• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

My first tube Amplifier VT4C DIY record

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#61
tim845 said:
Share my experience in building of 211SE

I used 3 stages to drive 211 before and it sounds very suck !!

Later I decided to use only totally two stages with interstage coupling and it sounds good. But the insterstage must be very high quality. I tried Lundahl's amorphous and Bartolucci and even Tango NC-14, the best is Bartolucci !!

I learnt a lesson that never using amorphous in SE !!!

Because of the easy driving voltage of 211, I believe that a total of 2 stages of a 211SE amp is enough and using interstage is the best selection but expensive.

I have a suggestion for your circuit:

Using plate choke and direct coupling instead of RC coupling.

Your driver tube 6C45 has very low ra with high gm and also easy to drive, using plate choke can swing out huge voltage and less distortion than RC coupling, even a plate choke is frequency dependent but still be good.

Using simple resistive direct coupling method (gain will be attenuated but still can drive 211 grazy !) and fixed bias.

I think this the least cost effective method even an additional negative power supply needed to cater for the resistive direct coupling.

Try it and will surprise you.

Tim
Click to expand...

Hi :
Your are expert.
I once consider chock direct coupling but no place could put in so I trade-off choice RC coupling.
Because then I decide made Analog EQ. Linearizer to gain more detail in front a stage.
Then I could gain any frequency in this stage even the loss of 211 Amplifier.
This is whole system concern and just follow my DIY plan.

Aster

Mr211's Blog - Yahoo!?????
 
#69
#73
I have plans to build a power amp around 211. To write the truth, the power tube will not be 211 but the german sibling, Telefunken RS237, as I already own several dozens of this nice bulb.

Power amps are very expensive if built around 211 tubes. You need definately 3 stages, at least one stage interstage transformer coupled to the power tube, and (last but not least) moster rectifiers tubes like mercury vapor 866.

I also have plans to build a Telefunken amplifier throughout, only with Telefunken input, driver, power & rectifier tubes (RE074 neutro as input tube, RS241 as driver and RS237 as power tube), rectified by Telefunken RGN4004 (for input and driver stages) and Telefunken RG62. The cost of only the tubes is estimated at 5.000 Euros per stereo pair, the cost of the amp is estimated at around 20.000 Euros only for parts and tubes, not labor hours.

If you want to push it to the limits, 211 amp will give you the best sound, but the cost for a serious amplifier is very high!
 
#75
Hi!

petavgeris said:
You need definately 3 stages
Click to expand...

While I agree that the most attempts to a 2 stage 211 amp are flawed because they typically lack headroom, it is possible with 2 stages with the proper tubes. My latest 211 amp shown on my blog is a two stage implementation.

If a preamp is available which can drive a step up input transformer, a two stage 211 can also be done with a DHT driver. I have done that in the past, using 801A as driver tube and even 211 as driver.

petavgeris said:
moster rectifiers tubes like mercury vapor 866!
Click to expand...

I like the 866s myself, but a 211 can also be done with other rectifiers, TV dampers are excellent for the purpose. For example the 6CG3 which I used in my last 211 amp. Please note that 866s don't like capacitor input filters, they are meant to be used with choke input only.

Best regards

Thomas
 
#77
I found a very interesting combination and already experienced.

Couple weeks ago my friend used one EL84 with a Lundahl interstage namely LL1677 to drive 211, the sound is very good !! Former structure was a paralleled 6463 interstage to drive 211.

The new structure is only an experiment but it did very successful. Lundahl LL1677 is implemented at an anti direction, i.e. primary as secondary and vice versa.

The screen grid of EL84 was connected to the centre tap of LL1677 (because secondary now is treated as primary, and there is only two equal winding group for the new "primary"), and we assume this can constitute a 50% load of plate.

Using cathode bias for EL84 at 25ma arround and by passed, plate voltage at 255V arround.

The new arrangement for LL1677 - secondary become primary, this makes it has a 120H inductance and 37ma direct current for core saturation right now.

The sound is good and if anybody has this iron, just try it and would make you big surprise.

The 211SE amp is a two stage amp. but because of the sensitivity of EL84, a pre amp is needed.
 
#78
Vinylsavor said:
Hi!



While I agree that the most attempts to a 2 stage 211 amp are flawed because they typically lack headroom, it is possible with 2 stages with the proper tubes. My latest 211 amp shown on my blog is a two stage implementation.

If a preamp is available which can drive a step up input transformer, a two stage 211 can also be done with a DHT driver. I have done that in the past, using 801A as driver tube and even 211 as driver.



I like the 866s myself, but a 211 can also be done with other rectifiers, TV dampers are excellent for the purpose. For example the 6CG3 which I used in my last 211 amp. Please note that 866s don't like capacitor input filters, they are meant to be used with choke input only.

Best regards

Thomas
Click to expand...

Yes, a 2-stage design with 211 tube lacks headroom seriously.
A nice tube to experiment is the german D3A in triode mode, with a mu of 77 and Rp only 1.9k, it would be a nice attempt. But if you want to squeeze this giant, it is better to build a 3-stage DHT design.
For those who have not played around with big rectifiers like 866, just try. If you consider SS rectifiers as a serious alternative to 866, then an attempt would be more than simply interesting!
My best option for 211 would be Telefunken RG 48, Western Electric 253A and RCA 866A (WE and RCA are all mercury vapor tubes). Sorry guys, I'm a Telefunken maniac!
 
#79
tim845 said:
I found a very interesting combination and already experienced.

Couple weeks ago my friend used one EL84 with a Lundahl interstage namely LL1677 to drive 211, the sound is very good !! Former structure was a paralleled 6463 interstage to drive 211.

The new structure is only an experiment but it did very successful. Lundahl LL1677 is implemented at an anti direction, i.e. primary as secondary and vice versa.

The screen grid of EL84 was connected to the centre tap of LL1677 (because secondary now is treated as primary, and there is only two equal winding group for the new "primary"), and we assume this can constitute a 50% load of plate.

Using cathode bias for EL84 at 25ma arround and by passed, plate voltage at 255V arround.

The new arrangement for LL1677 - secondary become primary, this makes it has a 120H inductance and 37ma direct current for core saturation right now.

The sound is good and if anybody has this iron, just try it and would make you big surprise.

The 211SE amp is a two stage amp. but because of the sensitivity of EL84, a pre amp is needed.
Click to expand...

Tim,
IMHO if a 2-stage power amp requires more than 1.2V of input to be fully driven, then the whole approach cannot be characterized as 'power amp', as a preamp is absolutely necessary. Personally I would like to have my power amp fully driven to distortion with less than 1V of input. Why not including all the 3 active stages into the same chassis and have one less interconnect in your system?
 
#80
Agree what you said. But building an amp for self use is a seperate issue with a commercial one.

In fact, a normal listening level would not exceed 2W to 4W even transient music. 2W is a quite loud level at standard room condition such as 4M x 6M area. More than this, music detail will become vague and even turn the volumn at a higher level to make it louder, the music would not perform the same result and just make you annoying.

of course, you may claim that what about music hall but it is another story, it is true instrument and play a real music.

My belief is, make something by yourself then something should please yourself, you should not let something make you busy again and again.
 
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