Martin Poulin
picture from internet.
part selection is very good. Tube schematic is very close to a marantz 7.
very close to mundorf at low price.
picture from internet.
Hovland HP200 Preamplifier upgrade
Despite a generally good design and very good parts selection, some items were overlooked. (XLR board for example felt like as an afterthought)
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Added a bypass on the power supply
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Added regulation to the balanced board
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Changed coupling capacitors
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Added damping to the chassis
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deleted transistor buffer on RCA output
Done a 7 channel and a 5 channel
Heat stress is evident inside the top plate. (mod required to improve reliability)
all channel working perfectly
Done a 7 channel and a 5 channel
Krell showcase amplifier (3 rebuilds, picture combined from all units)
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Full recap done (using heavy duty parts and mostly 105 degree Celsius long life caps)
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Power supply section went from 80,000uF to 120,000uF (50% improvement)
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Preamp section bypass capacitor changed from 33uf to 82uf (250% improvement)
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Amp section 33uf capacitors replaced with 220uf (660% improvement)
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Feedback capacitor changed from polarized electrolytic to audiophile quality "Nichicon muse" non-polar (the green one in the pics)
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Input capacitor removed for direct coupling connection. (Krell products have coupling caps input still bugs me. A sonic bottleneck!)
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Power supply mods to remove heat stress issue and improve long term reliability (In stock form, driver board runs 24/7 causing much of the issues associated with long term reliability) After modifications, the amp now draws ~10watts from the wall outlet versus ~75watts.
full recap coming
full recap coming
Krell 300CX
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Switchable 240VAC, using 240V feed.
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Full recap done (127 or so capacitors replaced) - see bulged stock Panasonic capacitor on picture 2)
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New high end resistor in signal path added
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Internal fan added for capacitor longevity. The inside temperature actually dropped slightly more than 20°C or 68°F.
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New high performance discrete rectifier installed. (extra soft recovery)
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Speaker wire changed to 99.999% (5N) solid core silver wire
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New Hubbell power plug (stock was hardwired 240v in)
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New custom length power cord added
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Despite having multiple amplifiers throughout the years, this remains as my ultimate reference! ( now sold)
XLPS V3
All populated with Nichicon KA
XLPS V3
Musical Fidelity Phono Stage
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New outboard fully regulated linear power supply added
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Full recapped. Replaced the stock Jamecons to Nichicon KA’s
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Upgraded op-amp
using linear power supply with 7A regulator.
some damping too
Benchmark Media DAC2 HGC
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Onboard power supply (SMPS) replaced by an outboard fully regulated linear power supply, with a new connector in place of the 120V IEC inlet.
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Elna Silmic II local bypass added inside the DAC in addition to some Panasonic FM’s.
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Damping added
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A few local bypasses here and here.
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DC coupled (stock is not)
Whilst the stock unit was good, after my modifications…it became outstanding!
Kef LS50
A worthy speaker, and a great candidate for the following upgrades:
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New speaker wire (99.999% silver on the tweeter)
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A new crossover design for both the tweeter and woofer
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Mundorf Supreme silver+oil capacitor on the tweeter and foil inductor (2nd order LR crossover)
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Foil inductor and Jentzen capacitor on the woofer (2nd order LR + compensation added)
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Internal damping changed as well
The soundstage became much wider than the original design and more open with better detail.
The controversial Hifiman HE-6
Historically hard to drive headphones, never use with sub-par amplification which makes your ears bleed.
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Stock cable replaced with braided cooper to a 99.999% solid core silver wire.
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Rear dampening and dust protection fabric removed.
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Internal dampening added and fine tuned by ear.
Now these are more open, with lifelike bass and midrange. Treble is much more airier.
Overall…success!
200Wx5 RMS 8ohm 400Wx5 RMS 4 ohms 100pounds....
125 of them, from the main boards.
only opamp left in circuit, my long time favorite AD chip.
200Wx5 RMS 8ohm 400Wx5 RMS 4 ohms 100pounds....
Krell TAS Amplifier
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Now working on 240VAC (switch inside)
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Complete board recap with Nichicon HE capacitors
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Main power supply caps replaced with 380LX caps (much higher uF’s)
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Input buffer redesigned from balanced line receiver (3 generic quality op amps classic design) to single chip. Top of line 1200 series balanced line receiver.
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5N silver wiring for the input.
