Would a line stage be beneficial for my SimpleSE. I originally wanted to have at least the ability to switch inputs in a passive mode but now realize I may need more than that.
I don't need additional gain. Or, at least I think I don't. It seems that the output from my tuner is much lower and it sounds really great. But when I switch the cables to use my CD player, it seems to sound clipped and might even have some harmonics being produced. What's interesting is that this clipping appears even when the volume is low on the SimpleSE amp. I conclude from this that it is possible I am overdriving the 12AT7. Would a line stage control the input level to keep it consistent. Is my assumption correct?
Can someone please help with this dilemma?
Thanks.
I don't need additional gain. Or, at least I think I don't. It seems that the output from my tuner is much lower and it sounds really great. But when I switch the cables to use my CD player, it seems to sound clipped and might even have some harmonics being produced. What's interesting is that this clipping appears even when the volume is low on the SimpleSE amp. I conclude from this that it is possible I am overdriving the 12AT7. Would a line stage control the input level to keep it consistent. Is my assumption correct?
Can someone please help with this dilemma?
Thanks.
I'm guessing that I should have searched the forum first since this question has been asked/answered a million times and that is why no one responded.
I just did a search and it looks like the Aikido line-stage would be the answer to my problem. I would be able to select multiple inputs and control the line-level. Has anyone used the combination of SimpleSE and Aikido line-stage? Before I purchase this can someone please let me know if this sounds like a good idea?
Thanks
Andy
I just did a search and it looks like the Aikido line-stage would be the answer to my problem. I would be able to select multiple inputs and control the line-level. Has anyone used the combination of SimpleSE and Aikido line-stage? Before I purchase this can someone please let me know if this sounds like a good idea?
Thanks
Andy
Thanks SY. I will look into this. I really love these tube based amps. I can't believe I waited this long and used solid state. I was a Novice for amateur radio when I was 16 (WN2AMH) but it was basic theory on vacuum tubes so I need to ramp up my skills. Thinking of getting back into HAM as well. Believe it or not, I used to enjoy CW.
Perhaps it was issued before freq. was refered to in Hz.
As SY mentioned, a "unity" gain line stage seems appropriate to your situation. One of the effective methods of buffering a volume control is a constant current sink (CCS) loaded cathode follower. High gm/low RP types make superior cathode followers. The current production ECC99 and 6n30p, along with the NOS 5687, have the requisite characteristics. The CCS used in "El Cheapo" and the DIY Audio PCB are candidates for this project.
A bipolar PSU is indicated for the buffer, as it eliminates a cap. in the signal path on the I/P side.
Hi
You could look at this extensive blog of John Broskie. Lots of interesting circuits, but I believe that the second and third circuit presented under "back to bipolar power supplies" are extremely simple and will work pretty fine (but so will many others)!
http://www.tubecad.com/2007/04/blog0104.htm
Good luck, Erik
You could look at this extensive blog of John Broskie. Lots of interesting circuits, but I believe that the second and third circuit presented under "back to bipolar power supplies" are extremely simple and will work pretty fine (but so will many others)!
http://www.tubecad.com/2007/04/blog0104.htm
Good luck, Erik
The advantage of using cascoded SS device CCSes as loads is a HIGH AC impedance, without I2R heating losses. That, in turn, promotes maximum linearity from the CF.
A look at the ECC99 data sheet suggests to me that the 150-0-150 winding of Hammond a 369BX power trafo bridge rectified (end to end) by 4X Schottky diodes and choke I/P filtered would make a satisfactory bipolar PSU. Put a 30 H. Hammond 157G choke between the CT of the rectifier winding and ground. That way, a single "beefy" inductor serves to filter both rails. A pair of 15 KOhm bleeder resistors connect ground to the O/Ps of the bridge. A HIGH WVDC 10 nF. ceramic cap. goes in parallel with the 30 H. choke to protect the SS diodes from inductive kick back spikes. Stacked 15 muF. 'lytics followed by paired lighter duty chokes (say Hammond 156Ms) and a 2nd cap. stack complete the PSU. RC sections following the initial LC setup might be feasible at the lowish draw in this preamp.
A look at the ECC99 data sheet suggests to me that the 150-0-150 winding of Hammond a 369BX power trafo bridge rectified (end to end) by 4X Schottky diodes and choke I/P filtered would make a satisfactory bipolar PSU. Put a 30 H. Hammond 157G choke between the CT of the rectifier winding and ground. That way, a single "beefy" inductor serves to filter both rails. A pair of 15 KOhm bleeder resistors connect ground to the O/Ps of the bridge. A HIGH WVDC 10 nF. ceramic cap. goes in parallel with the 30 H. choke to protect the SS diodes from inductive kick back spikes. Stacked 15 muF. 'lytics followed by paired lighter duty chokes (say Hammond 156Ms) and a 2nd cap. stack complete the PSU. RC sections following the initial LC setup might be feasible at the lowish draw in this preamp.
Hi Eli
I agree with you, so my earlier post was not ment to state that the idea you described was not good... it is just that the AIKIDO output stage is maybe easier to build, and with the high PSRR an appropriate power supply would not be hard to make.
Anyway your last post has taught me a new thing: filtering of a dual supply rail using a single choke. I didn't know it could be done this way! Thanks!
Erik
I agree with you, so my earlier post was not ment to state that the idea you described was not good... it is just that the AIKIDO output stage is maybe easier to build, and with the high PSRR an appropriate power supply would not be hard to make.
