Tuesday, January 31, 2017

Sound Valves M60i Monoblock Rebuild and Review

Sound Valves M60i  Mono Power Amplifier

Today were showcasing a set of M60i Monoblocks I've acquired for my personal setup, a third Black faced M60i came with the trade thats still in repairs.  The M60i came with a "Ultra-Vent" proprietary case to protect the tubes and from what I can ascertain  with two faceplates, black for early productions and a brushed silver.

From the literature I have found on Sound Valves;
"Sound Valves is the name taken after Dynaco stopped selling DIY kits in the 1990s and set up shop in Columbus Ohio. The M60 amplifier could be considered the next version of the Dynaco MKIII.

The M60 audio circuit topology is a four stage, single channel power amplifier. The front end consists of an all triode, Class A gain stage, phase splitter, and low impedance drivers. The output stage uses 6550 tubes and operate in triode or ultra-linear mode selected by a switch between the output tubes and transformers (NOTE: Manual states the switch can only be used when amp is off). In triode / ultra-linear mode the first 17W / 30W are pure Class A, switching to Class AB1 for a maximum RMS output of 30W / 60W. Below is the information from the manual."

Each of these units were exhibiting similar issues I related to an initial design defect with regard to electrolytic voltages and factory sub-par components grades. Early failure of the 12Vdc regulated IC was apparently imminent as well from research I suspect to the initial current limiting resistor values and its current handling rating. Another issue is the premature burn up of a 15V zener which is erroneously noted as a 10V on the schematic. 

The construction consists on a outboard choke, Bell type Power and Audio Output Transformers that are exceptionally heavy and I think overkill for their output rating...which is NEVER a problem with in comes to tubes! The main circuit is on a single heavy layer double soldered PCB assembly with PCB-Type Ceramic sockets. Quality components such as Bourns, Nichicon were used during the initial construction.

The Chassis is made of two pieces of bent Chromed Steel (U-Body) with smooth corners and a fine finish. The rear outputs are a 5-way binding connectors with 2,4 and 8 OHM taps. The Tiffany style Gold-Plated RCA input is of heavy construction and feels very solid.

In each units all of the electrolytic capacitors were replaced with Nichicon PW high temp  (105C) versions with the same diameter for the chassis cutout with an increase of operating voltages to 250V. The two 4.7MFD BiPolar were replaced with VP Nichicons as well. Original Af path films and coupling films were all replaced with high grade MKP Polypropylene and ECW PP's films which made a significant impact. Several of the current limiting resistors were increased to 5W handling power as well as all of the small-signal BJT's and MOSFET to modern On-Semi, MicroChip and Fairchild TO-92 devices. The 12V circuit is based off a LM7812 type IC which was replaced with Fairchild robust, high heat (180C+) TO-220 7812's devices.

All new Electro-Harmonix compliments were purchased; 12AT7/12AU7 and two 6550 EH's.

Audio Notizen (PER Serial#)



Friday, January 27, 2017

Line Magnetic LM-518IA Review

Line Magnetic LM-518IA Integrated Amplifier

Here were showcasing the build quality and performance output of the popular Line Magnetic LM-518IA Integrated Amplifier.  I wanted the opportunity to get elbow  deep into this amplifier because I am quite skeptic of its offerings. The LM-518IA demands a fairly mid-high price for a 22W SET from China, yet the available technical information from the manufacturer and history is incredibly lacking on the unit. This is always a big flag to me. This will not be a subjective audio session review..I don’t understand those or why folks read them…this is a technical break down…so lets dig in!

Line Magnetic History:
Line Magnetic, from research was establish in Zhuhai, China in 2005 by brothers Zheng Cai and Zheng Xi. Their board product range includes reproductions of high-end West Electric topologies and proprietary designs. Their production line compasses DAC, tube CDPs amongst stand-by models designated to integrate one system brand synergy.  The LM-518IA Integrated Amplifier is the mid-range SET amplifiers using LM’s purpose built 845 tubes, sitting below their KT-120 tubed 100W 501IA Integrated Amplifier. 

...presumably the staff at Line Magnetic

The 845 designed by RCA and released in 1931 was primarily used in radio transmitters is a unique hi-fi tube. The 845 is a three-element direct heat tube using a thoriated tungsten filament working at parameters of 75W anode dissipation w/ 1250V, the filament requires a 10V 3.25A.

