Description

Hello all,

My involvement in audio has been an evolving journey for many years now, but about six years ago, I decided a return to Tannoy speakers was something I had to do. I sold my Dynaudio Contour 5.4's, and purchased some HPD 315 drivers and crossovers on Ebay UK.

I had enclosures built in Pennsylvania by Frank Wyatt, of 1 7/8" net MDF (an inner 3/4" laminated to an outer 1 1/8" layer), with a Sapele Pommelle veneer. They are 150 liter bass-reflex, and weigh 192 lbs. each; sans drivers and crossovers.

I built outboard crossovers using Mundorf SIO caps, 12 gauge Alpha core inductors, and Dueland resistors, with silver solid core 14 gauge hookup wire.

I like them so much, they are the speakers I will have till I leave this earth.

After several years with a VPI Scout Signature, I wanted to venture into the idler wheel turntable world, so again on Ebay UK, I bought my Garrard 401, and did a DIY restoration on it. Frank Wyatt built a plinth for me, which I later modified extensively with Purpleheart side pieces (keeping the original 3/8" thick Bubinga center section), and milled Purpleheart edging on the top edges, and framing the Garrard chassis.

I then installed the Dynavector 501 arm (so nice to not have the VPI wobble!). Several cartridges are available in my collection, two Actutex (LPM 415, LPM 320), the Soundsmith retipped Dynavector XX2MKII, Zu Denon 103R with ESCCO white sapphire cantilever and Paratrace stylus mods, which is my favorite by far.

I bought a used Modwright SWP 9.0 SE phono stage, put NOS tubes in it, and installed an upgraded power supply provided by Dan Wright. I feel no compulsion to change to a different phono stage.

I wanted to try a tube line stage, so I sold my much-loved Sonic Euphoria passive, bought a Transcendent Sound Grounded Grid kit, in which I used NOS Amperex 12AU7 tubes, Clarity Caps output caps, Goldpoint stepped attenuator and switching, mil-spec silver hookup wire, and Bent Audio remote volume control. This is an amazing sounding line stage, I see no need to change.

Next came the Assemblage Audio SET 300B, which I sent to Chris Johnson for upgrades, caps and resistors, using Kiwame film resistors, Jupiter Paper Beeswax caps, and Nichicon caps. With the EML XLS 300B tubes the Tannoys sound lush, detailed, and very much like live music, especially well recorded Jazz LPs.

Lastly, some would say I devolved, but to have a quality backup in case of tube failure, and to save hours on the 300B output tubes, I decided to give Class D Audio a try. I bought a 125 Wpc CDA 254 kit a try, and really enjoyed it. I installed an additional amp module in it, running in bridged mono mode, it bumps the output up to 500 Wpc, which snaps the Tannoys to attention, and they sound excellent.

My old five channel amp gave out, so I built another CDA 254 class D amp, with an added module, and I was able to convert it to a three channel amp, with 125 wpc for the surrounds, and 500 watts for the center channel. All in all, a very cost effective set of amplifiers that are every bit as good as some of the higher priced amps I've used over the years.

At this point, at my age ( I turned 70 in February), I am happy to stand pat with what I have, I am enjoying the best sound I've ever had the pleasure of listening to at home.

As of 9/2016, I've completed additional sanding/polishing of the enclosures for my Tannoy HPD 315 drivers. This time, I got it right. Up next, a redo of the Garrard 401 plinth.

Refinishing of the plinth for the Garrard 401 has been completed. Removed face and top pieces, made replacement 1" thick Purpleheart face with inlay, all new top pieces, and new arm board from Purpleheart and Australian Mallee Burl.

Added photos of redone plinth.

Regards, and enjoy,
Dan         

More turntable photos added Mar, 2017 

Added new photos 11/12/2018

Added SET 845 Audio Renaissance 845 integrated amp, just picked up on 4/20. Makes my Tannoys sound the best they ever have.

Added RCA 5693 Red Metal tubes in the SET 845 amp, made for a nice improvement in SQ.

Regards,
Dan

08/09/2019

Added Benchmark DAC 1 Pre, my digital front end sounds very much improved with this DAC. I know there are better ones available, but not in my price range. May be the best $500 purchase yet. I also discovered how much I was missing with a Musical Fidelity X-CAN driving my Sennheiser HD 600's, they sound amazing, who knew how much I was missing? (Not me!)

