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Old 20th December 2009, 02:57 PM   #461
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i build the Hiraga Optime Tarnsimpedance RIAA. Actually there was not much to build because i had already the RIAA part from another project. So i had only to insert C1. I found a mistake in my last drawing. C1 should have 100nF and not 10nF. It can be connected in two ways : to the positive supply or to ground. The connection to he supply had 0.5dB more gain but i decided to put the cap to ground because it was more compact to solder. All other measurements were the same. I used the LT1468 as opamp and a AD711 as servo. The servo will not do any harm because it is very slow. If in doubt you can add a low pass filter in series with the servo output like 10kOhm and 1uF.
The sound i got was good, fat and dynamic. After listening to two records i found it a bit on the analytic side. I usually like the LT1468 very much. It has a one stage folded cascode bootstrapped current mirror layout with a lot of gain so distortion from this OP is one of the lowest you can get. The sound can be slightly "matter of fact" and i missed the lush sound of the Telepath. I substituted for an OPA827 and most of the sound of the Telepath was suddenly there. More relaxed and liquid with very good differentiation of tonal colours. After some more records i still found the sound a bit "grey" so i changed the tone arm cable from a 1.5m run of Wire World Silver Eclipse 5.2 that had worked so well with the Hiraga Optime - Telepath to my Spiral Grove 0.5m chaos-fractal cable and suddenly the sound opened up to the wall to wall size i sometimes get if i have luck. tonal balance was restored too and there was much more resolution and micro detail without spittyness. My dear subjective friends, whatever the experts tell you : cable is very audible especially when you get closer to the tone arm. I have no hard scientific fact to offer but i have a feeling what happens. Anyway the sound is now 90% of the Telepath and has no right to be that good. the telepath is not cheep and slightly better but this can be build for 300,-€ including cabinet. Do not skimp
on the power supply. I use four power supplies in a "double - double - mono" configuration with coils in the supply lines and hope that Salas circuit sounds even better.
Some other tips : I use 47kOhm for R9. That gives a curve that looks like a straight line that rises by 0.5dB from 20kHz to 20Hz. I found that response best in my system subjectively. My Titan is not short on treble and my speakers are very extended on top and i sit close so you may opt for 220kOhm that will give a response that is + - 0.1dB. my measurement limit. I use Vishey/Röderstein MKP1837 1% and simple 1% metal films here. By coincidence C1 and C6 have the same value so you can buy a bunch and select as close as you can. 100nF is not an exotic value anyway so most Diy´ers should have some in their stock.
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File Type: pdf Hiraga Optime Transimpedance RIAA 2.0.TSC - TINA.pdf (59.3 KB, 194 views)
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Old 20th December 2009, 10:58 PM   #462
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After cooking my famous ginger chicken soup for my family i had more time for listening. I am preparing for Holgers visit so i looked what i could improve still. Cranking up the sytem full (that is so loud that it whould destroy my speakers) i still heard a faint hum. I found it came from my unshielded chaos, fractal cable. I build a shield from copper tape and braid i had ripped of a CX100 coaxial cable, connected the shields to the Hiraga earth and the hum was gone. The sound improved too : cleaner in the bass and more liquid in the midrange- treble. Strange that this short cable is so important. Sound is now very similiar to the Hiraga-Telepath combination with the exception of the stratosferic treble where the Telepath has the edje in resolution and speed. That can be explained in two ways : 1: i am using better parts in the Telepath like Panasonnic FM, Dale RS55 and Polystyrol capacitors for the RIAA, 2: the Telepath has a 2 stage RIAA and a very fast and strong output buffer. The poor OPA827 in the Transimpedance RIAA has to amplify 50dB in the bass and 30dB in the midrange treble plus driving a 5m long video coax cable. Still i like the treble performance very much. It´s sweet like liquorice and i could imagine listeners that prefer that over the Telepath.
Anyway, i will play this combination for Holger and switch later to the MPP low Z with inductive RIAA.
Holger, when you read this please bring Romans Preamp with you. Roman will borough it to me now. It´s a Vacuum State, so now i have a chance to listen to it in my home.
I have also more good news. i am dedicated to build a compleet DIY system with phonostage, preamp, poweramp and speakers, so stay tuned. I will try to use designs that are popular here like the B1 buffer and the Pavel Mosfet Buffer and will try to squeeze as much performance out of them as posibe.
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Old 20th December 2009, 11:05 PM   #463
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Quote:
Originally Posted by Joachim Gerhard View Post
Holger, when you read this please bring Romans Preamp with you. Roman will borough it to me now. It´s a Vacuum State, so now i have a chance to listen to it in my home.
Roman already emailed me. Of course I'll bring the RTP.
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Old 21st December 2009, 12:05 AM   #464
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Thanks Holger. This is much apreciated.
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Old 21st December 2009, 01:11 AM   #465
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Just for fun i designed a passive RIAA version of the Hiraga Optime Transimpedance.
It has the following advantages: !: Gain split equal and frequency independent over two stages. 2: Strong and fast output stage for driving long cables. 3: Some people like passive RIAA better.
OP 1 could be an LME49710, OP 2 = OPA134, OP 3 = LME49713 or AD844.
I took the closest values for cap and resistors i could find. The formulae are : R15 x C2 = 3180uS, R1 x C2 = 318uS. C2 is quite big and i would recommend Evox/Rifa PHE450 here. They come in 5% tolerance but are mostly better, more like 2%. It should be no problem to find well matched pairs.
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File Type: pdf Hiraga Optime Transimpedance RIAA Pasive.TSC - TINA.pdf (59.2 KB, 160 views)
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Old 21st December 2009, 11:10 AM   #466
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Hi Joachim,
I have been off this forum for a while, when I spotted this thread yesterday.
I have been playing with various phono stages, and I am still trying diy solutions that give me all I need for exciting audio playback one day.

