ANK 300B Interstage Monoblocks

2a3 speakers as in sensitive enough. We were Klipsch people for 30 years. Our latest units are just over 92db@ 1meter 1w so our low powered stuff sits.

Nothing new on the amp side of things. It's colder now and we're all class A. I did just fix one of the Citation II's and I might try strapping the pair and see what 120w does for my top hats. It's going well. Healthy, exercising eating, and drinking well thank you. And yourself?

 

Luckily I do but it's a PP 2a3 so a bit easier.

 

KT120 output tubes?
Work and work from home. as usual. The best part of it is I'm able to work with loud music. I made several batches of 120 minute cassette recordings and that's what I been listening to everyday on 8 hour work session (4-120 min)
Besides that I'm doing fine and thanks for asking...
I have a new project amp. Were building a 50 watts per channel 6c33c-b monoblocks. Actually I want it integrated with a bunch of trigger modifications and tape in and out on 2 channels. But the guy is complaining because its gonna be a big amp and very heavy for him to custom design build. He's actually gonna follow-up on Tuesday with the layout. I wanna use 100% copper wound on all transformers. So I might have to call your buddy in Vegas,,,, ElectraPrint.

 

Okay that sounds good. How many watts can you juice out of your amp?

 

15 watts and AN-J speakers works perfect.

 

Right on. that's excellent power! The one that I like about the push pull is the bass dynamics. There is still 3d but not as juicy as the set amps. (atleast on my amp) But I'm very happy with the whole outcome. Playing mostly all coverage and type of music, excellent 3D, very strong on 100 hz and below is a big plus for me.

 

Makes me glad I have 2 el84 amps, and some nice vintage el84's I picked up years ago.
I do have a 300B amp, but I don't think it's of sufficient quality to justify some of these big gun 300b's. I cringe a little bit forking over $150 each.

Now, if I had Jaytor's amps or the Luxman 300b amp I'd probably go for it.

 

Interesting. Well I may give the Taks a try at some point in the future.

In the meantime, my WE tubes showed up a day early, despite Fedex tracking still showing delivery tomorrow when I checked at 8:00AM this morning.



I put my Pass XA60.8s aside and connected my new amps to my main system on Sunday.



An audiophile friend (also a forum member) came over to give me a hand and we listened to a couple songs on the Pass amps before switching. Initially I goofed and hooked up one channel out of phase and I couldn't figure out why the vocals sounded so recessed with no center image. About half way through the second song it dawned on me. After swapping the speaker leads, it sounded WAY better (obviously). On my current speakers, which are 92.5db/w efficient, the 300Bs didn't sound quite as effortless as the Pass amps, particularly at higher volumes, but still sounded quite nice.

Initially, I was running the 300Bs full range (no high-pass filter). I switched to the high-pass input, and sounded a bit more relaxed (less wasted power in the bottom octave or two). The amps definitely have some more breaking in to do though.

Once I have my new speakers completed, which are considerably more efficient (98db/w line sources), I am sure that these amps will have more than enough power.

I plugged the WE tubes in about an hour ago. I've got some folks working upstairs refinishing my wood floors and making a lot of noise, so I haven't been able to really assess how they sound, but the improved midrange clarity was immediately obvious. When first powered on, there were a lot of little clicks and pops coming through the speakers, but these have all but gone away at this point. I have read that it takes a number of hours for these little noises go to away, and up to 500 hours for the tubes to fully break in.

I'll report back once I've got some good break-in on the amps and tubes.

 

Looking fantastic Jaytor and congrats on your WE's I hope they exceed your expectations. Also sorry that we all hijacked your thread for a bit with out tube discussion.

 

Congrats of the nice setup!

 

Jaytor, well how do those amps sound now?
Thanks

 

They are sounding pretty sweet, but seem to still be getting better as they burn in more. They've been playing 7-8 hours a day since I've had them in my system, so they have a little over 100 hours on them with the new tubes.

I've pretty much decided that I'm going to sell my Pass XA60.8s and stick with these. The new amps are a bit less dynamic, but this is one area where they are improving, and I think with my upcoming speakers which are 6db more efficient, they will work really well.

