Recommendations needed - 12ax7 / ECC83 for phonostage

[Shaunmaxr]

Hi all, I am looking for some advice as to where best to source three (including a matched pair) of 12ax7 valves for my minimax phono preamp. It also takes a 6x4 rectifier but not sure if I need /want to replace this.

I have the stock valves that came with the amp from Eastern Electric and I’ve had it for 10 years now, just upgrading my main amp and want to try something better that will do the rest of my system justice. (Michell Gorbe/SME m2/9 / Lyra/ Sugden Masterclass/ Goodman Magnum K’s.) 

I’m bit wary of eBay so would really appreciate some guidance for reputable resellers.

I’ve read a fair bit about different types, my budget is a few hundred dollars. 
Thanks in advance !
 

 

 

[xlr8or]

This very much depends on whether you would like pursue new production tubes or vintage types. eBay is fine for both if you look at the previous feedback/score of the seller - the higher the better.

 

Low noise tubes would be something to think about in a phono stage. Vintage types such as the E83CC with triple mica construction would be a good starting point. Mullard or Brimar box plate square getters are also recommended.

 

Edit: Here is a nice pair for you to consider from a trusted seller that is also an SNA member:

 

https://www.ebay.com.au/itm/CSF-Thomson-France-early-1960s-12AX7S-ECC803S-strong-matched-tubes-/164316442919

Edited February 21, 2021 by xlr8or

[Shaunmaxr]

Thanks Kirk, I am definitely more than happy to have a bit of fun trying vintage types.

 

I haven't heard of those CSF Thompson France ones before but I'll have a good look.

 

If I went for those CSF say (for the second stage and buffer stage of left/right channels - according to my manual)  do you have any recommendations for the centre position on my Minimax (first amplifier stage for both channels) and for the 6x4 voltage rectifier? The seller has a Telefunken 12AX7 ECC83 for $96 or Soviet 12ax7 triple mica grey plate at $20.

 

Another seller has a GEC 6x4 for sale here  https://www.ebay.com.au/itm/GEC-CV4005-6063-ruggedised-6X4-rectifier-tube-New-in-orig-Box/303886745866?hash=item46c10fc10a:g:Re4AAOSwp4ZgH00-

 

Any thoughts on these options. I guess Im trying to squeeze as much out of the preamp as I can within reason.

Edited February 21, 2021 by Shaunmaxr

[xlr8or]

For the first stage, I would recommend this one:

 

https://www.ebay.com.au/itm/VINTAGE-MULLARD-1957-12AX7-ECC83-BOX-PLATES-BRITISH-MADE-VALVE-TUBE-/193504004091

 

Regarding the 6X4 my vote goes towards this Genalex U78:

 

https://www.ebay.com.au/itm/303886745866

 

Edit: Here is another earlier vintage U78:

 

https://www.tubemonger.com/GEC_GENALEX_1958_59_CV4001_6X4WA_NIB_England_p/2060m.htm

Edited February 21, 2021 by xlr8or

[Shaunmaxr]

Kirk, 

I grabbed this one as the auction was ending. 

 

https://www.ebay.com.au/itm/GEC-CV4005-6063-ruggedised-6X4-rectifier-tube-New-in-orig-Box/303886745866?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2748.l2649

 

 

Edited February 22, 2021 by Shaunmaxr

[Rhythm Willie]

I've been through a number of NOS tubes (GE 5 star, RCA Cleartops, Mullards etc), without spending a fortune I would try some new JJ Goldpins, you might be surprised.

[xlr8or]

9 hours ago, Shaunmaxr said:

Kirk, 

I grabbed this one as the auction was ending. 

 

https://www.ebay.com.au/itm/GEC-CV4005-6063-ruggedised-6X4-rectifier-tube-New-in-orig-Box/303886745866?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2748.l2649

 

Excellent work. Please report back with your listening impressions when received. You can then also invite me and others over to have a listen.

[Shaunmaxr]

9 minutes ago, xlr8or said:

 

Excellent work. Please report back with your listening impressions when received. You can then also invite me and others over to have a listen.

I might do that.

 

I have had the Minimax with stock EE tubes since circa 2010 but having just upgraded my integrated from a Sugden a21A to an Ia4 it got me thinking I should try and see what this thing is capable of.

 

I've also grabbed the British Mullard Box Plate, and the pair of the French CSF Thompson as well.  Hoping the French and the English get on well for a change.

 

Quite looking forward to the post arriving now. I'll let you know how it goes.

 

 

[PKay]

On 22/02/2021 at 8:13 PM, Shaunmaxr said:

I might do that.

 

I have had the Minimax with stock EE tubes since circa 2010 but having just upgraded my integrated from a Sugden a21A to an Ia4 it got me thinking I should try and see what this thing is capable of.

 

I've also grabbed the British Mullard Box Plate, and the pair of the French CSF Thompson as well.  Hoping the French and the English get on well for a change.

