845/211 driver circuits

[Celsius]

I think that if your speaker have over 88db for me the sound of the 211 is better and easy to drive and don´t need NFB,
211 bias -70v with a d3A, E280f or with 6e5p ( with preamp ) have a very good sound.
Source follower change the gentle sound of the tube for me.

My last 211 monoblock
Load with CCS or gyrator low Z, you will have a very good amp.

An externally hosted image should be here but it was not working when we last tested it.

 

[MelB]

Celsius. Nice setup, bet it sounds awesome.

 

[hooman]

I think that if your speaker have over 88db for me the sound of the 211 is better and easy to drive and don´t need NFB,
211 bias -70v with a d3A, E280f or with 6e5p ( with preamp ) have a very good sound.
Source follower change the gentle sound of the tube for me.

My last 211 monoblock
Load with CCS or gyrator low Z, you will have a very good amp.

An externally hosted image should be here but it was not working when we last tested it.

can you check dht tube in drive ?sound of dht 3d and balance .

 

[Celsius]

I would like to do , which one dht do you recommend, I use normally the 6e5p and I am very happy, I think that is one the best tube driver.

 

[hooman]

i have 6e5p .... sound is good but not best . i used vt25 and b405 philips ....re074 telefunken ....

 

[Celsius]

Yes but difficult to acquire maybe 4p1l or modern WE 101D

 

[hooman]

dht tubes are different world of sound .my friends 211 amp has 3 dht tubes .
211.....vt25.....b405.
8k output Amorphous chock....oil caps ....1050v ....12w output .

 

[hooman]

Yes but difficult to acquire maybe 4p1l or modern WE 101D

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

 

[Celsius]

dht tubes are different world of sound .my friends 211 amp has 3 dht tubes .
211.....vt25.....b405.
8k output Amorphous chock....oil caps ....1050v ....12w output .

Hoonan why you do use 8k only I think that 211 run better on 12k to 16k, I am waiting to finish the case of my new 211 with custom made with 14k OPT

 

[Bandersnatch]

Stick with Thoriated Tungsten... 801A, HY40 come to mind. 842 if you can find them. 811-30 is another...as is 811-10.
cheers,
Douglas

 

[hooman]

Hoonan why you do use 8k only I think that 211 run better on 12k to 16k, I am waiting to finish the case of my new 211 with custom made with 14k OPT

in factory data in 1250 v need 11 k but 211 in 1050 ...... 8 k .

 

[hooman]

you can use 20k .

 

[HollowState]

Maybe something different like a grounded grid cathode drive.

 

[Bandersnatch]

H-S, that presents a load significantly below the plate resistance of the driver element( the triode connected audio beam tube ).

I am doing a PP cathode drive amp. It uses a 600R line driver output TX secondary to power the cathode circuit. The front end is two stage; an EL84 LTP driving Plate-to-grid FB'd TV sweeps, likely 6CB5A's. The finals are zero biased. With the zero bias, I take the bias circuit out of the equation; I don't want another power supply on the grids for when they go positive. The finals are HY51A's with B+ adjusted to set their idle current and attached to a 10k a-a OPT.
cheers,
Douglas

 

[frankwilker]

Hi,
there is an excellent circuit at the Lampizator Website from the austrian "Röhrenklinik".
The circuit is for tuning a Music Angel 845 MKIII.

 

[Bandersnatch]

The usual B+ levels associated with 845's leave much latitude in driver/voltage amplification stage design...there are many volts to play with... if you want a triode driver, find a few type HY40. Think 3 6SN7's in parallel with a 40W plate and a Thoriated Tungsten cathode.
cheers,
Douglas

 

[jazbo8]

H-S, that presents a load significantly below the plate resistance of the driver element( the triode connected audio beam tube ).

Hope I got this right... does not seem like "significantly" below.

Input impedance of 845 = (1200+10000)/(5.65+1) = 1,684

Plate resistance of 6CA7 (triode) = 2,556

 

[kaputt]

you can use 20k .

Maybe for an active setup in which you use that amp for lows and/or mids. The interwinding capacitance of a 20k:8k transformer will be so high that you are lucky getting a -3dB point at 18kHz.

 

[Bandersnatch]

IDK about that jazbo...input impedance seems much more comparable to output impedance. IIRC for cathode followers it heads for 1/gm, and from the papers I have read, at a first order the number comes out to be 2/gm.
cheers,
Douglas

 

[jazbo8]

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