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    Best Rectifier and Driver Tubes for Latino VTA ST-70?

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    Chris A

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    Post by Chris A on Tue Oct 15, 2019 12:48 pm

    Hi Everyone,

    This is my first post. I live in London, UK.

    A year ago I purchased a Bob Latino VTA ST-70 in kit form. My first ever valve amp! It was great fun to build, assisted by Bob’s excellent assembly instructions.
    I elected to have tubes included with the kit. This is what I have:

    1. Rectifier: ‘Electron Tube’ branded 5AR4, made in China
    2. Driver Board (low gain): 3x RCA 5963
    3. Output Stage: 4x EL34. None of these tubes have any markings on them.

    The amp drives a pair of Klipsch Heresys. In this form, the amp generally sounds great. I listen mostly to 60s onwards rock/pop/American jazz-rock/Zappa. No jazz, classical or opera. My only minor moan is that the system is a little bass light. The Klipschs roll off at 50Hz which is a bit disappointing for a 12" speaker. However, in all other areas the sound is superb, at least to my ears.  

    I am wondering whether it could sound even better…

    I would like some advice/guidance on what would be the best rectifier and driver tubes to use. I’m after top quality and longevity; I’ll pay ludicrous prices for 50+ year old Mullards or whatever if that really is what will work best with this amp.

    My plan is to stay with the existing output tubes for now; once I’ve got used to the sound resulting from changing the rectifier and driver tubes, I’ll move on to the outputs in a year or so.

    Also with regards to the driver tubes I understand that the centre one does something different to the outer two. Something to do with splitting/inverting? Please can someone enlighten me? Should the centre tube be a different type to the outer two, or should I stick with three identical ones? If so, should they be matched?

    Many thanks, Chris A


    Last edited by Chris A on Tue Oct 15, 2019 5:18 pm; edited 1 time in total
    Bob Latino
    Bob Latino
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    Post by Bob Latino on Tue Oct 15, 2019 1:00 pm

    The best tube rectifiers that you can use in any VTA amp is the Mullard GZ33 or GZ37. Since you are in the UK (where they were originally made), it may be easier to find one of these two tubes. The Ebay UK link below is selling them for 75 pounds ..

    Mullard GZ33 tube for sale on Ebay UK

    Bob
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    Chris A

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    Post by Chris A on Tue Oct 15, 2019 5:17 pm

    Hi Bob,

    Many thanks for your recommendation regarding the rectifier tube. I've ordered one. Can you or anyone share your thoughts re the best driver tubes and whether the centre one should be different to the outer two or a matched triple?

    Regards,

    Chris
    Bob Latino
    Bob Latino
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    Post by Bob Latino on Tue Oct 15, 2019 5:44 pm

    Chris A wrote:Hi Bob,

    Many thanks for your recommendation regarding the rectifier tube. I've ordered one. Can you or anyone share your thoughts re the best driver tubes and whether the centre one should be different to the outer two or a matched triple?

    Regards,

    Chris

    Hi Chris,

    The center driver tube may be the same or different than the two outer driver tubes. The two outer (phase splitter/inverter) driver tubes should be the same. On all the VTA amps (made since April of 2012), you can use any 12AU7, 12BH7, 5963, 5814, 6189, Mullard CV4003 or ECC82 driver tube. It is also important that you DO NOT USE 12AT7, 12AX7, 12AV7, 12AY7 or 12DW7 tubes in any modern VTA amp. These tubes, although plug compatible, have too much gain and other incompatible characteristics that can cause problems with the amps. One problem is that you can blow the LM334 current regulator if you try one of the latter tubes.

    Bob
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    Sonicbliss

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    Join date : 2019-10-21
    Location : Southern California

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    Post by Sonicbliss on Mon Oct 21, 2019 9:45 pm

    Chris,
    Find some "Voice of Music" branded 12au7's for the side driver positions and a JAN 6189 (sylvania or GE) for the center position. Tighter balanced tubes are better. This will sound nice with the Heresy's. are the Klipsch on stands, or floor. Floor is better, about 12 inches from the back wall for better bass.
    Cheers!!
    corndog71
    corndog71

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    Post by corndog71 on Tue Oct 22, 2019 11:59 am

    Having owned a pair of Heresey II's years ago I know exactly what you're talking about. Sadly, the only way to improve bass response that I could find was to add a subwoofer.

    deepee99
    deepee99

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    Post by deepee99 on Fri Nov 01, 2019 9:04 pm

    Do what Bob sez: a genuine Mullard GZ-33 is a very robust tube that sounds as good as it looks.
    I wouldn't wait for that Sino 5AR4 to melt down and hurt something. The Russian-made Gold Lion 5AR4 is I'm told up to the task for new issue, but it sure lacks the beauty of a GZ-33.
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    B&WTube

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    Post by B&WTube on Tue Nov 12, 2019 1:11 am

    I am a noob, but change my setup regularly as I am nailing down the sound I want.