Anyway your last post has taught me a new thing: filtering of a dual supply rail using a single choke. I didn't know it could be done this way! Thanks!
Erik
Erik,
I'm the last person to criticize Broskie. However, I believe the Aikido has gain and this thread's originator needs a "unity" gain design.
The trick of the choke in the ground leg is also useful in a unipolar supply, to avoid exceeding insulation limits. People tend to forget that PSUs are inherently differential. We make them single ended or bipolar by grounding a point.
I have a marked tendency towards "overkill" in PSU design. I take the admonition to build on granite, not sand, very seriously. The PSRR of a CCS loaded cathode follower is excellent. Still, a low noise and well regulated PSU can't hurt.
FWIW, Santiago is in the same time zone as Plainsboro. While you head towards Summer, we head towards Winter.
I'm the last person to criticize Broskie. However, I believe the Aikido has gain and this thread's originator needs a "unity" gain design.
The trick of the choke in the ground leg is also useful in a unipolar supply, to avoid exceeding insulation limits. People tend to forget that PSUs are inherently differential. We make them single ended or bipolar by grounding a point.
I have a marked tendency towards "overkill" in PSU design. I take the admonition to build on granite, not sand, very seriously. The PSRR of a CCS loaded cathode follower is excellent. Still, a low noise and well regulated PSU can't hurt.
FWIW, Santiago is in the same time zone as Plainsboro. While you head towards Summer, we head towards Winter.
Eli,
I apologize up-front if I am not understanding you. I believe at a high-level you are saying that the PSU has a tremendous influence on the output of a line stage/preamp and that if I intend to build the Aikido, I should use this type of PSU to supply power? Clearly, you are leaps and bounds ahead of me with experience and knowledge. I have a basic background from my Amateur Radio days about 30 years ago and have a knack for not forgetting anything I have learned.
So is it fair to say I use the Aikido in conjunction with this type of PSU?
I apologize up-front if I am not understanding you. I believe at a high-level you are saying that the PSU has a tremendous influence on the output of a line stage/preamp and that if I intend to build the Aikido, I should use this type of PSU to supply power? Clearly, you are leaps and bounds ahead of me with experience and knowledge. I have a basic background from my Amateur Radio days about 30 years ago and have a knack for not forgetting anything I have learned.
So is it fair to say I use the Aikido in conjunction with this type of PSU?
Negative! The Bipolar PSU I outlined is intended for use with CCS loaded CFs. Remember, while it's a FINE design, the Aikido has gain and that's the last thing you need. AAMOF, you may have to add a padding resistor to the CDP I/P to make it behave like the tuner I/P does.
The sonic quality of the "unity" gain circuity I have in mind is (IMO) superior to that of your simple SE. That is not a problem, as you are likely to use the line stage with other amps you build in the future.
BTW, do you want a ganged stereo level control or individual controls for each channel? I highly recommend PEC hot molded Carbon controls. They sound good, without bankrupting you.
I built a 6SN7 Aikido. It does have too much gain, and I did pad it down with some resistance to reduce the input voltage. When I compared it to a simple passive 50K pot, the pot wins out, of course.
My amp has an input sensitivity of .7V to play at full volume, with a 100k input impedance. (Much like the original poster).
With an amp that does have a high input impedance, is there any advantage to using a CF as an output buffer?
P.S. I did learn quite a bit building my Aikido. It is a fine design if you need gain. I think I'll rip out the parts and use them to build a a single-ended EL-34 amp now. I just need to buy some output transformers.
P.S.S. I might just try a TVC now for a preamp...
My amp has an input sensitivity of .7V to play at full volume, with a 100k input impedance. (Much like the original poster).
With an amp that does have a high input impedance, is there any advantage to using a CF as an output buffer?
P.S. I did learn quite a bit building my Aikido. It is a fine design if you need gain. I think I'll rip out the parts and use them to build a a single-ended EL-34 amp now. I just need to buy some output transformers.
P.S.S. I might just try a TVC now for a preamp...
Thank you Eli. I do expect that this will not be the last amplifier I build. I now understand what you have recommended. I agree with having the highest quality preamp since any imperfections it introduces are amplified it would seem to me this is where you need to lay down a solid foundation to build upon.
Eli Duttman said:Erik,
I'm the last person to criticize Broskie. However, I believe the Aikido has gain and this thread's originator needs a "unity" gain design.
The trick of the choke in the ground leg is also useful in a unipolar supply, to avoid exceeding insulation limits. People tend to forget that PSUs are inherently differential. We make them single ended or bipolar by grounding a point.
I have a marked tendency towards "overkill" in PSU design. I take the admonition to build on granite, not sand, very seriously. The PSRR of a CCS loaded cathode follower is excellent. Still, a low noise and well regulated PSU can't hurt.
FWIW, Santiago is in the same time zone as Plainsboro. While you head towards Summer, we head towards Winter.
Hi Eli
In my previous post I was referring to a schematic by Broskie with only the second stage of the Aikido, fed by a bipolar power supply. This stage has no voltage gain, it is only a buffer with high PSRR (I tried to attach the schematic, but it did not work). I imagine that your idea could perform even better, but it could also be more complex to build, don't know.
Since saturday I am at my parent's place, a small town in Brazil. I already visited some people, working on something for the university...but actually getting claustrofobic from this small town. In three weeks I am going back to hothot Santiago, backpacking for three weeks through Argentina, work somewhat more at ECLAC, and afterwards finally back to the Netherlands.
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