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Binaural 16th September 2009 10:06 AM

Vacuum State RTP3C
Hello all,
I've been in the mood to change up my analog setup a bit lately. I have been using an Aikido phono stage with lundahl step up transformers. I have thought about building a new phono pre, and have decided on the Vacuum State RTP3C.

I just have a couple of questions about it. Has anyone built/heard this unit? I know it's extremely subjective, but if anyone has heard it, could they describe the sound of it? Also is there anything I need to know about building this particular circuit? It seems pretty straight forward, but I just wanted to seek the expertise of someone who has possibly gone down this particular path before. I appreciate any help, thanks. Hope to hear from you soon.

Holger Barske 16th September 2009 10:25 AM

I strongly advise to read Allen's "tube preamp cookbook", which describes the development of the circuitry over the years. You'll have a lot of fun reading it and and all the information you need.
BTW: I do have an RTP3 at home ATM (borrowed from a friend). It is one of the most neutral, detailed and fastest preamps I have ever listened to. It's not that warm and sweet tube thing, it is... well, straight in ya face :D

SY 16th September 2009 10:38 AM

I haven't heard this preamp in a familiar system, but the design is VERY similar to one I've been using since the '80s. Allen has engineered it superbly well and I think you'll be quite happy. I would strongly suggest the use of his boards, if available- high bandwidth circuits can be tricky to stabilize. And do not stint on the power supply; the PSR of the cascodes is 67% of bupkis.

jazz 16th September 2009 02:31 PM


I have not build the rtp3c but the fvp5. I've been living with the fvp for years and wouldn't part with it whatever. The rtp should be better. In fact since i'm going balanced after building the alephX and pumpking, my next try is going to be the rtp5.

Indeed read Allen's preamp cookbook and build a proto, it's fun.


Shoog 16th September 2009 02:59 PM

I cannot comment on the Phono aspect of the RTP3C, but have built two versions of the FVP5 (without phono). Absolutely brilliant detailed, punchy and clean sound. Both versions have been mostly point to point builds and have shown no instability. Allen Wright only recommends his Super Reg to supply it, but I built a simple three stage CLCRC which is fine.
I listened to it up against an Aikido and can say that they sounded almost the same. If you use a different volume control then this is likely to swamp any of the sonic differences between the line stage circuits. This is not totally surprising since they are very similar circuits. If you include the Super Regulator then you will probably hear a more pronounced difference


Binaural 16th September 2009 08:41 PM

Shoog, I was hoping to hear from someone who has heard both. I wasn't planning on using the super reg since I've already built Broskie's Janus regulator. I was planning on using this with the RTP. Does anyone have any experience with the differences between these 2 power supplies. Does one sound significantly different from the other?

planet10 16th September 2009 11:08 PM

My RTP is under construction.... stay tuned.


M Knight 3rd October 2009 09:32 AM

If you are going to build the older iteration, the RTP3C, it will be relatively straightforward if you avail yourself of Allen's documentation.

If you are going to build the latest iteration, the RTP3D, you will have to put your thinking cap on, because the documentation is out of date.

If you construct to a (self-imposed) high standard, you will likely find building one of these a trial by fire, but you will be amply rewarded with, as HBarske above says, a neutral and detailed preamp that can hold its own against much more expensive gear. And it looks the part, too.

M Knight 3rd October 2009 10:57 AM

Another reason to read The Tube Preamp Cookbook is that it contains a neat little circuit for matching J-FETs. Whether you will be using (increasingly scarce) 2SK369s, as in the earlier versions, or (readily available) BF245s, as used in the latest incarnation, they will have to be matched, obviously. Allen still sells matched pairs of 2SK369s.

Luke 3rd October 2009 11:12 AM

I dont think the RTP3C comes as boards or kits. I think its a product.

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