fdegrove said:
Hi the circuit is cd enhancer II
http://www.ultranalog.com/cdenhancer/cdenhancer2_3a5.pdf
The reason I asked is cause, Remco has 3 versions of the circuit, which generally have tubes with an rp of around 7.5k (this is an adequate load for the dac chip to drive directly), and a mu between 14 and 35. So I was just interested to see if there are any other tubes that fit this criteria and are known by experienced people to sound good...
6sn7 is a candidate, what do you think of this valve?
But I can happily live with the 3a5.........
Thanks
Raja
Hi,
So far I have used multi-pole video connectors (DIN-style) with no trouble at all.
Cheers,😉
So far I have used multi-pole video connectors (DIN-style) with no trouble at all.
Cheers,😉
Hi,
I think it's among the better valves but unfortunately it's rather difficult nowadays to get hold of the best sounding ones.
There are alternatives of course, just don't forget it's also a lot bigger in size than the 3A5s and use octal type sockets.
Whether it's worth the trouble redesigning the DAC to take the 6SN7 I'm really not too sure.
Perhaps Remco can give you the final word on this matter.
In the meantime you may want to get a idea of what this valve can do and try building a preamp with it?
Cheers,😉
I think it's among the better valves but unfortunately it's rather difficult nowadays to get hold of the best sounding ones.
There are alternatives of course, just don't forget it's also a lot bigger in size than the 3A5s and use octal type sockets.
Whether it's worth the trouble redesigning the DAC to take the 6SN7 I'm really not too sure.
Perhaps Remco can give you the final word on this matter.
In the meantime you may want to get a idea of what this valve can do and try building a preamp with it?
Cheers,😉
ECL85 regulator
Hello Frank,
I tried your ECL85 regulator today on my BDT amp and it works wonderfully. I made a slight modification, I used an 0B2 VR tube since I already had several on hand. I had to change the voltage trim pot since I could not figure out how the circuit could work with the 10K pot listed in the schematic. The 0B2 is a little higher voltage than the 0G3, but only by 15V or so. I wound up using a 200K pot set to a little less than 100K, which gives me the 250V output. This value pot makes sense to me, its a voltage divider from the output voltage to match the reference voltage (minus the grid bias of the triode of course).
Anyway with those changes it works great, the regulation is very good. I'm quite impressed.
Right now the regulator is running the whole amp, but I bought enough parts to make multiple regulators so each stage and channel gets its own. But Thats going to wait awile. I have a bunch of new caps and transformers burning in first.
Thanks for the circuits,
John S.
Hello Frank,
I tried your ECL85 regulator today on my BDT amp and it works wonderfully. I made a slight modification, I used an 0B2 VR tube since I already had several on hand. I had to change the voltage trim pot since I could not figure out how the circuit could work with the 10K pot listed in the schematic. The 0B2 is a little higher voltage than the 0G3, but only by 15V or so. I wound up using a 200K pot set to a little less than 100K, which gives me the 250V output. This value pot makes sense to me, its a voltage divider from the output voltage to match the reference voltage (minus the grid bias of the triode of course).
Anyway with those changes it works great, the regulation is very good. I'm quite impressed.
Right now the regulator is running the whole amp, but I bought enough parts to make multiple regulators so each stage and channel gets its own. But Thats going to wait awile. I have a bunch of new caps and transformers burning in first.
Thanks for the circuits,
John S.
Hello John,
Thank you for pointing me to the error in the diagram, it has indeed a 33K resistor missing right above the trimpot.
If only a few volts of adjustment are needed a 33K resistor should do to set the trimpot for 250V with the load I used on it.
Naturally a different load will likely require more adjustment then the 10K pot would cater for.
In that case it may well be wiser to opt for a 20K pot.
A different VR tube will indeed work to bump up the output of the reg a little (if that's what needed) but ideally some resistor values would require recalculating as well for the regulator to work best.
You may also like to fine tune the value of the feedback cap (0.330µF on the diagram you looked at) which will affect the regulator's response time...Design is always a matter of making compromises as I'm sure you know....
While trawling the net I also found a very similar reg to mine by Gary Kaufman but using a stack of Zener diodes en lieu of the VR tube.
I prefer VRs for several reasons (they're looking cute being one of them) but of course you're free to have your own vices. 😉
I'll correct my own diagram and repost it here.
In the meantime here's Gary's work which may be easier for people wanting to work with a PCB iso of P2P :
Another 250 VDC series regulator.