 

Quite looking forward to the post arriving now. I'll let you know how it goes.

 

 

How did they go?

[PKay]

I have just ordered a EAR Phonobox and was wondering about same replacement valves. The current valves are 13d16 which are made for EAR. The phono is brilliant in so many ways and has a neutral presentation but I was hoping to add a small touch of warmth while retaining the quietness and dynamics of the current system. 
 

I would appreciate any suggestions. 

[muon*]

5 hours ago, PKay said:

I have just ordered a EAR Phonobox and was wondering about same replacement valves. The current valves are 13d16 which are made for EAR. The phono is brilliant in so many ways and has a neutral presentation but I was hoping to add a small touch of warmth while retaining the quietness and dynamics of the current system. 
 

I would appreciate any suggestions. 

I read that there is a jumper in the power supply to change to 12AX7, the 13d16  is said to be like a 12AX7 but is 13v.

 

Edit: strange that is this review they say that you have to use the 13d16

https://hifiandstereo.com.au/reviews/ear-yoshino-phonobox-tubes-that-work-a-review/

 

If not tubes, you can change the character by replacing the output cpacitors with something like Jupiter Copper Foil/Oil ones. I did this in a 834P copy with great results.

Edited October 7, 2021 by muon*

[PKay]

4 minutes ago, muon* said:

I read that there is a jumper in the power supply to change to 12AX7, the 13d16  is said to be like a 12AX7 but is 13v.

I’m not sure why EAR changed to these valves. It was meant to be around reliability. 

[muon*]

8 minutes ago, PKay said:

I’m not sure why EAR changed to these valves. It was meant to be around reliability. 

Or maybe Tim is quirky and doesn't like people rolling tubes in his products, like that review suggests *shrug*

[PKay]

39 minutes ago, muon* said:

Or maybe Tim is quirky and doesn't like people rolling tubes in his products, like that review suggests *shrug*

Sadly he has passed away and we won't know he chose that tube.

 

The phonobox is brilliant and very neutral particularly for a valve amp.  I was guessing that it is due to the valves used.

Edited October 7, 2021 by PKay

[muon*]

I'm familiar with the 834P circuit but don't know what changes they may have made with the Phonobox.

I guess without knowing the data on the 13d16 or better still the conditions It's operating under, stuck with them.

 

Although an option when ordering is either being fitted with those or 12AX7's (ECC83), but no idea if something needs to be changed to accommodate them, maybe there is a jumper like some have suggested.

 

Technical Specifications:
 

VALVES:
Three 13D16 (optionally fitted with ECC83)

CONNECTIVITY:
One Phono MM & MC Input (RCA)
One Line Output (RCA)

DIMENSIONS AND WEIGHT:
Weight: 3.5kg Black Aluminium
4.0kg Chrome
Length 320mm
Width 180mm
Height 65mm

PERFORMANCE:
MM Input sensitivity: 2.2mB for 1 V @ 1kHz (53dB)
MC Input sensitivity: 0.22 mV for 1 V @ 1kHz (73dB)

OUTPUT:
Two Unbalanced Stereo (RCA) 5V into 600 Ohms

POWER:
Power consumption: 20 watts

[xlr8or]

On 07/10/2021 at 7:18 PM, muon* said:

Or maybe Tim is quirky and doesn't like people rolling tubes in his products, like that review suggests *shrug*

 

Tim did this in a lot of his designs including when he was with Luxman in the mid 1970's. The 8045G and 6240G are typical examples of new custom made tubes introduced to the market by Tim. Once EAR Yoshino was formed he started to also relabel tubes as his own. In certain instances this practice went beyond relabelling. The tube designation was changed to a new type.

 

Regarding the EAR Phonobox, the 13D16 almost sounds like an extension of the Brimar 13D 9-pin dual triode series from the 1950's, but it is not. I've read about the switch as well, but then I've also read the unit has to be ordered with 12AX7 tubes to have it use this type of tube.

 

Tim also deployed CCS heating in his tube designs. This means you can't roll his selected tube types to other tube types. That doesn't mean you can't roll tubes, it just means your limited to rolling the one tube; in this case the 12AX7, the most ubiquitous tube used in the audio world.

 

I own the 864B and Acute. I've owned the 834P (all versions), 88PB and MC4. My advice would be to try and get it fitted with 12AX7 tubes. Also, as @muon* has suggested, the caps should be rolled as Tim used a lot, and I mean a lot, of inferior grade caps, resistors etc. in his designs. I had a number of discussions with him about this and always came off second best. Mounting tubes upside down (e.g., in the 890), using flimsy PCB's and poorly riveted bush connections for screwed cover removal, including even in the Phonobox, suggests a level of caution is needed in opening up this unit to tube roll. My recommendation is to remove the cover once and leave it off permanently, if you intend to roll the tubes.

Edited October 9, 2021 by xlr8or