 

Congrats! and glad you like it. I been running my amp for over a year now like a marathon. I have a fan continuously blowing on the side of the amp and miraculously It didn't blow up my tubes for that long.
I have the same feeling on my amp. When I first got it, It already has that monster sound but I notice as the months go by without even adjusting or tube rolling, my amp vastly improved and just sounds bigger. I cant believe a 14 watt can pump so much bass dynamics on a 140 watt tower speaker.
Besides the timer and the motorized volume pot that I'll be installing, I will not add anything on the tone section. Not even a high dollar german capacitor. My builder nailed the sound that I was looking for.
Congrats to your new amp. Looking good from here.
CCG

 

Thanks Jaytor…very infectious build you accomplished. Your attention to detail is very impressive.
I’m trying to find a good schematic to build a single 300B. Finding a good driver tube has been fun & I think I found a good candidate out of Germany. I’ve always been a fan of iron.
I was also wondering if you consider the new WE300B sound to your liking?

 

Thank you. The WE 300Bs are clearly better than the Linlai tubes I was initially using to check out the amps when first built, but I don't have anything else to compare them to. They sound very nice though, and still seem to be slowly improving. Vocals, in particularly, sound very smooth and natural, and there is more clarity in the upper frequencies compared to my Pass amps.

I have a new (to me) set of speaker cables on the way (Kimber Select KS-3035) and I'm looking forward to hearing how these affect the sound.

You should check out Tom Christianson's "Darn Good 300B". He used to sell PCBs for this amp, but you could certainly build it point-to-point.

 

Jaytor: Congrats on your fine craftsmanship. Am using 4 amps myself with custom switching boxes that allow me to switch between 300B, Pure Class A, Power A/B and variable (Pass M2x) amps and find that each has its own arena in which it excels. Have you considered keeping your Pass and building simple line and speaker switching boxes to use them both? Works for me.

 

Thank you. That sounds pretty cool. My issue is the amount of space the Pass amps take up. These amps are really heavy, so hard to move around, and I don't have space for them and the 300Bs at the same time. We have french doors in the middle of the front wall so I want to keep the space between the speakers as clear as possible.

Do you have a photo online of your listening room? I'd be interested in how you manage all these amps.

 

Have two identical stereo systems with the same 4 amp setup -- takes some space so I use a fairly large audio stand and arrange all carefully. Cannot add photos to this site and do not wish to use the 3rd party apps. PM me with your contact e-mail and will be glad to send you some photos, including the switching boxes and a BoM for the parts. The only issue with the speaker selection box is maintaining the cable integrity and I use 8 awg cable to make this happen along with all-copper fittings and switches. No loss or signal alteration in the result and you can switch between any of the 4 in under five seconds each. Of course, the turn on and warmup time is another issue and tube amps, apparently, do not want to be run without a load.

 

Wow! This is one of the nicest of builds I've seen. I am guessing from the pictures that it is a parallel single-ended design with interstage transformer coupling. If the current WE reissues are anything like the prior reissues, you can expect quite a long life from those tubes. Good luck on longevity as 300b tubes are quite pricey. If you can, have the tubes tested after operating for a couple of hundred hours. Parallel SET operation can lead to one tube testing much stronger than the other in a pair. I don't know why that happens, but, I noted it with my parallel 2a3 SET amp. I sort of ignored the "problem" because, imbalance notwithstanding, the amps continued to sound good.

 

Thank you. Yes, this is a parallel SET with interstage transformer coupling.

Yes, I have heard about the tubes becoming somewhat imbalanced after a while. I'm not sure that really matters though. It will reduce maximum power output somewhat, but I don't think it should have any other ramifications. So I'm not too worried about it.

 

Hello Jaytor–
Very excited to find this thread, and read of all of your progress with this build. I trust you're enjoying your amplifiers immensely. I built these same kits myself last year, apparently just some months before your thread appeared. I wish I'd have had half of these ideas then! Like you, I needed a balanced input and also chose the 1:1 Jensen transformer, and have been happy with the result. I did also change some of the stock resistors and caps with some iterative tuning once all was assembled. Also opted for the new WE 300bs, after listening to the Takatsuki and other options. One struggle I'm having while going through all the changes/improvements you've incorporated, is that because you started with them in place, there can be no before/after POV. I wonder if you have any insights you could offer into prioritizing mods like the Neurochrome Maida regulator vs. the Tent Labs supplies? Just proceed from an upstream to downstream approach? I'm also looking at Tent Labs heater supplies for the 6SH7, do you have any thoughts on those as opposed to the DIYSupply boards you used? Thanks SO much for posting your work and providing such an inspiring build! Cheers.

 

Hi @sonoelectrico. I’m glad you are enjoying your amps. You are right that I didn’t have the opportunity to A/B compare the changes I made and some probably had very subtle differences.

