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Old School Power Amplifiers Using Modern Components Built to Order (Archive).

This Page shows the History of custom Power Amplifier builds for customers

With the Chinese making superb Aluminium Cases nowadays - I have designed and built some hand built quality Power Amplifiers which are so popular that I could just build nothing else - they sell like hot cakes and sound spectacular!

Using the custom built LJM range of Power Amplifier "Clone" Boards readily available on Ebay - I currently use 2 of the LJM Amplifier models (there are quite a number of LJM Clone Amplifiers available including KRELL clones) - these have proven to be the best and most sturdy:

LJM QUAD 405 Clone (100 Watts per channel) shown with my mini-mount HeatSinks:
LJM Quad 405

LJM L10 Clone (350 Watts per channel):
LJM L10


2 case styles have been used - the Single Case BZ3207P (External dimensions: Width 320mm Height 70mm Depth 248mm) and the Dual Case Model using 2 of the smaller 2107 case (212 wide x 70 high x 257mm deep) - one for the amplifiers and one for the PSU.

BZ3207P Case 2107 Case

The MKI Quad 405 Stereo Clone built into the BZ3207P cases proved very popular.
I have built around 10 of these single case types of varying versions - all sold to HI-FI buffs.

The introductory single case BZ3207P versions have been phased out now due to technical reasons and high production costs - I have none of these enclosures left now.

The Dual Case versions (shown further below on this page) are now the prefered build as they have proven to be HUM FREE.

Squeezing all the parts into the case is an art - yet the finished Power Amplifier sounds open, powerful and very "grunty".
All the power amplifiers I build are based on a number of component parts - some proprietry and some designed and built in-house under the ReelAudio Banner.
MKI Quad 405 Clone MKI Quad 405 Clone Rear
MKI Quad 405 Clone MKI Quad 405 Clone Inside


The MKI, MKII and other custom hybrids of the ReelAudio Quad 405 Clone Single Case units have a number of important parts inside which the standard Quad model does not have.
MKII Quad 405 Clone Parts

The internals of a MKII Single Case 405 Clone:
1. Speaker protection Board.
This unit constantly measures the DC from each Power Amplifier. On power-up the output of the amplifiers are kept switched off while the amplifier stabalises. Once this has been measured to less than 0.3V DC then each channel will be switched on - thus protection the loudspeakers from initial thumps. Continuous measurements are maintained to ensure the amplifiers are behaving - if one should show signs of DC Voltage then that channel will be disconnected from the loudspeaker.

2. +12V DC Regulation Board (ReelAudio)
This board produces a stable +12VDC for the Speaker Protection Board and the VU Meter Lights

3. +50VDC and -50VDC Monitor Board (ReelAudio)
This board measures the main + and - Voltage rails to the power amplifiers. Should one of the rails fail - then the other rail will also be switched off - thus protecting the Power Amplifier components.

4. Meter Drive Board (ReelAudio)
This board is connected to the loudspeaker outputs. As the volume increases then the VU meters will follow and show sound levels.
On later models this board is supplied with an additional front panel switch to allow lower power level VU monitoring.


Other Internal Components:
a: Heavy Duty 225VA 35V-0-35V Toroidal Transformer

b: 50 Amp Heavy Duty Full Bridge Rectifier

c: 10,000uF 63V High Quality Smoothing Capacitors

d: Fusing:
220 - 240VAC Mains Input - 8 Amp Quick Blow
+50VDC - 8 Amp Quick Blow
-50VDC - 8 Amp Quick Blow
+12VDC - 1 Amp Quick Blow
Each Quad Clone board has additional 4 Amp Quick Blow Protection Fuses x 2 on their DC input Rails.

e: Optional input Volume Control


Let's have a look at the MKIII Quad 405 Stereo Clone built into the Dual 2107 Cases.
All built to order - these versions are absolutely HUM FREE as the Power Supply is in one case and the Amplifier components in the other.

The cost of the lovely special cases from China is high (the transportation DHL costs being almost as high as the cost of the case!)
Additional CNC costs and time for the build contribute to a higher price than the single case version which is now being phased out.

MKIII Quad 405 Clone Dual Case
Optional switching shown: VU meters +10dB setting and Backlight switch
MKIII Quad 405 Clone Dual Case No Meter Switching

The 'Darth Vader' Version which has now proved to be most popular!
Due to the sales success of the Dark Lord version with its' menacing looks I have a number of these units currently being Black Anodised to celebrate the opening of the new Star Wars film.

