design work) as it sits on my lap in the loungeroom, not the desk. So today I decided to try connecting the iPad, via the Apple lightning to usb cable, to my usb dac and headphone amp. It works!!! And sounds so much clearer, tonally transparent and dynamic it’s fabulous! It really shows up the limitations of the iPad dac and headphone connection. And now I can use the iPad for high quality listening without a wifi or Bluetooth connection :-)
AMR-iFi R&D
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Pundit
Post by rocl on Feb 1, 2019 20:49:11 GMT 12
for my macbook pro(2009 so now 10yrs old! who said technology becomes obsolete?) i bought a 2nd hand Dragonfly red. $200 and for youtube pretty good. not quite in your league colin, but i don't do a lot of youtubing so i'm not going to spend heaps.
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Post by colinf on Feb 1, 2019 22:05:10 GMT 12
Ok nice, the Dragonfly is great value for money I’ve heard. I thought I might have a go at making a more affordable usb dac as well soon, possibly using AKM dacs. I suspect people who stream music from the computer regularly are those more interested in the music or content rather than the means by which to listen to it. But it can be shown that for a modest outlay the sound quality can be improved greatly with devices like the Dragonfly and DacMagic. Anything I eventually make will have to be satisfying to listen to!
AMR-iFi R&D
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Post by colinf on Feb 2, 2019 15:34:03 GMT 12
Also conveniently forgot to mention the LHP-1 headphone amp and DHP-1 Dac/headphone amp also double as line stages with RCA line outputs on the back. I use an LHP-1 in my main system as it drives the transformer input on my hybrid poweramp well.
AMR-iFi R&D
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Pundit
Post by beeman on Feb 3, 2019 13:09:04 GMT 12
Would your turntable power supply be configurable for my Denon RP53 idler drive. It uses 110v so currently plugs in through a stepdown transformer. The motor is huge much bigger than a Garrard 1HP +. As an idler all your comments about smooth power supply ring true just in this case the supplies will be bigger. Sorry, I have no fundamental; understanding of the science so please excuse me if this is a silly question.
Graham - could this suit our next potential build?
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