The LM-518IA is billed as a  22 Watt per channel Single-End Triode (SET) Class A Integrated Amplifier. The 518IA uses two 12AX7 (V6/7) voltage amplification tubes, two 6P3P (V3/4)  driver tubes and two 845 (V1/2) output tubes along with a 5AR4(V5) rectifier tube. Also useful is the front meter display injunction with the V1/V2 bias adjustment, the front meter assists in obtaining the 70mA current. Along with the bias adjustment a Hum-Balance is equipped and easily adjustable with a small screw-driver. The control points consists a Alps attenuator and a multi-line in selector or main-in. 

Tube complement:
845 x2, 6L6 x2, 5AR4 x1, 12AX7 x2
Output power:
22W + 22W
1% (1kHz)
Input Impedance:
Output impedance:
4, 8, 16ohms

Performance Reports:
Below are performance reports on the actual output of the LM-518IA using a 8 and 4 OHM Dummy loads...not some "self" emulated speaker simulator....none of my results are weighted or averaged, this is a what I consider a true representation. To keep the article un-bias I will not weigh in on a output conclusion here.

(8 OHM) LM-518IA

(4 OHM) LM-518IA

Build Quality:
The first few things I noted was the aesthetic impression and weight! The 518IA is incredibly heavy..always a good sign..like most amplifiers the weight is distorted through the rear chassis with the large power transformer centrally located, flanked by the two output transformers. 

Chassis & Finish:
The finish of the 518IA is a gorgeous almost gloss heavy white powder coated over the irons that looks flawless and classy. The chassis has a brushed aluminum finish and front plate is a meter matching off-burnt orange metallic color.  The brushed chassis cover is a very clean product used as a U-shaped chassis, I should note the corners and vents of the 518IA are very very sharp, sharp enough to cut skin or a careless child, none of the edges feature a smoothed over edge or even beveled.   The rear plate has a very plastic/white metal feel that has a printed/painting white finish subject to easy mares.  The bottom plate is painted top and bottom with 4 single screwed base feet featuring an brushed aluminum cap over plastic. The tube cage is also powder coated the same gloss-white finished as the iron covers, which banana-style pins to snap securely into the chassis. I really like this idea, yet it does have some significant wiggle room, is easy removed by a child and will not provide any protection I suspect in the case of a fall or blunt force as the grates are far to spaced out and thin.

The 518IA has a series of three line-level inputs and one set of Pre-In level inputs. All the inputs are gold-plated Tiffany style metals. These seem incredibly robust and sturdy, one of my favorite hardware components of the 518IA.

  In contrast the output terminals which consist of a two channel 16,8 and 4 ohm terminals. The 5-way binding posts feel exactly like the cheaper plastic bodied type available on eBay and surplus speaker suppliers. The caps are loosely constructed, non-locking do not contain a end retaining washer. The AC power inlet is a standard IEC plastic connector which feels firm and secured, the supplied power cord is clean, robust and heavy gauged. 

The two controls on the front of the 518IA are the volume and selector function. The volume knob is illuminated with a green indicator that flashes during the -soft start procedure. Both are bright aluminum finish that appear to be milled which is nice to see. However the selector positions exhibit some torque on the rotary controls gangs when turned and locked into a position, with only X1 set screw to retain the knob this extra torque appears to be contorting the internal selector switch, this particular unit auditioned has been service once already for this repair which required a new selector switch within several hundred hours of use only. A secondary set-screw should be utilized here. The power button is a typical push-button type with a aluminum cap and shaft, the action feels very solid and the hepatic feedback is good.

Starting the core hardware, the tube sockets employed in the 518IA are all gold-pin ceramic sockets for the AX7, all are very secure, especially the front end 12AX sockets. The massive 845 sockets are also a ceramic base which offer a very heat hardened solid socket that should last ages.

As mentioned the motorized Alps volume potentiometer is the standard in high-grade audio logarithmic potentiometers which also offers the protection of potted enclosures.  The bias IC circuit contains SMD controlled components and precisions Bourns trimmers which I personally use in our restorations here at Hallo-Fi All of the heavy wattage current limiting resistors are chassis mount type on their own separate chassis mounts which I like to see for 2W+ components due to the heat they exhibit. 

The use of custom stand-alone PCB assemblies are evident through the construction which in some cases is better than eloquent point-to-point.  Each of the large filtering capacitors (470MFD/450V) and full-wave bridge rectifier use a custom PCB for their associated networks. They appear to be properly screen-printed with good solid copper tracing and dual layer PCB’s which should stand up to the heat of unit quite well over time.

