Tekton Double Impacts

Hi All, I wanted to introduce myself. I'm Aric Kimball the owner/sole proprietor of Aric Audio, and say thank you for some of the nice comments on the amps that I build. I wanted to say, that I specialize in building high-end Tube gear that can compete with gear costing many times more. I build all of these myself by hand- using point to point wiring, and with only very high quality components. I have lots of products on my site, and since these are built to order- I can also customize products to your needs. If anyone has an interest- feel free to contact me through my site (www.aricaudio.com), or you can message me using the message feature here as well. Best wishes, Aric

Thanks guys- it's much appreciated!

Hey Kenny, I really appreciate the kind words on my build and am glad that you’re happy with your amp! Perhaps I can shed some light on the driver tube: My test preamplifier has up to 35 db of available gain (using 12AT7’s), and in my testing I found the 6SN7 would drive the 2A3 easily- with lots of headroom from my preamp’s volume control. In Kenny’s system, his preamp is configured for a lower gain structure that needed to be pushed higher for the same drive from the 6SN7. By substituting the 6SL7 (raising the gain of the driver), it allowed his lower gain preamp to reach the same overall drive available to the 2A3. Both the standard 2A3 and JJ 2A3-40 have the same input requirements. Aric

Hey guys, just a generic note on my test preamp. I use this as a unit for my bench only (it's not something I design for consumption), and it has a variable output level as well as input control that can reach up to 35 db (generally 35 db is not used in everyday testing). I was simply stating that using that preamplifier, I was able to get plenty of drive into the 6SN7 driving the 2A3. Using a lower gain preamp, the 6SN7's can still be driven, but needed a bit more volume on the preamp to do so. The 6SL7 simply has more gain in front of the power tube- needing less preamp drive at it's input. 

+Charles1dad

I believe your summation was very succinct and en pointe! If I may add, since music- by it's very nature, is about conveying emotion, it would make sense that very feeling would carry over into our affinity towards whatever equipment helped get us there :-) 

@ Mac48025- Tom, that’s great news! I’m glad to hear you’re enjoying the amp already. I really enjoy hearing people that are happy with my products, as I take a lot of pride and joy in building them! Let me know your thoughts once she’s had a chance to full break-in. Also, if you have the opportunity, the KT150 sounds very good in this design- it’s a bit "bigger" sounding than the 120’s, but has an extra splash of micro-detail at the top and bottom ends (making the midrange seem to have more space in between notes). I look forward to your assessment!

@Teajay- Thanks a lot Terry- I really appreciate the kind words you put out there. It means a great deal to hear, and furthers my ambition to build these. Now.....I’ve got to hear that MicroZotl and get this 6SN7 preamp out to you! Best wishes, Aric

Hey David, I would absolutely be up for a parallel 2A3, or the same using 300B's if you're seeking the sweet mid-range of a true SET. A very competent design could be built using relatively standard parts that won't break the bank as well. A big part of the synergy of the sound produced simply relies on good synergy between components. I can also design around the 211 or 845's (I'm working on a very high end build now for a client around those tubes). Feel free to message me anytime with any ideas you have and I would be happy to work with you on a build! Best wishes, Aric

Tom, Thanks for making that recommendation as well- it's greatly appreciated! I believe the larger Pentodes used in Triode-mode can really get you 90% of the way to the signature SET sound while getting you greater power and control over the drivers. I'm glad you're digging the Transcend 120/88 amplifier! Best, Aric

@sbayne - Thank you for that, it's much appreciated. 

@charles1dad  and @sbayne -  With regards to AC or DC. With Pentodes, tight twisting and layout of AC filaments can reduce all but the slightest of "ear to the speaker" hum. With Triodes, the 2A3 seems receptive to AC using good layout. However larger magnetic fields are induced with higher voltage and/or current filaments tubes (like the 845 which I would only use DC for the filaments). It seems the 6B4G (requiring 6.3 volts at 1 amp), would be a good candidate for AC heaters (since the draw and field is not large- even the KT series tubes get by with AC- and they draw almost twice the current). AC seems just a hair more "lively" in my opinion. That said, a good, simple circuit with respect to layout/lead dress, and using good quality parts in the signal path, and a good driver stage- should still yield a very lively system. Aric

