Driver tubes for 300b amps

seanrr

Well-Known Member
Some people have told me that 300b amps sound better when the driver tube is a pentode (I am not sure why). I guess this was the case in the WE91 circuit. Do others agree with this? If so, why? I am looking at eventually buying a nice 300b amp. I may have one made for me, perhaps by Min of Tube Audio Lab, or I may try to pick up a used one. Most of the used ones I find, however, are driven by triodes like the Bottlehead Paramounts v. 1 (12AT7) or Welbourne Labs (6SL7). Do you think looking for something driven by a pentode would be worthwhile - I am hoping this purchase will curb my upgraditis for some time - thus, I am taking my time.
 
300b lover here.

There is no best driver tube. Everything adds a flavor and you might like a pentode driven 300b amp the best.

I like the 6sn7 the best. Don't feel the 6sl7 us quite up to it. My highly modded Welborne DRD uses a 6n1p and sounds fine to me.

Re "upgraditis": rolling driver tubes can be fun and cheaper than buying a new amp.
 
Try the 5965. A friend of mine made 4 very nice sounding SE 300B amps. He did a lot of testing with various driver tubes, found the 5965 provided enough swing to drive the 300B to full power.
 
I would consider an 6EJ7, it's a 9pin pentode that's gotten a lot of use in DIY circles as
both ran pentode or triode "strapped", so if you didn't like it ran pentode you can always
strap it, it has solid gain and trans-conductance to drive the 300B as a triode or pentode
as well, I've used a fair amount of them they do work well and sound good. (cheap to) :)
 
I would consider an 6EJ7, it's a 9pin pentode that's gotten a lot of use in DIY circles as
both ran pentode or triode "strapped", so if you didn't like it ran pentode you can always
strap it, it has solid gain and trans-conductance to drive the 300B as a triode or pentode
as well, I've used a fair amount of them they do work well and sound good. (cheap to) :)

Do you prefer it over a 10Y, if cost is not a determinant?
 
These suggestions are helpful. I should note, however, that I am not designing my own amp, but I am looking for one to buy - thus, my options are more limited. I think I can spend up to about $2K if I sell off enough of my old stuff to which I no longer listen. But, since that would be a huge step in upgrading, I want to get something I will likely be happy with for awhile (or at least holds its value enough to sell off if I upgrade). So...I have been looking for used items, and I am talking to a couple of amp builders who can make a very good 300b amp for about $2k (without the 300b tubes). I was considering buying used paramounts, but I was unsure if a 12AT7 could really drive a 300b to its maximum, and some people I know agree with Martin that Pentode tube drivers really are the best (plus, I have not tried that combination yet). Anyways, what should I be looking for in a $1K-$2K budget to really make my Tannoy speakers sing? If the difference is minimal between $1K and $2K, I might try to go towards the $1K range, but it seems that the difference between the $1K budget and the $2K budget is usually the quality of the transformers, which to me seem important if the circuit is a good one.
 
Have you compared 2A3 and 300B amps with your speakers? A lot of people, myself included, like the 2A3 sound better. They are both good, so you have to listen to decide what's your preference, but for that kind of money I'd want to be sure.
 
Have you compared 2A3 and 300B amps with your speakers? A lot of people, myself included, like the 2A3 sound better. They are both good, so you have to listen to decide what's your preference, but for that kind of money I'd want to be sure.

I am actually running my Tannoy speakers now with a 2A3 bottlehead Stereomour. It does sound very nice, especially with the right 12AT7 driver tube, but I would think that I would probably get more out of the Tannoys with a few more watts. They are 95db speakers, and I think the 2A3 amp will run my other system with 100db Altec 604s better. However, I might be wrong. I do indeed like the 2A3 amp, and it is much more sane finding NOS 2A3 tubes.
 
Sorry, you did mention the Stereomour. My bad. At a typical 8 watts, a 300B is only going to be 3 or 4 db higher than the typical 3.5 watts of a 2A3. Not earth-shaking-ly different. And the 2A3 IMO handles bass better, but differences in output transformers can even out the playing field.
 
I am actually running my Tannoy speakers now with a 2A3 bottlehead Stereomour. It does sound very nice, especially with the right 12AT7 driver tube, but I would think that I would probably get more out of the Tannoys with a few more watts. They are 95db speakers, and I think the 2A3 amp will run my other system with 100db Altec 604s better. However, I might be wrong. I do indeed like the 2A3 amp, and it is much more sane finding NOS 2A3 tubes.

Sound thinking in my opinion. I have Tannoys and 604s, 300B amps and 2A3 and as much as I love 2A3, they do not cut it power wise on the Tannoys. Jumping from 3 to 6w (real-world usable) makes a big difference when you are right on the edge of barley enough power.

Frankly, I'd even prefer 300B power on the Altecs if I could ever find/build a 300B amp that sounded near as good as 2A3 but the only time I heard one, it was a one-off c3M pentode driven 300B with Electra-Print iron - not something you can buy commercially.
 
I have two 300B set amps, one with SRPP 6SL7, other with pentode C3m more refined and detailed .Maybe the engineers at Western Electric did know their stuff after all, all these years back?
 
I have two 300B set amps, one with SRPP 6SL7, other with pentode C3m more refined and detailed .Maybe the engineers at Western Electric did know their stuff after all, all these years back?

Do you by chance have the schematic for the one using the C3M?
 
Do you prefer it over a 10Y, if cost is not a determinant?

In this particular environment yes.

I know pepole have used them as a driver but I wouldn't, the gain is to low at 8
and the transcon is low as well, you'd have to feed it an bunch of input voltage
and it would still have trouble truly driving it well with the grid current of a 300B
and the miller capacitance, it would have "reduced" high frequency performance
and higher distortion then a well laid adequate driver would.

Where the 10Y really shines from my perspective is a separate preamp/linestage.
 
Do you by chance have the schematic for the one using the C3M?




300b2maisonc3met.gif
 
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