Thank you for trying it. Very glad you like it so much.
Cheers,😉
Thank you for pointing me to the error in the diagram, it has indeed a 33K resistor missing right above the trimpot.
If only a few volts of adjustment are needed a 33K resistor should do to set the trimpot for 250V with the load I used on it.
Naturally a different load will likely require more adjustment then the 10K pot would cater for.
In that case it may well be wiser to opt for a 20K pot.
A different VR tube will indeed work to bump up the output of the reg a little (if that's what needed) but ideally some resistor values would require recalculating as well for the regulator to work best.
You may also like to fine tune the value of the feedback cap (0.330µF on the diagram you looked at) which will affect the regulator's response time...Design is always a matter of making compromises as I'm sure you know....
While trawling the net I also found a very similar reg to mine by Gary Kaufman but using a stack of Zener diodes en lieu of the VR tube.
I prefer VRs for several reasons (they're looking cute being one of them) but of course you're free to have your own vices. 😉
I'll correct my own diagram and repost it here.
In the meantime here's Gary's work which may be easier for people wanting to work with a PCB iso of P2P :
Another 250 VDC series regulator.
Thank you for trying it. Very glad you like it so much.
Cheers,😉
Frank,
I don't know if this has been asked before but would there be any benefit if I regulate the heaters for the 6SN7? I have plenty of 3-terminal regs here that I can use. Of course it will have a slow turn-on hopefully to prolong the tubes.
Regards,
Jojo
I don't know if this has been asked before but would there be any benefit if I regulate the heaters for the 6SN7? I have plenty of 3-terminal regs here that I can use. Of course it will have a slow turn-on hopefully to prolong the tubes.
Regards,
Jojo
Hi,
If you have the voltage to burn, certainly.
I'd recommend regulating the heater supply of any preamp.
Cheers,😉
If you have the voltage to burn, certainly.
I'd recommend regulating the heater supply of any preamp.
Cheers,😉
fdegrove said:
I think I do have the voltage to burn since the trafo has an 7-0-7 @ 3A winding that I can use. I'm still waiting for it to arrive though
.Thanks Frank!
Hi,
7 VAC in FWB would yield about 9.5 VDC.
A bit low for a regular 3-pin 7806 style regulator but since you have current to spare you can always opt for a voltage doubler or, better still, use a low drop regulator instead.
If that's hard to source you could go for a 7805 and insert 2 1N4xxx diodes between the groundpin and ground to lift the reg by 2*0.6 V.
In case you leave the CT floating you can treat the xformer as if it were a 0-14 VAC one which I suppose is the easier way out.
Cheers,😉
7 VAC in FWB would yield about 9.5 VDC.
A bit low for a regular 3-pin 7806 style regulator but since you have current to spare you can always opt for a voltage doubler or, better still, use a low drop regulator instead.
If that's hard to source you could go for a 7805 and insert 2 1N4xxx diodes between the groundpin and ground to lift the reg by 2*0.6 V.
In case you leave the CT floating you can treat the xformer as if it were a 0-14 VAC one which I suppose is the easier way out.
Cheers,😉
it would be Cliffcon from www.CliffComponents.com and is the same connectors used on the World Audio Design preamps.was ist los? said:
fdegrove said:
I'll just treat it as a 0-14 and use an LM317 with a trimmer pot for adjustment range within 6-7V.
Thanks Frank!
6SL7 for phonostage?
Frank:
Excuse me, just want to ask for your idea to use 6SL7 in your phonostage, of course, may need some modification, right?But, how?
Thanks!
Cy
Frank:
Excuse me, just want to ask for your idea to use 6SL7 in your phonostage, of course, may need some modification, right?But, how?
Thanks!
Cy
Hi,
As the 6SL7s are quite different animals, the entire RIAA correction will require recalculation....
Something I can't be bothered with for several reasons:
Other than that it's really very time consuming to get it right I would also recommend against it because:
- 6SL7 are far too microphonic and noisy for phonostages especially if you want to use it to the max., use a high output MC or use it in combination with the MC Hammer MC headamp.
- excellent 12AX7s or better still 7025s (low noise version) can still be had at "reasonable" prices from NOS brands such as Tesla, EI or, more exotic but not always better, Mullard, Valvo, Philips.
I select for now noise, low microphony and as close to a true twin triode in circuit as I can get.
That takes me about a dozen tubes/brand.
Current manufacture 12AX7s that are worth your while are the JJs and some older Sovtek 12AX7WAs (not WB or WC) especially if you can have your selected ones cryo treated.