The compliment of capacitors was nice to see, the use of a high temp (105C) Nichicons and low impedance PW’s, again as we use here and Japanese Rubicons.  I did see a review that quotes these as "German high-end Film capacitors"...That I think is purely marketing , I have found little info on German Neglex capacitors anywhere, all of the film construction I suspect to be Solen MKP capacitors  or the like simply rebranded..but do not mis-read as I think the Solen polypropylene film capacitors offer a very high grade of reliability and performance for an affordable cost.  The use of KOA MOX type resistors in the 1-5W are very dependable, robust resistors with and excellent track record, each leg is appropriately shielding thats exposed as well. (**EDITED to keep heads calm...)

All of the point-to-point busses, wiring and soldering appears well done and sturdy. No blobs or burnt wires, clean use of heat-shrinking and the topology was very well laid out and constructed, a good use of chassis space as well.


My time with the Line Magnetic LM-518IA has been very enjoyable. The unit appears to  bias reliably and consistently. The tube compliment is sound and of true and tried designs out there. The soft-start circuit appears perfectly timed and active when tripped into protection. Overall I would mark the LM-518IA a reliable and dependable amplifier if well cared for. I would personally recommend checking the bias before each session and never operate around animals or children if their able to access the unit easily.

The internal build quality I think merits the start of the asking price, yes priced out separately the costs of core components is reliantly cheap, but the outputs are of very high quality, Alps and large microfarad capacitors can bump up construction costs substantially. The exterior I feel leaves a lot to be desired, from the sharp corners, poor controller design and cheap speaker terminals I expect a great deal more there for a 4500$ machine.

Edith Piaf's Non, je ne regrette rien and Nina Simone's Suzanne on a older British Stage 2 Micromega CDP

Contrary to what I would like to present or typically do I would like to add a note on my listening impressions here.  The LM518IA is destined to be heard by one of the DeVore Fidelity line ups as is highlighted in several online reviews, having done so on a pair of O/93's in Madison, Wisconsin and now at home with a very modest and simple pair of Full Range folded horn Bk12s with the 126EN Fostex driver playing Edith Piaf's Non, je ne regrette rien and Nina Simone's Suzanne via a older British Stage 2 Micromega CDP...this integrated amplifier is very impressive...The upper and mid range is well presented, neither sharp nor contrasting. Totally enveloping the idea of a Class SET and its expectations. The lower end and synergy between peak to peak differences is impeccably defined and robust when needed...something often lacking in my experience with SET's. Some may waver at the performance factors but the LM518IA should be paired a high efficient Full Range and a possible super driver or again the DeVore's. 


Wednesday, January 25, 2017

Crown D-150 Power Amplifier

Crown D-150 Power Amplifier 

Today were highlighting the vintage Crown D-150 Power Amplifier. The D-150 is an extremely well regarded power amplifier, an under-the-radar machines used in many high-end mono and stereo setups for their known performance standards one would not expect from Crown. Often times we will see these amplifiers dedicated as tri/quad amp lo pass dedicated machines. The D-150 was available in two formats, industrial and home use with a faceplate and a few later models  D-150A &  (MKii). Sold during 1971-1974 the D-150 was compared to the larger DC-300 model which is DC coupled unlike the D-150. Uniquely the D-150 uses a pair of unbalance 1/4 mono jacks (25K)

The power supply stage consists of a simple full wave bridge rectifier at a total 18,000MFD filtering stage for the developed rails. These originals were replaced with modern Mallory can capacitors in this rebuild and new bypass films across the diode bridge (1MFD/1KV ECW Polypropylenes)

The driver stage, considered to be realistically a Class B (A+B) amplifier with a fixed Bias, adjustable by emitter resistor pass. The front-end differential stage utilizes a Fairchild (U)A739C OPAMP. The 739C is a high gain Dual IC with a 3-stage Class A PNP output stage. All of the electrolytic’s were replaced with VP and high temp (105C) Nichicon capacitors with an increase in operating voltages. The Bias was attenuated with new (10W) KOA resistors and a new 739C was sourced and install onto a chipset versus direct. New UF400# Ultra-Fast diodes and modern 4148 type installed as well.

Audio Notizen 

(Next to the Yamaha M-2..this is one of the best performing amplifiers of this period Ive tested yet!)

Tuesday, January 24, 2017

Brad's Marantz 1180DC Integrated Amplifier Restore

Marantz 1180DC Integrated Amplifier 

The Marantz 1180DC Integrated Amplifier is a somewhat rare and very aesthetically pleasing Marantz Integrated Amplifier, in the TOTL line up with the 1300DC model.  The 1180DC has identical stages of the Marantz 3250 Pre-Amplifier stage and a Model 170DC amplifier module and PS requirements.

