Shunt Regulated Salas Hotrodded DCB1 Build

[jls001]

After building omishra's DCB1 and hearing how phenomenally good it sounds, I was motivated to start building the Hypnotize version of the Salas DCB1 buffer. The Salas kit was purchased many months ago, but kept in cold storage due to the presence of the rather likable B1 in my setup. Later the B1 was modified as per spirovious' formula and it performed even better. It was on building and listening to omishra's DCB1 that I realised that it can probably be bettered with a kit I already have.

The DCB1 Original build thread over at diyaudio is here.

The Hypnotize version is similar to the Mesmerize version, but the later is designed to support multiple inputs whereas the Hypnotize is strictly one in, one out. Also, the Hypnotize is designed to be hot rodded, meaning more current is allowed to pass through the four MOSFETs to improve the sound. There are four levels of build - level 0, 1, 2, and 3.

Level 0 is the default version and runs about 70-80 mA of current and does not need heatsinks for the MOSFETs. Level 1 runs about 200 mA and needs medium-sized heatsink, level 2 is about 600 mA and needs about the same heatsink as a 30W Class A/B amplifier. Level 3 is the "insane" version and needs humongous heat sink.

The sonic differences in the levels is mainly in the focus and width/depth of the soundstage (or so I have read).

The power supply section is built into the board. It uses (linear) shunt regulation of Salas' design, unlike the more common linear series regulation.

Some WIP pictures of my build:

The bare board: it is very well made, and has lots of flexibility in choosing different-sized components.

The board partially populated: resistors are PRP, 1% film. The B1 part of the circuit uses four matched 2SK170 low-noise FETs, and unmatched 2SK170s in the shunt regulator. I think the bunch of LEDs are also part of the shunt regulation circuitry.

Fully populated, with test heat sinks for the IRFP240/9240 MOSFETs:

Toying with the idea olf using this heatsink for my planned Level 2 hot rod:

Special thanks to jai116 who kindly donated his unused 15-0-15V 120A toroidal for this project. Special thanks also to omishra who answered my queries about how to wire the inputs/outputs and volume control.

Even more special thanks to Rikhav for taking the trouble to import the kit (from Teabag at diyaudio).

Will update as the build progresses further.

 

[magma]

take inspoiration from peter daniels cabinets and patek builds

 

[sann]

Looking very tempting... Please compete soon.

 

[captrajesh]

the Hypnotize is designed to be hot rodded, meaning more current is allowed to pass through the four MOSFETs to improve the sound. There are four levels of build - level 0, 1, 2, and 3.

level 2 is about 600 mA and needs about the same heatsink as a 30W Class A/B amplifier. Level 3 is the "insane" version and needs humongous heat sink.

Toying with the idea olf using this heatsink for my planned Level 2 hot rod:

Is it still a buffer with unity gain or is there some gain?

Even if there is gain, does it require such huge heatsinks!!

 

[sachu888]

Is it still a buffer with unity gain or is there some gain?

Even if there is gain, does it require such huge heatsinks!!

Its a unity gain like B1. Heatsinks needed for IRF mosfets.

Regards,
Sachin

 

[omishra]

Shunt regulators are kind of heaters same like class A amplifier But these heat sinks are monstrous.

 

[baswamin]

Question for experts,

Should the shunt regulator be on the same board as the buffer to see the improvements? What if I make the same Salas shunt regulator on different board and use it to power dcB1 that Om made? Will it sound the same?

Thanks

 

[jls001]

Question for experts,

Should the shunt regulator be on the same board as the buffer to see the improvements? What if I make the same Salas shunt regulator on different board and use it to power dcB1 that Om made? Will it sound the same?

Thanks

Not an expert by a long stretch but the shunt regulator is simply the power supply. So it shouldn't matter if it was on the same board or outboard.

What is critical though is since the two LED banks are used to "tune" the output voltages, the LEDs must be closely matched to get symmetrical +10V/-10V-ish voltage. On the B1 side of the circuit, the Toshiba 2SK170 JFETs need to be matched closely as well to get symmetrical DC offsets.

Also critical to the sound are the four 220 Ohms resistors (the 1KOhms resistors that we play with in the stock B1) at the output stage. Lots of people have tried exotics and hear difference in the final sound. Kiwame, Takman, audio Note, etc are some names I remember having come across. So hotrodding is one half of the story - resistor rolling is the other half

BTW, is there a separate, general purpose board/kit available for a Salas shunt reg?

 

[jls001]

Shunt regulators are kind of heaters same like class A amplifier But these heat sinks are monstrous.

Yeah, they're monstrous for this purpose:lol:

This pair was for MyRef Rev C build. It was cut for the side panels. So if I put it inside the cab (as the width of the board is quite narrow), the height cannot be accommodated. I have to think of some alternative. Also, there is no way the cab can accommodate the 130VA toroidal. So may be a small cab for the toroidal transformer is needed. It's getting complicated

 

[magma]

why are you hell bent on the heatsinks to form the panel sides

70% amps with the heat dissipation you need have their sinks fully accomodated INSIDE the cab

just provide enough venting below and above the sinks on the base and top panel of the cab
i dnt see a problem

then everything can go in one cab

 

[baswamin]

Hello jls,

There is a general purpose board, one for low voltages and one for the higher. The one I bought is seen in this link.

