300B driving 845

[otto88]

Hi

The 300B is $$$, but its very linear, there are many options (vs eg the 45) and supply is pretty assured. So looking at the 300B driving 845 SE

I believe the 300b can be relatively sensitive to its driver, or in this case input
stage. Was considering 10Y, 26, 46, 71A, 76. Need to check sutrabvality.

(I recall there was a circuit(s) for a 300B driving 845 SE).

Any comments?

Thanks

 

[rknize]

The original AudioNote Ankoru, if I remember right, was 7044 -> 300B -> dual 845.

 

[ianc13]

The Ankoru was 300B driving 845 and the circuit was published in Sound Practices Issue #12. There is a PDF of the article on the internet if you search - you could loose an 845 per channel and run with a 10K OPT instead of 5K.

In the next issue was the Nuance 845 which is 6072A -> 300B -> 845SE. The original article text. schematic and parts list can be found at the author's website:

Nuance

Regards,

Ian

 

[ErikdeBest]

DHTrob uses the 300B to drive the GM70, using an interstage. The schematics are published at the GM70 yahoogroup!

 

[otto88]

It might be the Nuance I remembered, thank you. Unlike the Nuance, this project isn't quite "cost-no-object", though hopefully it will be the amp for my next few decades!

I found 2 versions of the Ankoru. The Japanese with parallel single-ended 211s and UK, yes 7044 > 300B > PSE 845 Audio Note Reviews

The UK Ankoru's designer Andy Grove said "Various input configurations were tried, all using the E182CC/ 7044 valve for its powerful sound. The original and best sounding configuration gave the amp so much gain as to be impractical. . . The 7044 was always run at a high current to really bring out its flavour".

Not sure, I guess by "powerful sound" he means not distorting at higher levels??

I see DHTrob drives the 300B with the 71A

(Though the 71A and 26 are very susceptible to electrostatic coupling from surrounding metal objects, there are ways of dealing with this http://www.diyaudio.com/forums/tube...b-amp-post1493018.html?highlight=#post1493018)

Back to the question: Apart from electrically being up to the task of being the front end for the 300Bs, my question is about the ol' subject of SE tone . . Some tubes and circuits bring out the SE "magic", others are "clean" . .

Would the 6072A be considered clean? Of those I mentioned - the 10Y, 26, 46, 71A, 76 - what is their tonal signature?

 

[RolandPSP]

my question is about the ol' subject of SE tone . . Some tubes and circuits bring out the SE "magic", others are "clean" .

Anyone care to expand on this, ideally with some examples of SE DHT circuits that capture the magic like kondo and shindo achieves ?

Would be i think very helpful and should be a thread on its own.

 

[gabdx]

Don't limit yourself to the tubes and how they sound, they will sound as good as the design is built around them.

Driving the 845 with a 300B is overkill. You can realize same or better sound with less costly to operate tubes with the anode drive directly with a capacitor.

the 845 tube can get 30Watts under 1% if you regularize the grid bias to protect the tube from auto-destruction when drawing too much grid current.

It would be happy to have a 6sn7 as driver too if no grid current is necessary 20Watts power.

Other suggestions of drivers is EL34 wired in triode.

You can use local tube feedback which will greatly help with 845 requirements. Use a big capacitor too to couple it. like 5uf instead of the typical 0.22 uf.

 

[MelB]

I did 6SN7 > 6B4G (2A3 Variant) > 2xGM70.

1.2 Vrms input yields 244 V peak to peak drive voltage for the GM70. Most CD players etc will output 2 Vrms.

 

[45]

Hi

The 300B is $$$, but its very linear, there are many options (vs eg the 45) and supply is pretty assured. So looking at the 300B driving 845 SE

I believe the 300b can be relatively sensitive to its driver, or in this case input
stage. Was considering 10Y, 26, 46, 71A, 76. Need to check sutrabvality.

(I recall there was a circuit(s) for a 300B driving 845 SE).

Any comments?

Thanks

It might be your best choice, second choice....worst choice. If you don't give any clue on what you want to achieve and what sort of money you want to invest one can really say everything and its contrary without getting to some useful conclusions.....

What "type of" 845 are you going to use? Which transformer? Do you want to reach full power with low distortion down to 30Hz (which is already an excellent result) or else? What output power? 15W, 20W, 30W, 40W? etc...

 

[hooman]

Do you want to reach full power with low distortion down to 30Hz (which is already an excellent result) or else? .

you made yourself before amps like this?full power to 30 hz and low distortion . we have italian company for good power amp in hifi market or instrument..

Don't limit yourself to the tubes and how they sound, they will sound as good as the design is built around them.

Driving the 845 with a 300B is overkill. You can realize same or better sound with less costly to operate tubes with the anode drive directly with a capacitor.

audio tubes all are good for sound .but some are diferent .i blive some of them is magic in right circuits.
who test the ecc801s telefunken in first stage of 211 amps ?3d sound
tray with sylvania 12at7wa in place of ecc801s.

 

[gabdx]

magic sound comes from the amplification stages,

To me I want to listen to the 845 tube distortion, not the 300B + the 845, maybe if you want to have a soup. I prefer to have dinner.

 

[deafbykhorns]

I sure like my 300b driving a gm70

 

[wredny]

What kind of load do you use for 300b, interstage?

 

[deafbykhorns]

Custom Monolith Magnetics interstage. I tried several other methods and this was the most dramatic change. I suspect it would be similar with the 845

 

[wredny]

You read me like a book. I bought chinese 300b 845 amp as sort of kit and playground. It's capacitor coupled and according to my calculation does very poor job in driving power tube. I was going to go with replacing 7500 ohm resistor with choke but after looking at the prices I figured I might as well go with the 1:1 interstage and give it some room for a2 operation. Can you gents recommend an affordable interstage for testing purpose that would work in my application? 300b supply is 410V.

 

[deafbykhorns]

I used a Hammond for testing but ended up with the monolith magnetics (custom). The Hammond are limited to 25ma but thats not actually a bad thing, distortion is low. I also tried a pair of Silk which you can easily run up to 60-70ma. The monolith was best because the additional inductance. All of these allow some a2 operation My supply was about the same voltage which was ideal. I actually used a 2.5v 40watt 2A3 JJ tube with great results

 

[wredny]

Thanks a lot! Any expirience with lundahl IS?

 

[Celsius]

I have made three different amps with the 211. For me the magic and clear sound has been with 6e5p triode > 2a3 > 211

2a3 have many cheap options with really very good sound, 10y maybe is the best but with less option to buy.

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

 

[deafbykhorns]

I have made three different amps with the 211. For me the magic and clear sound has been with 6e5p triode > 2a3 > 211

2a3 have many cheap options with really very good sound, 10y maybe is the best but with less option to buy.

Absolutely!!!
My setup is a 6E5P-JJ2A3-GM70


wredny--
A Lundahl 2753 at 25ma might work (about the same as the hammond IT)
Or you could use a 1671
Both the above would require the cathode resistor be changed (assuming its cathode biased)
A LL1677 is rated for a 300B but its a 1:2 step up

 

[wredny]

My plan is to try jj2a3 once 300b I got are done.

Lundahls you mentioned are exactly the ones I was considering but I was hoping to get practical feedback, especially in occasional a2 ops. Do you think it's better to stick with higher inductance or current?

Step-up would increase impedance too much...