ANK Audiokits Valve Amplifiers
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"It is becoming increasingly obvious that applying transformers at every stage of an amplifier yields a great benefit in sound quality, provided of course that the transformer in question is of an appropriate quality and design. Replacing any coupling capacitors with a well designed and correctly matched driver or interstage transformer yields an almost shocking improvement in sound and should be tried to fully understand what a good wide band transformer has to offer."
PETER QVORTRUP: AUDIO NOTE UK
 
     
   
 

The interstage monoblocks
a uniquely different amplifier

The Interstage amplifier is our highest and most extreme expression of Single Ended Amplification reserved only for the true connoisseur audiophile. The Interstage transformer design style is currently used on Audio Note's top of the line On Gaku 211 amplifiers.

The unique design style makes use of an interstage transformer on each channel - rather than having an additional tube driver stage, the interstage transformer takes over this task for ultimate authority! The Interstage Mono Block provides a level or realism and detail that you may not have experienced.

related product: Interstage C-Core

   
   
 

Development

Recent enhancements to the blocks have taken them to a totally new level. We have a new Mains transformer - the T-195 dedicated to the Legend & Interstage MonoBlocks for both parallel and single Triode configurations. We have enhanced the Choke to anew CH-170 for 300ma capacity. The Interstage transformer is bifilar wound and sits on a very large Core for maximum bass response.

The mechanical design of the unit is second to none using all stainless steel metric hardware; countersunk screws and removable insert plates for a truly fun build experience. Power supply and driver circuitry is all hardwired and uses the latest Mundorf Mlytic 4-pole capacitor technology.

 

Feature list

  • 50 cm deep x 24.5 cm wide for compact locations
  • Increased lower case height to 6.3 cm
  • Ultra sturdy 3mm aluminum chassis powder coated black with solid copper insert plate
  • Parallel or Single Triode models available
  • Professional wiring guide provided
  • Higher rated Mains Transformer (300Ma )
  • Larger 1:1 Interstage Transformer for superb bass response
  • 5U4GB rectifier tube, 6SH7 driver tube
  • New Power Supply with Mundorf 4 pole Mlytic technology

 

     
 

Copper insert plates

The Interstage MonoBlocks now ship with the new copper insert plates for both single and parallel 300B configurations!

Along with that, we have standardized on the new high quality black teflon valve bases for both 4 and 8 pin. The sockets are the same phyical size and are keyed so that the tubes can only be inserted the correct way.

The Audio Note traditional venting pattern is used. The plates are coated in a high gloss clear coating so they are protected from scratches and will never change color. A stunning addition to these phenomenal amplifiers.

 
     
 

The circuit

The new Interstage Mono Block Kit is comprised of a 6SH7 input tube - this was selected by Andy Grove for a number of technical reasons related to input impedance and input sensitivity of the power amplifier in mating with the L3 Line.

The 6SH7 is readily available and not overly expensive. It comes in a glass tube version or with a black metal case. NOS tubes are available in the $5 USD range and upwards. This tube feeds an interstage transformer designed specially by Audio Note for use in the Interstage Mono Block Kit. The Interstage transformer drives the Triode 300B in single ended mode. The Triode then drives the output transformer - TRANS-152.

The input sensitivity is around 2V which is ideal for a power amplifier and ideal when mating with Audio Note's M3 Line pre-amplifiers. We are using the top of the line Valve Bases in the Interstage Mono Block for both 8 pin and 4 pin. We are also using Audio Note Hardwire Tag Strips.

   
  Top schematic - output stage circuit.
Lower schematic - power supply circuit utlizing 4 pole capacitor technology.
 
  Building your Interstages in easy to follow steps
 

We provide easy to follow, step-by-step wiring instructions with the manual. Check out the detailed wiring guide for the 300B PSE version by clicking on the schematic right. Using an interstage transformer dramitically reduces wiring complexity and they are easy to build.

The InterStage Mono Blocks have been designed so you could start off with this IE core version and then later upgrade to double C-Core.

   
 

Kit preparation

We prepare the parts in 15 separate sections with all IEC cabling and twisted wire making it easy to work through each build stage. The result - your kit is a joy to build!

