I understood that the problem is the price of 8 KT88s...
But what about 6CD6GA / 6EX6? They are cheap too...
Last edited:
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.
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
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
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
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...
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:
A quick Google search revealed that your amp should be fitted with EL34's, not KT88's or 6550's.
I don't have a lot of experience with the current crop of EL34's. If the SED EL34 is still the same tube as the late 90's brown base Svetlana, then it should be fine.
Note that the current "Svetlana" tubes marketed in the US (and perhaps elsewhere) are NOT made by Svetlana in St. Petersburg. They are yet another Reflector tube with one of Mike Matthew's many brands stuck on it. From what I can see, the EH, Svetlana (Reflector, not SED), Mullard (Reflector, not NOS), and Sovtek EL34's all seem to have the same structure inside. The mica supports in the Svetlana and Mullard are different from the EH and Sovtek, but identical to each other. Im going to go out on a limb and say that these tubes all use most of the same parts. The micas are different, but thats no big deal. Cathode coatings may be different as well, but I wouldn't count on it. My guess is that the Svets and Mullards spend more time on the pumps and get culled a bit better than the cheaper EH and Sovteks, but that's about it. What can I say... I'm a cynic
I don't know much about the JJ's other than that JJ tubes in general seem to have a high failure rate. I also have no idea on the Shuguang tubes. Back in they day they were often good for a fireworks show, but i have heard that quality has improved. Who knows?
Anyway, that's my take on the state of modern tube production. Kinda makes a guy want to give it up and start tinkering with transistors
I don't have a lot of experience with the current crop of EL34's. If the SED EL34 is still the same tube as the late 90's brown base Svetlana, then it should be fine.
Note that the current "Svetlana" tubes marketed in the US (and perhaps elsewhere) are NOT made by Svetlana in St. Petersburg. They are yet another Reflector tube with one of Mike Matthew's many brands stuck on it. From what I can see, the EH, Svetlana (Reflector, not SED), Mullard (Reflector, not NOS), and Sovtek EL34's all seem to have the same structure inside. The mica supports in the Svetlana and Mullard are different from the EH and Sovtek, but identical to each other. Im going to go out on a limb and say that these tubes all use most of the same parts. The micas are different, but thats no big deal. Cathode coatings may be different as well, but I wouldn't count on it. My guess is that the Svets and Mullards spend more time on the pumps and get culled a bit better than the cheaper EH and Sovteks, but that's about it. What can I say... I'm a cynic
I don't know much about the JJ's other than that JJ tubes in general seem to have a high failure rate. I also have no idea on the Shuguang tubes. Back in they day they were often good for a fireworks show, but i have heard that quality has improved. Who knows?
Anyway, that's my take on the state of modern tube production. Kinda makes a guy want to give it up and start tinkering with transistors
VTL had so many models all with all sorts of variations in tube types and almost similar model type names. Defiant, is probably correct about the deluxe 100 using el34s. I also find the small tube complement in the OPs amp a bit odd. Most smaller VTLs use(d) 12AT7 and/or 12BH7 as drivers and phase-splitters.
Last edited:
Hi, can anyone enlighten me that whether is this a VTL compact 100 or is it a VTL deluxe 100, are theses two the same using el34? Whats the diff between both of them? As i check the internet i could only find VTL compact 100, nothing on the De Luxe model.
Mine is the 2 pics attach and it reads VTL De Luxe 100, it is original wth kt88, drive ecc82 and ecc83? when i bougth it about 10yrs ago.
Thanks in advance.
http://i697.photobucket.com/albums/vv339/sgkho249/hifi/DSC02237.jpg
http://i697.photobucket.com/albums/vv339/sgkho249/hifi/DSC02234.jpg
Mine is the 2 pics attach and it reads VTL De Luxe 100, it is original wth kt88, drive ecc82 and ecc83? when i bougth it about 10yrs ago.
Thanks in advance.
http://i697.photobucket.com/albums/vv339/sgkho249/hifi/DSC02237.jpg
http://i697.photobucket.com/albums/vv339/sgkho249/hifi/DSC02234.jpg
Last edited:
I've email them twice, but did not receive any reply. Thats why i came to diyaudio for help. and i came to the right site, all of you are so helpful.
thank you all
Thank you, will have a look at those KT77, BTW you have any expreience with them. How do they sound compare with kt88 or 6550.
thanks
Well i've had these VTL deluxe 100 for more than 10 years. But recently only 3yrs back started to use them again. They have very deep soundstage, wonderful amp.
The thing is that i bought it with kt88, ecc82, ecc83. If Defiant and you are correct, than i think the previous owner have change all the tubes. As you said its 12at7 small tubes, but mine is ecc83/82, i know that ecc83 can replace 12bh7a but what about 12at7. i've search and found out that most VTL uses 12at7, i'm also confuse about it, but really can find anything on VTL Deluxe 100
Thanks again
There is no need to be confused. The right tubes for your amp are EL34 power tubes and 12AT7 small tubes. I have looked up an old edition of the VTL Book and it confirms what Defiant and I have told you.
Now go out and get yourself a set of correct tubes for your amp. For the EL34, my choice would be the SED Winged C EL34 as this is supposed to be from the factory that made the original Svetlana EL34 tube, probably the most balanced sounding modern EL34. It is what I use.
tube_new_sed
For the 12AT7, get the ElectroHarmonix 12AT7WA (non gold pin). You could use EI branded 12AT7 but this are a bit "fuzzier" and lacks a bit of detail and clarity when compared to the EH tube.
Cheers
Now go out and get yourself a set of correct tubes for your amp. For the EL34, my choice would be the SED Winged C EL34 as this is supposed to be from the factory that made the original Svetlana EL34 tube, probably the most balanced sounding modern EL34. It is what I use.
tube_new_sed
For the 12AT7, get the ElectroHarmonix 12AT7WA (non gold pin). You could use EI branded 12AT7 but this are a bit "fuzzier" and lacks a bit of detail and clarity when compared to the EH tube.
Cheers
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.