VTL Siegfried II Input Tube Swapping

[Ron Resnick]

The VTL Siegfried II amplifier uses one 12AT7 and two 12BH7s.

Which replacement tubes have you experimented with? How did the replacement tubes change the sound of the amplifier?

Thank you!

 

[Bbock]

The VTL Siegfried II amplifier uses one 12AT7 and two 12BH7s.

Which replacement tubes have you experimented with? How did the replacement tubes change the sound of the amplifier?

Thank you!

Ron, if I may be so bold, even though I don’t have your amps, I believe there is some family DNA with my Manley amps, which use the same 12BH7 and 12AT7 combo. I have found that the 12AT7 makes the most difference in the tonality of the amp. I settled on RCA blackplate from the 50’s for the 12bh7.

For the 12at7, if you are looking to add a nice midrange glow while keeping extension at both the treble and bass extremes, I have found the NOS GEC 2900 (rare and expensive) work very well. Almost indistinguishable from those are the inexpensive NOS Brimar 13d9. If you are looking for a more flat response with a very extended top end, I’d try NOS Telefunken. I can’t remember which Telefunkens I tried, but were all very similar In sound.

There are plenty of 12at7 choices. I’m sure others will chime in with more ideas.

 

[cjfrbw]

If the anode voltage is not greater than 200 volts on the input tubes, a substitute for 12AT7 that I found better sounding than the Tele 801s is the Raytheon CK6414. The tube is incredibly built to a high standard, has a slightly lower gain, and was used in the early tube based computers. They aren't that expensive, either, compared the fashion boutique tubes. They have a larger glass envelope than most 12AT7 types.
Of course, if the anode voltage is much higher than 200 volts, which it usually isn't, then all bets are off.
I don't really think of 12AT7 types as being mellifluous, but the 12BH7 types might be. 12AT7 types are usually chosen for moderate high gain and higher transconductance than 12AX7 types for driving the next stage. Mullard type 12AT7 types might be the most warm sounding.

 

[Ron Resnick]

ECC81, ECC801, ECC801S can replace 12AT7?

6SN7 can replace 12BH7

If you are looking for a more flat response with a very extended top end, I’d try NOS Telefunken. I can’t remember which Telefunkens I tried, but were all very similar In sound.

Thank you very much for your suggestions!

Today they replace the stock 12AT7s with Telefunken ECC 801Ss. They actually smoothed out the treble region? Does this sound like an unexpected result to you?

 

[Ron Resnick]

Ron, if I may be so bold, even though I don’t have your amps, I believe there is some family DNA with my Manley amps, which use the same 12BH7 and 12AT7 combo. I have found that the 12AT7 makes the most difference in the tonality of the amp. I settled on RCA blackplate from the 50’s for the 12bh7.

Thank you very much for the suggestions!

I will look for a matched quad of RCA black plate 12BH7s. I have a pair of these, but not a matched quad.

 

[Tbzc]

I have experimented with both 12 AT7 and 12BH7 in VTL Siegfried II. NOS RCA 12BH7 did not have important influence on the sound therefore I have focused on 12AT7. I have tried quite some of them, including new ones like Psvane and EH, but found them to technical sounding. Much better were NOS Philips and Mullard. Especially later gave magical injection of musicality and smoothness.

 

[Bbock]

ECC81, ECC801, ECC801S can replace 12AT7?

6SN7 can replace 12BH7


Thank you very much for your suggestions!

Today they replace the stock 12AT7s with Telefunken ECC 801Ss. They actually smoothed out the treble region? Does this sound like an unexpected result to you?

Ron, the treble extension on the Tele’s is what I would expect. I never found them etched in my system. They could be on someone else’s system with different amps/preamps than ours, but I’ve never heard them to be harsh on Manley/VTL.

 

[Ron Resnick]

I have experimented with both 12 AT7 and 12BH7 in VTL Siegfried II. NOS RCA 12BH7 did not have important influence on the sound therefore I have focused on 12AT7. I have tried quite some of them, including new ones like Psvane and EH, but found them to technical sounding. Much better were NOS Philips and Mullard. Especially later gave magical injection of musicality and smoothness.

Thank you!

 

[mtemur]

ECC81, ECC801, ECC801S can replace 12AT7?

6SN7 can replace 12BH7


Thank you very much for your suggestions!

Today they replace the stock 12AT7s with Telefunken ECC 801Ss. They actually smoothed out the treble region? Does this sound like an unexpected result to you?

ECC81 is European term for 12AT7. Besides other variants 6201, ECC81 and ECC801S can replace 12AT7. I recommend Philips TS65 gold pins from 60’s.

6SN7 can not replace 12BH7 they’re totally different tubes. One is noval other is octal.

I used a couple of Telefunken ECC801S tubes over the years. IMHO they are very linear sounding that resembles transistor sound but never bright or harsh.

 

[mtemur]

I will look for a matched quad of RCA black plate 12BH7s. I have a pair of these, but not a matched quad.

It’s almost impossible to find NOS RCA black plates, square getter 50’s 12BH7 tubes in quad. I have both black plates and gray plates versions of RCA 12BH7 tubes and IMHO 60’s gray plates are good enough.

 

[Ron Resnick]

Ron, if I may be so bold, even though I don’t have your amps, I believe there is some family DNA with my Manley amps, which use the same 12BH7 and 12AT7 combo. I have found that the 12AT7 makes the most difference in the tonality of the amp. I settled on RCA blackplate from the 50’s for the 12bh7.

For the 12at7, if you are looking to add a nice midrange glow while keeping extension at both the treble and bass extremes, I have found the NOS GEC 2900 (rare and expensive) work very well. Almost indistinguishable from those are the inexpensive NOS Brimar 13d9. If you are looking for a more flat response with a very extended top end, I’d try NOS Telefunken. I can’t remember which Telefunkens I tried, but were all very similar In sound.

There are plenty of 12at7 choices. I’m sure others will chime in with more ideas.

Did you ever experiment with Mullard 12AT7s?

 

[Bbock]

Did you ever experiment with Mullard 12AT7s?

I haven’t, but that’s actually a good idea. I’ll search a pair out. I am currently enjoying the Brimar 13d9’s.