Regards,
Dan

09/23/2019

Added what is the best line stage I've ever had, the Modwright SWL 9.0. This piece has completed the quest to attain what is my ultimate goal in my system's sound quality. There is now a new liquidity, and completeness to the sound my system never had before. As this category says, "Done For Now", but maybe should be "Done Forever".

Regards,
Dan

04/13/2020

Upgraded surround speaker with very nice Andrew Jones designed Pioneer x-Z9 monitors. Concentric midrange/tweeter with a bass driver, built by KEF. Sound and look beautiful. 
12/04/2019
Added new photos of turntable with red Albert King LP

May 8, 2020

Replaced my old Kef Reference 100 center channel speaker with new KEF Q 650c center channel speaker. This is a very good upgrade in multi-channel music listening, and home theater as well.

June 8, 2020

Just added newly built 3C24 amp, built for me by Paul Birkeland  of Bottlehead. It has the refinement like an SET 300B, but the power response similar to the SET 845 amp. Sounds beautiful, too.

Regards,
Dan

September 12, 2020

Installed new Audio Technica AT440Mlb moving magnet cartridge. Always wanted to know what they may sound like, so I bought this one on Ebay. I'm really enjoying the sound of this rather inexpensive cartridge. Makes me want more.

Sepember 23, 2020

I added an Audio Technica AT ART-9 moving coil cartridge.

It's already my favorite cartridge, with only two hours on it.

Regards,
Dan
Read more...

Room Details

Dimensions: 34’ × 16’  X large
Ceiling: 11’


Components Toggle details

    • Arcam AV 9 Pre-amp Processor
    Just added to replace defunct Primare SP 31. Excellent, so far.
    • Benchmark Media Systems DAC 1 Pre
    Just installed this DAC 1, which I bought off US Audiomart. It's sounds great just out of the box, best my digital front end has sounded yet. I'm very happy with this DAC, and now I understand what all the fuss was about. I'm sold.
    • Esoteric DV 60 Universal Player
    Universal player, XLR, HDMI connections, multi-channel capability.
    • Arcam FMJ DV139
    Universal player. Has flown rings around the Esoteric DV-60 in sound quality.
    • Modwright w/power supply upgrade SWP 9.0 SE Phono Stage
    Tube phono stage, with upgraded power supply from Modwright.
    • Modwright SWL 9.0 Line Stage
    Just bought from Dan at Modwright, it's had an upgraded power supply, new tube board, and the MWI caps added. It has turned out to be the missing link in my system, and can say with near certainty, that I am Done For Now!.
    • Garrard 401 with DIY Plinth
    DIY restoration of a vintage Garrard 401 idler-drive turntable, on which I just completed a six week redo of the custom DIY built plinth, due to problems getting the finish right. I sawed the front off, and removed all the top pieces. A 1" thick slab of Purpleheart with an oval Australian Mallee Burl inlay flanked by a different hardwood species I can't recall were added. A new arm board of Purpleheart and the Mallee Burl was made, and the pivot-to-spindle distance was adjusted to provide for easier cartridge to headshell connections.

    Top pieces were fashioned of Purpleheart, and a new labor-intensive finishing process (new to me, anyway), of Waterlox Tung Oil Sealer/Finish, followed by Waterlox Gloss Tung Oil finish. At least a dozen coats were applied between the two, each coat requiring 24 hours between applications. Thanks to Pierre France for his help in guiding me on the tung oil finish.

    I serviced the motor, cleaning, oiling, and replacing the suspension springs. Glad to finally be done, and finally satisfied. Analog withdrawals were starting to set in, but it now looks better, and sounds better as well.
    • Dynavector DV 501
    Bi-Axis Tonearm. DIY rewire with Cardas wire. This arm works well with a diverse group of cartridges, to my surprise.
    • Audio Technica AT ART-9 Cartridge
    Moving coil cartridge, just installed. After only about two hours of run-in, at 47K, it's already the best cartridge I've ever owned.

    I've determined my analog front end is much better than I realized it was. I've never enjoyed my vinyl as much as I am now,
    • Audio Technica AT 440Mlb
    Recent purchase, new AT MM cartridge. I've always been curious about AT cartridges, so I bought this one off Ebay. I really like the sound of it, actually pretty good, considering the low price.