MKIII Quad 405 Clone Dual Case "Darth Vader" Version MKIII Quad 405 Clone Dual Case "Darth Vader" Version
Latest Versions improved PSU components and Wiring harness
Latest Versions improved PSU components and Wiring harness
Latest Versions improved PSU components and Wiring harness" Version
Latest Versions improved PSU components and Wiring harness

All the dual case versions have a heavy duty multicore connecting cable with plug/socket.
This allows the units to be placed side by side (the same width as a standard CD player) or stacked as shown above.

The internals of the PSU module and the Amplifier module are shown below:

MKIII Quad 405 Clone Dual Case PSU Internals" 1. Fusing:
220 - 240VAC Mains Input - 8 Amp Quick Blow
+50VDC - 8 Amp Quick Blow
-50VDC - 8 Amp Quick Blow
+12VDC - 1 Amp Quick Blow

2. 50 Amp Full Bridge Rectifier

3. +12V DC Regulator Board

4. +50V and -50VDC Rail Protection Board

5. 2 x 10,000uF 63V Smoothing Capacitors

6. Heavy Duty Toroidal Transformer

7. Mains On/Off switch

MKIII Quad 405 Clone Dual Case PSU Internals" Power Amplifier Section

1. Speaker Protection Board

2. Meter Drive Board (ReelAudio)
Top switch = Up for +10dB setting, down for Full Power Monitoring
Bottom switch = Meter Back Lights on and off

Each Quad Clone Power Amplifier Board also has 2 x 4 Amp Quick Blow Protection Fuses

MKIII Quad 405 Clone Dual Case "Darth Vader" Version MKIII Quad 405 Clone Dual Case "Darth Vader" Version


The MKIV Quad 405 Clone was built as a one off for a customer who subsequently bought one of my standard L10 systems.
It uses the larger Amplifier Case and separate PSU Case with a 1 metre high Current Connection Cable.
This allows the Power Amplifier to be placed within the Hi-Fi Stack and the PSU possibly placed somewhere else.

Totally Hum Free.

MKIV Quad 405 Clone Dual Case "Darth Vader" Version MKIV Quad 405 Clone Dual Case "Darth Vader" Version
MKIV Quad 405 Clone Dual Case "Darth Vader" Version MKIV Quad 405 Clone Dual Case "Darth Vader" Version
MKIV Quad 405 Clone Dual Case "Darth Vader" Version MKIV Quad 405 Clone Dual Case "Darth Vader" Version
MKIV Quad 405 Clone Dual Case "Darth Vader" Version MKIV Quad 405 Clone Dual Case "Darth Vader" Version

The MKV Quad 405 Clone was built as a specific 19" Rack Mount Version for Studio work.

It uses a 2 U high vented case.

Its' main feature is that it has 2 new Reelaudio Balanced Line input conversion units with both 1/4 stereo Jacks and XLR inputs (you can use either).
Each channel input has a Gain control and Volume control for meticulous adjustment to the studio environment.

Available with 2 mono jack loudspeaker outputs or 2 sets of 4mm banana post outputs as shown

50% deposit required to manufacture this special.
405 Clone model available without meters (as shown) on a 2 week lead time Email Paul. (meters cannot fit)
L10 Clone model available without meters (as shown) on a 2 week lead time Email Paul.
The case is quite tight for space as you can see - L10 model only - add 60 for a unit with the front VU meters and switching added.

MKV Quad 405 Clone 19 inch Rack Version MKV Quad 405 Clone 19 inch Rack Version
MKV Quad 405 Clone 19 inch Rack Version Balanced input boards" Version MKV Quad 405 Clone 19 inch Rack Version
MKV Quad 405 Clone 19 inch Rack Version

The L10 (350 Watts per channel) Stereo Version

All the L10s are built within the dual case style (Darth Vader Black by Default).
They have an even more heavy duty Toroidal Transformer to deliver the power needed by such a powerful Amplifier.

L10 Stereo Power Amplifier

All the same protective component parts as in the Quad 405 Clone models - the L10 versions have more power - hence more heavy duty internal components.

L10 Stereo Power Amplifier L10 Stereo Power Amplifier
L10 Stereo Power Amplifier L10 Stereo Power Amplifier

Here we have a custom build L10 Power Amplifier with my Passive and Active PreAmplifier.

The Power Amplifier has a main switch on the rear to put all units in Stand-By. The custom power switch on the PSU front escution shows a Red LED condition. Once pressed, the Power Amplifier comes out of Stand-By and powers up in the normal way (power switch turns Green).

