Bottlehead Forum
General Category => General Discussion => Topic started by: tubefrk on August 16, 2012, 06:30:48 PM
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Hi all, is there a posability of an M/C phono in the making? I sure could use one....
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We've been trying things for a couple years. We have learned so far that a tube sounds better than a stepup transformer - and we've had some really great transformers in house. The problem is finding a reliably quiet tube and building a quiet circuit around it. We've kind of suspended the project in favor of the DAC research lately, but the most recent prototype is still around and I think we just need to get back to it. I do at least have a concept and circuit topology, and I am convinced it is possible.
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Thank you Paul, for the get back. If I'm the only one crying for this i'ts probably not worth you'r time and energy. I'll keep hoping. Thanks again, Mike
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Paul, what are your feelings on a hybrid unit? ie. Op amps in the front end, and a tube on the output.
Bernie.
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Paul, what are your feelings on a hybrid unit? ie. Op amps in the front end, and a tube on the output.
Bernie.
In my experience, hybrids have never sounded as good as tubes. This goes for power amps (solid state last stage) as well as small-signal preamps (opamps, or even just a FET, at the input). I have not heard everything, and am still willing to be surprised, but it hasn't happened (in this area) yet.
The same goes for feedback and transformers. Feedback was easy, it's been clear to me for a long time. I do hear that tubes with feedback sound better to me than solid state with feedback, but zero feedback tubes sound even better. (For my taste, single ended sounds better still, even compared with zero-feedback push-pull DHTs - but at least I do respect different opinions on that one!) But it took me a long time to agree with Doc B. on transformers. I love them, but have to acknowledge that if you can get away without them it's better.
Sometimes these things are necessary - we've had many many years of great satisfaction and success with the Foreplay, which has a cathode follower, i.e. feedback. And the big Bottlehead speaker system has many cathode followers in the active crossover. But now that we have tried the 300B direct-output preamp there is no question to my ears that it is better. I'm sure we will compromise these principals off and on in the future, but I'm always looking for ways to do it without compromise.
Interestingly, at least to me, is that a solid-state current source as a plate load does seem to sound better than a choke. The bigger the better for the choke, but the current source still "wins". So, I have some rules of thumb as above, but there is no substitute for listening, and I continue to learn new things.
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For whatever it might be worth, this project has the full support of the Bottlehead Manual Writer's Union.
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The Mexican Bottleheads Association also approved it.
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To me the hard part for Paul Joppa is the variable loading and multiple gain settings. I guess loading can be selected by DIP switches or one pair of nice resistors but the variable gains, that will be a PITA.
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Nah, I have a lock on the gain issue, and I see no reason the input impedance should be impossible either. Right now it's just the noise question. Based on the physics, tubes can be as quiet as the best transistors or FETs - we just haven't yet been able to build something that approaches the theoretical possibilities. I know it has been done in the VHF/UHF radio frequencies, and I think I know enough about low-frequency noises to get around them, so I remain confident that we can do it if we put enough effort into it. Maybe after the 300B preamp is released (which looks like it will be pretty soon).
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Excellent!
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You may want to find a good headamp to try with current products (if you own them) until a BH product becomes available. I use a rare but amazing Pioneer H-Z1 with my BH Tube Phone and custom Eros with great success (Pioneer Exclusive P3/Lyra Kleos/H-Z1/Tube Phono). There are current options that work well with BH gear but it's trial and error finding what works best for your system. I for one am excited about a future BH offering.
PJ, did you ever get to sample to the Blackburn Microtech 12AX7 tubes which used cathode ray tubes before they went under? Too bad that tech didn't make it....
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Never actually saw one. Too bad, the modern cathodes were clearly different and may well have been better sounding. 12AX7 has too low a transconductance to be quiet enough, but the AT7 might have worked.
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They went under before the at7 made it to production. One error in the last post, the tubes use micro cathode ray guns.
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Oh, how I wanted to try those tubes! Like the excellent, affordable Ampohm caps, some components that went out of production way to early.
As for my feelings on an MC phono stage, not sure, I'm sticking with MM and MI for now (and realizing that the Haniwa is not in my near future :-) ).
-- Jim
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I've been using those Microtech (Blackburn) planar tubes in the voltage gain section of my phono pre (CAT Ultimate).
I absolutely love them. Unfortunately, I just bought a few pairs before they went belly up.
They are very quiet,.. to a point. There is a noise floor waaaay down there that "whistles" like a cathode ray tube (big surprise huh?). In practical terms, I only hear it when I want to since it have to turn the gain almost all the way up to hear it.
I was really bummed when the went out of business and tried to scoop up as many as I could but I don't think there was anyone to reply. I can only hope that whoever bought the tooling will bring them back after the world wide meltdown ends.
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Thank you all for the replys. I would use anything that sounds good, hybrid or not, I still think it's a matter of cost to support a kit. I have been known to pull out those op amps and put in discrets, like the ones you can get from Parts conn. Brunson.... After tweeking, a cap change, some higher quality resistors, and OP Amp, cheep units sound pretty good . However not as good as some tube units, unfortunatly they are way out of my budget. Enter B/H save us all Mike, Burnt out guitar player from the 70's .