@charles1dad  It would seem similar to the issues when doing push pull in that one tube will either be pushing or pulling harder than the other. One way to avoid this is using matched tubes, or to have a variable bias for each tube (instead of a balancing pot used in many push pull design). However I do see that using closely matched tubes would help, although once they burn in their specs will drift somewhat and not always in the same way. By having a separate bias adjust for each tube you could fine tune the current each one is drawing. One drawback however to parallel SE is the double current requirements for filaments and the high voltage requirements. Best, Aric

@mac48025 - I'm really stoked that you're still loving the Transcend 88/120 amplifier, and I agree the 150's don't have the same "magic" in the midrange as some of the well-regarded KT88's. I occasionally switch back and forth between the types- and for loud, highly-percussive rock, or fast paced metal (I admit to listening to all genders of music regularly- but with a lean more towards alt-rock or jam-band), I think they can give a presentation of a good quality tube sound- but with power "feeling" more like it's in the 60 watt per channel range. However when I go back to critical listening (and not a "crank this baby up" type of song), I feel the midrange lushness of the JJ blue glass 88's in this amp are VERY convincing in presentation towards true SET realism. 

@sbayne The 6B4G does not seem hard to work with. It would appear to require a bit more of a swing at the grid to drive to full output than say a 2A3, but isn't anything difficult to achieve. It also requires similar voltages and output transformer. As far as keeping the amp quiet (hum free), following good grounding and chassis isolation techniques as well as a choke-filtered power supply should keep it silent. I don't have hum issues with any of my single ended amplifiers after learning good layout and grounding techniques. Aric

@evolvist  You do get more power in Ultra-Linear mode- which does suit heavier music a bit more, but I find the enjoyment of the music (be it soft strings or heavier music) to be more so in Triode-mode. The drop in power is much less noticeable than one would think- in some cases, it's not apparent at all. Aric

Also, something to note- is the 6G4B is capable of 5.5 watts RMS in single-ended mode (single tube), as opposed to 3.5 watts for the 2A3. Parallel 6G4B can do closer to 8 watts (the same as a single 300B). 

@sbayne  and @charles1dad - You're very welcome! Aric

@david_ten - Yes, I recall you mentioning getting the front end in place, and all of that worked out first. I hope that's following a good path and things are working out! As far as the options for an SE amplifier, the 845/211 is definitely going to have more power and slam over a 2A3, and arguably more SET tone than the KT88 in my Transcend SE, but also requires a much more robust parts list to get it to work. The chokes and transformers need to be able to handle 1,000 volts continuously for the 845/211, and it also requires double the capacitance, and many series parts in the power supply to handle those voltages (most caps, chokes, transformers, etc. rate a maximum voltage of 500-600 volts). So the build of an 845/211 amplifier is almost double the cost. That said, I believe the KT88 in the Transcend sits right in between a 2A3's midrange and an 845's power- and won't break the bank. The 150's are a quite a bit brighter and larger sounding than the 88's in this amp, but don't quite have the midrange lushness of the 88's. Aric

@tkcha  Cha's amplifier is a very robust build centered around the 845 DHT/211 tube, and will be using EL34's (also capable of a KT88) to drive the large voltage/current swings needed for the Input of the DHT. A 6SL7 will be the input stage, then the Pentode driver stage, and lastly the power tube. We're using Electra-Print output transformers and a choke (capable of handling 5 kV swings). This amplifier uses many upgrades parts including all Vishay chassis-mount resistors, Audyn "True Copper" caps and independent power supplies for both the driver/pentode stage, the 845/211 power stage, as well as DC on the DHT's filaments. All will fit neatly in a hard-wood wrapped chassis with mirrored-aluminum as the finished top plate. Aric

@charles1dad - This is a very robust power tube using very high voltages and requiring a very heavy voltage swing at it's grid to drive it. 30 watts is the absolute maximum this tube is capable of- and that's running it at it's absolute max specs (not a good recipe for reliability or distortion). The sweet spot for this tube is between 18-22 watts, and this amplifier will have fully user-adjustable bias controls to fine-tune the amount of current that it draws. 

