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Ladyday Signature MKII stereo amplifier
 NEW! The famous 91 circuit now available (see LD MKII three+) Note click photo at right to view larger.
Based on the original 300B theatre amp and the first hi-fidelity experience for many, this circuit uses the 310A pentode driver and 274b rectifier. Maybe this is the 'right' way to listen to a 300b - very powerful and tonally rich midband dynamics. Although the 91 has a reputation for being 'dark' sounding, the LD91 circuit implementation and choice of Tantalum resistors, silver wire, teflon caps for parts has overcome this and achieves 20-20k <-1db; 12-45k -3db. Of the possible drivers, this may be the best. The circuit is a little more complicated than SRPP or MU so allow extra time but it is well worth it.
Output transformers:
Used in some extreme high end amplifiers, these are wound with a 'perfect lay' technique using paper and transformer cores from Japan. 'Perfect lay' winding allows for tighter packing of layers and less interwinding capacitance so that a larger core can be used without sacrificing the high frequencies. The larger core is desirable to prevent saturation of the signal at high power levels and during transients. Bass plays deeper and at full rated power.
Multiple (5) taps on the secondary provide adjustable primary impedance from 2K to 8K so the following power tubes can be used: VT52/10Y/205D/45/50/PX4 /PX25/2A3/300B.
4/8/16ohm speaker taps: Nominal impedance ratings are often misleading. An 8 ohm rated speaker may be 6 or 12 ohms and often sounds better on 4 or 16 ohm taps. Always try different taps to determine which gives best sound. When the right tap is selected, soundstage will be bigger and sounds more energetic. Also 16 ohm taps allow using vintage high efficiency speakers. Connecting them to 8 ohms is a compromise.
The power transformer comes with all the voltage taps necessary for the advanced DIY'r to use all the above mentioned tubes: 2.5V/5V/7.5V-3A power tube filament taps.
400/300/ B+ supply and 2 x 25V buck/boost windings to get the desired B+.
5V/4A taps for rectifier, 6.3V and 10V - 1A for the input/driver tube heater supply. In addition, the Tentlabs/DIYhifi filament supplies can also be accommodated. Driver tubes can be 6SL7, 6SN7, WE310A, 6H30, 6C45pi, 417 etc.
The power transformer core material is the highest grade - H14 from Japan. Why is the core so important in a power transformer? Higher grade = less saturation = fewer windings needed = lower impedance = less power supply sag during transients and faster recovery.
The new chassis is non-magnetic with a copper ground plane. It is deeper giving more room for our beloved oil caps and big chokes if desired. Non-magnetic: ever breadboard a circuit - sounds great, but stick it in a steel chassis and the magic is gone? The LD Sig non-metallic chassis removes the magnetic interference effects of a steel chassis in the audio band.
30 Watt wirewound adjustable cathode resistor for the power tube is standard as is the choke for power supply and genuine Nichicon power supply caps. Copper ground plane standard. So... the sky's the limit here.
The LD Signature MKII stereo is improved in every way and offers even more flexibility as an experimenter's platform.
Prices are a little higher but there has been a major increase in quality. There is no getting around higher costs for parts and (transformer)iron and all manufacturers face the same choices. Beware the proliferation of tube amps which cut corners in the areas you can't see, with fake caps, re-sleeved caps, scrap iron cores and low purity copper -all common practices-, and sell for unbelievably low prices.
Specifications: (may change without notice)
• Power output, 300B: 7-9W x 2 RMS @ 1KHZ Class A depending on circuit
• Frequency response: 12Hz to 47KHz (-3 dB@5W) (20hz to 20k -0.5db)
• THD: <1% (5W@1KHz)
• Signal to noise: 90dB or better.
• Input sensitivity and impedance: 0.5V, 100K
• Power: 110/120/220/230/240V AC +- 10%, 100W
• Dimension (mm): 440(L) x 330(W) x 75/210(H)
• Weight: 26Kg
• Shipping Weight: 30Kg
• Standard Tubes (priced separately): 300Bx2, 6N9PJ(6SL7)x2, 5Z3PAx2 or
(Three+) 300Bx2, 310Ax2, 274bx2,
• NEW: Power transformer is low output impedance EI type, custom made with imported cores.
• Output transformer is larger imported core and 'perfect lay' windings.
• Speaker outputs: 0/4/8/16ohms
• non-magnetic chassis
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LD MKII One+: LD Mk2 Signature 300B DHT SET Stereo Power Amplifier Basic Kit:
Stereo chassis. (No tubes as standard).
Manual, parts and hardware complete for standard 6SL7 SRPP driven 300B.
Basic parts package, complete. now: Kiwame resistors and Obbligato capacitors are standard issue at Level1.
Standard parts included are not junk parts but typical of what you'd find in assembled high end retail product selling for 3X the cost. But the price is low so you can enjoy now and upgrade later
LD MKII Two+: LD Mk2 Signature 300B DHT SET Stereo Power Amplifier Premium Kit:
Stereo chassis. (No tubes as standard).
Manual, parts and hardware complete for parallel 6SL7 CCS loaded to drive the 300B.
Premium parts package, complete: Optimized Tantalum and Kiwame resistors, silver wire, teflon tinfoil coupling caps, Obbligato cathode, cathode wire wound resistor, teflon tube sockets, pure copper gilded speaker binding posts, silver plated RCA, WE connection Obbligato caps, SQ supermalloy grid choke - in other words - maxxed out with all the expensive bits you'd never find in high end off the shelf up to 4X the price. (No tubes as standard).
This is already a no compromise max-pak. The only other option applicable to this package would be the 'Go Higher' filament supply and your choice of 300Bs
LD MKII Three+:LD Mk2 Signature 300B DHT SET Stereo Power Amplifier Premium 91 Kit:
Gold recovered from the archives of the golden age of tube technology has swing! This refinement of the famous WE91 circuit uses a tiny amount of local positive feedback (can be left out if the word 'feedback' gives you the shakes) to give flat response to 20K (the original 91 circuit rolls off at 10khz and has a reputation for sounding dark). (No tubes as standard).
Includes Optimized Tantalum and Kiwame resistors, silver wire, cathode wire wound, teflon tube sockets, pure copper gilded speaker binding posts, pure copper gilded RCA 6 pin driver tube socket and 310A grid caps, new 310A/Russian (matched pr),5AR4 tubes, WE connection caps (Obliggato Caps 47uf, 12uf), teflon tinfoil coupling caps, 4 x oil cap for ps, silver hookup wire, instructions. Everything except 300Bs included.
This is already a no compromise max-pak. The only other option applicable to this package would be the 'Go Higher' filament supply and your choice of 300Bs.
Option 1: Basic tube set: 2 x 6N9P/6SL7 driver tubes and
2 x 5Z3PA rectifier tubes.
(for LDMKII one and two)
Option 3: Power Tubes (2 x Full Music mesh plate 300B Gold). Premium grade tubes with gold pins. Globe shaped glass, ceramic base. 5V heater. Matched pair.
Option 7: Go higher DIYhifi filament heaters.
The LD+ has the voltage supply to drive the DIYhifi filament heater supplies. This will make hum levels in the .2 to .5mv range possible. DC heating without draining the life from the music
(this special price only in combination with an amplifier kit)
Option 8: Fully Assembled :
Kit is professionally assembled and tested including any of the options above or below. You receive a complete ready to use product out of the box.
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