    Makes me even more curious about AT carts. I may have gotten myself in trouble, as curiosity is expensive in this hobby.
    • Acutex LPM M320 III STR
    Lowest Possible Mass, Tri-Induction Magnetic System, 20-45Khz, channel separation [email protected] 1Khz, weight 5.45g.
    • Denon Zu Denon 103R
    Potted moving coil in 6061 aluminum body/w ESCCO sapphire cantilever/Paratrace stylus upgrade. This cartridge has proven to be the best of all my cartridges, and not by a small amount. Beautiful.
    • Dynavector XX2MKII
    Moving coil cartridge. Just re-tipped by Soundsmith with their top-line OCL re-tip. Made a great cartridge even better.
    • Acutex STR 415
    Ultra-lightweight MM cartridge
    • TTW Copper Mat
    Solid copper machined mat, great addition to 'table.
    • TurnTableWeights VPI Heavy Brass Clamp
    TTW Brass clamp I modified so it will work with their copper mat. (Threads would not engage spindle threads).
    • Pete Riggle VTAF
    VTAF on-the-fly modification by Pete Riggle for Dynavector 501/Garrard 401 Teflon and burnt silver finish options
    • Orsonic AV 101b
    Headshell
    • Mint LP Best Tractor
    Etched-in-glass cartridge set-up tool
    • DIY Ultrasonic Record Cleaner
    I've just completed a DIY Ultrasonic Record Cleaning machine, this the creation of BBtx, of DIY Audio. I thought it a very unique design, one that melded convenience, simplicity, and build quality.

    If I were to say I am pleased with it, it would be an understatement. For a couple of hundred bucks, it can't be beat. I've hankered for one of these for years now, and thanks to BBtx my needs have been fulfilled.   
    • VH Audio Flavor 2 DIY Power Cord
    Built this AC cord for use with the Transcendent Grounded Grid preamp. Great sounding AC cord.
    • Paul Birkeland 3C24 Power Amp
    3C24 tube power amplifier. Paul, the designer/builder, brought over four different amp choices to try out on my custom HPD 315 Tannoy speakers. The 3C24 amp gave the best frequency balance, yet was nicely detailed as well.

    Still breaking in, but I'm greatly enjoying what I'm hearing this far.
    • Audio Assemblage (Sonic Frontiers) SET 300B
    300B SET Factory Upgraded, with EML XLS 300B Tubes. Just serviced by Paul Birkeland. All critical measurements were taken, two bad Blackgate bypass caps were replaced with higher-rated Nichicon caps, and the filament voltage was optimized to better suit the EML XLS 300B tubes.

    This amp now sounds incredible. Paul informed me the transformers in this amp are Magnaquest, to him about as good as you can get. He also informed me this amp sounds as good as any $5000 SET 300B amp available in today's market.
    • Emission Labs 300B XLS
    Robust drop-in replacement for 300B.
    • Class D Audio CDA 254
    Kit built Class D amplifier. Running two, in bridged mode, providing 500 Wpc into 8 ohms.
    • Class D Audio CDA 254
    Two channel amp converted into three channel by virtue of adding an additional CDA 254 amp module, RCA input, and single channel speaker terminals. Price for parts for modification: $194
    • Musical Surroundings Fosgometer
    Azimuth adjustment tool.
    • Custom built crossovers Custom DIY
    I've just completed an update on the crossovers for the custom HPD drivers. I actually used all the parts over again, including much of the solid silver hook-up wire. I made new mounting boards, and ran the wiring under the board, for a much cleaner look. I used heavy copper terminal lugs, which I modified to use a flat male spade connector, rather than wire. Wire runs are much shorter as well.

    I made new outlet cables, using Furutech locking bananas, and Cardas binding posts. I can't tell why, but this update improved the sound of these speakers much more than I expected. I've never heard electric guitar sound as it did on Steve Cropper and Felix Caviliere's "Nudge It Up A Notch", Cropper's guitar sounding just as he had wanted it to sound, with gorgeous tone, unlike anything I've heard before on a recording.

    Next is an internal speaker wiring update.