    FWIW, I had the Gold Lion 5AR4 rectifier, and tried the Webber WS-1 copper cap, with Thermistor. If you want to shift a little away from warmth to clarity this really helps clean up busy tracks with significant swings, such fast/complex guitar sequences.

    I have done some rolling and like the Gold Lion 12Au7 for the center driver. However, having this for all three was slightly too bright for my taste, so I rolled to Electro Harmonix Gold 12BH7’s for the phase splitters, and am quite happy.
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    TN Allen

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    Post by TN Allen on Tue Dec 03, 2019 1:50 pm

    "...The Ebay UK link below is selling them for 75 pounds ..
    Mullard GZ33 tube for sale on Ebay UK"

    Has anyone bought from the Ebay seller above?
    Is there a better, or more convenient, and reliable US source?
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    stewdan

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    Post by stewdan on Tue Dec 03, 2019 3:20 pm

    TN Allen ..... I have bought GZ37 and GZ33 Rectifier Tubes from Yitry in London. (The link that Bob provided and have always gotten good tubes.)

    I am currently awaiting delivery of a pair of GZ33 tubes.

    Stew
    ArlanB
    ArlanB

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    Post by ArlanB on Tue Dec 03, 2019 8:19 pm

    Just recently purchased a pair of the Mullard GZ33 from the above mentioned ebay seller (Yitry).  The tubes arrived well packed, surprisingly quickly from England.  The tubes are of excellent quality, appearing as if they were just manufactured.  The labeling is crisp with no evidence of handeling.  No I have not tried them yet, have a 5AR4 from Ruby tubes that has been in service for over a year now and is working well.  I don't want to upset the applecart just yet.  So as far as this sellers service goes, reasonable price, product as stated, and quick delivery. I would purchase from the seller again.
    deepee99
    deepee99

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    Post by deepee99 on Wed Dec 04, 2019 8:14 am

    ArlanB wrote:Just recently purchased a pair of the Mullard GZ33 from the above mentioned ebay seller (Yitry).  The tubes arrived well packed, surprisingly quickly from England.  The tubes are of excellent quality, appearing as if they were just manufactured.  The labeling is crisp with no evidence of handeling.  No I have not tried them yet, have a 5AR4 from Ruby tubes that has been in service for over a year now and is working well.  I don't want to upset the applecart just yet.  So as far as this sellers service goes, reasonable price, product as stated, and quick delivery. I would purchase from the seller again.
    Believe I've dealt with your chap, too, and would vouch for his integrity and quality and friendly reasonableness. IIRC he is a Turk and his wife is a Russian, and she does all the scut-work although his English is hard to understand.
    Another good former CCCP tuber is Olga from Latvia, is very good with eastern European military-issue valves. Don't panic if they take 6 weeks to arrive. Olga's straight.
    https://www.ebay.com/itm/McIntosh-MA5100-PreAmplifier-LED-Lamp-bulb-Filter-Upgrade-Kit-LED-5-x-bulbs/163124423577?_trkparms=aid%3D333200%26algo%3DCOMP.MBE%26ao%3D1%26asc%3D61007%26meid%3Dae4dddcc671046e2b01cd0026c5b06af%26pid%3D100008%26rk%3D10%26rkt%3D12%26sd%3D383289366857%26itm%3D163124423577%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100008.m2219

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    TN Allen

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    Post by TN Allen on Wed Dec 04, 2019 11:17 am

    Thanks for the reassurance, I ordered a GZ33 last night for an ST 70 I updated a few years ago. I'll add the diodes to the rectifier socket as well. I don't recall what tubes cost when I built the original kit in 1969, but I suspect with inflation over the past 50 years the 75 Pounds is probably about the same actual cost.
    deepee99
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    Post by deepee99 on Wed Dec 04, 2019 11:41 am

    TN Allen wrote:Thanks for the reassurance, I ordered a GZ33 last night for an ST 70 I updated a few years ago. I'll add the diodes to the rectifier socket as well. I don't recall what tubes cost when I built the original kit in 1969, but I suspect with inflation over the past 50 years the 75 Pounds is probably about the same actual cost.
    .
    Prices on my KT-88s and 6550s were in the $8.00 - $12 when bought new years ago.
    And to think guys threw this stuff out.
    GreggW
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    Post by GreggW on Wed Dec 04, 2019 11:35 pm

    Just counted my stash of 5V3As. Didn't realize I have 18 spares. They're pretty much bulletproof, long lasting, and are good for over 400ma. Haven't replaced one yet. Maybe I should sell a dozen and get a GZ33. I'd still have six spares....

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