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Specifications:

Power: 8.5 Watts Class A (Single)
20 Watts Class A (Parallel)
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Output Tubes: 2 x 300B or 4 x 300B
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1st Stage Gain: 6SH7
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Rectifier Tube: 5U4GB
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Front Insert Plate:: Solid Copper
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Inputs: 1
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Outputs: 1 x Stereo Pair 4, 8, 16 ohms
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Recommended Speakers: min 88dB
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Width: 24.5 cm
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Height: ?? cm
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Depth: 50 cm
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Weight: 48 Kilos
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Chassis: 3mm Aluminum with Black Powder Coat

 

Parts Compliment includes:

AudioNote Tantalum Resistors 2W (output)
1AudioNote Tantalum Resistors 1W or 1/2W (power board)
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Mundorf's Best Myltic Power Supply Caps
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PTFE Silver Plated Hookup Wire
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Elna Cerafine Signal Electrolytics
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Shuguang 300B Tubes
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Audio Note Speaker Posts & RCA's
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Ceramic Hard-wiring Posts
1 PTFE Silver Plated Stranded Copper Wire
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5U4GB EH Rectifier
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Solid Copper Insert Plate
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Interstage Monoblock
Single 300B

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Interstage Monoblock
Parallel 300B

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  "I feel that I owe you what will be a long overdue review of my Interstage mono blocks.

The build process was predictably smooth (I have built an Audio Note Kits DAC so this was expected) and took me a couple of weekends to complete. The time was well rewarded, as the resulting amps are really quite remarkable.

Simply put, with these amps, I am finding myself listening to more music than I have in a long time.  Unlike other high end audio products I have owned, I am not just reaching for my "good sounding" recordings (which sound awesome here as well),because everything I play through these amps just sounds so right and easy to listen to.  What has struck me most with the Interstage mono blocks is not only how amazing vocals sound, but also how arresting acoustic and electric guitar sounds. I have had more than a few "feels like they are in the room moments" and thats pretty awesome. The bass is also noteworthy, as I was not expecting clean tight and plentiful bass from a 20 watt tube amp. All of this, and the music just seems to come out of a totally dead quiet background with no audible hum or noise at all.

Sure there are other kits on the market, but I doubt that any of them come close to offering the level of quality and performance I am experiencing. I cannot thank you enough for offering a kit that performs as well as this one. Please do keep up the good work."
Blair Piersall Boston MA

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  audio note client review  
  "Success. The filiaments glow and power stays on!
I went ahead with the voltage measurements and the measurements checked out to within less than 5% difference from expected. This is probably within the variability of the mains voltage. Then I played some music. I literally froze in amazement where I was standing. The transparency and the detail and the liquid sound of the female vocalist was fantastic!! I was concerned about the adequacy of the bass with only 20 watts when I first ordered the kit, but in fact, the acoustic double bass had both depth and detail and much more in fact than my 125 watt/channel tube amp. WOW! - am I happy! "

"I finished the second amp yesterday afternoon and have been listening to all sorts of music. I am very happy with the result!! These amps are great!! The most amazing thing is what they do with female vocalists: The sound emerges from an absolutely quiet background - no trace whatever of hum - and the sense of presence is fantastic. Also, there is plenty of detail and bass for classical music."
Allan Smith, California
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  audio note client review  
  The kits arrived yesterday and I couldn’t be more pleased! I am completely amazed at the quality of all of the components and look forward to getting started this weekend.
Raymond Lindsley
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  audio note client review  
  Completed both the mono blocks, and oh boy, just them playing into some cheap speakers and using the volume off the cd player, it already sounds amazing. Just think what it will sound like when I have them with the rest of the gear playing………………..can’t wait……………….. Just magic……………
Tony
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audio note client review
 

I recently had the privilege of listening to a pair of the AudioNoteKits Interstage Mono Block Single SET at a friends house. I was completely blown away from what I heard. The Interstage Monos exhibited an incredible control over the music, and yet retained a delicacy to the nuances that make music, music!