    I've just completed changing some components in the crossovers back to their original values. 27ohm resistors changed back to 47ohm, .68mh inductors reverted back to the original .82mh. I'm beyond pleased.
    • Tannoy HPD 315 w/Hard Edge Conversion
    Twelve inch Dual Concentric HPD driver in custom enclosure.1 7/8" wall thickness with custom designed and built crossovers. Weight is 200lbs. each. Finished in Pommelle Sapele.

    A complete rewire of the internal wiring was just completed. I made a 1/4" X 1/2" Teflon terminal board, with double-ended male spade connectors at the speaker. Wiring was completed at the input end with new crimped and silver soldered connectors with color-coded heat shrink tubing, and color-coded electricians tape.

    The results are a major improvement in clarity, detail and dynamics. These great speakers have just gotten much better at the things I love about them.

    After further study of fine wood finishing methods, and purchase of additional sanding/polishing medium, I again sanded and polished the enclosures for my Tannoy HPD 315 drivers. Got it right this time, now they are done. Next is the plinth for the Garrard 401.

    Dan

    8/3/19
    Some of you may recall my changing resistor values in my Tannoys back to the original value, to good effect. In that same vein, I just modified the .68mh inductors back to their original value of .82mh. I felt at the time when the crossovers were first built, the high frequency output was out of line, so I reduced it to better suit how my system sounded at the time.

    I had saved the .82mh Alpha Core ribbon inductors, and I changed them out yesterday. The results have shown me how much my system, as a whole, has improved, due to how well it sounds now as opposed to back 8-10 years ago. I feel I'm now getting what I was supposed be hearing all along. It's a great feeling. Now I no longer wonder what Dr. Arthur Loesch was thinking when he gave me this crossover design so many years ago now.

    Regards,
    Dan
    • KEF Q 650c
    Newly added Kef Q 650c center channel to upgrade from my old Kef Reference 100 Center Channel speaker. The Q 650c is all I could have wanted or hoped for. Multi-channel music is way better now, as is Home Theater listening.
    • Pioneer S-Z9 Designed by Andrew Jones
    Nicely made small monitor speaker. Dual Concentric midrange/tweeter with an additional bass driver. Gloss Black, and a nice upgrade as my surround sound speakers, replacing the nearly twenty year old KEF Q 15.2 speakers I was using for surrounds. Multi-channel music now has better depth and clarity to it.
    • PS Audio Power Plant Premier
    Power regenerating system. Reduces incoming distortion, Multi-wave, and Clearwave (degaussing) capabilities.
    • Crown International XTI 2002
    Running bridged to single channel. This amplifier (rated @1600 watts into 8 ohms) has taken charge of the Tannoy 15" passive sub, and turned it into the most musical sub I've yet heard.
    • Tannoy Sub 15i
    15" Passive Tannoy subwoofer. with the Crown XTi 2002, does a superb job of matching, and augmenting, frequencies below 50 Hz.
    • Tempo Electric Big Twist Silver/ pair for each amp
    12 gauge solid-core silver in teflon tubing, 3 meters
    • Synergistic Research Various cable models
    Interconnects, speaker cables, and power cords different models.
    • DH Labs Silver Matrix
    From phono to phono stage, internal cabling in speakers and crossovers.
    • Vibra Pods various
    Pods and cones under amps and most components.
    • Walker Audio Reference Hi-Def Links
    Eliminates ultra high frequency hash in signal.
    • Audio Metallurgy AG-0
    Silver coated oxygen free 22ga. copper
    • Quasi-DIY Velodyne/Eminence
    An old Velodyne 1250-X sub that had a 12
    • RCA Red Metal Can 5693 Tubes
    Mil-spec (10,000 hour) tube to replace 6SJ7 tubes in my SET 845 amp.

    Amp is quieter, and better sounding.
    • DIY Cable Interconnect from Benchmark DAC 1 to Trancendent Sounds tube preamp
    Used WBT-0144 locking connectors, and DH Labs BL-1 Bulk Cable
    • Tannoy Crossover Schematic
    Crossover design donated to me by Dr. Arthur Loesch.

Comments 568

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Owner
Scar972,

Thank you so much for your kind comments, they are very much appreciated.

Jim, thank you for looking at my system photos. It was a labor of love. I had quite a time with my table saw after a bad problem with the finish, I'd just cut it off and put more wood on it, and try it again. You learn from your mistakes, and the table saw makes the mistakes go away, so wood is a great medium to work with. If it was steel, or something like it, it wouldn't be so easy.

