RSL Phono-Stage on its way

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ryansoundlab
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RSL Phono-Stage on its way

Post by ryansoundlab » Thu Jan 24, 2019 7:41 pm

Mark, et al,

Not that you guys have been holding your breath (haha) but yesterday I shipped the first production units of the Ryan Sound Lab Phono-Stage to Mark W and another person. He heard an earlier prototype but this final version has seen much improvement in the power supply (mostly) and I believe is ready for another go-round against whatever (Paradise?).

The key to the MC version (shown with the top off) is the use of the I-V "current mode" or "DrT" type of input which effectively grounds the cartridge output and uses every electron for first stage gain. Engineering-wise I'm not sure exactly why it sounds so much better than the typical "voltage amplification" mode but it does to my ears. I hope the AudioFlat regulars will be interested enough to try it out after it gets there.

It comes with an external linear power supply (I dropped the internal switching power supply) plus a heavy gauge cable that I had to make up myself because I couldn't find a suitable pre-made one. It uses 20g wires which are supposedly larger than you're supposed to put on a DIN connector. Anyway, it did make a difference compared to the run-of-the-mill commercial stuff.

Kit

Here are a couple of pix:

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sq225917
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Re: RSL Phono-Stage on its way

Post by sq225917 » Thu Jan 24, 2019 9:11 pm

Kit, that looks awesome as ever. I'm always in awe of your pcb layout skills.

Can't wait to hear what you've managed to squeeze out of it.
One more Paradise left to complete.

ryansoundlab
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Re: RSL Phono-Stage on its way

Post by ryansoundlab » Thu Jan 24, 2019 10:33 pm

Thanks for your interest as always. I hope this latest version meets at least some of your expectations.

PCB layout is simple - just spend hours, and hours, and hours, and hours in front of the computer getting it just the way you want it(!). Unfortunately, you can never use the "auto route" method - that only works for digital I think. There are better people than me out there, too. The thing is, I really enjoy it. Always liked geometry! The challenge is fun and the day goes by so fast.

YNWaN
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Re: RSL Phono-Stage on its way

Post by YNWaN » Fri Jan 25, 2019 3:27 pm

Yes, very interested and very interesting. Kit, it looks like your design has changed quite a bit! Of course i would be interested in trying it :).
Mark

ryansoundlab
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Re: RSL Phono-Stage on its way

Post by ryansoundlab » Fri Jan 25, 2019 5:57 pm

Mark,

I haven't heard back from Mark W about the unit I've shipped. He may be on travel or something. Once he gets it I'm sure you guys can figure out the best way to hear it. Since it is destined to become the UK loaner, I will ask him to ship it to you if some other arrangement doesn't work. I will be starting a loaner list at some point if there's enough interest. Thanks very much for wanting to listen.

The design has indeed changed a lot over time. It's been in development for over 2 years - crazy really. I tried all kinds of things (literally dozens of amp and power supply circuits) before settling on this final version. I think it's the best I can do. Hope that's good enough.

YNWaN
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Re: RSL Phono-Stage on its way

Post by YNWaN » Fri Jan 25, 2019 6:48 pm

I’m sure it will be terrific :).

Do you have any insights you have learned along the way, that you could share?
Mark

ryansoundlab
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Re: RSL Phono-Stage on its way

Post by ryansoundlab » Fri Jan 25, 2019 10:57 pm

Good question. I hope I have learned something! However, I've got my grandson here (5 years old) and I can't think about much else at the moment! Will try to post something later tomorrow.

ryansoundlab
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Re: RSL Phono-Stage on its way

Post by ryansoundlab » Sat Jan 26, 2019 9:09 pm

Mark, here are a few thoughts for you - insights may be too strong a word!

I knew from the start that I wanted an I-V (“current mode”) input stage after listening to a Dynavector P75. No comparison with a standard voltage input MC amp. This decision required a dual power supply (+/- voltages) and a differential input stage to keep the input at zero volts all the time. (Naim’s single voltage architecture was out.) I soon discovered that a multi-paralleled transistor diff stage was very unstable in DC and drifted all over the place with slight changes in temperature and cartridge characteristics (I had as many as 20 input transistors!) – an IC input was mandatory with matched transistors thermally connected in a single package. I tried those SSM2212 matched NPN’s but it wasn’t long before I decided that an entire ultra-low noise IC op amp was an even better solution. Comparing the three leading op amp candidates: AD797, LT1115, and OPA1611, I preferred the musicality a bit more on the OPA1611 while the hiss levels on all three were almost identical. These op amps are much more stable, but even so, there’s an offset adjustment needed since any DC offset at the input is multiplied by over 10,000 at the output in this design.

An I-V input necessarily inverts the signal to keep the input node at virtual ground, so the rest of the circuit had to not just correct for RIAA but also have another inverting amp in there (I wanted phase-correct output, unlike the P75), thus I ended up with a 3-stage amp directly connected to the unit’s output for superior bass response with a coupling capacitor between the 2nd and 3rd stages to allow for removing the variable DC offset mentioned above from the final output. What was amazing to me is that when I compared polypropylene (PP) to polyester (PE-Mylar) coupling caps, the PE cap clearly had the better toe-tapping and dynamic performance. In fact, the polypropylene cap had no signature at all compared to a piece of plain wire but had less life to it. Another thing that can’t be explained by engineering!

The power supply was much more of a challenge and took the longest to resolve. My original goal was to have a one-box MC/MM phono-only solution with an internal power supply but without having any mains power in it to avoid hum pickup. A part of the objective was to keep it simple and lower cost. This initially resulted in a P75-like wall wart supplying an internal high frequency, switching +/- supply. Nice and simple ----nut not good enough sounding as I found out from a couple of people trying prototypes. Yes, it was definitely better than a P75 but should have been even better.

Long story short (many iterations later), I found that a “good old” external, dual voltage, transformer-based linear supply, and elimination of the switching supply, was way ahead of the wall wart solution. Plus, another level of voltage regulation (I always seem to end up with 3 levels in series!) was finally added. Yes, it cost more but there’s no point in selling something that isn’t the best it can be.

The cable between the power supply and the main unit was the final challenge – there was nothing available with heavy enough wires in it - so I ended making my own with 20g wire. It’s a DIN connector, but 5-pin 180 degree (vs the HiCap 240 degree type) to make absolutely sure no one accidentally tries to attach a HiCap to the RSL Phono-Stage.

So that’s a very brief summary of development events over the past two years. I have nothing to hide so if you have any specific questions, I’ll be happy to answer them

REXTON
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Re: RSL Phono-Stage on its way

Post by REXTON » Sun Jan 27, 2019 12:07 pm

Now this should be very very interesting. Following this thread with great anticipation and also comments from fellow paradise owners.
TT Garrard 401 (Fully Bastin'd)
Phonostage Paradise (4 Box)
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RogStat
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Re: RSL Phono-Stage on its way

Post by RogStat » Tue May 28, 2019 12:32 pm

Hi, What is happening with the RSL phono stage please as all has gone very quiet since January?
Regards

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