Hi all, I just wanted to briefly outline the scope of Tom's 300B SET build. It will be a single chassis stereo amplifier, using dual 5U4G rectifiers (both in parallel to provide double the current capacity), and a 6SN7 per channel for the input and driver stages. Single capacitor coupled output to the 300B, running the 300B at 66% dissipation for longevity and to produce 8 watts per channel. A choke-filtered power supply, and robust filter stages after the rectifier will produce a very black background. In addition each 300B will have its own independent filament transformer. DC on the 6SN7 filaments will provide low noise for the input/driver stages and reduce the overall noise floor to nil (generally not an easy task for a 300B based amplifier). All power resistors will use Vishay chassis-mount/heat sinked units to reduce internal heat, and essentially the entire amp will be built to provide twice the current that the circuit requires for lower heat/better reliability. The amplifier weighs close to 50 lbs, and will be 17" wide x 12" deep, x 3" tall (minus the wooden side rails). Price is $3,600 including EH 300B power tubes, (2) Sylvania NOS 5U4G's, and (2) RCA 6SN7GTB's for the drivers. 2 year warranty on the amplifier as well. 

Hey Charles, you're very welcome! With regards to filter stages, I am a believer in using good quality electrolytic bypassed with a high quality metalized polypropylene. To get a film capacitor of the correct UF ratings to effectively smooth ripple, size restraints come into play. Good low ESR caps can make for a very quiet power supply circuit. Aric

I also wanted to add that in any build I undertake, I like to maintain a "form flows function" approach (and also follow the KISS rule), by keeping all power circuitry towards the rear of the amp near the AC inlet, and all signal paths towards the front and/or out to the sides. Then find the average operational points of the tubes, and design around that. Use transformers rated for at least 33% more than the duty cycles of the circuits.Then the use of high quality parts come into play (the sum of the parts gives a synergy- much like the blend of a good recipe), keep wiring paths short (twisting filament wiring to cancel AC fields, shielding signal wiring wherever it may encroach a power circuit, etc.). Lastly isolate the chassis from audio and signal grounds and use a star/single point termination for the ground reference. I’ve found that maintaining all of these aspects in any build yields a reliable and typically a great sounding piece of gear.

Just my 2 cents. The L pad or power dropping resistor would not need to be rated at that high of a wattage if it’s placed after the mid-range bandpass filter, since most of the low frequency content is already rolled off by the capacitor in the high pass. Reasonably a 50 watt resistor would be more than enough there in the circuit. Additionally the midbass cones are much higher efficiency than standard Hi Fi midbass drivers so the tweeters nay not need quite that much padding. This is just based on my own speaker building experience- I have no direct experience with the Tekton speakers per se. Best regards, Aric

@evolvist - I almost spit my Cheerios out when I read that ;-)

@stfoth - Anytime! I'm always up for a new build. I'm up for pretty much anything, even custom builds if you had something specific in mind. 

@mac48025 - Thank you Tom- it's much appreciated! I made some good headway today- gotta call it quits for the weekend tho. Back at it Monday ;-)

Lula,

The chassis is 18.5" wide X 13.5" deep x 3.5" tall, with the power transformer sitting about 4.5" above that (with the tops of the 300B’s extending above those about an inch). Weight is just under 55 lbs unboxed- closer to 60 lbs packed. The amplifier uses two 5U4 rectifier tubes and independent transformers for each circuit in the unit. Best, Aric

Thanks for the kudos Tom- I'm glad you're enjoying the 300B! Just a note for anyone curious for more detail regarding the amplifier. It uses a single 6SN7, that uses one triode of the tube for the input signal gain, and the second as the driver for the 300B. Each stage has a defeatable cathode bypass capacitor, which boosts the current coming from the stage. Up, or "On" enables the cathode capacitor, and Down removes it (allowing a current-dependent "feedback" and lowering the gain of that stage). With both of them up, the gain architecture of both stages is quite high- and as such is susceptible to noise (especially with the gain control of the amp at full tilt- or close). These can be adjusted depending on the preamplifier's gain used, and allow you to "tailor" the gain architecture of the amp. It can also be used as an integrated with both bypass switches set to UP- and driven directly from a source (DAC, CD player, etc.). 

Regarding the "cheater plug" suggestion, it was suggested as a test to determine whether a ground loop may have been present or not. All audio gear has some sort of signal ground reference to circuit ground- some are isolated and some are not. I isolate the chassis from ground via an RC circuit, however another component may try to find "ground" through the signal. Sometimes moving a component to a different AC circuit, or lifting a ground somewhere in the signal path can eliminate AC-induced ground noise. 

