[sfig]

Sorry, I meant two octets.

[SteveFord]

I would tend to stick with what VTL recommends even if the tube models are in the same family.
I think that it was my MB250s which were set up for 6550s from the factory but the previous owner stuck in Ei KT88s.  A bias pot went and took out a tube one night (it kind of looked like something out of a science fiction movie) so I called up VTL.
They have a modification kit for using KT88s which was not installed in my amps.  Rather than go through that or take my chances with a tube vendor's recommendations to the contrary I bit the bullet and went with 16 Winged C 6550s and all is well.

[carusoracer]

I have all three of the heavy favorites.
3) Winged C Svetlana
2) GL KT77
1) Treasure Series from Shuguang.
All IMHO. And run in two different Amps. Pretty consistant,rock solid bias.

Good luck

[Gopher]

I just ordered some tubes from goodcomponent.com which shipped yesterday.  Cheapest black treasure tube prices I've seen but I can't speak for their service.

Check out grant too--as implied above, with an order that big they may be able to alleviate some of the sticker shock.

I can now vouch for this seller.  I ordered some red label 845Bs from them last week which shipped Friday and arrived today (monday).  Very quick service, well packaged and great prices.

[ulysses]

Gopher, did you have to pay import duties for the tubes purchased from goodcomponent.com? How was shipping cost determined and paid for?

Thanks!

[Gopher]

No import duties, but shipping was a little steep.  I paid $30 to ship two 845 tubes.  Next time I need to buy from them, I'll probably get a few sets of different things to hit a sweet spot with shipping expense.

Still $30 delivery for what would be considered a domestic overnight shipment (leaving friday arriving monday) is pretty darn good.

[ulysses]

Gopher, thanks for your response. Do you mind one more question about goodcomponent.com? I can't find anything on their website about whether they test and match tubes. Did you discuss this with them?

Sfig, I apologize for highjacking your thread re goodcomponent.com, but I also have something to say about VTL amps and tubes. I've owned VTL MB-125 monoblocks for eleven years. For the past 2-1/2 years, I've run Genalex Gold Lion KT77 reissue tubes purchased from Jim McShane with no problems. Prior to that, I used SED winged "C" EL34s purchased from Upscale Audio, also with good results. I can't say anything definitive about the sound quality of the Gold Lions vs. the SEDs because I changed the tubes so long ago, plus the Gold Lions were new and the SEDs were definitely tired after four plus years of use. However, my impression is that the SEDs maybe had a slightly warmer midrange and possibly slightly better soundstaging. The Gold Lions probably have better frequency extension and more body or solidity.

[Lefty052347]

I would consider Electro Harmonix 6CA7EH.  They have a bigger bottle than standard EL34s and dissapate heat well.  The Tube Store sells them for $38 a pair.

Regards,
Dean

[ulysses]

Dean, your comment is very interesting. I'm considering eventually replacing the Genalex Gold Lion KT77 reissue tubes in my VTL MB-125 monoblock amps with the new Shuguang Treasure "Black Bottle" 6CA7-Z tubes. However, the Treasures, like the Electro Harmonix 6CA7EH, have a much bigger bottle than standard EL34s. I'm concerned about heat buildup with the Treasures with the bigger bottles because the tubes would be so close together.

[Gopher]

Ulysses,

I did not inquire as to the tester that they do use, but do know they offer matched tubes.  I don't know if their matching protocol is as fancy as some of the domestic distributors of the line like Grant Fidelity, but I was operating over budget and didn't think it mattered as much to have my power tubes matched as I have to bias each mono block independently anyhow.

I am not the most technically savy about tubes and such, but I'd drop Clark a line with any further questions.  My transaction went perfectly, the price was right and the speed at which it reached me was unreal.

[Ericus Rex]

Dean, your comment is very interesting. I'm considering eventually replacing the Genalex Gold Lion KT77 reissue tubes in my VTL MB-125 monoblock amps with the new Shuguang Treasure "Black Bottle" 6CA7-Z tubes. However, the Treasures, like the Electro Harmonix 6CA7EH, have a much bigger bottle than standard EL34s. I'm concerned about heat buildup with the Treasures with the bigger bottles because the tubes would be so close together.

I've gone from slim EL-34s to Big Bottle 6CA7s to KT88s in my Music Reference RM-9 and have never had a problem with heat buildup.  The KT88s have the largest bottle of the three and give off the most heat so I would think going to 6CA7 in your case would be no problem at all.

[bruce.weiland]

Hi,

I don't mean to hijack this thread, but I do have some VTL questions. 

I recently bought a pair of VTL MB-225T's.  They were originally manufactured in January of 1993, and update to 6350 phase splittes, and other updates in 2000, by VTL.  (I bought a TL-5 from the same era, variable feedback adjustment - no manual).

These amps were designed with the EL34's.  The circuit board has a label of MB 350.  I do have the owner's manual, but it is VERY rudimentary.  I would like to better understand the tube layout.

Are the 8 output tubes paired front row to rear row, left to right in each group of four, or left bank of four to right bank of four, for push/pull? 

I appreciate any response.   

Bruce

[ulysses]

I have the same question as Bruce. Each of my VTL MB-125 monoblocks uses four power tubes marked 1 through 4. Tubes 1 and 3 are in the front row, and 2 and 4 are in the back row. Are the push-pulls pairs 1-2 and 3-4, or 1-3 and 2-4? Hopefully someone can help us out.

[bruce.weiland]

Ulysses,'

I can't speak to the arrangement in your amp, but...

The Manley designed (Dave 225,240,200,etc), and refined (Eveanna 250, 500) are arranged so that the tubes on each side of the mono blocks are in parallel. 
 
For a 225, four to the right, four to the left.  For a Manley Neo-Classic 250/500 five to the right, five to the left.

If one tube in the quartet or quintet goes bad, you can take it out and still use the amp.  As one approaches clipping the side with one less tube would clip sooner.

 

Bruce

[ulysses]

Thanks, Bruce!

[bruce.weiland]

Ulysses,

You are welcome.

If you turn the amp over and remove the bottom plate, it will probably be clear from the circuit board traces, which tubes are in parallel. 



You can see the traces running to the left and right to the tube sockets in this bottom view of one of my MB-225t's

Bruce

[ulysses]

Thanks for your help, Bruce. I previously looked at the traces/wiring of my VTL MB-125 monoblocks, but I don't know enough about tube circuits to understand how the tubes work together. It's embarassing for me to admit this because I'm a hardcore do-it-yourselfer.

Thanks again!

Phil Morris
Wilsonville, OR