NOS valves in a Croft preamp. A 'wow' moment!

[pankon]

Well, it is one of those rather rare 'wow' moments, when you do something, a small change, an adjustment, or anything and then out of the blue a major sound upgrade is achieved...

I've had this Croft SuperMicro II, which I purchased during my studies in the UK in 1989. When I purchased it after many auditions of equipment, I had the impression that the SuperMicro blew away all preamps at its price range and also many others costing many times as much. It was so open, transparent and convincing that I became a Croft fan ever since.

I have been listening to the SuperMicro with great pleasure, initially with a set of Musical Fidelity MA50 power amps (SS mono blocks, class A) and for many years afterwards paired with a Croft Series7. Almost one year ago, I had the preamp serviced by Glenn Croft and at the same time Glenn performed some upgrades, also bringing it to R-spec (R=regulated). That was a MAJOR upgrade! The sound became more composed, wider, tighter, with better imaging, deeper and yet more controlled bass. I was impressed (and very pleased, taking into account the cost-effectiveness of the upgrade).

Yesterday, a installed a pair of NOS Tesla E83CC in the phono stage of the SuperMicro. Nothing else. With only a few hours on the Tesla valves, two questions come to my mind:

1) Why had I never thought of this ever before? How can I have been missing this potential of the SuperMicro since 1989?
2) Why doesn't Glenn fit all his gear with high quality NOS valves? I am sure he is facing the hard reality of component cost, but then again there is so much more to be gained. Croft clients should be able to enjoy the full potential of the gear.

For the moment, I am getting much more detail than even before, with more resolution between instruments and voices but in a very relaxed manner. And the pace of the music is better. Yes, it is a cliche, but I am listening to records I've known all my life and I am discovering small things I never knew they existed on the record. The greatest improvement is on the realism of acoustic instruments and vocals. Buena Vista Social Club, Ella Fitzgerald, Neil Young, etc.

I hope my NOS Teslas will further improve, while breaking in. I will report again after 100h+.

In the meantime, the two further upgrades that I am planning for the SuperMicro are the following:

a) have the stock power supply upgraded to an external power supply (Glenn says it will give the sound more body and make it more lifelike. Can it be???)
b) substitute the stock GE 6463 valve of the line stage with an even better one. Any suggestions perhaps?

Phew, I had to get this 'out of my system' and share my upgrade experience. It was indeed one of those rare 'wow' moments. So gratifying...!

[Jimbo]

Hi Panos,

glad you have found the NOS Tesla ECC83's work well in your Croft preamp. I would use nothing else, they are simply superb especially the Tesla ECC83 32's
I have tried my Croft set up with the KEF LS50 speakers also and find it a great combination.

Now I must try some 7R mono's!

[Firebottle]

Hi Panos,

Great to hear you have opened up the sound of your Croft.

2) Why doesn't Glenn fit all his gear with high quality NOS valves? I am sure he is facing the hard reality of component cost, but then again there is so much more to be gained.

Yes, it is a cliche, but I am listening to records I've known all my life and I am discovering small things I never knew they existed on the record.

I believe Glenn fits the valves he does due to the uncertainty of supply of NOS valves, apart from the cost as you say.

It is so satisfying to hear more in well know recordings, just more enjoyment

[pankon]

Hi Panos,

glad you have found the NOS Tesla ECC83's work well in your Croft preamp. I would use nothing else, they are simply superb especially the Tesla ECC83 32's
I have tried my Croft set up with the KEF LS50 speakers also and find it a great combination.

Now I must try some 7R mono's!

Yes, NOS Tesla E83CC sound great in the phono stage of the Croft SuperMicro preamp. Mine should be from the 60's. Now, I have to see whether I should try another NOS valve in the line stage (instead of the GE 6463 that's fitted).

Although I own the KEF LS50, IMHO they are NOT the ideal combination with the Croft amps (and in that system of mine I don't have the SuperMicro, but the Micro25R and a set of Series7R mono blocks). The KEFS are really difficult to drive and require the volume to be turned high, in order to perform better. Changing from the standard Series7 to 7R mono blocks allowed to get a better control on the KEFs, but still the synergy is not ideal, at least not in my ears -)).

[Jimbo]

Try and get hold of some Spendor SP2's they are simply stunning with the Croft, indeed Glenn used to use them regularly.

With regards to the Micro 25R I would recommend you have the line stage changed to the RS spec which is a 12BH7a valve with non inductive resistors. Takes some time to run in but benefits the whole preamp as the phono stage runs through this.

[pankon]

Hi James,

as a matter of fact, my Micro25R does have the line stage with the 12BH7A valve (a Synlavia one). It produces more realistic ('grown up' -)) sound than a ECC82. I will just need to replace the JJ ECC83S valves of the phono stage with a pair of NOS Tesla E83CC, like the ones I installed in my SuperMicro.

With respect to the speakers, I am thinking of changing the LS50 with a pair of Harbeth, probably the SHL5Plus. I wish I could go up to the M40.2, but I am afraid that the cost may be too high in comparison to what the SHL5Plus offers.

Try and get hold of some Spendor SP2's they are simply stunning with the Croft, indeed Glenn used to use them regularly.

With regards to the Micro 25R I would recommend you have the line stage changed to the RS spec which is a 12BH7a valve with non inductive resistors. Takes some time to run in but benefits the whole preamp as the phono stage runs through this.

[Jimbo]

I did not realise you had the 12BH7a line stage, good move in my opinion.

As the Harbeth SHl5 plus is a bit expensive I would consider the early SHL5, I recon they have better cones and are more musical than the radial material they build the new SHL5 from. Just my opinion but I heard an early ShL5 recently and it sounded very nice indeed.

[OD1]

Gents,
I would like to try some Tesla ECC83 32's in my Croft 25R, put have been put off so far due to not wanting to buy "fakes".
Could you please advise where you purchased yours from, or any good sources in the UK (not EBay) ?

I currently use new issue Genelex Gold Lions in the phono stage, Yellow print Sylvania 12BH7A in the linestage & Nos Mullards in the
power supply.

Thanks in advance
Oliver

[Jimbo]

Gents,
I would like to try some Tesla ECC83 32's in my Croft 25R, put have been put off so far due to not wanting to buy "fakes".
Could you please advise where you purchased yours from, or any good sources in the UK (not EBay) ?

I currently use new issue Genelex Gold Lions in the phono stage, Yellow print Sylvania 12BH7A in the linestage & Nos Mullards in the
power supply.

Thanks in advance
Oliver

Oliver, there is a chap called Mullardman who sells NOS Tesla ECC83,s on ebay. He is very reliable and good person to deal with. I have bought from him.

[OD1]

Thanks James,