New project - Allen Wright RTP3

[Dowser]

Picked this up recently - for me a bit expensive, but still for less than the two Super Regulator boards would cost me to buy from Vacuum State (which seems to be the only bits they still sell as DIY objects).

Half built line stage only RTP3;

Line boards seem to be complete, but do not think it has ever been tested (seller said he powered up the heaters of the valves a few years back and they all glowed...but that doesn't say much does it!).

Super Regulator per channel is good - but power supply the original builder intended would not have made best use of it (see below).

4 channel stepped attentuator in place for volume, but no selector switch and a bit of a pigs ear in the wiring...need to start again. One of the USPs of this pre is that it runs fully differential (balanced), so with a 4 channel selector you can have each input at both + & - polarity.

Seems to use a mix of enameled single core wire and multi-strand - seems Allen (sadly passed now) recommended thin single core silver wire.

More piccies - underside of line stage;

One of the Super Reg boards - I have some official Vaccum State documentation about replacing the op for an AD797 and removing the LM317 for sonic improvements;

Stepped Attenuator - 50K - which is right I think (if I add the phono stage, the 50k is part of the RIAA cct I think);

Hotch potch wiring;

Power supply - I need to do better than this I think - I believe Allen recommends even separate heater supplies per valve/stage! On the good news front, I think that is a Vacuum State power supply PCB - you feed it mains, then goes out to your transformers, then receives back and rectifies. Need to read up a little.

For now, I've just ordered the cookbook Vacuum State still sell, I think that has further technical design details of the RTP3. Then I guess I'm going to need some help

I think one member here has built one of their own from scratch - who else has heard one? I assume it is worth persevering with, seems to have a good reputation on the market place.

Thanks, Richard

 

[GWM]

Oooh good luck with that,considered building one but realised it was beyond my skill set.There was a thread on the TNT site but it doesn't seem to work anymore,there are a number of threads on DIY audio though that are worth a read.

 

[Dowser]

Cookbook received and read, an excellent if slightly opinionated read! A really good mix of theory and practical & relevant beyond just Allen‘s designs. Strange I never stumbled over this guy before.

Now I need to strip mine down to see just what version I have, seems there were a few. The FETs used in each stage also need to be matched, so guess I’m going to have to strip it to make sure they are.

 

[Arkless Electronics]

Very nice!

 

[Alex M]

Hi Richard,

Good luck with the RTP3. The TPCB is a great resource, and will give you a good introduction to Allen's design philosophy, and also to his route towards the RTP3C.

I have to say, though, that there are handful of things that tell me this isn't an official VSE kit. The front panel is a giveaway, with the lack of source selector switching and of the single volume control, where Allen always preferred dual mono controls. It also looks as if the chassis has been designed from the start to only contain the line stage module, which strikes me as suspect - I've never seen a photo of an RTP3 without at least the spaces on the chassis for the phono modules. On top of that, the minimal PSU is a bit of a giveaway. On the other hand, it does look as it has been built with care following Allen's instructions - my guess is that it has been built from scratch from the construction manual CD that VSE used to supply.

Anyway, you do have a pair of "proper" SuperReg boards and pretty much all you need in the chassis to get this going. The fact that you have ten valves in the line stage mean the circuit is based on the RTP3C, since previous versions (and the RTP4 and RTP5) used MOSFETS in place of at least one of the valves. Did you get the schematic with the preamp? If so, what is the date on it?

You may be aware of the long-running and scenic thread on DIYaudio on building the RTP3 - a long read, but lots of interesting discussion.

Alex

 

[Dowser]

Many thanks Alex - the seller reckoned he bought it from Allen (And was not too complimentary of his customer service skills), but then had it with A builder Allen recommended. He also thought he’d paid for a phono stage, but is selling as a line amp as the phono modules never arrived. Hard to tell, the seller was an enthusiast but is very old now and was a bit confused. I don’t have a schematic for the pre, but do have various documents on improving the super-regulator boards - must check if there is a date on them.

I bought this knowing it is really beyond my skill, but want to at least understand what I have and how to get it running. Your pages are a helpful resource, thanks, as are the DIYAudio threads.

@Arkless Electronics - Jez, you know his work?

Richard

 

[Arkless Electronics]

Many thanks Alex - the seller reckoned he bought it from Allen (And was not too complimentary of his customer service skills), but then had it with A builder Allen recommended. He also thought he’d paid for a phono stage, but is selling as a line amp as the phono modules never arrived. Hard to tell, the seller was an enthusiast but is very old now and was a bit confused. I don’t have a schematic for the pre, but do have various documents on improving the super-regulator boards - must check if there is a date on them.

I bought this knowing it is really beyond my skill, but want to at least understand what I have and how to get it running. Your pages are a helpful resource, thanks, as are the DIYAudio threads.

@Arkless Electronics - Jez, you know his work?

Richard

I know of it and in some ways it parallels some of my own in my highest end kit, which is mostly hybrid valve and SS. I'm more familiar with the phono stages than the line stages though. It has the Jez seal of approval as still SOTA and no I wouldn't be interested in sorting it out for you... in case you were going to ask

 

[Chops54]

That's a good score Richard. I don't think you'd have much trouble sorting it out. I always fancied a go at this but felt a scratch build was too much to take on. You've got a great start here and the balanced phono stage doesn't look difficult to build either. Yes the 50K attenuator is correct and should exhibit the same impedance at all settings.
As an aside I've used the Vacuum State protractor to align my cartridges for as long as I can remember. It always seems to work well for me