The 1180DC have a gorgeous facade to the faceplate finish, touting two PHONO and multiple high-level inputs along with a AC/DC coupling feature and auto defeat of the AF stage tone controls. The 1180DC uses a particular slotted constructed for the PCB’s to fit perpendicular to each other versus lead wires. All of these connection must be inspected separately due to a high rate of solder joint damage from askew amplifier positions or physical abuse.

Power Supply P800 (designations)
The 1180DC power supply is shared with the AF stage PCB assembly to reduce the footprint. Due to the proximity of the original voltage regulators some significant heating issues were noted in the area. In relation the voltage regulators were replaced with modern, heavy duty TO-220 MJE On-Semi devices with new thermal compound applied.   The original 1S class and 10D diodes were replaced with modern 4148 and Ultra-Fast UF400# type diodes. Also noted were the use of DS-133 anode to cathode diodes which were replaced with custom configured UF4007 type diodes.   Remaining TO-92 BJT’s were replaced with TO-92L KSA/KSC low noise modern Fairchild devices. Electrolytic’s were replaced with high temp (105C) long life life Panasonic FC and Nichicon PW capacitors with an increase in operating voltages. 



The original filter capacitors at 15,000MFD were increase to a 22,000microfarad filtering stage modified to address the lower response sag by increasing reserve capacity and filtering potential.

PN00 Protection
It should be notated the SM indicated the incorrect test points for the offset points, which should be correct to reflect JN01/09 to ground for references.This assembly had obvious heat issues reflecting capacitors issues on the 1180DC.  All of electrolytic here were replaced with high temp (105C) Nichicon PW capacitors with an increase in operating voltages. The original common cathode diode was replaced with a modern TO-220 MUR1620 type rectifier device for better heat sustainability and associated BJT’s to TO-92L KSC/KSA type modern fairchild devices. 1S type diodes replaced with a modern 4148 type and the relay to a MY4 DC24 type. 



P700 Driver Assembly
On the 1180DC the driver stage is mounted to a single symmetric PCB design and a complimentary  TO-3 output stage. Unique to this is the integration of a SIP packaged 2SK109 differential pair Dual FET device. This particular came in with major defects, burn resistors networks and low leak notated at two NPN output devices along with current limiter damages. 



The only major issue with the Marantz 1180DC is the use of heavily populated glass pack diodes and thermally coupled diodes on the foil-side of the PCB, which is held with a very poor and dried out glue. This glue overtime is eating away at the conformal PCB coating and disintegrating the copper traces as well! At least a dozen + traces had to be routed/repaired or reflowed on this PCB…I can assume most 1180DC out there today feature this issue and will be its failure point if not addressed. The capacitors in this stage were all replaced with a audio grade Nichicon KT with an increase in operating voltages. ALL of the AF path mylar films were removed and replaced with high grade audio WIMA polypropylene film capacitors! Bourns trimmers installed to calibrated and 1S diodes replaced with modern 4148 type.  

The bias is pre-determine via a constant current source for the 1180DC setup so no bias to adjust on these, though significant offset issues are known on these. ALL of the small signal transistors were replaced with modern low noise Fairchild TO-92 devices along with the driver pair devices with new thermal compound and mica inserts.  QT1-4 current limiting BJTs were upgrading to TO-92L type transistors for better thermal characters and modern low noise equivalents. Q717-720 were matched to 1% BETA and replaced with low noise fairchild devices, then thermally coupled. 

AF Stage PE01 & PH00 Filter Assembly
The AF Stage/RIAA and PS all share a single PCB on the 1180DC.  All of the capacitors on the pre-amp PE01 were updating to a Nichicon PW low impedance type and Nichicon KT audio grade capacitors with an increase in operating voltages. High grade MKP polypropylene films for the .47 input films were installed as well. All small signal BJT’s were updated to low noise, modern TO-92 fairchild devices.



PH00 Filter,
The filter assembly is connected perpendicular to the front control PCB via pin connectors as the PE01 AF stage PCB.  All of the AF path mylar on this assembly were updating to high grade WIMA polypropylene films along with the .22 coupling films to high grade MKP PP’ type films on the rear of the assembly for room.  Nichicon Fine-Gold FG’s and KT /PW low impedance and audio grade capacitors with an increase in operating voltages installed. As above all the 841/1681 BJT’s were upgraded to low noise, modern TO-92 fairchild devices. 



As mentioned the RIAA is located on the AF PCB assembly.  The initial differential pair transistors were replace with 1% matched BETA with low noise fairchild T0-92 devices. Nichicon KT audio grade and PW low impedance capacitors with an increase in operating voltages installed along with high grade WIMA polypropylene film capacitors (1MFD.)



Audio Notizen