Hello!
Who has built a full feature preamp with Aikido Cathode Follower and Aikido Phono?
Assume the ACF has 6922, which volume control resistance should I use? Which tube in the Aikido phono is adequate?
What are the differences between ACF and BCF?
Finally, can I put a series regulator for either ACF or BCF?
Thanks!
Who has built a full feature preamp with Aikido Cathode Follower and Aikido Phono?
Assume the ACF has 6922, which volume control resistance should I use? Which tube in the Aikido phono is adequate?
What are the differences between ACF and BCF?
Finally, can I put a series regulator for either ACF or BCF?
Thanks!
I haven't built an full feature combing phono and line but I have built both the Aikido phono and Broskie's Tetra phono.
I built the Aikido phono with 12AX7 for gain and 12AT7 for CF. Even though they're not run hard, new production 12AX7 don't seem to last that long before going noisy, in my experience. I might change mine over to all 12AT7. Even Broskie in one of this blogs has grown disenchanted with 12AX7s. For power supply I used Broskie's PS-1, regulated filament and regulated B+ supplies. Use a large enough chassis to leave room between both power trannies and the Aikido board to minimize hum. I found this out the hard way.
The Tetra phono, IMHO, gets you 90% of the Aikido phono performance for a lot less expense and hassle. Because it's based on one of Broskie's CCDA (constant current draw amplifier) it doesn't need regulated B+ so one of his PS-3 supplies woks well.
If your power amp has enough gain and a high or high-ish input impedance you might not even need a CF stage. Just put a 100K pot on the output of the phono amp then go straight to your power amp.
Steve
I built the Aikido phono with 12AX7 for gain and 12AT7 for CF. Even though they're not run hard, new production 12AX7 don't seem to last that long before going noisy, in my experience. I might change mine over to all 12AT7. Even Broskie in one of this blogs has grown disenchanted with 12AX7s. For power supply I used Broskie's PS-1, regulated filament and regulated B+ supplies. Use a large enough chassis to leave room between both power trannies and the Aikido board to minimize hum. I found this out the hard way.
The Tetra phono, IMHO, gets you 90% of the Aikido phono performance for a lot less expense and hassle. Because it's based on one of Broskie's CCDA (constant current draw amplifier) it doesn't need regulated B+ so one of his PS-3 supplies woks well.
If your power amp has enough gain and a high or high-ish input impedance you might not even need a CF stage. Just put a 100K pot on the output of the phono amp then go straight to your power amp.
Steve
Thanks for your response!
I am absolutely giving the 12AX7 and 12AT7 a try for the Aikido Phono as it should give enough output voltage.
I have the Transcendent Sound Pinnacle 300B OTL, and it seems not quite sensitive in 8 ohm and even worst in 16 ohm.
Pinnacle 300B OTL
My speaker is a bookshelf that is 94 dB and made for low powered 300B SE with minimum impedance not lower than 6 ohm.
So ACF is a must for both digital and phono playback based on my observation.
Thanks!
I am absolutely giving the 12AX7 and 12AT7 a try for the Aikido Phono as it should give enough output voltage.
I have the Transcendent Sound Pinnacle 300B OTL, and it seems not quite sensitive in 8 ohm and even worst in 16 ohm.
Pinnacle 300B OTL
My speaker is a bookshelf that is 94 dB and made for low powered 300B SE with minimum impedance not lower than 6 ohm.
So ACF is a must for both digital and phono playback based on my observation.
Thanks!
The thing is you won't get any gain from a CF stage. If you need gain then I suggest you build an Aikido line stage. I've built a few based on 9-pin tubes. The Aikido 12Vac (6DJ8 version) works very well for a not large outlay. I also built an all singing, all dancing, P to P wired Aikido LS with regulated supplies for both filament and B+. It started out with all 6CG7 tubes running at 300 volts. I didn't like it, sounded too tube-y and slow. I switched it over to 6DJ8s running at about 180 volts and it was much quicker.
My Tetra runs all 12AT7s and has lots of gain. I've only had one tube get a little noisy. My Aikido phono has had 3 of the 4 12AX7s go wonky. If you need a line stage with gain chances are an all 12AT7 Aikido Phono would be fine unless you are using say a high output MC that has a lower output than a MM cart.
My Tetra runs all 12AT7s and has lots of gain. I've only had one tube get a little noisy. My Aikido phono has had 3 of the 4 12AX7s go wonky. If you need a line stage with gain chances are an all 12AT7 Aikido Phono would be fine unless you are using say a high output MC that has a lower output than a MM cart.
I have talked to my brother and he has dealt with a very low mu tube-like 26 for building a linestage. A Japanese company, Meister, suggested he uses a step-up input transformer and has an output transformer at the end. The result is very good.
He said that I can put a toggle switch with or without a step up in my case.
He said that I can put a toggle switch with or without a step up in my case.
IIRC, somewhere in the 150 to 200 volt range is typically used with a Broskie BCF using a 6922.
S.
S.
I have never had a good experience with a 12ax7, always found them touchy to noise and feedback. I tend to back off the gain a bit and use 12au7 although 12at7 is another option.
I have noticed some 12ax7 designs with 2 channels split across 2 12ax7's.
This suggests consecutive stages in a 12ax7 have problems with feedback between the triodes.
I know your going to say there are many good designs out there with 12ax7, I have just found it difficult to work with.
The EAR834P uses three 12AX7s. The output tube is a cathode follower where a AU7 or AT7 would likely be a better choice. All three tubes are split across the two channels. I scratched my head over this for a while the realized that the first gain stage would need to be the most quiet. EAR probably figured that they could get one quite tube out of every three randomly selected tubes so they wouldn't need to buy specially selected quiet ones.
One tube guru, I forget who, is of the opinion that 12AX7s were tubes only fit for cheap record players. Can't say I disagree. I sorted all of my old 12AX7s for noise and microphonics then sold them off to support other projects. I made about 3 or 4 hundred bucks in the process.
S.
One tube guru, I forget who, is of the opinion that 12AX7s were tubes only fit for cheap record players. Can't say I disagree. I sorted all of my old 12AX7s for noise and microphonics then sold them off to support other projects. I made about 3 or 4 hundred bucks in the process.
S.
There is nothing fundamentally wrong with ECC83/12ax7 as riaa stage. It depends on the rest of components.
Right now, I'm using 6DJ8, 6N1P, 6N2P, 6N6P. I have used 6N3, 6N14, 6N24 as well. All perform nicely, but the 6N2 is needed in the third position unless you want to use 12AT7 in first position and third. Personally, I think the AT7 has some ugly curves so I stay away from them most of the time.
One of the best combinations I've used was actually 6N3/6N3/6N2/6N3. I also build boards for an active buffer like the ACF but no Aikido-mojo for 6N3, 6N14, 6N24 and 6N1. The 6N24 is basically a 6DJ8 with a bastard pinout so it works nicely. Let me know if you want a pair of kits or something.
One of the best combinations I've used was actually 6N3/6N3/6N2/6N3. I also build boards for an active buffer like the ACF but no Aikido-mojo for 6N3, 6N14, 6N24 and 6N1. The 6N24 is basically a 6DJ8 with a bastard pinout so it works nicely. Let me know if you want a pair of kits or something.
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