GB Thread for Salas SSLV1.1 BiB shunt reg - diyAudio

I was planning of building +15-0-15V supply using this for preamps and hence I mentioned it.

Thanks

N
BTW, is there a separate, general purpose board/kit available for a Salas shunt reg?

 

[keith_correa]

It's getting complicated

Always does!

 

[omishra]

It's getting complicated

Always does!

There was my thinking to get essence or core of DCB1 separated from surrounding. So I created basic stuff.

Now shunt vs linear regulator - the novice people can imagine a water pipe which flow water from left to right

Linear Regulators are in series like valve in below image depicts.

It controls flow and regulates pressure.

Same happens to electric current and voltage.
Pro: Simple, easily configurable and quite like LM317/337.
Con: noisy with basic implementation like 78xx/79xx;adds some additional loss and resistance (cause of small heat loss) to current we call impedance.
e.g. LM78xx, 79xx, 317, 337 etc

For shunt regulators its like below. In any case you want output to be constant. So whatever extra voltage fed from left side input just dropped to sink so that output remains constant.
(see the leaking pipe analogy)

Output is regulated in a way that extra power is shunted to ground (dissipated into heat). So you get stable output.
Benefit: Low impedance of PS, low ripple.
Con: Inefficient and limited current.

Benefit vs cost, my vote goes to simple linear PS with with additional caps which make it quite (ineffective low noise) in audio line level circuits.

So this was idea I took from all this designs floating around me. I went for reusing my LM317/337 based CRC and LCL filters with additional caps on output.

Now I want Joshua to correct me with his experience of both kits. I am eager to learn from his verdict. cost v/s benefit.

 

[jls001]

why are you hell bent on the heatsinks to form the panel sides

70% amps with the heat dissipation you need have their sinks fully accomodated INSIDE the cab

just provide enough venting below and above the sinks on the base and top panel of the cab
i dnt see a problem

then everything can go in one cab

Now I have come around to accepting that line of thought. Earlier, I found it hard to accept heatsinks stuck inside the cabinet, mainly because they lose out on air circulation from the surrounding space. And I guess I was stuck with the image of monstrous power amps with fearsome heatsinks sticking out from the sides.

As you suggest, ventilation on top and bottom panels should do the trick. Even my current power amp has the heatsink hidden away inside.

 

[jls001]

Small progress report: I ordered the correct sized heatsinks. Now it is being anodized. Delivery early next week.

Thanks magma for taking me to a heatsink treasure trove

 

[jls001]

Some progress report pics on the cabinet for my Salas Hotrodded and Magma's DCB1:

1) Cabinet for Salas DCB1:

2) Lots of slots on the top plate to allow good air circulation:

3) Back panel:

4) Milled side wooden panel. The wood is milled from one surface to nearly half the depth, and then from the other surface to nearly half the depth of the wood, to create grille holes. Note that the outside surface of the wood has horizontal slots and the inside has vertical ones.

5) Rear panel painted and laser printed with labels:

6) This is magma's DCB1 cabinet. Top plate has much lesser slotted holes for ventilation. In fact it's hardly needed for a regular DCB1. Note the source selector switch placed on the rear panel. This is to reduce unnecessary wire run. Both the omishra DCB1 board and the Salas Hotrodded DCB1 board are single input boards, so we are using a simple DPDT to switch between two inputs. This avoids complicated source selector electronics though it may limit the number of inputs. Also, the incoming signal passes through the source selection DPDT switch and therefore may have a bearing on the sonics. Haven't tried many types of DPDTs but hopefully it shouldn't be the bottleneck.

7) Front panels - they're different as I need power switch on the front panel and magma doesn't want it. Volume knob positions also differ mainly because of the placement of the buffer boards:

8) Test fit of bracket for mounting volume knob extender. This is to keep the wiring from the DCB1 board to the pot as short as possible:

9) Footers for magma's cab:

10) The two cabs:

On magma's DCB1, for internal wiring he wants to use multistranded copper wires with silver coating and teflon insulation. I am planning to stick to CAT6 wires. Any idea for or against either, from sonic standpoint? Has anyone tried SATA cables for internal wiring? I know I have had lots of trouble getting secure connections with CAT6 wires but it usually boils down to dry solders due to lack of proper preparation of the wires before soldering. I now additionally have a nice solder paste which I plan to use for this build, so I am anticipating things to go smoother this time.

PS: these cabinets are magma's design and build.

 

[keith_correa]

On the back plate, what does CH1 & 2 expand to? "Choice" 1 & 2?

Aren't DPDT switches available in a rotary type? That way you could have used a knob in the front to control the switch and mounted the switch with an extender the way it's done for the volume pot.

 

[magma]

you are right keith
But it was a personal aesthetic choice for me

prersonally i didnt like the contacts on the rotary switchs that were availble to me
plus i personally didnt want anything other than the vol pot on the front panel - "aesthetic reasons for me"

two pots on either side look pretty generic for my personal taste

thats personally why i didnt use them on MY cab

i dunno what joshuas reasons are though
though i think joshuas layout probably makes a difficult and odd position for a rotatry knob - no symmetry etc

josh wanted the salas board and sink ti be away from the PSU
that meant both components had to be set on extreme ends

this left out only the centre for a pot

 

[jls001]

On the back plate, what does CH1 & 2 expand to? "Choice" 1 & 2?

dhinCHak 1 and 2

 

[jls001]

The layout for my Salas DCB1: