P2 Phono Stage - tube rolling noobie

[Mark Packer]

I've finally got an Audio Innovations P2. I'm one week in and enjoying it immensely.

Now of course, I'm wondering about tube rolling and wondering exactly where I will get the best bang per buck, rolling the valves in the signal path? The valve layout in my P2 is:

My inclination is the v3 the ECC83 followed by the v4 ECC82 and then v1 & v2. Is this correct?If not what would you suggest?

Please suggest some reasonably priced options and possible reliable sources.

 

[per-Sony-fied]

I wish I could help you as I had a P2 for 15 years or more & tried a few different tubes to up its sound quality over the years but (here's the but) I never really used my P2 for a number of years because my TT started rusting .

Recently I decided to sell my P2 to a PF member & all the valves I bought for it went with it including some rare blackburn valves made in Chelmsford . So to be honest my memory is not great regarding the fitted valves but if you contact @Colin131 he may be able to help since he was going to give it a good overhaul.

 

[Vinny]

some rare blackburn valves made in Chelmsford

That would be impossible - they can only have been made in one or the other. Valves made in Chelmsford would have been made by Marconi - Philips symbol epsilon. Blackburn code was capital B.

Philips badged ALL MANNER of valves, made all over the place, by all manner of manufacturers, but source (plus date, plus valve type) was part of the code on every valve. Not only did they badge sourced vales as one of the Philips brands (Philips, Adzam, and numerous others), but they also badged sourced valves for distributors - so a valve made in E Germany may have had a Philips code on but be badged Pinnacle, and so on, although the Philips code would tell you where it was made, and the fact that it had a Philips code meant that Philips had been the "middle-man".

Some of the source codes may be a little confusing today, as factories/products were sold between manufacturers. If memory is correct, the Marconi production was sold to Thorn (UK brands mostly Mazda and Brimar, but they also branded valves for distributors such as Pinnacle, Zaerix, Bentley, etc. etc. etc. etc., and sorced vast numbers of valves from Tungsram (Hungary)).

I have tried pretty much every type of valve immaginable, apart from Telefunken, in my Croft, and differences are mostly in the imagination. The P2 could well be different.

GENERALLY speaking, ECC83 are phono-stage valves in any phono-stage. GENERALLY speaking, anything else is power supply/control, plus some form of output valve(s). ECC82 is a common cathode-follower output valve.
One ECC83 would GENERALLY amplify and produce RIAA corection for one channel.

 

[per-Sony-fied]

When I say Blackburn valves I mean the legacy series called TechTube. I thought these were made in Chelmsford, in a factory, westway but I guess you could be right.

 

[Vinny]

Legacy tubes?
The UK factory supposedly making tubes currently?
If they are still running, I have not checked, they are based in the midlands - not a huge distance from me in Leicester, somewhere. I suggested to them that they try to contact the staff of Thorn EMI/GE Lighting in Leiceter, where I used to work, when it was closed down as valve manufacture is essentially IDENTICAL to lamp manufacture, as difficult to imagine as that might be for an industry-outsider.

If so, the source of anything that they own or make is open to debate. SUPPOSEDLY, the machinery came from Ei (former Yugoslavia), but originally tooled by Philips (after a VERY short spell running Siemens tooling). The official Ei story is that all the machinery was scrapped - the facotory closure was shambolic and accrimonious..

NO-ONE has the knowledge to reconstruct EXACTLY, any valve made by any company, except possibly the US manufacturer making power vales - company name and valves escape me presently.

Your pic' is not within a million, million miles of anything sold as a double triode valve by Philips. It looks like two of the "micro" valves from the dying days of tubes, when valve manufacturers tried to get near to transistor sizes, in this case, encapsulated into a standard tube envelope form the pre 1970's. The micro-valves have a name, but that too escapes me currently (a small number of current amp' manufacturers use them, and they are cheap as they have no significant use today, not even amongst audiophile kit).

Various of the trade mark brands that audiophiles cherish have been licenced to the two major factories pumping out valves today in E Europe. Although I suspect that "Blackburn" is not a word that can be trade-marked etc., so anyone could use it.

The TechTube Blackburn E813CC: A New Approach to Tube Design | audioXpress

 

[Vinny]

The tiny valves produced as valve use died, replaced by transistors and other semiconductors - Nuvistor valves. For instance -

6S52N-V Nuvistor Tube 7895 6CW4. Miniature Triode | eBay

 

[Mark Packer]

Thanks guys.

Suggestions of reliable sources would be appreciated too. EBay looks like a bear pit for valves.

 

[chartz]

I use old stock RTC (Philips) and GE valves, mainly, because I got them for free.
When these have reached the end of their lives… I don’t want to think about it.
But 10,000 hours is a lot of valve - and music listening - time.
About the hypothetical SQ, the jury remains out. Through my 40 years with valves - I built my first phono preamp in 1982, damn - I’ve always sought reliability before all else.