I just keep on trying until I get what I can live with..

Thanks again to you both, regards,
Dan  

Ag insider logo xs@2xislandmandan

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Dan,

The 401 looks beautiful with the custom plinth. Great looking combination with the Dynavector tonearm. Thanks for posting the pics

Jim Perry

jperry

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Dan, very nice system you have and I really appreciate all the DIY work that you've put into it especially the Garrard 401 and the Tannoy speakers. The rebuilt crossover looks fantastic and I bet it brings your speakers to new heights. Congrats on a great setup!

scar972

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Owner
Hi Jond, many thanks for your comments, it's much appreciated. Those projects you mentioned were due to a limited budget, and my enjoyment of DIY.

I never was a cabinet maker, but I did build my own home back in the '70's. That means I had to buy the tools to build my turntable, and learn how to use them. I found the most difficult thing  to do was to obtain a quality finish on whatever I built.

I finally wound up using twelve coats of tongue oil on the turntable plinth, which with 24 hours between coats, was a long, involved project. I've learned to really appreciate the guys are that really good at it. That's not me, but I persevere..

Thanks and regards,
Dan

Ag insider logo xs@2xislandmandan

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Hey Dan I've read your comments on Tannoy's so long I can't believe I never commented on your system. Looking fantastic love the cabinets you had built and those crossovers look amazing. And that 401 is a work of art really fantastic work! I can only imagine how good records sound with that table, your Art-9, that cool looking custom amp and the Tannoy's! Cheers!

jond

Center
Dan, Hana ML is really good. I just want to sit and listen :-) I can easily see myself living with Hana ML for a very long time. 

Ag insider logo xs@2xlalitk

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Owner
lalitk, I'm getting along with my ART 9 very well. Can you tell me a bit about what the Hana cartridge does for you? I've been curious about them too, but I'll have to live vicariously through your experience with your Hana, since I've pretty much gone over budget buying the ART 9.

I'm really enjoying my cartridge, how is your Hana treating you?

Best regards,
Dan

Ag insider logo xs@2xislandmandan

Center
Dan,  Congrats on the new cart. I almost went with ART9 but my dealer talked me into going with Hana ML. I guess, there is always a next time :-)

Ag insider logo xs@2xlalitk

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Owner
I just added a new Audio Technica AT ART-9 Moving Coil Cartridge cartridge. After only two hours, it's already my favorite cartridge I've ever owned.

Regards,
Dan

Ag insider logo xs@2xislandmandan

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Owner
A few days ago, I bought an Audio Technica AT440Mlb cartridge, due to curiosity about their cartridges. After getting it dialed in on my Dynavector 501 tonearm, after a few hours on the new cartridge, It has opened my eyes (and ears) to sound quality I've never heard from my system before.

I'm so impressed, I just ordered a new AT ART 9. I think I will be very pleased with the new cartridge.

Regards,
Dan

Ag insider logo xs@2xislandmandan

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Owner
Added birch ply support board under 3C24 amp, along with Vibra Pods/Cones.

Ag insider logo xs@2xislandmandan

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Owner
Added nighttime photo of 3C24 amplifier.

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Owner
A couple of nights ago, an output tube fried on my new 3C24 amp. Paul said to bring it down, he wanted to make sure the SMPS devices didn't cause the tube to go bad.

So, I made the long drive yesterday, and it turned out it was just the tube itself that went bad, and not the switch mode power supply. He had always used a tube power supply before for the tube heaters.

When I got it hooked up and warmed up, I put on a new CD of "Debussy * Rameau" by Vikingur Olafsson, on Deutsche Grammophon, and heard the most beautiful piano sound I've ever heard on any system. 'Course, I don't get out much, but I've still heard some pretty good audio systems in over forty years, so to me, this is significant.

Yes, I really do love this amplifier.

Regards,
Dan

Ag insider logo xs@2xislandmandan

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Owner
Al, thank you so much for your comments. This amp/speaker combination is the ultimate destination for me in regards to this aspect of system performance.

