845/211 driver circuits

[Celsius]

yes difficult so from 10 years before i start to buy dht tube for drive.you can use 2a3 or 6b4g

Hooman I finish my last amp with 2a3 driving the 211, thanks for your recommendation, is my best amp now, holographic sound and very fast bass., 6e5p ( triode ) + 2a3 + 211, thank you.

 

[Bandersnatch]

I got the number from the formula here: Input impedance of grounded grid stage?

I don't recall where I looked up the math, but it was for power triodes. The two come out comparably when loading is near plate resistance...and I am not quite ready to believe that loading matters that much.
cheers,
Douglas

 

[deafbykhorns]

I have the same but a CCS at the top of 6E5P and a GM70 for an output tube.
Running it at 1100v, 90ma
Sound is spectacular!

 

[Celsius]

I have made before two amps with 6e5p ccs low Z driving the 6c33 and other driving the 211, but the 2a3 driving the 211 is too much better. The space felling is wonderful.

 

[jazbo8]

Beautiful! Where did you get the top plate?

 

[Celsius]

I design all in 3d program and the case and front plate is made by my friend as a favour. who works is aeronautical company in Spain ( EADS )

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[jazbo8]

You are making us jealous!

 

[fasterbyelan]

Very nice Celsius.

Do you have the circuit for this beauty?

 

[fasterbyelan]

One of the best driver you can use is the Alan Kimmel choke coupled MuStage. Look up the last two issues of VTV magazine on it..

See here for the first (all?) 20 editions.

Issue 9 is also of relevance as it features the two biggish triodes under discussion here (link). I bought this copy a long time ago in anticipation of constructing something similar to the original AN Ankoru 845 PE amp. For those not familiar with this design it uses a 300B to drive the two 845's via an interstage tx. The designer published details of the design and the circuit in an edition of 'Sound Practise' (what a terrific magazine that was!) which can be viewed here.

 

[deafbykhorns]

I have made before two amps with 6e5p ccs low Z driving the 6c33 and other driving the 211, but the 2a3 driving the 211 is too much better. The space felling is wonderful.

How did you couple the 2A3?
I tried it several ways but ended up with a Monolith Mag. IT transformer, it was far better than RC or LC coupling

 

[JPS64]

For custom mechanical parts (panel, front, enclosure).

Schaeffer AG: Home

JP

 

[soulmerchant]

I find that this is a great way to have custom mechanical parts done:

Big Blue Saw - Waterjet and Laser Cutting - Instant Quote

Especially interesting if you wish to use stainless steel, and happen to be in the USA.

Ian

 

[Celsius]

How did you couple the 2A3?
I tried it several ways but ended up with a Monolith Mag. IT transformer, it was far better than RC or LC coupling

I coupled many times the 6e5p 30mA ( triode ) by CCS low Z to 211 or 6c33, I though if 6e5p can why not the 2a3 at 45mA, in my opinion the 2a3 give a big extra sound to 211, only that 2a3C is a little microphonic ( very big glass) I have ordered the Psvane 2a3b ( small glass) to check witch one is better.

 

[deafbykhorns]

How did you couple the 2A3 to the 211?
I would try a JJ2A3-40

 

[Celsius]

By cap ( Audyn Copper ) from CCS low z.

 

[deafbykhorns]

By cap ( Audyn Copper ) from CCS low z.

Try an IT if you have one handy, a Hammond 126 will do better than a cap in this scenario but you'll have to lower the operating load (which isn't a bad thing) a bit so it doesn't saturate. A plate choke will also do better than a cap as well. In order of preference- IT, Choke, Cap

Unless your doing a CCS on the 2A3? I'm having a little trouble interpreting your topology.

 

[audiowize]

A plate choke will also do better than a cap as well. In order of preference- IT, Choke, Cap

A plate choke requires a coupling cap.

 

[Bandersnatch]

Take the 211 to a zero bias point with its grid grounded, and drive its cathode through and IT from the 2A3. B+ around 500V and therefore idle current of +100 mA. You'll need about +/- 50V of input swing, so pick your IT ratio to deliver that...
cheers,
Douglas

 

[THD+N]

Here is the driver circuit I am using now. I posted it awhile back but under a different title.

Hammond 126B Frequency Response and More...

Attached are the current circuits for the interstage version of the 211 amp.

The 211 definitely likes an interstage transformer.

 

[Celsius]

Try an IT if you have one handy, a Hammond 126 will do better than a cap in this scenario but you'll have to lower the operating load (which isn't a bad thing) a bit so it doesn't saturate. A plate choke will also do better than a cap as well. In order of preference- IT, Choke, Cap

Unless your doing a CCS on the 2A3? I'm having a little trouble interpreting your topology.

View attachment 648547

Not have space for more transformer and cap sound very good,
I am looking Tango OPT for 211, Where can I buy or other brand with very good quality and reasonable price. ISO maybe?

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