The 12AT7 (ECC81), 12AX7 (ECC83) and 12AU7 (ECC82) all share the same pinouts. Since the low level stages in a VTL are cathode biased (and probably cap coupled) then an incorrect tube will work with varying degrees of success. Nevertheless, the cathode resistor and plate load resistors were chosen for a 12AT7, and that is what will work best.
Likewise, the 6550/KT88 and EL34 share a similar, BUT NOT IDENTICAL, pinout. Generally, a 6550 or KT88 will work in an EL34 socket, but not necessarily the other way around (it depends on whether pin 1 of the 6550 socket is grounded or not). Likewise, they have similar transconductance and similar bias points. That is why the previous owner was able to run KT88's in place of EL34's. That doesn't make it the best setup though - optimum plate loads for the two types are different.
Also, the DeLuxe 100 should be a fixed bias amp, which means that you will need to set the bias for a replacement set of tubes. Hopefully you know how to do so, and what the settings should be. 21khz and I agree on the use of SED EL34's. Besides sounding good, they are a tube I know for a fact won't complain when running 500V on the screen. Some lesser EL34's can have... issues.
Likewise, the 6550/KT88 and EL34 share a similar, BUT NOT IDENTICAL, pinout. Generally, a 6550 or KT88 will work in an EL34 socket, but not necessarily the other way around (it depends on whether pin 1 of the 6550 socket is grounded or not). Likewise, they have similar transconductance and similar bias points. That is why the previous owner was able to run KT88's in place of EL34's. That doesn't make it the best setup though - optimum plate loads for the two types are different.
Also, the DeLuxe 100 should be a fixed bias amp, which means that you will need to set the bias for a replacement set of tubes. Hopefully you know how to do so, and what the settings should be. 21khz and I agree on the use of SED EL34's. Besides sounding good, they are a tube I know for a fact won't complain when running 500V on the screen. Some lesser EL34's can have... issues.
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I would try the 6P3S-E from Jim Mcshane and bias them for around -25w dissipitation. Great tube at a great price. If you lke them stock up while they last.
Tube & Information Page
Brad
Tube & Information Page
Brad
Yes, a heavy duty version. From the above post it looks like the amp was suppose to have EL34s in them but he had KT88s in them. If this is the case than the 6P3S-Es should work fine.
I would buy from Mcshane, he weeds out the bad ones. Contact him and he could probably send you matched sets that have cold or hot bias acccording to the amp you use.
With the amount of tubes this amp uses it's a nobrainer. If you like them at this price point I would stock up for years to come.
Brad
I wouldn't have recommened this tube if I haven't tried it in both KT88 and EL34 amp with great results, can both of you say the same.
The OP used KT88 for years, if it didn't sound good do you think that would be the case.
If this amp allows the user to adjust the bias I don't see the problem. If it don't he looks like he is willing to get his hands dirty so all he would need to do is change the cathode resistors accordingly.
skho249, do a search on audio asylum to get more info on this tube since it's capabilty was discovered there.
Brad
The OP used KT88 for years, if it didn't sound good do you think that would be the case.
If this amp allows the user to adjust the bias I don't see the problem. If it don't he looks like he is willing to get his hands dirty so all he would need to do is change the cathode resistors accordingly.
skho249, do a search on audio asylum to get more info on this tube since it's capabilty was discovered there.
Brad
Isn't 6L6 has a 6.3v, 0.9amp. same as el34. But what's the plate voltage on both. Also 6p3s-e it has some good reviews on audio asylum where they replace el34 on a dynaco st-70 and seems that they have stock up with more 6p3s-e.......
Thanks Again Defiant
Those 6p3s-e are really affordable!!!
Hi Brad, thanks for the info. Yes I did look at the audio asylum on those 6p3s-e. For the price I also think that there shouldnt be any compliant, if it can fit into my VTL. In the VTL it has individual tube bias and also a central bias port. But I'm not sure how to bias an amplifier.
Yes I'm willing to get my hands dirty, and will try to locate the cathode resistor ASAP.
Thanks
I've been there and done that. As a general rule the 6L6 doesn't work well with the lower P-P impedance of the transformers typically used with EL34 and 6550/KT88 designs. They also have less gain than EL34s, 6550's, and KT88's.
6L6's, EL34's, 6550's and Kt88's all have 6.3V heaters. 6L6's only draw 0.9 amps of heater current, while EL34's draw 1.5 amps. The 6L6 types have smaller cathodes and cannot supply the peak emission of an EL34.
You can try the 6P3S, but I don't think it is going to give the best sound with the VTL's 4K OPT's. Hopefully the VTL has enough bias adjustment range and gain - the 6P3S and 6L6GC's need more negative bias and more voltage swing from the driver.
Look the idea is there roughly 3 classes in descending order of dissipation
(kt88 - 6550)
(EL34 - KT77)
(6L6 - 6p3se)
You should keep it in the class it was designed for. My advice is , if you are sure it ws meant for EL34's, and you need something within budget, go for JJ KT77's. Their quality control issues were solved a long itme ago, now they are fine, I have some myself. They sound very good to me.
(kt88 - 6550)
(EL34 - KT77)
(6L6 - 6p3se)
You should keep it in the class it was designed for. My advice is , if you are sure it ws meant for EL34's, and you need something within budget, go for JJ KT77's. Their quality control issues were solved a long itme ago, now they are fine, I have some myself. They sound very good to me.
found some info on bias and schematics. For starteres make sure your amp uses 10Ω resisters on the cathodes to measue bias. You should be able to measure the resistance at the bias port to ground with amp off. Bias your KT88s accordingly then give another listen.
I would contact VTL with your serial number to see if they can provide you with the book on this amp.
Audio Asylum Thread Printer
I would contact VTL with your serial number to see if they can provide you with the book on this amp.
Audio Asylum Thread Printer
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