DHT drivers - shootout

[andyjevans]

Can you guys contribute to a "shootout" of DHT drivers? I'm testing some in a 300B amp and I'll try and describe the results. I'd like to compare these with what you guys have found.

The input tube is 10Y, anode choke and teflon cap coupled to the driver. The driver is teflon cap coupled to the 300B and has a 15K resistor load, with 1.8K cathode resistor bypassed with 47uF polypropylene. Here's my listening notes so far:

46 at 10mA - Very subtle, excellent tone and timbre to instruments. Tonally neutral. Strings neutral/glossy, Vocals 3D

10Y at 10mA - Big sound with copious bass. Warm sound. Smooth with good treble. Strings mellow, Vocals round.

183/483 at 15mA - Opposite end of the sound spectrum from 10Y - thinner cooler sound. Strings "stringy", vocals a little flat. Sounds a lot like a 2a3 amp not quite on song.

71A at 16mA - How to describe this! Pretty psychodelic. I ended up last night listening to Fagen's Morph the Cat. Now, where the 46 is probably more subtle in the actual tone of each instrument - grand piano has richer overtones - the 71A is doing something else entirely. The colours of the instruments are like colour blocks, like Matisse, and these build up and superimpose just like a Phil Specter mix - kind of "wall of sound", with instruments jumping up in precise locations in the mix. Like listening from the recording console. Add to that a huge boogie factor - rhythms pound away relentlessly. It's a very effective rock sound, though not bad on classical. I enjoyed it a lot! Strings neutral, vocals 3D.

To come - 2a3

 

[Gluca]

Ciao. Thanks for sharing.

I prefer 10Y/801A at 25mA. Gotta build something with 71A.

 

[andyjevans]

Tried the 2a3 as driver. I have Sovteks, and they are just a touch edgy and coarse. Really need better examples to try. It's the same generic sound as the 183/483 which is effectively a 45. Neutral, not much to criticise really. These - and the 71A - all bias up about the same, which is 15mA. I'm really at max volume with all these, however - mu is about 3. I have reistor load, and that should really be a plate choke or an interstage to get the best out of these.

With the same setup, the 10Y biases at more like 10mA. Indeed, I should put more current through it as a driver. It does, paradoxically, sound great as a preamp tube with 6 or 8 mA through it, but a driver is another matter.

 

[andyjevans]

I've been listening to the 71A as a driver for three days now and I'm delighted - I'm in one of my favourite systems right now: 10Y, 71A, 300b

Next step - what kind of interstage or plate choke to couple it to the 300b outputs!

 

[palmas]

Hi all.
was browsing when I saw your tread, and I'm very interested in this:

I'm building a 10Y - interstage - 300B - interstage - GM70 amp.
10Y will be at 250V 18mA
300B at 400V 60mA
GM70 1150V 110mA

For the output I'm using Audionote TR310 C,
for the interstages I'm using Lundahl 1660/18 and 1677/60

Any comment or suggestions?

 

[zigzagflux]

Any comment or suggestions?

How about "Gadzooks !"

That's a serious amplifier. You trying to best Nikola Tesla ?

 

[palmas]

That is what I call a quality amp. I have a few using 845 and 211, and now I'm going a bit further, trying to make the best amp I can (and know how)
I also know how much time and money it takes to gather solid experience in designing and building great tube amps, that's why I welcome all comments.

For big amp, I prefer one I'm having some problems with: 833 in PP

 

[andyjevans]

I'm building a 10Y - interstage - 300B - interstage - GM70 amp.
10Y will be at 250V 18mA
300B at 400V 60mA
GM70 1150V 110mA

For the output I'm using Audionote TR310 C,
for the interstages I'm using Lundahl 1660/18 and 1677/60
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


That all looks pretty perfect. Go for it! You should get quite a big, warm lush sound. If you wanted to cool it down a bit you could substitute 46 or 2a3 for the 300b.

 

[palmas]

That all looks pretty perfect. Go for it! You should get quite a big, warm lush sound. If you wanted to cool it down a bit you could substitute 46 or 2a3 for the 300b. [/B][/QUOTE]


I was considering the 45 instead of the 10Y, decided on the 10Y to cool it down. The 2A3 is not as good driver as 300B, and found some prone to toilet noises that disqualify them as drivers. The 46 I never used and don't even have a pair to try. Have some DHP (direct heated pentodes) I can use instead of the 10Y, but I think I will keep the 10Y, as it sounds just as I like it: fast and full.

I can publish some photos and teh schematics, but don't know if I can do this in this forum...

 

[JLH]

I was considering the 45 instead of the 10Y, decided on the 10Y to cool it down. The 2A3 is not as good driver as 300B, and found some prone to toilet noises that disqualify them as drivers. The 46 I never used and don't even have a pair to try. Have some DHP (direct heated pentodes) I can use instead of the 10Y, but I think I will keep the 10Y, as it sounds just as I like it: fast and full.

I can publish some photos and teh schematics, but don't know if I can do this in this forum...

The 2E24 triode wired sounds very nice. Try plate voltage of 180V, Vg = -22V which results in about 20mA of plate current.

Rgs, JLH

 

[i_should_coco]

The 2E24 triode wired sounds very nice. Try plate voltage of 180V, Vg = -22V which results in about 20mA of plate current.

Rgs, JLH

You don't happen to have any triode curves? What sort of Rp does it have?

Thx.

 

[JLH]

You don't happen to have any triode curves? What sort of Rp does it have?

Thx.

Mu of about 7 and Rp of about 2.8K when triode wired. I think user name "316a" on this board might have the curves for it.

 

[i_should_coco]

thx!

 

[MartinV56]

that the 300B as driver?,thanks

 

[MartinV56]

that the 300B as driver?,thanks

 

[Diy martin]

Hello,

Have anyone used the 31 triode as a driver or output tube
I have a couple of these beauties laying here

 

[andyjevans]

Great to hear you are using the 31 - really like this tube, it's very musical. But surely you don't get much output? What's the operating point as an output tube? Andy

 

[Diy martin]

I have used the 31 as a pre amp tube , very nice but microphonic.
At this moment I am using the 46, nice but not as fresh as the 31.

Hope to finish my new SE- 71A amp soon, driver for the 71A is the E86C ccs loaded, outputs are the James 6123 transformers

 

[zobsky]

Can you guys contribute to a "shootout" of DHT drivers? I'm testing some in a 300B amp and I'll try and describe the results. I'd like to compare these with what you guys have found.

The input tube is 10Y, anode choke and teflon cap coupled to the driver. The driver is teflon cap coupled to the 300B and has a 15K resistor load, with 1.8K cathode resistor bypassed with 47uF polypropylene. Here's my listening notes so far:

Curious, .. what B+, and accordingly plate resistors / voltages did you use with the drivers?
Thanks

 

[andyjevans]

HT on the driver stage is about 400vDC. Have now tried:

46, Rload 7.5k, Rk 1.8k
10Y Rload 15k, Rk 1.8k, Vk 18v, 10mA
71A Rload 15k, Rk 1.8k, Vk 29v, 16mA

All the above sounded very good indeed in their different ways - 46 was very good at instrumental timbre, 10Y was a big warm sound and very lifelike, 71a had a particularly good synergy on a lot of material, making it quite seductive to listen to.

Probably the 10Y is the best overall trube, but you could make a case for any of the three. They were also better than 183 and 2a3 which were flatter and blander, though very musical.

Hope that helps! I haven't spent much time optimising any of these operating points - other priorities. Suggestions welcome.