Post by colinf on May 23, 2017 12:23:03 GMT 12
Hello everyone, I am writing here to show off my audio creations. I'll be getting a website up and running soon. I am currently making a passive line stage (SV-1), a SS phono stage (MM-1) and MC pre-preamp (MC-1) and a headphone amp (HP-Ge). The phono stages both use Sonic Imagery Labs discrete op-amps, and the headphone amp runs in class A, and uses NOS Russian germanium transistors for a nice warm tone. Colin Farch Clear Image Audio NZ Brightwater, Nelson.
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Post by colinf on May 23, 2017 12:25:26 GMT 12
The bamboo-fronted SV-1sb silver litz wired passive preamp on the left, the SV-1s acrylic-fronted passive pre in the middle and the HP-Ge Class A headphone amp.
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Post by colinf on May 23, 2017 12:30:20 GMT 12
 The rear of the SV-1  From left: HP-Ge headphone amp, SV-1s, MM-1 phono stage, MC-1 pre-preamp for MC cartridges. They are sitting atop my beloved Sansui BA-F1 poweramp (that's not for sale!)
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Post by Graham on May 28, 2017 10:12:28 GMT 12
Hi Colin
Very professional looking line up.
I'm considering getting an MC pre preamp at some stage, what price would yours be ?
I would need about 30dB gain.
Cheers
Graham
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Post by colinf on May 28, 2017 10:39:41 GMT 12
Hi Graham, I set the gain to 26dB (about 20 x) which suits my Dynavector 0.4mV just right. What cartridge are you using that needs so much gain? Although the Sonic Imagery Labs op-amp has low noise if you use it with some Ortofon 0.1mV cartridges the noise could become greater with higher gain such as 30dB (32 x). The thing is to try it and see. My unit is $550. Regards, Colin.
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Post by Graham on May 28, 2017 10:48:54 GMT 12
Hi Colin
My only MC cartridge at present is my very rare and rather unusual Excel Pro 81, but I could in the future be tempted to buy something more conventional.
The Excel has only 0.2 mV output and internal resistance of 3 ohms. Suggested load is 100 ohms.
It is running quite happily into the MC stage of my Project Phonobox SE II.
I tried it into a LE Pacific based Pre preamp the other day and it wouldn't make a sound at 100 ohms load. We can only presume the cartridge output was to small to activate the 2sk170 jfets.
Cheers
Graham
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Post by deano1974 on May 28, 2017 13:59:25 GMT 12
Hi Colin they look fantastic is there any chance that you would be willing for us guys in auckland to demo these?
Manager & Product specialist at Rapallo AV & HI-FI
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Post by colinf on May 28, 2017 15:40:14 GMT 12
Hi Colin My only MC cartridge at present is my very rare and rather unusual Excel Pro 81, but I could in the future be tempted to buy something more conventional. The Excel has only 0.2 mV output and internal resistance of 3 ohms. Suggested load is 100 ohms. It is running quite happily into the MC stage of my Project Phonobox SE II. I tried it into a LE Pacific based Pre preamp the other day and it wouldn't make a sound at 100 ohms load. We can only presume the cartridge output was to small to activate the 2sk170 jfets. Cheers Graham Hi Graham, your cartridge does indeed seem to be quite rare and the only info I could find on it is what you've seen already. It looks to have a mildly rising top end. I'm not sure the S.I.L. discrete op-amp would be just the ticket for it as it tends to be very clear and there is no 'flab' in the sound. It might not flatter it the way you'd perhaps like. It has a very lively open sound but I think the Jensen 990C discrete op amp (another high end low noise pro op amp) would be more sympathetic. It has a slightly warmer tone so might not be as fierce in the top end. I can set it up for 100ohms and a gain of 30dB if you like, and you could try it.
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Post by colinf on May 28, 2017 16:04:14 GMT 12
Hi Colin they look fantastic is there any chance that you would be willing for us guys in auckland to demo these? Hi Deano, Sure they could be demo'd. What system? Both the passive preamps you see have been sold so I'll make another few. They are proving to be very popular. I think a little word about where they fit in in the spectrum of Hifi expense would be in order here. I originally built these discrete opamp based units to see how good reasonable-cost SS could sound. They do sound quite lively and open and are definitely a step up over normal op amps. My best phono stages have always been valve ones, that I've been making in some form or another since the early 90s. I am planning on making a circuit board to allow them to be more easily built and thus bring them out of the bracket of stratospheric cost. My biggest pre-preamp is yet to be built into a box and is an elaborate all-valve design. (You can tell I have a slight obsession with MC headamps and stepups!) I like valve MC headamps the best but they can be finicky to set up, are high-maintenance and generate more noise than SS or transformer. But they are so transparent! So with these SS units they are my minimum non-stratosphere-cost standard for sound that you can listen to for a long time and not become too fatigued.
