Question - ECC88 and other related valve

[montesquieu]

Just pondering what valves to put in my Radford STA100 (just to while away the time).

I already have plans to try a quad of the new Sophia KT88-ST tubes. I'm a KT88 fan from way back ... I'm hoping Will will set up the amp to take KT120s should I want to check those out in it, but first of all I want to use it with the valves it was designed for. The Sophias are expensive but not so expensive as GECs.

Input valve is an ECC88, followed (rather unusually, possibly uniquely) with a pair of EF184 pentodes, which provide the splitter function.

I have a supply of pristine, NOS EF184 Mullards, thanks to Valvebloke's eagle eyes who sent me in their direction.

However the ECC88 is a puzzle - I'm a bit confused about what I can use in there. For example I've had great results in the past with assorted JAN 6922s (both Phillips and Sylvania) - but I dont know if they can be used as ECC88s despite what some ebay sellers have in their listings. Also there's the 6DJ8 which I think is just another name for the ECC88 - or is it?

Can anyone enlighten me here? And possibly suggest some sensible choices for this position.

I've never really been one for exotic, fragile of 'NOS' valves after a few bad experiences years ago where stuff went 'phut' at great expense within weeks or even days. So new production even if expensive could be sensible, otherwise decent sounding but bulletproof is the priority. I only need two.

Sophia KT88 looks cool but of course won't be visible in the Radford:

[Firebottle]

The ECC88 is a far better valve than the 6922, it is a lot more linear.
The 6DJ8 is an equivalent.

Go for Telefunken valves, they really are good. If you can get Will to make the Radford accommodate the PCC88, which has a different heater voltage, you can get NOS Tesla for around £6 each.

[farflungstar]

Can't comment on the smaller tubes Tom, but I'd definitely recommend trying kt120s - specifically designed for audio and in my opinion superior to 300b/845/88 which I've lived with. Of course it's subjective but they are dynamic in a way I haven't heard before with other tubes.

[montesquieu]

Can't comment on the smaller tubes Tom, but I'd definitely recommend trying kt120s - specifically designed for audio and in my opinion superior to 300b/845/88 which I've lived with. Of course it's subjective but they are dynamic in a way I haven't heard before with other tubes.

I know, I have some experience of KT120s, heard quite a few KT120 amps including the Leben 1000p which was very good indeed, had it driving the Tannoys for quite a few weeks ... but it all depends on the implementation. I also owned a KT120 PP recently which was perfectly decent, but was effectively blown away by 25w of Radford EL34 STA25, something I would never have expected. This was an amp specifically designed for KT120s. It's far from automatic they'll sound any better than KT88s.

I want to start off with the Radford running good quality KT88s. Later, I can experiment.

[montesquieu]

Go for Telefunken valves, they really are good. If you can get Will to make the Radford accommodate the PCC88, which has a different heater voltage, you can get NOS Tesla for around £6 each.

Hmm I actually have a set of five Telefunken PCC88s (NOS when fitted not long before I bought the amp) that I removed from my EAR 912 when I got it ... it was sounding different to when Petrat came to demonstrate his, and it was Peter's sound that I preferred. So I replaced them with factory PCC88s from EAR and preferred that. I had been planning to sell them on. Not sure I'd mod the amp though. I know the Telefunkens can be very expensive I recall having a pair at some point or maybe that was ECC83s?

[Jazid]

Hmm I actually have a set of five Telefunken PCC88s (NOS when fitted not long before I bought the amp) that I removed from my EAR 912 when I got it ... it was sounding different to when Petrat came to demonstrate his, and it was Peter's sound that I preferred. So I replaced them with factory PCC88s from EAR and preferred that. I had been planning to sell them on. Not sure I'd mod the amp though. I know the Telefunkens can be very expensive I recall having a pair at some point or maybe that was ECC83s?

That would be either... If you want a guaranteed pair of gold pin NOS E88CC frame grids then drop me a line.

Sent from my GT-I9195 using Tapatalk

[Batty]

PCC88s, are they 7v heaters?

[montesquieu]

PCC88s, are they 7v heaters?

yes compared to 6.3v for ECC88. I assume that means you can generally use ECC88 in a PCC88 application, but not the other way round without modification.

[Batty]

I would have thought 7V across the ECC88 heaters would be a no no as it is too high.

[forsell]

yes compared to 6.3v for ECC88. I assume that means you can generally use ECC88 in a PCC88 application, but not the other way round without modification.

The other way round: PCC88 in ECC88 application. However filament voltage should be no lower than 6,3 V. This is not always the case when you MEASURE the real voltage across the pins of heater in real world amps. Some amp manufacturer do not follow the prescribed 6,3 V. According to valve manufacturer specifications allowable tolerances was +/-10% hence with a PCC88 running on 6,3 V heater voltage you are just "on the edge" but it is still OK.

ECC88 breed:

1) Standard quality

ECC88 = 6DJ8 = CV5358 = M3624 = 6Н23П

1st: European valve code
2nd: American valve code
3rd: British code (special applications valve), "CV" stands for "Common valve"
4th: British code (special applications valve)
5th: Russian code

2) Same specifications, higher quality for special applications (military, public services, telecommunication etc) Longevity min. 10 000 hrs

E88CC = CV2492 = Cca = 6922

3) Same specifications, 7V filament voltage

PCC88 = 7DJ8

1) and 2) fully interchangeable as they only differ in quality. 3) interchangeable with limitations as specified first.