input tubes for 300b

[jrenkin]

I have been following and reviewing several new and old threads regarding SE 300b amps. Thanks to all the new and more experienced posters for all their input, thoughts and ideas.

I am going to fish for more opinion here, regarding input tubes.

I have seen many different input/driver tubes used in different configurations. The following is a quickly acquired list: (in no order)

717A
ECC81
CV4024
6sn7
5687WB
5842
D3a
437A
El34
6EM7
5691
6C45P1
EL84
2A3

Any others?
And what are some wonderful thoughts on these? Strengths, weaknesses?

I would like to stay away from transformer coupling, although the pluses and minuses of that might be interesting too.

Also, what are opinions of what a 300b tube wants? High voltage swing, high current, low impedance, etc. and what might get us there.

Thanks!

[leadbelly]

Originally Posted by jrenkin

Also, what are opinions of what a 300b tube wants?

Opinions? I guess those old tube manufacturers wasted their time publishing datasheets. I guess I'll have to chuck all the tube design handbooks I bought too.

In all seriousness, your list is deeply flawed. You are just throwing out tube types, irregardless of whether they were used for multiple stage, single stage, or hybrid stage driver circuits. To what end?

[jrenkin]

Well, yes. I am just throwing out tube types. These are tubes I have seen used in 300b SE designs.

I am seeking opinions on why one might choose one over the other. This could include multiple, single or hybrid stages. Do they sound better, are they easier to implement, require multiple stages or a pre-amp, and so on.

I am not looking for anyone to tell me which tube to use, just what different people have been drawn towards and why.

I guess "opinions" on what a 300b needs for input is not the right term. What are idea input parameters for a 300b (current, Vp-p, etc.)?

By the way, I am seeking thoughts, insight and meaningful discussion. Not criticism. Keep that for yourself.

[leadbelly]

Hey, I've been here a long time, I know that whenever you ask a question that is too broad you are bound to be disappointed with the replies. And I just love how these threads drive up the cost of tubes to boot.

Nonetheless, I'll throw you out a few like 6EJ7, 6J32P, 6J52P, 6688, 7788.

[jrenkin]

Thanks! Yes, broad question, but I don't have expectations. I like to hear how people think about things like this.

Are those tubes you particularly like? What about them do you like?

[tomchr]

From what I understand, the 300B wants to be driven by a stage with low output impedance. Some paging around in Morgan Jones would yield some ideas for topologies along with the tube characteristics that are desirable for those topologies. Why not start there?

This may not be a single-stage solution. A gain stage (common cathode) followed by a cathode follower is - as far as I can deduce from forum trawling - a common solution. For myself, I plan to use a 6J5 (because I have them) as a gain stage and another one as a follower. I might use a MOSFET as a source follower - like George (tubelab) does in his Tubelab SE. I figured I'd experiment and play for a while.

~Tom

[azazello]

E180F, E280F Phillips - amazing tubes. /I used for my 2A3 RCA/

[anubisgrau]

Originally Posted by azazello

E180F, E280F Phillips - amazing tubes. /I used for my 2A3 RCA/

i agree, but not the same sounding! beware - E180F is softer and more harmonically rich. E280F has a bit harder sound and more gain and you have to take that into serious account when you design your amp to avoid input/driver stage saturating the amp too early with too much amplification.

generally i don't think i've heard a better sounding driver than properly implemented E180F but i should be quiet about it, the tube is still cheap.

you don't need to drive it triode stripped, some people like a bit more bounce you get from a pentode driver.

my experience comes from 2A3, 6B4G, 300B and 10Y amps and E180F is brilliant in all of them. leaves a definitive stamp of claritiy and harmonical richness and minimizes the influence of the power tube (though soundwise my preference remains 10Y/801A - though not in a shishido IIT A2 circuit).

[PhilippeS]

6E5Pi, 6E6Pi, EL(PL)802, 12HG7, 12GN7, 7788(E810F)

[azazello]

If someone is interesting my schematic E180F & 2A3 RCA
Picasa Уеб �лбуми - Azazello - KVM