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No more input capacitor (stock version used sub-par Wima MKS4)
damping added
Huge 10,000uF Mundorf bypassing the main +12V DC supply (work not by me)
MiniDSP 4X10HD
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Stock generic caps replaced with the excellent Panasonic FM’s.
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Removed both the input and output DC blocking capacitors (DC offset remains below 9mVdc)
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Added an over sized external power supply (7 Ampere double regulated and 80VA toroid with significant uF reserve bank)
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Dampening added everywhere
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Power switch added on the DSP (for convenience)
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Opamp upgrade to AD8599 (changed one on top, the one underneath left stock as I had not enough room to change them)
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- Last 2 pictures from a fellow DIYer that I've corresponded with. He used shielding and went crazy on main PSU bypass with Mundorf caps. He claimed great result with those 2 extra steps. (he copied most mods I has already done and kept wanting to improve the SQ)
internet image
internet picture
all opamp have been changed to AD797 and capacitors are now audiophile grade
internet image
Dynavector P75
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New chassis
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New linear power supply replacing the stock SMPS
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More bypass all around
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AD797 op amp upgrade (on dual socket)
push out impressive power in a small box.
Run cool now.
Behringer NU3000
Class D amplifier
Inexpensive and very poor sounding per stock form.
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Removed input filters and mono switch.
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Upgraded the op amp.
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Upgraded the power supply (input section).
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Replaced the speakon connector with traditional 5 way terminal.
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Installed an RCA input socket
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Bypassed the volume control
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Changed the stock fan to a much more quiet one.
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Added heat sink on the SMPS (new fan has less air flow)
Whilst the amp remains lower in the quality scale, the sound significantly improved.
4 of them!
ugly but so effective!
Parasound A21 Power Amplifier
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Added fully regulated power supply for the input and driver stages
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New nichicon gold tune power supply capacitance (KG)
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EMI filtering added
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Added a high-performance double rectifier (discrete style)
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Significant bypasses added
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Signal purity achieved by removing input gain, resistors and relays. Mono switch and input buffer and added silver input wire.
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Critical dampening of the chassis
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New output speaker wire (instead of a long PCB trace)
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Ceramic fusing
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This resulted in a much better amplifier than stock version. Good controls on bass and midrange.
very tight fit... There is 4 of these as amp design is fully balanced dual mono.
they use a DAC to control volume, interesting.
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Krell KAV-400xi
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Full recapping using audiophile grade Mundorf and Nichicon KA&ES
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Installed soft recovery rectifiers
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Chassis dampening added.
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EMI filtration added
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Silver wiring on the output
original faceplate
original board+ 2 LM3886 module for powering turntable motor
original faceplate
Roskan XPS1 Power Supply
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The original unit had a decent sinewave generator but poor output module to drive motor.
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Replaced original output module with a gainclone module
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Lm3886 gives an output impedance of 0.2 ohms (limited by protection resistor) and has drive to spare.
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Fully adjustable (0.5Vac-25Vac output capacity)
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Set at 16.5Vac as per Roskan specs
Yulong D100 DAC
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New sockets installed to allow operational amplifier swap
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Currently using the Analog Device AD8599 (all 4 opamps)
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Power supply capacitors changed to Elna Cerafine (nos)
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Bypass power supply scattered around.
A Classic with fully regulated powersupply.
Local nichicon on heaters DC supply. Local mundorf on B+ for phonostage section
Audio Research SP8
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Complete Mundorf capacitor upgrade
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Local bypass added (Mundorf on the high voltage)
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New CRC heater supply with better regulator
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Wiring upgraded
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Augmented linestage feedback to reduce gain. As a result, the output impedance dropped. (customer request lower gain)
fairly nice box
picture taken before I"ve added another 330uf on the main power supply
Analog Acoustics – Asian entry level tube amplifier
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The stock unit ran incredibly hot (12.5watts per output tube that are rated at 12watts. Poor design choice. I dropped dissipation to 10watts for long term reliability and almost no audio power loss)
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Changed all cathode caps to Nichicon KA’s
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Changed coupling caps to NOS Auricap
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Added 330uf on the power supply (100% improvement)
Early version one
almost perfectly as original in here as original wiring remained in place
Denon POA Monoblock - refurbished
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Done on a budget and retained as much stock component as possible.