 

[Vinny]

Suggestions of reliable sources would be appreciated too. EBay looks like a bear pit for valves.

In reality, there are just two options as to source if you are looking for old valves - EPay and from trustworthy individuals outside of the Bay - such as via here, but prices for the common types of old amplification valves have soared, and soared and soared.

In terms of popular types, I only bought ECC83, ECC82 and 12BH7 valves (and their equivalents) back about 3 years ago and the most that I paid was probably around £35 for a single valve, and plenty were nearer £10-15 each, and I have valves from all the likely factories, except Telefunken. I refused to pay the £70 or so per valve for NOS Telefunken valves back then. These days I do not look................ Fortunately pre-amp valves last for ever (almost).

Valves used for power supplies are, or were, I have no need to check, still "cheap" - my Croft also uses 85A2 and ECL85.

 

[per-Sony-fied]

Legacy tubes?
The UK factory supposedly making tubes currently?
If they are still running, I have not checked, they are based in the midlands - not a huge distance from me in Leicester, somewhere. I suggested to them that they try to contact the staff of Thorn EMI/GE Lighting in Leiceter, where I used to work, when it was closed down as valve manufacture is essentially IDENTICAL to lamp manufacture, as difficult to imagine as that might be for an industry-outsider.

Certainly, a very short run on these. Barely got off the ground before production ceased. Must have been one of the lucky few to purchase a couple. Was in two minds to "sell" them with the phono stage. Something tells me they must be worth a bob or two due to their rarity or maybe not?

 

[Vinny]

Something tells me they must be worth a bob or two due to their rarity or maybe not?

They do look like two Nuvistor triodes encapsulated into a standard conventional thermionic valve glass bulb. If so, the components inside are worth only a very few ££, but as an oddity/collector's item????
About the only way to judge any value would be if any have sold online recently. HiFi Shark will find any that have.

 

[Colin131]

I've finally got an Audio Innovations P2. I'm one week in and enjoying it immensely.

Now of course, I'm wondering about tube rolling and wondering exactly where I will get the best bang per buck, rolling the valves in the signal path? The valve layout in my P2 is:

My inclination is the v3 the ECC83 followed by the v4 ECC82 and then v1 & v2. Is this correct?If not what would you suggest?

Please suggest some reasonably priced options and possible reliable sources.

Sorry for the delay in posting on this thread. Been a bit busy.

I haven’t used the P2 since the first week or so I had it. Thanks for selling me it Steve. It’s in really great condition. Steve had a problem with hum and some of it was down to noisy trimmer pots but I think it was mostly from the T2 step up transformers, as with my S&B TX103 step ups hum is not a major problem.

I need to do some things to the P2 - adjustments etc, and want to upgrade some parts. I am using other phono stages at the moment.

I looked into the P2 a lot and have identified some issues. Guy Sergeant (who designed it) of Puresound told me that one of the three pairs of Jensen coupling caps were changed in value from the original spec of 0.22 uF to either 0.071, 0.068 uF(or 0.047 uF in some examples), as the filtering was too low in frequency and not needed. I went through the maths with some kind assistance from Simon Shilton (of SJS Electroacoustics). In my particular P2 the wrong set of coupling caps appears to have been changed in value (the second set in the 2nd stage has been changed in value instead of the first set/first stage). With the second set changed to 0.071 uF instead of 0.22 uF, the resultant high pass filter in that second stage has a -3dB point of 23 Hz, which is too high. This can give an issue for getting enough bass extension.

Also, If the power amp you use has an input impedance below 100 K ohms, having a 0.22 uF cap on the third stage (the output stage) won’t be high enough in value, also rolling off the bass further. If that cap value is changed to 0.47 uF minimum (or preferably 1uF or higher), the P2 would be more compatible with a wider range of preamps, power amps and integrateds with somewhat lower input impedance.

I was having issues with bass extension, and am sure these issues are the reason why.I had another P2 in the past, 15 years ago, and had the same bass extension issue. It was the main reason I sold it on.

So I intend to soon swap the 1st and 2nd set of coupling caps around so that 0.071 uF caps are in the first stage, and 0.22 uF caps are in the second stage. In the first stage the -3dB point with 0.071 uF caps is around 3 Hz, which is still plenty low enough. With 0.22 uF value it was about 1 Hz!

Changing the second stage coupling caps to 0.22 uF gives a -3dB point of 7.3 Hz (instead of 23 Hz) which Simon Shilton told me looked “about right”. Pic here of the proposed swap. https://i.postimg.cc/5yR2ySzN/62-DF0-C10-4-F75-4-E6-F-9-D83-BACE5-C073257.jpg

Guys original circuit diagram shows that the cap value change is supposed to be in the first stage, not the second stage.
https://postimg.cc/cv0qDF1Z

The other thing I want to do is raise the coupling caps on the output to 0.47 uF or higher as mentioned above. I’ll have to buy some new caps for that. The problem is getting good quality PIO or Copper foil caps that will fit (as there isn’t much space). Standard metallized polypropylenes will definitely fit as the size is a lot smaller for a given value, but would be a downgrade. Caps I’ve found that are a perfect fit are Jupiter copper foil and wax 0.47 uF 400 V caps. Pricey though (about £150 for a pair).