The PA2205 PreAmplifier external PSU is also powered on at this time. If the Power Amplifier PSU switch is pressed again - everything shuts down to Stand-By Mode again.

The Passive and Active PreAmplifier shown is also a "Special" where the Headphone socket has been moved to the rear panel.
You may see the PA2205 PreAmplifier details by {Clicking Here}.

L10 Stereo Power Amplifier with PA2205 Passive and Active PreAmplifier

Ready built units with their new CNC'd front logos.

Each Power Amplifier (and PreAmp) can be customised with your own logo too!

New CNCed fronts

L10 350 Watt Mono Blocks also available - 4 cabinets in all.

L10 Mono Block Amplifiers L10 Mono Block Amplifiers
L10 Mono Block Amplifiers L10 Mono Block Amplifiers

The Latest Production L10 Mono Block Units in Darth Vader Black - Note the Volume control now on the Rear.

L10 Mono Block Amplifiers
L10 Mono Block Amplifiers
L10 Mono Block Amplifiers

All the dual case units have 3 x 20mm fuse holders on the rear.

Also there is a hidden 20mm fuse (3.15Amp slow blow) in the IEC Mains input module (slide out holder).

+52VDC = 8 Amp Quick Blow
-52VDC = 8 Amp Quick Blow
+14VDC = 1 Amp Quick Blow

Power Supply Fuses

Which Amplifier should I choose? The Quad 405 Clone or the L10?

Here is a short email recently sent to a client to answer the Question.

"Hello George.

I've been developing the Quad 405 clone and the L10 power amplifiers for the past year and a half.
The culmination of the design has now been developed into the twin case units for both amps.
This negates hums caused by heavy duty toroidals radiating AC 50Hz close to the very sensitive inputs of the Power Amps.

Most of my production is for the Black anodised fronts with meters included. Quantities of pre-CNC'd cases are in stock.
Other variants are now built specifically to order - taking up to 4 weeks for specials (the special non-blacked cases need to be delivered from China etc).

The figures you quote for the L10 are correct in that it will deliver 350Watts into 2 Ohms - although I would not recommend a 2 Ohm consistent impedance at high power for too long.
Remember the impedance of a loudspeaker is variable dependent to the frequency employed.
If 2 x 4 Ohm loudspeakers are paralleled on one amplifier output then the Amplifier will be working very hard. Generally, a nominal 4 Ohm minimum impedance loudspeaker is to be recommended.
Remember, dependent to the frequencies in use, a 4 Ohm loudspeaker can present less impedance to the amplifier than the 4 Ohm specified.

The Quad 405 Clone delivers 100 Watts into 4 Ohms - less into 8 Ohms.
Although my designs use High Power Toroidals developing plus and minus 50 Volts DC to the rails - the original Quad only had 40 Volts DC on each rail.
Thus my design is capable of delivering 120Watts RMS per channel into 4 Ohms.
The efficiencies (ie: amplifier gain) of both units are similar - they both use the clever Quad 405 current dumping design which makes the units very solid.

With a higher current toroidal in the L10 and the increase in the number of working power transistors - the overall power levels possible are higher with the L10 than the 405.

If the efficiencies of your loudspeakers are low then you will need a higher power amplifier to drive them. These efficiencies may be due to smaller magnet capacity or heavy damping on the cones and spiders - all of these are another subject - where I should write a book.

Remember, the only reason that heavy duty loudspeakers used for public address work or in Discos can take lots of Watts is that they have huge magnets, low damping on cones etc and of course alloy coil formers which can take the heat developed in the loudspeakers when in use. Most Bass units are enhanced by folded horn cabinet technology which almost doubles their efficiency too.

HiFi speakers have been developed with sound quality in mind rather than power capability. The internal crossovers splitting frequencies to each of the drive units is carefully designed to keep the Xover points transparent - therefore dB efficiencies are similar across the frequency spectrum. Thus colouring by the loudspeakers is minimal - and the term HiFi (being there) is more true with well designed loudspeakers.

Also, Power Amplifiers will affect transients within the music.
Normal domestic power levels are around 5 Watts RMS for high/normal dometic listening levels. If the amplifier has more power capability in reserve then sudden changes in the music levels can be catered for without amplifier clipping/distortion.

A 350 Watt capable amplifier will, of course, give more of this reserve power should it be needed - thus although you may not be using the system at anywhere near its' full capability, then it is more desirable to have the reserve in hand.