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​Installed a high quality Holton Precision 500w/4ohm module
as well as DC feedback caps (nichicon muse)
Bryston BP1
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Modified the power supply caps (more than doubled the amount of microfarads)
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Added a new feedback capacitor
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Now DC Coupled!
rear sticker, front mirror finish faceplate is engraved and about impossible to take in picture...
4 opamp are used 2 as a buffer to feed the volume control and 2 as gain stage after the volume control after this, there is a transistor based buffer to feed the RCA output.
rear sticker, front mirror finish faceplate is engraved and about impossible to take in picture...
Symphonic Line Preamplifier (previously updated the matching power amp but forgot to take pictures.)
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Upgraded the power supply caps (>2 x the micro farads and tripled it in some areas, using mostly Elna Silmic capacitors.)
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Added a new feedback capacitor
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Removed the transistor buffer stage (not needed)
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New top of line AD797 opamp used
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Equalized the power supply draw
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Added main line filtering
great designed unit, Chinese copy of...
plumbing potty doesn't look very good but once cover is on, you do not see it. And it work very, very well, I use it a lot for sonic, not for aesthetics.
great designed unit, Chinese copy of...
Melodious Audio MX-U8
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USB to SPDIF ASE/EBU bridge. Highly recommended.
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Upgraded power supply caps (roughly doubled the amount of micro farads and removed the stock "fake" capacitors)
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New bypass capacitors
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Dropped LED display intensity (much too bright)
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Lots of internal dampening added (crystal oscillator and transformer)
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Upgraded the rectifier bridge and added EMI filtering.
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Note: The unit is very receptive to "feet" tweak. I used DIY bamboo feet, but depending of your rack and overall system, it may not be your best option.
from 3300uf to 6800uf :)
used "thru hole" Panasonic FR (7000hours rating) and oversized the values.
Krell HTS 7.1 Preamplifier (internet photo)
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Complete recap of power supply board and analog boards with 7000hrs Panasonic FR’s on the analog boards
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CDE caps for the analog power supply.
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Added over-sized power supply capacitor
1/8" cork sheet glued
Parasound D3 Player
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Partial recap of SMPS with Panasonic FM and FR capacitors
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Bypassed audio output capacitor (removed and replaced with wire, which provides more signal purity and less coloration)
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Upgraded most capacitors on main audio board with Panasonic FM/FR’s.
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Chassis dampening added.
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Since the stock audio OPA2134 opamp is high quality, I chose to leave in, as changing would yield minimal benefits at best.
Yep, I have 4 to do
work by measuring main PSU current
Classe CAM-200 Mono Amplifier
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Complete recap with LowZ capacitors
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New soft recovery rectifier installed
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Added bypass caps on output board (none in the stock unit, which was a mystery to me)
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Input buffer deleted (Burr Brown OPA2134 opamp based)
obviously obsolete part now.
Classe CDP-1 CD Player (Vintage)
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This unit arrived “dead” and had obviously been been repaired a few times before I got it. I quickly discovered the LM7805 regulator was blown.
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Complete recap required
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Clock upgrade
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Output stage completely overhauled and a new Class A opamp replacing the transistor based output buffer.
Classe CDP-10 CD Player
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Customer requested a complete overhaul
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Complete recap with much beefier low impedance capacitors all around.
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Upgrade of opamp (and new socket added)
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Rectifier upgrade to Soft recovery
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Regulator upgrade
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Clock upgrade
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Chassis dampening
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A few signal resistors were upgraded
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Class A output stage
full damping added.
Classe Ct-10 Tuner
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Complete recap with Elna Silmic II
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Upgrade of opamp (and new socket added)
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Regulators upgrade
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Chassis dampening
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Few signal resistors were upgraded
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Class A output stage (RCA socket only. XLR out is class AB)
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Removal of RCA BJT output stage with signal being sourced from the XLR output
True dual mono constructon with double regulations stage on all stages.
Buffer output for RCA and XLR connection.
Mies P1000 phono stage
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Sparko op amp installed (at client request)
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Bypass of output capacitors
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feedback capacitor upgraded
Mid-fi unit, restrained from spending much on improvement but those 3 trick should already improve the unit significantly.
Original operationnal aplifier, the OPA2134 output stages aren't the most dynamics
Brinkmann Edison phono stage
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Tube change (they need to be matched)
No upgrade were performed, I just replaced the worn tubes in the unit and sent it back to the owner.