Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 24th October 2011, 02:45 PM   #1
diyAudio Member
 
Join Date: Oct 2011
Default VTL deluxe 100 monoblk (KT88) need help?

Hi, I'm new here, hope to find some help on replacing my VTL deluxe 100. Using 4 kt88 with driver ecc83 and ecc82 (x2) It has been years of listening to it, now thought of replacing the 8 kt88 to 807 or 6bg6 or even 12e1. Done a little research and found that:

1. For 807 I need to change all sockets adding topcap etc....affordable tubes

2. For 6bg6 do I need to change the sockets, adding the topcap etc.... Affordable tubes.

3. For 12e1 no need to change the sockets, only adding topcap etc.... Abit off budget.

4. Those tubes that I didn't mention that can replace kt88 are out of my price range.

All sockets pin position are different so I've to find sockets adaptors.

Anyone kind to share their experience on these tubes that best suit my VTL.

Thanks in advance.

Kho
  Reply With Quote
Old 25th October 2011, 02:23 AM   #2
diyAudio Member
 
Join Date: Feb 2009
Why would you want to use tubes other than the KT88? There is no reason why the alternatives you have suggested will sound better than the KT88. If you want to improve your VTL there are other ways of doing it.
  Reply With Quote
Old 25th October 2011, 02:34 AM   #3
diyAudio Member
 
Join Date: Jan 2010
Quote:
Originally Posted by Sgkho249 View Post
...
4. Those tubes that I didn't mention that can replace kt88 are out of my price range....
I understood that the problem is the price of 8 KT88s...
But what about 6CD6GA / 6EX6? They are cheap too...

Last edited by kem69; 25th October 2011 at 02:39 AM.
  Reply With Quote
Old 25th October 2011, 02:35 AM   #4
llwhtt is offline llwhtt  United States
diyAudio Member
 
Join Date: Jun 2008
Every VTL/Manley amplifier I've seen has PCB mounted tube sockets which would be a real PITA to change the type of socket.

Craig
  Reply With Quote
Old 25th October 2011, 03:01 AM   #5
diyAudio Member
 
Join Date: Feb 2009
If it is the replacement cost of 8 KT88s that is a problem, I would say it makes no sense "ripping apart" (and it will take some ripping apart to achieve what he wants) an amp to save a few bucks on tubes. KT88s are in current production and surely should not be considerably more expensive than good NOS 807s. The cheap ones are just that and I have had several where the anode electrode caps just fall off the tubes. You also need to consider adjusting the operating points, different coupling caps etc to optimise the amp around the different tubes.
A new set of KT88 should give Kho many more "years of listening" without hacking the amp.
  Reply With Quote
Old 25th October 2011, 04:16 AM   #6
diyAudio Member
 
Join Date: Oct 2011
Quote:
Originally Posted by ihear21khz View Post
If it is the replacement cost of 8 KT88s that is a problem, I would say it makes no sense "ripping apart" (and it will take some ripping apart to achieve what he wants) an amp to save a few bucks on tubes. KT88s are in current production and surely should not be considerably more expensive than good NOS 807s. The cheap ones are just that and I have had several where the anode electrode caps just fall off the tubes. You also need to consider adjusting the operating points, different coupling caps etc to optimise the amp around the different tubes.
A new set of KT88 should give Kho many more "years of listening" without hacking the amp.
Thanks, ihear21khz,
I've had these amp for many years with kt88(old Chinese tube), but I think I've made a bad choice about a year ago and got myself another 8 Shuguang kt88-98. Now after 1+ years I just want to change and try some new things(tubes) what will you recommend, for a direct replacement? With minor adjustment on the power amp and how to go about doing it?
Appreciated
Thanks
  Reply With Quote
Old 25th October 2011, 04:24 AM   #7
diyAudio Member
 
Join Date: Oct 2011
Quote:
Originally Posted by kem69 View Post
I understood that the problem is the price of 8 KT88s...
But what about 6CD6GA / 6EX6? They are cheap too...
Hi, thanks
Will 6cd6/6ex6 direct fit, with minor change in socket pin? Have you done it before and how do they(6cd6) sound to your ears? They looks close to 6bg6 too. Will they have great differences with kt88?

Thanks
Kho
  Reply With Quote
Old 25th October 2011, 04:38 AM   #8
diyAudio Member
 
Join Date: Oct 2011
Quote:
Originally Posted by llwhtt View Post
Every VTL/Manley amplifier I've seen has PCB mounted tube sockets which would be a real PITA to change the type of socket.