Somehow I don't see me do that with NOS 6SL7 nowadays.....
All is not lost for the *SL7s however, you could still use them with a passive RIAA circuit at the expense of some gain.
If you use the line buffer with the 12BH7A after that, the high Zout won't be any problem.
There may even be an octal version of that tube but I doubt it.
Either way, that buffer isn't a problem whatever tube you pick, even the rather mundane 6922 would do but would be better suited to the 250V B+ version of the preamp that's been posted here...somewhere.......
As you can guess I'm really very badly documented on this type of active RIAA correction. Whatever I had, way back then, got lost in between moving places and I never found anything elsewhere useful since.
I vaguely recall I had the idea from a Brimar document but I'm not too sure either....Ah....Tempus fugit........
Thank you for your interest.
Cheers,😉
As the 6SL7s are quite different animals, the entire RIAA correction will require recalculation....
Something I can't be bothered with for several reasons:
Other than that it's really very time consuming to get it right I would also recommend against it because:
- 6SL7 are far too microphonic and noisy for phonostages especially if you want to use it to the max., use a high output MC or use it in combination with the MC Hammer MC headamp.
- excellent 12AX7s or better still 7025s (low noise version) can still be had at "reasonable" prices from NOS brands such as Tesla, EI or, more exotic but not always better, Mullard, Valvo, Philips.
I select for now noise, low microphony and as close to a true twin triode in circuit as I can get.
That takes me about a dozen tubes/brand.
Current manufacture 12AX7s that are worth your while are the JJs and some older Sovtek 12AX7WAs (not WB or WC) especially if you can have your selected ones cryo treated.
Somehow I don't see me do that with NOS 6SL7 nowadays.....
All is not lost for the *SL7s however, you could still use them with a passive RIAA circuit at the expense of some gain.
If you use the line buffer with the 12BH7A after that, the high Zout won't be any problem.
There may even be an octal version of that tube but I doubt it.
Either way, that buffer isn't a problem whatever tube you pick, even the rather mundane 6922 would do but would be better suited to the 250V B+ version of the preamp that's been posted here...somewhere.......
As you can guess I'm really very badly documented on this type of active RIAA correction. Whatever I had, way back then, got lost in between moving places and I never found anything elsewhere useful since.
I vaguely recall I had the idea from a Brimar document but I'm not too sure either....Ah....Tempus fugit........
Thank you for your interest.
Cheers,😉
Well i've held off this project long enough and it's time to order parts. Frank, will these connectors work for the umbilical cord?
http://www.cui.com/adtemplate.asp?invky=302364&catky=619701&subcatky1=223110&subcatky2=398846
http://www.cui.com/adtemplate.asp?invky=936640&catky=619701&subcatky1=223110&subcatky2=612346
http://www.cui.com/adtemplate.asp?invky=302364&catky=619701&subcatky1=223110&subcatky2=398846
http://www.cui.com/adtemplate.asp?invky=936640&catky=619701&subcatky1=223110&subcatky2=612346
Hi,
They look very similar to the ones I used.
Electrically speaking there isn't much current flowing through them so the 100VAC insulation at 2A should do nicely for 300VDC at 15mA max/channel.
Cheers,😉
They look very similar to the ones I used.
Electrically speaking there isn't much current flowing through them so the 100VAC insulation at 2A should do nicely for 300VDC at 15mA max/channel.
Cheers,😉
Hi Frank,
May i know what is the purpose of having both the diode (IN4007) and MKP caps (10uF/400V) on your linestage?
Thanks.
May i know what is the purpose of having both the diode (IN4007) and MKP caps (10uF/400V) on your linestage?
Thanks.
fdegrove said:
Hi all,
i am building power supplies for these preamps and i noticed the power transformer specified in frank's design is 300va, any particular reason why so? and if monoblocks are to be made these means a whopping 1200va of transformers!
i am going ahead with a single 300va for the 2channels line amp, and 2channels phono preamp power supplies, any comments?
thanks a lot in advance.
i am building power supplies for these preamps and i noticed the power transformer specified in frank's design is 300va, any particular reason why so? and if monoblocks are to be made these means a whopping 1200va of transformers!
i am going ahead with a single 300va for the 2channels line amp, and 2channels phono preamp power supplies, any comments?
thanks a lot in advance.
How about 100mA power tranny for 2-channel linestage and mm phonostage using 12bh7 and 7025 tubes respectively?