Best wishes, Aric

Also to note, it's midrange and higher frequencies that damage our hearing, lower frequencies (like earthquakes) don't seem to present much of a threat. 

@corelli - Indeed the transformers are Hammonds, and the output transformers are 30 watt SE units. I've compared them head to head with some others that cost twice as much (I won't name names), and there hasn't been any discernible differences I've found under lots of extended A/B testing. 

Also that slight bit of hum occurs at higher gain settings- with the amp's volume near max and the two cathode switches flipped up. This was my first 300B build, and as such I based the front end on the popular two stage 6SN7. The 6SN7 is a current master- but a voltage weakling. As such it needs the cathode bypass caps engaged to give the extra 3 db per stage (unless your preamp outputs close to 2 volts). In future builds, I would opt for a 6SL7 in the first stage with it's voltage strengths- to drive the 6SN7, with no cathode bypass caps. That would give plenty of gain and really push the noise floor down to nil. 

@mac48025 - If you ever choose to go that route, I'll cover the mods if you want to be without her for a week and ship her back. 

Best, Aric

Hi Charles, Thanks for the kind words and sharing the driver info on your 300B.. It appears the 6EM7 was used to drive vertical deflection circuits in CRT TV's and can even be used as a power tube in a 1.5-2 watt amplifier. Definitely a lot of similarities to a 1/2 6SL7 and 1/2 6SN7- the best of both worlds it would seem. Best wishes, Aric

Thanks very much, I appreciate the kind words! Best, Aric

@mac48025 The Audyn True Copper series caps we used in your builds have competed favorably against the Jupiter and Mundorf caps at least in tube amps and preamps. I've seen several reviews where they stood head to head and even took home the ribbon for having a great response throughout the entire spectrum- especially in the midrange region. Nothing wrong with the caps you mentioned- but also wanted to throw in some other options! I've also used the Audyn Cap Plus as my go-to budget cap in several speaker designs. It's very neutral, yet revealing, and gives that nice black background between passages. Another option in lieu of replacing the large value caps (220uf for instance), is to bypass 10% of the value with a high quality film cap (so 200 uf 'lytic and 20 uf film in this case). 

Bypassing ’lytics in power supplies is definitely a notable improvement- second only to using large film or motor-run caps (in my opinion). In speakers, I find it a mixed bag, but have had "decent" results in bypassing a large series midrange band-pass capacitor in the high pass of the midrange circuit. In most cases those don’t get much bigger than 20-40 uf for the most part, so just replacing them using a mid to high-quality film can still be budget-friendly (and more practical). Large films do take up lots of space for sure. In fact in some of the smaller monitors I’ve built, I’ve even re-calculated the net internal enclosure volume to counter the volume displacement of the large cans!

I just saw that I could get a 280 uF in 1,100 volts- I'm sold! 

I had actually shelved one a couple of months ago, but was thinking a pair of these caps in series would be perfect for the B+!

@charles1dad  Those are good questions! For a cost no object, I would likely go the exclusive film cap route in the power supply- since even the best 'lytics will tend to drift with age (however good quality modern caps last MUCH longer than those of the 70's and 80's). What I like to do in most cases, is use electrolytics bypassed with small film in the first stages where massive filtering is required, and then have the last stage be pure film since it's the last part of the filter before the audio stages. 

As far as coupling? That's another tough one. Inter-stage trafos are technically superior in the phase region (where multiple stages are required), and also when you need a step up or impedance matching transformer. However iron has it's drawbacks in terms of frequency extreme rolloffs, so you trade "possible" phase issues for "possible" response issues. However in practice using good quality parts- these issues are small and splitting hairs so long as the design is done right. 

I for one think that high quality caps can get a design that sounds phenomenal so I typically don't look into the interstage transformers much. However, on a tube that requires a huge voltage swing and lots of low current to drive it (ex: 845, 805, GM70), it's almost necessary to use an interstage trafo as there's so much in the signal path otherwise. 

@333jeffery - Someday perhaps! I think my first 1kV triode will likely be the 805 or 845, as I've got the basics on a design down for those. The GM70 is very similar, but in all cases these designs are not cheap to do right. Using over 1,000 volts and requiring 2-3 stages to drive these huge tubes is a very deliberate complexity. The 300B, and 2A3 are next in line as far as needing low current, high voltage swings. The easiest tubes to drive are the Pentodes or Kinkless Triodes (KT88, KT120, KT150). The general rule is the less stages in the signal path- the easier it is to make an amp that sounds transparent in my opinion. 