Craig
Hi Craig, thanks,
You are rite, but will it be better to use tube adaptors so that I can still use the kt88 if I want. Would love your advise on the different type of tubes eg: 807, 6bg6, 12e1, 6cd6(ken69) on the VTL.
Sorry what's PITA?

Thank you again
Kho
  Reply With Quote
Old 25th October 2011, 07:40 AM   #9
Defiant is offline Defiant  United States
diyAudio Member
 
Defiant's Avatar
 
Join Date: Oct 2011
Location: Somewhere in America
PITA=Pain In The ***. Like a hemorrhoid.

You aren't going to accomplish anything by hacking a perfectly good amplifier. The output transformers have impedances set up for KT88's/6550's.

The 807 and 6BG6's are simply 6L6's with anode caps and revised ratings for different services (transmitter/modulator and horizontal deflection amplifier respectively). The 807 uses a completely different socket, while the 6BG6 uses the same socket but different pin-out. Of course, both also have their plate connected to a top cap, and they are significantly taller than a KT88 or 6550. Worse yet is that they have much lower screen grid voltage and screen dissipation ratings as well as plate dissipation ratings and smaller cathodes with less current capability. The screen ratings are the biggie - run either in an amp built for a KT88 that runs 500-525V on the screen (which your VTL does) and the tube will almost certainly run away and self-destruct, possibly damaging the amp in the process. That is assuming the amp has enough bias control range to bias the tubes somewhere below meltdown in the first place. You could run them strictly as tetrodes with a reduced screen voltage (350V max), but you never get near the power of the KT88/6550, and distortion will be higher due to the lower than ideal (for a 6L6 type) impedance of the OPT primary. All in all it would be a disaster no matter which way you try it.

The 12E1 is a pass regulator tetrode that has enough Pd rating and cathode current rating, but it has the same incompatible basing and screen grid limitations as the 807 and 6BG6. Try that one at your own peril. Keep a fire extinguisher handy and take pics of the smouldering wreckage if you do.

The 6CD6 is a typical high perveance sweep tube. Once again, the basing is totally incompatible. It has a huge cathode, but a low Pd rating (less than half that of a 6550) and a VERY low screen voltage and screen PD rating. Put 500+V on that tube's screen and watch the fireworks. The 6EX6 is very similar to the 6CD6 and has the same limitations. There are some seriously beefy sweep tubes that have high (and quite conservative) PD ratings and high DC current ratings, such as the 6KG6/EL509, 6LF6, 6KD6, and a few others I can't remember. However, ALL of them have different bases and ALL of them have much lower screen voltage ratings.

The fact is that the 6550 and KT88 were designed specifically for audio apps in tetrode, UL, or triode operation with high screen voltages, high Pd, and relatively large cathodes. The only other audio tubes that share some of these characteristics are the EL34/6CA7/KT77 and 6L6GC/KT66, and neither has the Pd and screen ratings of the 6550 or KT88. You could probably run an EL34 and maybe a 6L6GC (ONLY the 6L6GC, 6L6GB's and earlier will definitely not survive, and an amp designed for KT88's and 6550's may not have the bias range to bias a 6L6 type) in your amp, but you risk overheating the screen and having the tube run away if you ask it to deliver anything close to the amp's rated power. Plus, the OPT will be a poor match for the 6L6GC so distortion will be higher and power even lower, IF it even survives the attempt.

In short, your amp was designed to use 6550's and KT88's. The only other tubes that will definitely work are the NOS Ei KT90 (which VTL used as OE tubes in some of their amps back in the day). I would even be leery about some of the current production 6550's in a VTL. My suggestion would be to save your money and pony up for an octet of good quality KT88's or 6550's. Do some research to find out which ones are reliable with 500+V on the screen and sound good in your amp. Don't try to be cheap and end up ruining your amplifier...

Last edited by Defiant; 25th October 2011 at 07:46 AM.
  Reply With Quote
Old 27th October 2011, 04:16 PM   #10
diyAudio Member
 
Join Date: Oct 2011
Thanks Defiant,

You are right, I shouldn't destroy my amp. Save the money and get some good kt88 or 6550. Which will you think kt88 or 6550? I've heard from a friend that 6550 sound better.

Thanks in advance.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
EL34, KT88, High Voltage?, VTL.. kegger Tubes / Valves 20 4th July 2009 01:41 PM
vtl deluxe 300 mb namseok Tubes / Valves 0 13th March 2007 11:17 AM
VTL Compact 100 Monoblock x 2. sstong Tubes / Valves 4 17th October 2004 03:49 AM
VTL deluxe 300 amps - adjustment question audiomatic Tubes / Valves 7 23rd June 2004 07:23 PM


New To Site? Need Help?

All times are GMT. The time now is 01:50 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2