As I wait for Matt at MPS to put the final tweaks on his version of Z-565 OPTs to start another amp build, I'm looking for a tube preamp kit or well documented build from scratch clone article to start. It will be used with my EFB ST-35 amp because I'm curious about differences in a tube pre and the Mac C-24 presently there - not because I'm unhappy with the C-24. Searches on Erhard Audio's PAS 3 series New Generation don't yield much info - meaning there are few results returned - but are almost all positive. Any other suggestions on different units or input from Erhard users on The PAS 3? If I did go the PAS 3 route with his boards - tone controls or no? They're present on the C-24 and my MA5100, but I can't say I really apply them. Thanks
Opinions Please on Tube Preamp Kits / Documented Build From Scratch Options
- Thread starter Troutbear
- Start date
I'm very partial to the octal Aikido, to me it's just a great-sounding preamp. Tubes4HiFi sells a very nice board for it, and I also have some mono boards without the power supply that I ordered based on a scratch build over at Audiokarma. Be happy to send you some. John Broskie sells boards and power supplies over at Glassware but he's been out-of-stock for ages now.
Tubes4Hifi also has a new SP20 noval kit that I'm not familiar with but looks interesting. The Elekit preamp kit is also supposed to be very good.
Tubes4Hifi also has a new SP20 noval kit that I'm not familiar with but looks interesting. The Elekit preamp kit is also supposed to be very good.
Seconding the Aikido (although in my case, I went with the Aikido LV with 6GM8 tubes). Is super quiet, very linear, and very easy to assemble. IMO, the Aikido is a much better option than the PAS 3 as it has 40+ years of advancements in technology and theory. Looks like John has retired a lot of his older boards in favor of newer designs (the Octal and the LV have both been out-of-stock for a while, but the Noval Stereo Rev. F is available, as are several Power Supply boards).
If you are interested in a tube buffer rather than a preamplifier, I have an assembled Aikido Cathode Follower (ACF) board on the shelf.
If you are interested in a tube buffer rather than a preamplifier, I have an assembled Aikido Cathode Follower (ACF) board on the shelf.
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I built a lovely preamp designed by our own @paul_b . Big thread with lots and lots of mistakes at the beginning. I ended up building two of the Revision 3 preamps. One with fixed B+ and one with switchable B+. Final build/schematic starts about (link below). I've been totally happy for the last three years.
Pre-Amp Build
Pre-Amp Build
I built a lovely preamp designed by our own @paul_b . Big thread with lots and lots of mistakes at the beginning. I ended up building two of the Revision 3 preamps. One with fixed B+ and one with switchable B+. Final build/schematic starts about (link below). I've been totally happy for the last three years.
Pre-Amp Build
That looks like fun!
Appreciate the inputs. I'll research those include the 53 pages of threads in the link, although the astetics of the SP20 w/ digital display and remote is a negative to me.
@Paul-b - yes to your 3 questions. Chassis fab being mechanical is actually a comfortable area. I said well documented on the non-kit path because I feel comfortable implementing, but electronics is not my area of design background - if that helps calibrate on the handholding part. Best case would be circuit board w/ point to point next in line I guess rather than a complete kit as I would prefer to source my own components although most kit folks don't follow that approach I know. The ST35 amp was great - boards from Dave G and the rest of the mechanical pieces from Dynakitparts then Mouser and a few other component sources.
I'm curious as to the 12AX7 comment as I see those in many preamps from the Mac C22 through other "vintage" preamps.
@Paul-b - yes to your 3 questions. Chassis fab being mechanical is actually a comfortable area. I said well documented on the non-kit path because I feel comfortable implementing, but electronics is not my area of design background - if that helps calibrate on the handholding part. Best case would be circuit board w/ point to point next in line I guess rather than a complete kit as I would prefer to source my own components although most kit folks don't follow that approach I know. The ST35 amp was great - boards from Dave G and the rest of the mechanical pieces from Dynakitparts then Mouser and a few other component sources.
I'm curious as to the 12AX7 comment as I see those in many preamps from the Mac C22 through other "vintage" preamps.
Most older audio sources required much more gain than is needed today with the "standard" CD 2V output, 26db + was not uncommon.