Drat! Too late to edit. That should’ve been "as far as needing high current (low impedance), high voltage swings".

@charles1dad  Anytime! I appreciate you asking for my insight on the subject. Best, Aric

Thank you, and I edited to attach the link in my last post. 

@corelli - I am unable to see how to attach photos directly to the post, but I can post a link to Tom’s newly transferred amp.

https://www.facebook.com/AricAudioSystems/posts/1716034395113257

If I could insert a bit here about clean power. Generally the cleanest power you’ll get is by using batteries. I’ve installed a couple of small standalone systems for a friend of mine who lives off the grid, and it’s a basic solar panel battery charging system. Where he can, he uses 12 or 24 volt devices so that the system runs directly from the batteries. However when 110-120 VAC is required he uses a very high end power inverter. The power inverter’s output is not super clean however, and an isolation transformer and then line conditioner is used to flatten out the peaks and obtain a true AC RMS voltage. I would not recommend a generator for your sensitive electronics unless a good line conditioner is protecting them from it. Generators provide very poorly regulated dirty AC power by nature which has lots of spikes and dips directly related to the load being put on the generator (and the motor will surge and race with a varying load). These spikes are very damaging for SMPS units such as those in flat screen TV’s and many DAC’s, or digital audio equipment. For tube gear, it can cause issues as well. If you use a generator, make sure you use some really good AC line filtering between it and your electronics. I have a Generac 5,000 watt continuous generator and when there’s a power loss I disconnect my PC and TV’s from it as well as my audio gear. I’ve repaired many TV’s for people who’ve lost them due to using a generator either in an RV, or during a power outage. Those power supplies receive a spike and usually don’t make it. Some devices can survive several such spikes, but just a caution that it does have the potential to damage electronics if/when run directly from a generator. Best, Aric

No problem, and you were probably fine with the line conditioner, I just wanted to point it out as a caution for those who were interested to that end. 

I also agree wholeheartedly on the "pressure lock" a solid subwoofer can put on the lowest fundamentals of the bass. I came from being a bass player for most of my life and am very particular to that low end being produced accurately and with aplomb!

Yes indeed! All of that stuff was great! I wish I still had some pictures, unfortunately those are long gone.

@stfoth - Remember DB drag racing? Weren’t some of the SPL kings hitting in the 150’s? In a former life I was an installer, and remember half ohm stable competition amps that put out thousands of watts into that load. They were "rated" at 25 watts x 2 into 4 ohms- so they would qualify in a lower power class. Oh, and FWIW I was an installer for the SQ (sound quality) portion, not the SPL. They were two distinct categories. Ahh the 90’s!

Hey guys, I just wanted to chime in and let you know that a couple of new products have been added to the site using the new chassis and I'll have more to follow including a Push-Pull triode mode/UL mode amp using el34,kt88,120's and 150's. The standard offerings can also be built into the new chassis for an upcharge that simply covers the cost of the chassis and/or transformer covers (if desired). You can contact me through my site or PM if interested. I also wanted to say thank you Tom for the kudos man! Best wishes, Aric

Hey guys! First, thanks Brian for posting about the Motherlode! Secondly, the gain needed for a line stage is dictated by the amp- not the speakers’ sensitivity. An amplifier has a voltage and impedance requirement at the input - to drive it to full output. One amp can need 10 db of gain while another needs 25, and yet another 35. Respectively a phono stage provides over 40 db of gain to bring the cartridge level up to line level. There are many 6SL7 based preamps, and even 12AX7 preamps, and the gain is adjustable on the preamp output. On the same (but obscure note), a McIntosh schematic I recently looked at has no less than 4-1/2, 12AX7 stages- per channel. One single 12AX7 stage can drive a 6550 tube to full output. Now THAT’S a ton of gain ;-) Best regards, Aric

Exactly! I tend to want to design with some headroom in mind as there's nothing worse than running out of gain while the amp is just starting to open up. Like a governor on a hot rod.... No bueno!

And thanks for the kind words as well Tom!

Already have the badge on its way- chrome, engraved with stainless allen screws no less ;-) Will be putting it up on my site once it's complete!