The past year or so has been a transformative time for me. I came across Paul when I called and talked to Dan Smalle, owner of Bottlehead, when I was searching for a tech that could do some repairs on my SET 300B amp, Dan suggested I contact Paul Birkeland, a designer/tech for Bottlehead. I did so, and wound up taking my amp to him.

Paul replaced some bad caps and then adjusted the filament voltage to match the EML XLS 300 B tubes I was using. He did this work as I watched, and when he finished, I asked him how much I needed to pay. He said twenty bucks! I paid him $120, which I thought was still underpaying him. All my dealings with Paul have gone this way.

As I mentioned earlier in system comments, Paul brought several amps to my home (about one-and-a-half hours away from my home on Whidbey Island, a week ago last Saturday) for me to try. I had been searching for some time for the ideal amp, and thought the SET 845 was the one I needed. Finding an affordable one was not doable. Paul designs his amps to run well with affordable tubes, and he proved it to me with his visit.

To answer Grannyring's question about the cost of my new amp, it was $3400. Paul gave me $900 on a trade-in for my SET 845, and nice collection of tubes for it. It's the best money I've ever spent in all my years in audio.

So for me, meeting Paul Birkeland was a Godsend. He has earned my trust and respect and admiration as well. And, my thanks for Dan Smalle of Bottlehead, who made it all possible. I'm very grateful for their help. And Al, for you and Atmasphere, and so many others on this forum, my appreciation goes out to you as well. Thanks for all you do for our community.

My very best regards,
Dan Thomason

Ag insider logo xs@2xislandmandan

Center
Congratulations on the fabulous results you are getting with the new amp, Dan!

And thanks for posting Paul's excellent and very informative writeup.  It's always good to read a well stated presentation of the tradeoffs and considerations which led a designer to choose a particular design approach.  And his writeup is certainly among the best examples of that I can recall seeing.

Enjoy!  Best,
-- Al
      

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Owner
Grannyring, Paul doesn't really have his own website. 

If you PM me, I can get you in touch with him. 

Regards,
Dan

Oh, and thanks for your comments re my system!

Ag insider logo xs@2xislandmandan

Center
Can you help me find a website or contact for your new tube amp? Like to learn more about pricing as I am most interested in purchasing. 3c24 Tube amp. 


You have a very nice system! Very nice work on your crossovers. 

grannyring

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Owner
I asked the designer/builder of my new amp, Paul Birkeland, how it was possible to make what would appear to be quite a low-powered amp, to deliver the beauty and impact that it provides. It just doesn't seem that it should be feasible, though it surely does do just that, in spades.

His reply is on this page.

Regards,
Dan

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Owner
Well, back in the early 90s, the Japanese started resurrecting audio amplifier technology from the 30s, you will see this referred to as the "triode renaissance".  These were 45, 2A3, 50, and 300B amps that were really simple, zero feedback single ended amps, and they are the basis for a lot of what we still sell at Bottlehead to this day.  The huge downside to all of this is that these little directly heated tubes don't make a whole lot of power unless you get really big ones (845/211) and run them at really high voltages.  Even then, most of those big tubes will only give you 15 to 20 watts running off a 1kV power supply on output transformers that are very difficult to manufacture properly.  

There are some ways around this though.  The traditional directly heated single ended triode amps run the output tubes in class A1, where the grid of the output tube never draws any grid current.  If you design an amplifier to push the output tubes into class A2, you can get a little extra power.  In order to do this, the circuitry behind the output tube needs to look more like its own power amp, so the designs get a bit more involved and complicated.  The grid of a power valve when transitioning from A1 to A2 becomes a really low load that's quite difficult to drive.  To press things even further, there are many directly heated transmitting triodes like the 3C24, 811A, 801A, 810, and even the 211 that can be biased so that they draw grid current at idle, and this opens up some operating points that allow for far higher power output.  While a tube like a 300B with a plate dissipation of 40W won't deliver much over 10W, a tube like the 811A with a plate dissipation of 40W is capable of nearly 20W of output when run in class A2.  

For driving the grid positively, a coupling capacitor is no longer an adequate means of connecting the power valve to the driver stage.  Instead, such amplifiers will use an interstage transformer, a directly coupled cathode follower, or a directly coupled solid state device.  From my experience, interstage transformers perform much better when they have a predictable load impedance on the output side, which is far from what happens in this kind of amplifier.  The solid state directly coupled option is totally workable, but not all that ideal given the voltages present and the need for a monster heatsink, so I use a directly coupled cathode follower.  This technique was well developed by Michimori Hirokuni, although I opt to use choke loaded cathode followers rather than actively loaded cathode followers.  

