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Old 5th March 2010, 04:28 PM   #1
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Default Tony's 300B (standard model)

I've started this thread to briefly give my impressions of a 300B that Tony and Thomas built late last year. I've run this amp at home for some 2 months. It currently powers Alpair 7s in Pencil 7 cabinets.

I'm currently using the following valves (tubes)
2 X Full Music 300B Deluxe Edition matched pairs (cost around $300 USD)
1 X RCA vintage 6SN7 (centre input)
2 X Russian 6SN7 vintage military grade (driver stages)
1 X Zaeux 5U4G vintage (rectifier)

I've tested a total of four 300B amps over the last 3 years including this unit from Tony. Up to the time of listening to Tony's amp, I've remained unimpressed by 300B's. I'd more or less given up on 300B's being mated to Markaudio drivers, thinking this is one match not made in heaven. Compared to Brian Cherry's Joplin 2a3, no 300B to date has measured up in musicality, until the arrival of Tony's and Thomas's amp.

I got to know Tony around 4 months back following an offer to visit his studio in Tuen Mun in the New Territories of Hong Kong. The door to Tony's studio opened to reveal a veritable treasure trove of exotic hand-built amps on parade at the far end of the room. I sat down to take in a Stockfish recording on CHR-70's in a 5 Litre BR powered by this 300B. I've built some 23,000 drivers to date and been party to countless listening sessions. With all this time and effort under my belt I'm not easily won over by any amp or source until I've had plenty of time to take in their characteristics. All the same I was immediately impressed with Tony's efforts. For the first time, I was listening to a 300B that "lit my musical fire". This amp was full bodied, rich, musically smooth while outputting allot of signal detail through the CHR's cones, all this with no vices.

The afternoon went on with other amps being wheeled out, all impressive but I kept coming back to this 300B. I'd taken the trouble to bring a couple of my prised rectifiers so we popped in the Zeaux, that upped the listening pleasure, such that I took this amp home the same day.

It's lived in my home ever since, initially serving CHR's in BRs' now Alpair 7's in Pencil 7 cabs. The amp is run every day. It's the audio hub for the TV, CD, DVD and the Mac Mini. We're regularly swopping inputs are there's only 2 but it's a small price to pay given the quality of this amp's output. Recently, my beloved Japan model Sony CDP 333EX CD player gave up. Its replacement is an Accuphase DP65. That was an excellent investment as the source does more justice to the downstream side of the system.

Summarising, Tony and Thomas put allot of effort into their amp designs and while I'm not a tech guy on amplification, I know a good amp when I hear one. Given my audio driver design and build experience, I'm very particular when it comes to amps. I concentrate on every single sonic detail since my life is spent building speaker drivers. For every amp I like, there's four or more that I don't so that's how picky I am. These guys go to allot of effort to get the component mix right. I gather Thomas has some 20 years of build in the audio industry and it shows given the results I'm getting.

I've now commissioned another 300B from these guys, this time with hand-wound transformers and a big bag load of vintage goodies. I'll report on this amp when it arrives ( I hope next week).

Cheers

Mark.
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Last edited by markaudio; 6th March 2010 at 12:51 AM. Reason: typo mending
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Old 6th March 2010, 12:59 AM   #2
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I've had 3 emails asking me about matching 300B with Markaudio drivers, saying no problems with their set-ups. My apologies to anyone who enjoys 300B's on my drivers (or other makes), I'm was talking purely in personal terms in my first post and meant no offence to those folks who like and use 300B. I'm glad to hear that you're running 300B with much pleasure on my drivers and other makes.

I've had 2 requests asking me about the price paid for my 300B amp. Tony can build to order and also has demo units like mine. With the Full Music matched 300B tubes, I paid 1,030 USD. Tony's prices vary according to component selection. One other thing to note is the amp's chassis. Mine is made from Oakwood. I think Tony's made another 300B using more expensive timber and from my memory, a different ciruit and vintage UK transformers. I think this amp is above mine in his intro thread:

Introduction to Twin Audio

Best to email Tony for more details. Hope this helps,

Mark.

Last edited by markaudio; 6th March 2010 at 01:08 AM. Reason: typo mending
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Old 6th March 2010, 02:35 AM   #3
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Hi Mark,

Thank you very much for your selection on Twin Audio 300B amplifier and appreciate you to open a thread to push. Our 300B class A single end amplifiers are built with good quality and the sound is well-matched with Mark Audio Alpair 7, 10 & 12.

Tony.

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Old 6th March 2010, 03:02 AM   #4
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Circuit is very important for such kind of direct heat triode like 300B. We make use of the medium-mu twin triode 6SN7s as two stages to drive 300B. A single 6SN7 (in the middle of the three 6SN7s) as input voltage amplifying stage pushes a pair 6SN7s (left and right) as driver stage. The driver stage 6SN7s push 300B in SRPP circuit. We think this circuit can achieve more balanced sound with smoothness for 300B.

Last edited by Musik007; 6th March 2010 at 03:11 AM.
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Old 6th March 2010, 04:00 AM   #5
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Capacitor coupling was used between the input and driver stages and between driver stage and 300B. We selected Red TRW 0.25uF film capacitors in Mark's 300B. Can select other brands capacitors for coupling according to personal tastes.

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Old 7th March 2010, 01:22 PM   #6
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The power transformer of this 300B amp:
H14 EI steel core
Power: 250VA
Size: 96 x 67
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Old 7th March 2010, 01:25 PM   #7
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Output transformers of this 300B amp:
EI steel core in 0.35mm thickness
Power output: 25W
Size: 96 x 45
Fequency response: 20Hz-30KHz
Primary impedance: 3.5K ohms
Secondary impedance: 4 ohms and 8 ohms
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Old 11th March 2010, 03:54 PM   #8
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Full Music 300B Deluxe limited edition:

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Data sheet:
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Old 11th March 2010, 03:57 PM   #9
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Full Music 300B Deluxe, good sonic performance on the amplifier.

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Old 11th March 2010, 04:48 PM   #10
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Quote:
Originally Posted by Musik007 View Post
Circuit is very important for such kind of direct heat triode like 300B. We make use of the medium-mu twin triode 6SN7s as two stages to drive 300B. A single 6SN7 (in the middle of the three 6SN7s) as input voltage amplifying stage pushes a pair 6SN7s (left and right) as driver stage. The driver stage 6SN7s push 300B in SRPP circuit. We think this circuit can achieve more balanced sound with smoothness for 300B.
Me too.. I currently use RC coupled 6J5 into 6SN7 SRPP. Consider fixed bias on the 300B with 70mA - 80mA @ 400V B+ and a 3K - 3.5K opt.

Your amplifier looks very nice! (And reasonably priced as well.)
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