The classic preamp circuit would use a very high gain triode, such as a 12AX7, and then wrap it in a bunch of feedback. This lowered measurable distortion and lowers the circuit's gain. Most of these circuits have a readily identifiable sonic signature and tends to restrict the sound staging abilities of the preamp. Not all implementations of the venerable 12AX7 suffer this fate, but the usual 12AX7 circuits are just rehashes of older circuits.
Dan
The classic preamp circuit would use a very high gain triode, such as a 12AX7, and then wrap it in a bunch of feedback. This lowered measurable distortion and lowers the circuit's gain. Most of these circuits have a readily identifiable sonic signature and tends to restrict the sound staging abilities of the preamp. Not all implementations of the venerable 12AX7 suffer this fate, but the usual 12AX7 circuits are just rehashes of older circuits.
Dan
The other issue with the 12AX7 preamp is that the amount of current that they can swing at their outputs is microscopic. Even if you have a 12AX7 cathode follower with its adequately low output impedance, feeding that into a subwoofer plate amplifier can cause some substantial limitations. This wasn't as much of an issue back in the day, as input impedances were relatively high on most equipment and interconnect cable lengths were kept pretty short.
Plus one on the BeePree! I have the second version of it and am set. I don’t so much as look at preamps now. It’s end game good!
ANK ( Audio Note Kits), for my money!!! Have built many kits including Bottlehead, Tubes4HIFI and a few others over the years and none gave the fit and finish or quality of parts or end result sound like the ANK gear. They’re built like a tank, look great and sound bloody fantastic!!!
After more reading, including of course the suggestions above, I’m thinking perhaps an Aikido line stage. They appear to gather several good comments across a few years. I can’t work up enthusiasm for a 300B preamp simply given the cost of chasing NOS tubes to explore vs what those go for in a 12AX7 version - call me boring but if a Mac 20 or 22 wasn’t so elevated these days I’d grab one of them 12‘s included.
I‘m a bit put off by the limited source (I’m presuming) blocky caps in the current Noval edition pcb on the TubeCAD site though - seems to stymie component choices I’d think - plus the board density appearance. Also why the PS has 3 heat sink components sets while my PS in the ST35 sails through with a single in Dave’s board. Open to explanations on why to not be concerned however
Erhard Audio has a version influenced by the Aikido line stage in his PAS mod section. So I’m leaning toward it plus his newest phono board. Wrote to Holger to ask if there are chassis mounted transformers readily substituted for the pcb mount ones in his PS card that’s SS regulated. For no great objective reason likely, I’d just prefer that approach. During my reading, I believe I’ve seen where the gain in this board has been dropped over the years - so perhaps that addresses a 12 tube concern
I‘m a bit put off by the limited source (I’m presuming) blocky caps in the current Noval edition pcb on the TubeCAD site though - seems to stymie component choices I’d think - plus the board density appearance. Also why the PS has 3 heat sink components sets while my PS in the ST35 sails through with a single in Dave’s board. Open to explanations on why to not be concerned however
Erhard Audio has a version influenced by the Aikido line stage in his PAS mod section. So I’m leaning toward it plus his newest phono board. Wrote to Holger to ask if there are chassis mounted transformers readily substituted for the pcb mount ones in his PS card that’s SS regulated. For no great objective reason likely, I’d just prefer that approach. During my reading, I believe I’ve seen where the gain in this board has been dropped over the years - so perhaps that addresses a 12 tube concern
You could certainly make an Aikido clone and design your own PC board. If you're not selling it, I doubt Broskie would care.
I would suggest that there's a strong possibility that those blocky caps you hate the appearance of so much are replacing what might otherwise be electrolytic power supply capacitors, so would you rather have the electrolytics? What about the shape of the packaging of a capacitor is detrimental to the sound?
Do all components mounted on a heatsink serve the same purpose? Are Dave and John supposed to have a conference call to set the standard number of parts mounted to heatsinks in their kits? The design goals for the power supply section of a tube preamp are very, very different than a tube power amp/integrated amp. If you read the product description for the Broskie PCB, the need for three heatsinks is pretty clear based on the capabilities he is claiming for the board.