Instead of buying a load of pricey tubes I suggest to spend some money on some basic maintenance and parts upgrades first. All the electrolytics in the P2 are now 30 years old and should all be replaced. It’s not expensive. You could just go for big standard ones or slightly better ones - such as various Nichicon Caps for about £40 total cost. These are what I intend to get. A more pricey option is Mundorf HV or Audio note basic electrolytics.

This is the most important maintenance to do.

If you fancy some small upgrades too for a reasonable price, what I plan to also do is this. Change the RIAA standard polystyrene caps for either copper foil polystyrenes (if i can find any such as Nobles (suggest by Guy)). Simon suggested Amtrans AMCH instead which are more readily available. Should be a nice upgrade. - need to be very spot with values though as the Amtrans are 5% tolerance. They need to be measured with an accurate capacitance meter.

I want to also change some of the stock metal film resistors to tantalums or (if on more or a budget) to 2W Kiwame Carbon films. Changing the parallel 47K input resistors and 1 M ohm output resistors is a good start. Then the anode load resistors as a priority after that. (This is what Simon suggested)

Change the wire wound resistors in the PSU section to 5W Kiwame Carbon films.

Change the standard cheap electrolytic cathode bypass caps (there are six of them: 2 for each signal tube) to either Elma Silmics or OS Cons (suggested by Guy). Very cheap to buy Silmics. Black gates are probably even better but discontinued and much harder to find.

This cost of the parts for this maintenance (changing the electrolytics) and some small upgrades is not expensive. £100 is so (unless using the tantalum resistors). If you can solder yourself this is a no brainier IMO before changing any tubes.

For further bigger upgrades I’ve been advised that the original Jensen coupling caps can definitely be improved upon. Also sometimes older PIOs can leak too

The Jensens PIO caps were good choice for good price/performance ratio at the time but they maybe aren’t so clear sounding by modern standards and can apparently sound a bit fuzzy. Simon advised me to go for Dueland JDM copper foils, Jupiter copper foil in Paper and wax, Audyn copper max, or Hovland musicaps (but they are discontinued). I’ve researched well into all these caps and only ones that will definitely fit easily into the P2 are the Jupiter caps in the 400V version, which are a bit pricey but perfect sizes. The Duelunds might possibly fit in the first and second stages with some work and apparently have as good if not better performance than the Jupiters.

I’m going to do mine in stages, - change the electrolytics, swap those Jensen caps around, change the pair of output caps (likely to the Jupiters in 0.47 or maybe even 1 uF if there is a way to somehow squeeze them in), and upgrade all the coupling caps

You might want to replace the 22K trimmer pots in the regulation stage too if they are noisy. I have some new ones but not done it yet. Also it’s best to set up the voltage of the value regulation system using the trimmer pots and a multimeter. I have some instructions written by Kevin from Definitive Audio. You are looking to get 4.5 V across two particular resistors by adjusting the 22K trimmer pots. In my experience this works well and makes the sound more focused and tight.

Pics here
https://postimg.cc/ct4hfrGS

https://postimg.cc/ns4d9xft

As for tube upgrades, one of the tubes could be a Mullard but I found having them all as Mullards made the sound too smooth and dark. I’d recommend other vintage tubes like Brimars, Philips, Siemens or others people have recommended. Maybe a mix with one or two sets of the tubes Mullards. A single Mullard ECC82 (or military equivalent) with some light use for the second stage shouldn’t be too expensive. More pricey for the ecc83 in the first stage (the input tube). You might need to find lower noise tubes as in the P2 noiser tubes can be an issue, if you speakers are more sensitive ones. Guy said that it’s particularly important that the pair of ECC82s in the output stage are quiet. I have personally found you can get issues with noisy tubes in any of the signal positions. I used headphone a lot and they are higher sensitivity than most speakers, so a quiet noise fooor is important for me.

Recommend Mullards for the OA2s and a NOS rectifier. Maybe Mullard or Brimar etc.

Different brands of tubes in all three sets of the signal tubes (ECC83 and the three ECC82s) will affect the sound. I’m not totally sure if the tube(s) in one of the stages is supposed to affect the sound more than others but I find they all do to pretty much the same extent.

Like I say though, I’d concentrate on maintenance and a few basic upgrades first, and fixing the cap values if your second set of coupling caps is 0.071 or 0.068, or 0.047 uF. I’d check that first.

Hope this helps, and also for anyone else with a P2 that wants to overhaul it.