46 tube pre

jaymanaa · 3rd October 2006, 11:22 PM

I really hate to ask for schematics, but I haven't been able to find a single one using the 45 or strapped 46 in a MM phono pre, and designing something on my own is way down the road (if ever) for me. I'm not completely sure why I'm stuck on the idea, except for all the good things I've heard about the 45 being a very "musical" tube. I thought about a power amp, but I don't think 1 or 1.5 watts would really be enough power, even on horns. I seem to do ok on about 3 at present. I just figured that this might be a way to enjoy the sound that the 45 has to offer. Any and all advice or opinions would be most welcome, and thanks in advance, Jay

phn · 3rd October 2006, 11:44 PM

I don't have what you look for. But Susumu Sakuma has some pretty interesting designs. There's no stand-alone phono preamp. That should be no problem, should you get that far.

http://www10.big.or.jp/~dh/

astouffer · 4th October 2006, 12:40 AM

Unless you use a step up transformer or three, theres not enough gain. A MM cart outputs a few millivolts and most amplifiers need around 2 volts input. The 45 would be more useful as the final output of a preamp instead of an input stage. Well filtered DC or battery operation for the filaments would be a MUST. Sure its possible but take into consideration the gain of a 45 is only 3.5.

If you want direct heating then you may want to consider battery tubes used in portable radios or even pencil tubes.

phn · 4th October 2006, 12:51 AM

astouffer is correct, of course. A driver triode like the 27 would be a lot better. But even that one doesn't have enough gain. Sorry, I'm not up on DH tube models.

You will need something like two high mu stages (say 60 or more) or three medium-mu stages (around 30).

Again, look at Sakuma's designs. Mostly DH. Maybe there's something you like.

anatech · 4th October 2006, 02:39 AM

Hi jaymanaa,
Did anyone tell you how much 45's go for? It's an early output tube, and poorly suited for your application as many have pointed out. I have a few and wouldn't waste them on a preamp. There are better tubes for that as has been pointed out.

The '27 has been used, and others. If you really want, you could use some '01's. Maybe 4 or 5 per channel. Noisy.

Why not look at some RF triodes. Singles.

-Chris

Eusebius · 4th October 2006, 07:17 AM

I agree with all the above. If you want more power, use a 2a3 or 300b output, and go Push Pull if you need the power. Use the 46 as a driver tube - it's great for that.

For the first stage - whether you put it in the amp or the preamp - you can use a 7193/2C22 with a mu of around 20. This may give you just enough gain if you use active loads or an interstage after the 46.

But really to get the best sound, stick a battery DHT in the first stage. Anything like 01A, 12A, 26, 30, 31 etc. A current source for the filaments is absolutely vital, though they'll work (less well) off a couple of voltage regs in series, especially with a CMC at the end. Batteries are not necessary these days - there are solutions. You should not get much hum, but remember to float the filaments and use a cathode bypass cap (47uF polypropylene is nice). You will probably get microphonics ranging from acceptable to horrible. This is something you will have to experiment to deal with, but it requires a SOLID chassis with some weight in it, decoupled from the stand and damped as much as possible. Any ringing in the chassis and you're in trouble.

My solution has been to go balanced - I get much less microphonics. I couple each channel of the filaments of the first stage in series and use a current source. I use a CCS under the diff pair, which can be 01A, 12A or whatever, mu of around 9. The useful thing about this arrangement is that you can put a balanced DAC stage directly into the grids, even if the DAC signal has DC on it of a volt or two - the CCS takes care of it. And for single ended inputs you can ground the second grid. In my own system this first stage goes into a SRPP 7913 stage and the outputs are 6AH4. Enough volume for me. Mu goes 9>20>8. I found that the DHT was most important in the first stage, though conventionally it's only used in the output stage.

jaymanaa · 4th October 2006, 09:36 PM

Thanks for all the replys. Lots of good ideas to investigate. I just started reading Rozenblitz again last night for the umteenth time, and some of it may be seeping in. I'm gonna dig through my pile of "old" tubes and see what I can come up with. I'm for sure trying to stay away from 9 pin minatures, for looks and roominess under the socket for working. Thanks Again, Jay

astouffer · 5th October 2006, 01:14 PM

One tube that never gets much mention is a 3A5. Its a dual triode with a common filament and a mu of 15. Could be useful but I suspect they are badly microphonic.

anatech · 5th October 2006, 01:19 PM

Hi Jay,

Quote:

I'm for sure trying to stay away from 9 pin minatures,

Send them here to a good home!

Kidding.

-Chris

Eusebius · 5th October 2006, 02:50 PM

One tube that never gets much mention is a 3A5. Its a dual triode with a common filament and a mu of 15. Could be useful but I suspect they are badly microphonic.>>

Not that microphonic - a friend is using them in his line stage. But, and it may be a big but, his is a balanced circuit and these DHTs are less microphonic in balanced circuits - don't know why but it appears to be the case. Still 3A5 isn't expensive and you could run SE in and out of a diff pair with a CCS under it.