It would be a mix of the performance of a phonoclone, which, in my incarnation, give that certain slam, the interaction of bass and drums and rhythm guitar, that goes right down to your bones when heard live and, sometimes, on master tapes (or direct copies), but rarely on vinyl (let alone CD), but lacks transparency and resolution compared to a toshiba-fet input, no loop feedback design, that in turn doesn't (re?-)produce that certain slam.

I have been partly successful with a rambeyrolles input stage, but with loading of the folded cascode output instead of loop feedback, and and a no loop feedback second stage and passive RIAA. Still, the other stages are superior in their special department.

In the meantime, I use an odd one-stage design that sounds good in respect to complexity and price. No audio nirvana, though.

Your reports sound, well, sound, so I will eventually try some of your ideas. (a friend of mine runs audio physik speakers that sound great, that is a reference for me as well)

I looked again at your Hiraga Optime: you chose npn instead of pnp-devices. Maybe it slipped me, but do you have an explanation for this choice?

Thanks for this comprehensive thread!

Rüdiger
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Old 21st December 2009, 02:23 PM   #467
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Hi Onvinyl !
Yes, the Rambeyrolles has some issues to solve. I build the Hiraga Optime with PNP but have shown the NPN circuit. They both work, just reverse everything. Some people like PNP better because of lower noise but i think with this optimised transistors it is no issue.
I looked at your one-stage-design and think it is not bad at all. What i would do is to use the output of the 2SJ74 too for amplification. You waiste a lot of potential here..
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Old 21st December 2009, 03:16 PM   #468
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Originally Posted by Joachim Gerhard View Post
What i would do is to use the output of the 2SJ74 too for amplification. You waiste a lot of potential here..
Yes, as soon as I see an elegant way to do it while keeping it single stage.


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Old 21st December 2009, 03:27 PM   #469
Salas is offline Salas  Greece
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Why not a njfet with a current source underneath like a DCB1 for output?
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Old 21st December 2009, 04:11 PM   #470
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Joachim, Holgar,
If you are getting to hear a Vacuum State RTP3C/D, a word of advice.

Please do NOT listen to it until it's been on for AT LEAST 24 hours. For whatever reason, it sounds quite ugly until it has really warmed up - and once it's on, leave it on please. It's intended to run constantly, 24/7/365.

That does NOT burn out the tubes - in fact they last much longer if never turned off!

Second point: it's a conventional voltage input on the phonostage which has provision for loading Rs. I strongly suggest you use 47k, and nothing lower.

The RTP has enough input overload headroom as to not be affected by any ultrasonic cartridge resonances - and 47k loading allows the full dynanics of the cartridge to shine through.

Attached is a schema of the phono section, it feds a balanced selector and attenuator, and a simple/complex line stage.

If you send me your mailing address, I'll send you a Xmas present.

Very interested in your opinions.

Regards, Allen
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File Type: jpg RTP3D-Phono-Schema.jpg (175.7 KB, 612 views)
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