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Post by colinf on May 28, 2017 16:08:48 GMT 12
 The aluminium cases for my serious valve phono stage, about to be painted.
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Post by colinf on May 28, 2017 16:15:13 GMT 12
My fourth glass-box valve preamp, made in about 1994. I still use it now. It's messy inside, noisy with its one-triode MC headamp and has real depth and space to the sound.  how to upload a photo on fb
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Post by deano1974 on May 28, 2017 16:22:45 GMT 12
Wow very impressive... To answer your previous question Im very interested in your MM phono as I only use MM and to have an option of multi inputs is definitely appealing for me, I currently use a modified parasound phono thats have extensive capatence and loading options Do you have any feedback on your phonostages? Cheers
Manager & Product specialist at Rapallo AV & HI-FI
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Post by colinf on May 28, 2017 17:40:45 GMT 12
Multi inputs...how many? It means there will need to be a switch in the signal path, not hugely desirable at low levels but do-able. Feedback...I demo'd the first prototypes in Melbourne last year and the consensus was that they sounded crisp and lively but the connectors on the back were not exciting. I used ones that were too cheap in an effort to keep the cost down. I'm using Neutrik Rean sockets now, they are vastly better. Also the lack of loading options. Capacitance is the main factor with a MM cartridge to achieve good frequency response. Most MM cartridges start to roll off around 18 to 19kHz so I have incorporated a mild lift in the RIAA response that counters that. The capacitance is set to 100pf for RF filtering but the slight lift in the RIAA means there is less need to fiddle with capacitance loading to achieve full frequency response.
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Post by michaelw on May 28, 2017 18:33:02 GMT 12
... interesting design approach. what is considered "mild lift" ? and if you use a mm with flat response or with a rising hf ? 
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Post by colinf on May 28, 2017 19:18:11 GMT 12
I insert a small resistor in series with HF part of the eq which makes it rise by about 3db up to 20khz. If the cartridge has a flat response like an Ortofon 2M Black there is no need for this resistor but Shure V15s sound more open with it. I should really make it a variable resistor so the user can vary it to taste. I use a test record for frequency response testing. I haven't seen a MM cartridge with rising response. If you connect the pre-preamp to the MM stage there is no need for the lift resistor as MC cartridges have very low self inductance and extended electrical frequency response.
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Post by Owen Y on May 28, 2017 19:44:17 GMT 12
An aside: It's popular in some circles (incl some phonostage manufs) to also incorporate the 'Neumann Time Constant', an addit corner freq lift at around 50kHz in the RIAA EQ - to compensate for the HF limiters that were reportedly used on Neumann cutting lathes & thus restoring flat HF response, extension & 'air'. I tried it on my phono stage & did not care for the addit brightness, but I'm told that some nice carbon films is the answer. NZer, the late Allen Wright, was a big proponent of this feature. (Digression sorry  )
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Post by colinf on May 28, 2017 20:05:42 GMT 12
Yes that's true. Your reminding me of this has convinced me to add a switch or variable HF control on the MM stage. I'll get to it! I fiddled with such a control in the 90s and found that no one setting was right for everyone so left it out. But that's a shame as the increase in air when used set up just right is very welcome.
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Post by michaelw on May 28, 2017 21:35:01 GMT 12
switchable is a good idea, 3db is a not inconsiderable boost...
i've listened to more than a few phono stages and the very best followed riaa closely, without need for any extra lift.
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Post by colinf on Jun 1, 2017 20:29:58 GMT 12
I've been fiddling with that HF lift resistor value again. Amazing how much difference it makes to the sound. It needs to be adjusted just right for each system, and also ends up compensating for people's perception of top end, and also speaker frequency response. As well, the frequency response of MC stepup transformers. There are too many variables to consider in choosing one value for this resistor. I think it might be good to have it adjustable by using a trimpot accessible from the back panel.