3rd October 2006, 11:22 PM	#1
jaymanaa diyAudio Member Join Date: Jan 2006 Location: Kansas	46 tube pre I really hate to ask for schematics, but I haven't been able to find a single one using the 45 or strapped 46 in a MM phono pre, and designing something on my own is way down the road (if ever) for me. I'm not completely sure why I'm stuck on the idea, except for all the good things I've heard about the 45 being a very "musical" tube. I thought about a power amp, but I don't think 1 or 1.5 watts would really be enough power, even on horns. I seem to do ok on about 3 at present. I just figured that this might be a way to enjoy the sound that the 45 has to offer. Any and all advice or opinions would be most welcome, and thanks in advance, Jay __________________ "Make everything as simple as possible, but no simpler" Einstein

4th October 2006, 09:36 PM	#7
jaymanaa diyAudio Member Join Date: Jan 2006 Location: Kansas	Thanks for all the replys. Lots of good ideas to investigate. I just started reading Rozenblitz again last night for the umteenth time, and some of it may be seeping in. I'm gonna dig through my pile of "old" tubes and see what I can come up with. I'm for sure trying to stay away from 9 pin minatures, for looks and roominess under the socket for working. Thanks Again, Jay __________________ "Make everything as simple as possible, but no simpler" Einstein

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3rd October 2006, 11:44 PM	#2
phn diyAudio Member Join Date: Oct 2004	I don't have what you look for. But Susumu Sakuma has some pretty interesting designs. There's no stand-alone phono preamp. That should be no problem, should you get that far. http://www10.big.or.jp/~dh/

4th October 2006, 12:40 AM	#3
astouffer diyAudio Member Join Date: Jun 2004 Location: Pittsburgh, crumbling wasteland	Unless you use a step up transformer or three, theres not enough gain. A MM cart outputs a few millivolts and most amplifiers need around 2 volts input. The 45 would be more useful as the final output of a preamp instead of an input stage. Well filtered DC or battery operation for the filaments would be a MUST. Sure its possible but take into consideration the gain of a 45 is only 3.5. If you want direct heating then you may want to consider battery tubes used in portable radios or even pencil tubes.

4th October 2006, 12:51 AM	#4
phn diyAudio Member Join Date: Oct 2004	astouffer is correct, of course. A driver triode like the 27 would be a lot better. But even that one doesn't have enough gain. Sorry, I'm not up on DH tube models. You will need something like two high mu stages (say 60 or more) or three medium-mu stages (around 30). Again, look at Sakuma's designs. Mostly DH. Maybe there's something you like.

4th October 2006, 02:39 AM	#5
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi jaymanaa, Did anyone tell you how much 45's go for? It's an early output tube, and poorly suited for your application as many have pointed out. I have a few and wouldn't waste them on a preamp. There are better tubes for that as has been pointed out. The '27 has been used, and others. If you really want, you could use some '01's. Maybe 4 or 5 per channel. Noisy. Why not look at some RF triodes. Singles. -Chris

4th October 2006, 07:17 AM	#6
Eusebius diyAudio Member Join Date: May 2006	I agree with all the above. If you want more power, use a 2a3 or 300b output, and go Push Pull if you need the power. Use the 46 as a driver tube - it's great for that. For the first stage - whether you put it in the amp or the preamp - you can use a 7193/2C22 with a mu of around 20. This may give you just enough gain if you use active loads or an interstage after the 46. But really to get the best sound, stick a battery DHT in the first stage. Anything like 01A, 12A, 26, 30, 31 etc. A current source for the filaments is absolutely vital, though they'll work (less well) off a couple of voltage regs in series, especially with a CMC at the end. Batteries are not necessary these days - there are solutions. You should not get much hum, but remember to float the filaments and use a cathode bypass cap (47uF polypropylene is nice). You will probably get microphonics ranging from acceptable to horrible. This is something you will have to experiment to deal with, but it requires a SOLID chassis with some weight in it, decoupled from the stand and damped as much as possible. Any ringing in the chassis and you're in trouble. My solution has been to go balanced - I get much less microphonics. I couple each channel of the filaments of the first stage in series and use a current source. I use a CCS under the diff pair, which can be 01A, 12A or whatever, mu of around 9. The useful thing about this arrangement is that you can put a balanced DAC stage directly into the grids, even if the DAC signal has DC on it of a volt or two - the CCS takes care of it. And for single ended inputs you can ground the second grid. In my own system this first stage goes into a SRPP 7913 stage and the outputs are 6AH4. Enough volume for me. Mu goes 9>20>8. I found that the DHT was most important in the first stage, though conventionally it's only used in the output stage.

5th October 2006, 01:14 PM	#8
astouffer diyAudio Member Join Date: Jun 2004 Location: Pittsburgh, crumbling wasteland	One tube that never gets much mention is a 3A5. Its a dual triode with a common filament and a mu of 15. Could be useful but I suspect they are badly microphonic.

5th October 2006, 02:50 PM	#10
Eusebius diyAudio Member Join Date: May 2006	One tube that never gets much mention is a 3A5. Its a dual triode with a common filament and a mu of 15. Could be useful but I suspect they are badly microphonic.>> Not that microphonic - a friend is using them in his line stage. But, and it may be a big but, his is a balanced circuit and these DHTs are less microphonic in balanced circuits - don't know why but it appears to be the case. Still 3A5 isn't expensive and you could run SE in and out of a diff pair with a CCS under it.

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