Still, a big challenge remains with these transmitting triodes.  They have very, very high internal impedances.  To cope with this, you can use really high impedance iron (iron that is impossible to make well), or you can implement some feedback to mate these transmitting valves with a more conventional output transformer.  Within the subset of feedback amps like this, many use feedback around the entire amp, some use cathode feedback around just the output stage, and some use local feedback.  From my experiences, putting feedback around the entire amplifier results in highly conditional stability.  An amp like that might play just fine on a Magnapan speaker, but the amp would oscillate on an ESL.  While cathode feedback around the output stage is effective at dealing with the issues specific to the output valve itself, there are other issues that creep up in terms of driving the transmitting triode itself, and cathode feedback doesn't resolve these issues.  When studying Hirokuni's work, I noticed that as his projects developed, he would take all the local feedback he could get and ultimately use just enough global feedback to get the amp to work properly.  

For the 3C24 amps and other similar amps that I make, I use a local feedback loop that goes from the plate of the transmitting triode back to the plate of the first stage driver tube.  When done properly, there is no longer any requirement for global feedback.  I can set this up to get the maximum allowable power from these valves while using an output transformer that is not all that crazy to produce.  In my 811A SET amps, as an example, the plate impedance of the 811 is around 35,000 ohms at my operating point, but with the local feedback I drive this down below 1000 ohms so I can mate the 811A to a 3K output transformer.  These designs are not so sensitive to the speakers used and the exclusion of the output transformer from the feedback loop maintains more of the character of a more traditional zero feedback SET amp.  

What you end up with is an amp that's a little snappier than a 300B or 2A3 amp, but not quite as mellow and relaxing.  You also get dirt cheap old stock output tubes, as you've now noticed! 

Ag insider logo xs@2xislandmandan

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Owner
I also finally found out a new item added to your system description won't make to the Virtual Systems page. As far as I remember years ago, a new item was just added to your system page and description, and went on to the forum page. Not so anymore, takes an old dog a long time to learn new tricks.

Ag insider logo xs@2xislandmandan

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Owner
June 8, I added to my system the new 3C24 amp Paul Birkeland built. He actually brought four different amps to try, 811 mono-blocks, shunt regulated 300B mono-blocs (I really considered buying this pair), 3C24 mono-blocks, which sounded nice but ran out of power a bit too soon to consider, and the 3C24 stereo amp.

The 3C24 stereo amp had everything I wanted in an amp. It was the best-built of all the amps, with much better parts quality, and plenty of power to be a good match for my custom-built Tannoy HPD 315 speakers.

The tonal quality was the best I've heard from any amp, anywhere. After several days and nights listening to this amp/speaker combination, it is like a wonderful gift has been given to my system, with beautiful frequency response and tone, and great ability to produce dynamic response.

I love this amp.

Regards,
Dan

Ag insider logo xs@2xislandmandan

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Owner
Lalitk, thank you for your comments, they are much appreciated.

Regards,
Dan

Ag insider logo xs@2xislandmandan

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Owner
Just replaced my old Kef Rederence 100 center channel with Kef Q 650c. Much better for multi-channel and home theater. Been wanting this for many years, along with upgrading my surround speakers, which was also done recently with Andrew Jones designed, Kef built Pioneer S-Z9 speakers.

Multi-channel and HT listening is much improved.

Regards,
Dan

Ag insider logo xs@2xislandmandan

Center
Dan,  I have to handed to you on the level of detail and efforts put forth with Tannoy’s. WOW!!! I completely agree with your assessment of 845’s driven Renaissance amp vs SET 300B. Enjoy. 

Ag insider logo xs@2xlalitk

128x128
Owner
Purchased a pair of Andrew Jones designed bookshelves, built by KEF for Pioneer, to be used to upgrade my old surround speakers, KEF Q 15.2.

They look and sound good (along with new 32" tall stands)  The speakers have a concentric tweeter/midrange and a bass driver. This purchase has made a nice upgrade to my multi-channel system.

Regards,
Dan 

Ag insider logo xs@2xislandmandan

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