I’m assuming you built your amps in the standard enclosures which might make some of the mods more difficult to fit in.

Sonically, I think the biggest upgrade is using the tent labs DHT supplies on the 300Bs. These will allow the tubes to operate more linearly since the power supplies are high impedance at audio frequencies so won’t interfere with the behavior of the tubes as a low impedance supply will.

Using this supply for the 6SH7 won’t really provide any advantage compared to a voltage regulated supply since the filament is isolated from the cathode. So you’d want to pick a supply with the lowest noise.

Whether it’s worth adding a DC supply for the 6SH7 would depend on whether you are getting any hum or noise (particularly hum) on the output.

Likewise, the Maida regulator should help reduce hum and noise, but if you aren’t hearing any as currently built, this might not be worth it.

Another builder on Audiogon has reported problems with arching in the rectifier tube. If you are experiencing this, the soft start will likely prevent this by reducing the inrush current on power up.

My amps are completely silent even putting my ears right up next to the speaker drivers.

Jay

 

All great info and this makes perfect sense to me, I really appreciate getting your perspective! Yes, as you guessed, I used the standard enclosures, and it does look like there is sufficient real estate available to incorporate any or even all of these ideas– excluding the few that I don't think apply for me (i.e. the speaker protection circuit, or the additional (Zobel?) RC on the input), which I don't think I need as I haven't observed any oscillation or heard anything untoward in the high freq's. While the warm-up with a simple thermistor is a bit noisy ;-), I don't think it sounds like it could damage my ~99db w/m speakers, and I'm not seeing any arcing on the rectifiers at all. I'll start with the Tentlabs supplies on the 300Bs as you recommend and the ISS, and proceed from there. As the amps sit today, they are the quietest of the 4 pairs of SET amps I have on hand. I need to have my ear within about 6-8 inches of the speaker drivers before I can hear anything. Thanks again for your detailed advice! I'll post my results here when complete.

 

I had a chance over the weekend to try some of these modifications, and wanted to report back on my results. 1) I installed the Neurochrome Intelligent Soft Start board (ISS) and connected it in 'auto' switching mode, so that it's triggered by the OEM rocker switch. It works well, and sounds like it calms the somewhat aggressive squelch I used to hear upon start up. 2) The TentLabs Filament supply boards for the parallel 300Bs were fairly quick and easy to install; I removed the original DC supply from the amps, drilled and tapped some holes for 10mm stand-offs, secured the boards, unsoldered the in/out connections, attached the new boards via the screw terminals, trimmed the voltages to 5.00V exactly, and was just amazed by the improvement in sound! Noticeably quieter, yes, but more importantly in my setup, a significant improvement in clarity, and perceived resolution from the very top to the very bottom of the frequency range. The improved sense of vitality and presence strike me as enhancements of the exact qualities that would draw someone to an amp of this kind in the first place. The stage seems to expand and get deeper, and the sound is just a bit more disengaged from the speakers as an identifiable source of the sound. This was VERY worthwhile in my setup! How it might compare to the sound of the Rod Colemen supplies, I don't know, but I am curious! 3) Next, I tried the same general process on the Heater supplies for the 6SH7 drivers, replacing them with the TentLabs Heater supplies. This was less successful. It seemed that the new DC supply on the drivers robbed some life back out of the sound, and gave the impression of being somewhat over-damped in character. I went back and reversed the change entirely. I am wondering if this is due to my lack of understanding of the driver circuit itself, and if I actually need to modify a driver cathode leg? I understand these heater supplies are intended to be fully floating, and I just dropped it in without modifying the circuit at all. Can anyone tell me if I need to remove a cathode resistor, bypass cap ground leg; and if so, which components exactly? Thanks SO much to the OP, @Jaytor for the inspiration and detailed write-up, I owe you a real debt of gratitude for the improvements I'm enjoying now!

 

I'm glad to hear you had success with at least some of these mods.

I'm not too familiar with the Tent Labs Heater supplies. They don't provide much detail on how these are implemented on their website. I'm wondering whether the AC voltage from the mains transformer is high enough to allow the regulator to work effectively.

Assuming you still have the center tap of the mains filament winding (blue/white wire) connected to the resistor voltage divider (the 330K/47K resistors across the 220uF cap), then the filament voltage should be correctly set. This should not be a floating supply - it needs to be referenced to the cathode voltage (approximately 90V with respect to the cathode). You should not need to make any changes to the resistor and cap connecting the cathode to ground.