Everything came from a pitch black back round and from the first notes I was drawn INTO the sound stage. This was the most emotionally involving evening I have ever had spinning tunes. Familiar songs sounded new again, old discs that I had written off as bad, were brought back to life.
Chris Rodgers

audio note customer quotes
  audio note client review  
  I'm listening to the 300B monoblocks as I write this.... and I have to say (as a frequent listener to live music) that the resolving power of these amps is unbelievable. Music that I know well was previously a caucophony.... now I hear every detail and it's all perfectly placed.... who would have thought? So... where from here.... the Ongaku?
Archie
audio note customer quotes
  audio note client review  
 

I recently replaced my Kit1 with a pair of Interstage monoblocks and am really impressed with the results. I built the parallel version which of course has more power than the Kit1.

I found the monoblocks in a whole different league than the kit1, a weightier presentation of the music and greater dynamics. Bass presentation is more precise and there's just more to the music. I lack the vocabulary to describe it fully so I'll never make a reviewer but I just find I'm more emotionally drawn into the music, probably due to a more lifelike sound-stage and more flowing presentation of the music.
Rick Ford

audio note customer quotes
  audio note client review  
 

My Audio Note Parallel 300B monos have done only 100 Hours against 500 Hours. But I can tell you that I observed a big difference between my EL34 based - 50 Watts Six Packs and AN Monos. The sound is much more open in the MID and High Band. Surprisingly, they produce astonshing Bass which may be due to Insterstage design and Double C Core Output TX.

There is NO hum - even within 4 inches from the woofer after connecting with Multiwave Option in PS Audio's Premier Power Plant. Output level can be compared with 50 Watts Push-Pull Six Pacs amplifier. I am curious to know, how will it sound when it completes 500 hours of Break-In.
Abbhijit Dey

audio note customer quotes
  audio note client review  
 

First impressions are that they are just absolutely out of this world. The detail is incredible especially when combined with the DAC.
They look stunning with those black transformer covers and at night the tubes have a nice blue glow. The bass extends well into the low frequency range and the trebles are crystal clear.

There is nothing better out there in my opinion that even comes close to the quality of your kit. It is truly magnificent.
Vincent Gore-Rowe

audio note customer quotes
  audio note client review  
 

I must say the monoblocks are authoritative-they control the mid/bass drivers well. I can feel the bass but it is never bloated, just about right for me. At the moment the mid to lower registers shine. I hear quite a bit more details from my CDs, and the imaging is rock-solid.

Guess these are early days yet. But if things are so good now, I can't imagine what it would be like when the amps are run in. So I'll reserve full assessment until then.
Michael Cheong - Single Triode C-Core 300B Mono Blocks

audio note customer quotes
  audio note client review  
  I have to say that the M3/mono-block combination is really quite something. I am currently running them in, so I will reserve full judgement (and a write-up) for a couple of weeks... that said, there is certainly quite a difference from the Kit One. The sound is fuller, and more defined - especially when there is more going on.
I am also very pleased with my decision to get the parallel 300b's. The benefits of the extra power is very noticable. The M3-mono-block combination seems now perfectly matched with my Ariels. It's real something to hear...
Mark Leece - Parallel 300B Mono Blocks
audio note customer quotes
  audio note client review  
  ...But then you listen and the sound - WOW the improvement was unbelievable...
...The mono's control of the speakers is absolutely fantastic right through the range...
...The improvement in sound quality was a shock (yes jaw dropping)- I had never heard anything like this before....
Paul Clark UK - Single 300B Mono Blocks
audio note customer quotes
  audio note client review  
  I will also like to say a big thanks to Peter, Andy & Co !! for coming up with these products as I would like to call "musical time-machines" (it takes me on fantastic musical journeys to extraordinary musical happenings through the times of recorded music), and also Brian at Audio Note Kits and Upgrade Audio here in Norway !!
Rune Saevik - Parallel 300B Mono Blocks
audio note customer quotes
  audio note client review  
  First, I must tell you, that we are very happy with the Interstage-Monoblocks! The sound from both types are absolutely fantastic! Even a very deep Bass.incredible! It is a very good instruction manual.
Thank you very much for the finest Audio Kits.
From 2 customers who bought a 2A3 monoblock and 300B monoblock
audio note customer quotes
  audio note client review  
  They sail through transitions and the music sails as well. The whole presentation isnít subdued, itís exciting! But where there used to be a limit, the bar has been raised much higher. I can listen to The Who at near deafening levels and not want to lower it just because ďI Canít ExplainĒ is about to open up with an onslaught of electric guitars...
Doug Lindley
audio note customer quotes
 
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