Logarithmic Scales:
Remember, to double a 1 Watt amplifier (in dB levels) you need a 10 Watt amplifier. To double a 10 Watt amplifier output - you need 100 Watts.
So the difference between a 100 Watt Power Amplifier and a 350 Watt Power Amplifier is not that great - yet transients in the music will be handled a lot better.

I have looked at developing a 1000 Watt per channel unit - yet the production costs for cases, toroidals etc are huge.
I feel the L10 350 is more than capable to deliver sufficient reserves for all domestic HiFi settings.
The 405 Clone is also good assuming the loudspeakers attached are high efficiency units. The choice is yours George. Both Amps are Good - it depends on what you want out of the amplifier as to which you chose.

My amplifiers are pure analogue old school designs. No computer chips - just pure design for the job intended."


Prices for the units shown above do not include carriage costs.

To view the Ebay Sale and Pauls' other Items for sale CLICK HERE

Please Note: There are a lot of crimp terminal and spade terminal connections within each unit.
As well as being crimped these are also soldered for a secure long term connection.

Also Note: Each "Special Version" Unit I am asked to build requires a deposit of 50% sale price prior to works being undertaken.
Usually "Specials" need a 2 week lead time to allow sourcing specialised cases, CNC work etc that may be required.

"Standard" twin case Amplifiers are available from stock (2 to 3 days delivery).

Lots of customers want an Amplifier to suit their specific requirements.
Modifications, additional sections, re-design of other parts are all possible - even specific circuit boards designed and manufactured.
I am very flexible and like a 'challenge'. My electronic and design skills have been built up over 45 years in the analogue world within the Hi Fi and Sound Industry.
Please give me a call or send an email to discuss your "Specials" requirements.

Warranty:

The ReelAudio Custom Built Power Amplifiers are guaranteed for a period of 12 months from the date of purchase.
Normal Usage is implied by the word 'Guarantee' and 'Warranty'.

REELAUDIO MAKES NO WARRANTY, EITHER EXPRESS OR IMPLIED WITH RESPECT TO ANY PRODUCT, AND SPECIFICALLY DISCLAIMS ALL OTHER WARRANTIES, INCLUDING, WITHOUT LIMITATION, WARRANTIES FOR MERCHANTABILITY, NON-INFRINGEMENT AND FITNESS FOR ANY PARTICULAR PURPOSE. REELAUDIOS' SOLE OBLIGATION AND LIABILITY FOR PRODUCT DEFECTS SHALL BE, AT REELAUDIOS' OPTION, TO REPLACE SUCH DEFECTIVE PRODUCT OR REFUND TO BUYER THE AMOUNT PAID BY BUYER THEREFOR. IN NO EVENT SHALL REELAUDIOS' LIABILITY EXCEED THE BUYER'S PURCHASE PRICE. THE FOREGOING REMEDY SHALL BE SUBJECT TO BUYER'S WRITTEN NOTIFICATION OF DEFECT AND RETURN OF THE DEFECTIVE PRODUCT WITHIN NINETY (90) DAYS OF PURCHASE. THE FOREGOING REMEDY DOES NOT APPLY TO PRODUCTS THAT HAVE BEEN SUBJECTED TO MISUSE (INCLUDING WITHOUT LIMITATION STATIC DISCHARGE), NEGLECT, ACCIDENT OR MODIFICATION, OR TO PRODUCTS THAT HAVE BEEN SOLDERED OR ALTERED DURING ASSEMBLY, OR ARE OTHERWISE NOT CAPABLE OF BEING TESTED, OR IF DAMAGE OCCURS AS A RESULT OF THE FAILURE OF BUYER TO FOLLOW SPECIFIC INSTRUCTIONS.

IN NO EVENT SHALL REELAUDIO BE LIABLE TO THE BUYER OR TO ANY THIRD PARTY FOR ANY INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL, PUNITIVE OR EXEMPLARY DAMAGES (INCLUDING WITHOUT LIMITATION LOST PROFITS, LOST SAVINGS, OR LOSS OF BUSINESS OPPORTUNITY) ARISING OUT OF OR RELATING TO ANY PRODUCT OR SERVICE PROVIDED OR TO BE PROVIDED BY REELAUDIO OR THE USE OR INABILITY TO USE THE SAME, EVEN IF REELAUDIO HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

Units are Designed and Hand Built by:
Paul Baldwin
www.ReelAudio.Co.UK
admin@ReelAudio.Co.UK
12 Tack Lee Road
Yapton
Arundel
West Sussex
BN18 0HB
neverfinished0@hotmail.com
Tel: 01243 553231
Mob: 07858 089421

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