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Post by foveaux on Jun 4, 2017 19:10:38 GMT 12
go for it colinf I'm a dweeb when it comes to all the techno babble - however all strength to your arm for having a crack with these products. I really like the cosmetics, but as deano1974 anticipates: punters need to hear the gear and be convinced. Your fourth glass-box valve preamp, reminds me of the innards of Croft micro gear - if the sound (which I have heard and rate highly) is in this league, then...wow! I'd be interested in auditioning your HP-Ge Class A headphone amp. (runs in class A, and uses NOS Russian germanium transistors) - what price? Look forward to the website - keep us posted cheers, f
"I see music as a lifetime affair." [Rory Gallagher]
"Free - I miss that band, but when I look back, we were very young" [Paul Rodgers]
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Post by colinf on Jun 5, 2017 18:04:05 GMT 12
Hi foveaux, Thanks for the encouragement! I'm currently working on the website so it should be going shortly. The glass phono stage has been running all this time, I've only updated the power supply with new regulators and new tubes. The 417 tubes in the MC stepup stage need changing about every 2 years as they become noisy or out of balance. I've tried all sorts of stepups including jfets, opamps, transformers, but keep coming back to the tube, even if it is less reliable and needs attention every now and then. The best of the normal stepups is the Lundahl LL1941 transformer, followed by the Sonic Imagery Labs discrete op amp (in the MC-1). They are about the only op amp I can listen to for long periods, successfully resolving harmonic texture. Most jfets I've tried seem to cut back the dynamic range slightly and make the sound somehow drier. The HP-Ge headphone amp resulted from my memories of what my audio experiments showed in the 1980s. I made several amp circuits then, first with germanium transistors. Then I thought I should really use modern transistors because they'll be better. They certainly are more convenient to use having higher voltage and current ratings, and a lot less electronic leakage. But somehow the germaniums generally have that nice warm presence that has more in common with tubes. I find them less fatiguing to listen to over time. By contrast almost all the silicons have a bigger sound but are harsher and less interesting to me. It's $550, same as the SS phono stages. PM me if you'd like to try it. What headphones are you using?
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Post by Owen Y on Jun 5, 2017 19:30:50 GMT 12
Hi colinf - re. the WE417A tube, I am reminded of the legendary Arthur Loesch phono preamp, which I had always wanted to try. I even got some 417As, but never did build it. This is a version I believe. The last stage is a 5687. 
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Post by colinf on Jun 5, 2017 19:47:48 GMT 12
Wow that's great! I remember fiddling with circuits just like this in the 90s including 417s and 6gk5s. The 6gk5s proved to be quite microphonic but sounded good. 6cw4 nuvistors sounded better. But try getting a quiet one! I never did get around to using the 5687 in a line stage but I'm sure it would be nice. I used it in the driver stage of a push pull 211 amp. I see Arthur used a 2sk170 on the input. I used parallel 2n4220s with heat regulation in a similar circuit in my early phono stages, as they sounded more transparent than the Toshibas. Cascoded with a bipolar transistor at low voltage. The tubes in the cascode position sounded too coloured. The tubes in the MC input position were always more lively than the jfets but lacked reliability and were very prone to external noise sources such as heater supply and shielding.
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Post by foveaux on Jun 6, 2017 10:59:59 GMT 12
Hi Colinf I'm using Beyerdynamic T90; and for reserves have: AKG701, Sennheiser HD25 and Yamaha HP1 (these Yammys are at least 30 years 'young' - and you know what? they still sound great!) My Headphone amp is the Mapletree Ear+Purist HD (valve) At $550 your HP-Ge headphone amp is nicely placed! cheers, f
"I see music as a lifetime affair." [Rory Gallagher]
"Free - I miss that band, but when I look back, we were very young" [Paul Rodgers]
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Post by guitardude on Jun 6, 2017 11:37:08 GMT 12
Hi f,
Daresay Colin will chip in here but I have Q701 that were driven quite happily by the headphone stage in the preamp that Colin built me. Even drives my HD800 quite comfortably. Cheers
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Post by colinf on Jun 26, 2017 14:29:41 GMT 12
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Post by michaelw on Jun 26, 2017 15:08:24 GMT 12
nice !
only one transformer, otl ?
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Post by colinf on Jun 26, 2017 15:19:24 GMT 12
No, the Plitrons haven't arrived yet. That's the space next to the tubes.
AMR-iFi R&D
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Post by guitardude on Jun 26, 2017 15:24:07 GMT 12
Didn't know you were building KT150 monoblocks. You kept that quiet !
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Post by colinf on Jun 26, 2017 15:42:32 GMT 12
:-) It uses roughly the same circuit as the EL34 amp but with 80w class A output for lots more grunt. Also very costly at $6k as it uses all high end parts.
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