Premier Five: EL34, KT77 or 6550

From tubes to solid state.
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MLAS
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Premier Five: EL34, KT77 or 6550

Post by MLAS »

Hi Guys,

Have a Premier Three & Five combinations and I think the EH 34 powertubes need be changed.
I consider this three offerings from New Sensor:
1. EL 34 Mullard;
2. KT77 from Genalex;
3. 6550 from Tungsol,
Need 16 in total of them so NOS is out of the question.
In know of course that the three options are all orignating from the Reflektor plant in Russia.

Any advice/suggestions?

Thanks in advance.
Big Dog RJ
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Re: Premier Five: EL34, KT77 or 6550

Post by Big Dog RJ »

Hey mate, that's a wonderful combination of CJ pre-power classic. They don't make amplification like that anymore, unless it was to cost a fortune...

In my experience, I have not come across an amplifier based on an EL34 (ultra-linear mode) being able to directly take in other types of output tubes, such as the KT series or 6550's, without having to modify the base circuit for the output stage. These are pentodes, and differ slightly in the main circuit which is based on EL34's. If you have already checked with CJ regarding these tube types on your Premier 5 amp, that would be the safest way to go.

I remember when I had my VTL's with EL34's, it had a switch on the front panel that allowed you to change from Tetrode to Triode mode without having to modify internally, and would halve the output stage in terms of power. I don't think a CJ EL34 designed amplifier can take other pentodes as direct replacements for the output stage. Better double check with CJ though.

Cheers, RJ
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Re: Premier Five: EL34, KT77 or 6550

Post by Big Dog RJ »

Re. to the tube types and their sonic signatures; this is what I have found over the decades:

EL34- very musical sounding, superb midrange, depth and layering, superb resolution, and good tight bass, with fast transient response.

KT77- widely used in Quad amps back in the hay day; equally good midrange and depth, soft on bass and very warm sounding. Very relaxing and pleasing to listen to for endless hours.

6550- more powerful and dynamic. great low bass but not as fast and low compared to KT120 / KT150- power beam tetrodes. More fuller sound with more bloom to tones and low frequency.

It all depends what type of music you mostly listen to and what type of sound you want to achieve from the amplifier. All three types are great, depends on personal preferences and your speakers.
Hope you are able to find something that suits your tastes.

Have a good one, RJ
MLAS
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Re: Premier Five: EL34, KT77 or 6550

Post by MLAS »

Big Dog RJ wrote:Hey mate, that's a wonderful combination of CJ pre-power classic. They don't make amplification like that anymore, unless it was to cost a fortune...

In my experience, I have not come across an amplifier based on an EL34 (ultra-linear mode) being able to directly take in other types of output tubes, such as the KT series or 6550's, without having to modify the base circuit for the output stage. These are pentodes, and differ slightly in the main circuit which is based on EL34's. If you have already checked with CJ regarding these tube types on your Premier 5 amp, that would be the safest way to go.

I remember when I had my VTL's with EL34's, it had a switch on the front panel that allowed you to change from Tetrode to Triode mode without having to modify internally, and would halve the output stage in terms of power. I don't think a CJ EL34 designed amplifier can take other pentodes as direct replacements for the output stage. Better double check with CJ though.

Cheers, RJ
Thank you very much for your concern in this matter.
I've seen a Premier Five with 6550's and the Premier One in its first incarnation had them too.
I thought the trio was interchangeable and I just have to modify the bias because the 6550's need a little bit more.
But your right the safest way to operate is to contact CJ themselves and I will post their reaction.

Thanks also for your review of these three powertubes.
My inclination would be towards the KT77 because that's the sound I love the most.
Must say that all the ragged edges disappeared after I substituded my solidstate pre-amp for the Premier Three.
I was a bit shocked (actually a lot, but with the sound it makes it is mellowing away 8-) ) about the general build quality and parts layout of this pre-amp but I solved it myself more or less. See: viewtopic.php?f=10&t=1022
MLAS
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Re: Premier Five: EL34, KT77 or 6550

Post by MLAS »

Big Dog RJ wrote:Hey mate, that's a wonderful combination of CJ pre-power classic. They don't make amplification like that anymore, unless it was to cost a fortune...

In my experience, I have not come across an amplifier based on an EL34 (ultra-linear mode) being able to directly take in other types of output tubes, such as the KT series or 6550's, without having to modify the base circuit for the output stage. These are pentodes, and differ slightly in the main circuit which is based on EL34's. If you have already checked with CJ regarding these tube types on your Premier 5 amp, that would be the safest way to go.

I remember when I had my VTL's with EL34's, it had a switch on the front panel that allowed you to change from Tetrode to Triode mode without having to modify internally, and would halve the output stage in terms of power. I don't think a CJ EL34 designed amplifier can take other pentodes as direct replacements for the output stage. Better double check with CJ though.

Cheers, RJ
You were right:
The amplifier design and bias voltage is setup for EL34’s , do not use other tube types in this amp.

Thanks,

Jeff Fischel
General Manager/Senior Technician
conrad-johnson design inc.
703-698-8581
http://www.conradjohnson.com/
Big Dog RJ
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Re: Premier Five: EL34, KT77 or 6550

Post by Big Dog RJ »

Back in the hay day, and when my mate had the CJ dealership, I remember several customers requesting for different types of tubes on their power amps. Then CJ would take these "pre-orders" and design the amp around that particular tube. In fact I did the same with my premier 11A, requested it to be changed from a pentode using 6550's to a triode "XS" version with EL34's- sounded superb!

They still do this for certain models and also offer various configs. For example, the ARTsa can be ordered with either KT120's or 6550's, and can also be factory installed for EL34's operating in triode mode. This also halves the output power but increases the level of musicality to a remarkable level!
If I'm correct, I think they also offer this for the LP125 series as well as the Classic amplifiers but not on the CAV45. The CAV45 is a pure EL34 design and an absolute gem!

If you are able to get CJ to do the mod with your preferred tube being the KT77, I am sure that combination would sound marvellous!
Have a good one and do let us know how it goes, cheers
RJ
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