I think just based on these questions that you would be best suited with Audio Note equipment.
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In my scratch Aikido I built the circuit p-to-p, which isn't at all difficult. I used a 6X5 rectifier, a single 20uF cap, followed by a Neurochrome Maida regulator. Those are not cheap but they are wonderful with an Aikido. You can dial in the voltage for different operating points. It also helps to be able to adjust the voltage to get the noise cancellation just right. For the filaments I used a 6V in > 6V out regulator from v4lve lover over at DIY audio. The preamp is dead quiet.
I'm going to do a new build with the PCBs I mentioned and the two regulators and see how that works out.
I'm going to do a new build with the PCBs I mentioned and the two regulators and see how that works out.
Thanks Zach. The Maida is reads to be a nicely done piece and the price doesnt seem out of line for the performance advertised. While this might still be a comfort stretch for me I’m certainly glad to learn of it and with their instructions still a back-up potential. Appreciated
paul_b. Actually, I could not design my own pcb for a clone. Early up I attempted to answer the question on skill level. In the career that got me to a point where I’m relaxing more with time to explore audio again, I designed and led teams to design and develop many methods for manufacture of assemblies that enhanced the performance of military and commercial aircraft systems and a few ground defense vehicles - but those were mechanical, I’m not an EE I hope that’s not a requirement to participate in this forum but if so, fine there are others. The blocky caps - not intended as a detrimental term - simply suggested to me a potential of limited scope component options. I read the PS-21 site description and grasp as far as I can the function of the three regulators - but not sufficiently to fully comprehend the differences in their application vs other power supplies that seem - to my level - simpler. None of this is intended to disparage John B’s designs In the least. The many positive comments I found on it are what brought me to consider the configuration or it’s influenced derivatives.
paul_b. Actually, I could not design my own pcb for a clone. Early up I attempted to answer the question on skill level. In the career that got me to a point where I’m relaxing more with time to explore audio again, I designed and led teams to design and develop many methods for manufacture of assemblies that enhanced the performance of military and commercial aircraft systems and a few ground defense vehicles - but those were mechanical, I’m not an EE I hope that’s not a requirement to participate in this forum but if so, fine there are others. The blocky caps - not intended as a detrimental term - simply suggested to me a potential of limited scope component options. I read the PS-21 site description and grasp as far as I can the function of the three regulators - but not sufficiently to fully comprehend the differences in their application vs other power supplies that seem - to my level - simpler. None of this is intended to disparage John B’s designs In the least. The many positive comments I found on it are what brought me to consider the configuration or it’s influenced derivatives.
From the Aikido PCB product info:
"each channels's B+ RC filter is made up of pure polypropylene (no electrolytic) capacitance [...] The two big black boxes each hold 50µF of polypropylene capacitor that is rated for up to 550V and 15A"
When I build custom amplifiers, I charge a bit extra to use those same caps. The expected lifetime is extremely high, the ratings are ludicrously high in just about every way, and they are fairly compact for being film caps at the rated voltage/capacitance. These are a very good engineering choice and I would struggle to think of something else that could go in that spot and do a better job.
"each channels's B+ RC filter is made up of pure polypropylene (no electrolytic) capacitance [...] The two big black boxes each hold 50µF of polypropylene capacitor that is rated for up to 550V and 15A"
When I build custom amplifiers, I charge a bit extra to use those same caps. The expected lifetime is extremely high, the ratings are ludicrously high in just about every way, and they are fairly compact for being film caps at the rated voltage/capacitance. These are a very good engineering choice and I would struggle to think of something else that could go in that spot and do a better job.
paul_b - I appreciate your inputs on the caps. Given your impressive work, these are encouraging recommendations and your perspective is appreciated. As I read more on the Aikido line stage, it looks like there are several tube mix options to be used but I guess I'll simple order a board to get the instructions and plow through those choices. As I think I noted above, it would feed my ST-35 but I'd also like to try it on a SS amp - perhaps my old Hafler DH-200 or a Mac MC250 if a nice version rolls into Audio Classics. Generally, I don't see phono stages noted in threads on these Aikido preamp builds but I guess that could be a separate item - not a near term need anyway but a one day would like to have.
