Salas hotrodded blue DCB1 build

Ok, been stuffing the boards with parts I have available. If we are looking at the board horizontally on top right IRFP240 it looks as if there is an insertion hole missing for one end of the 470r resistor.

Also, the BOM states that there are 4 sk170 matched, where on the board do they go?
 
Ok, been stuffing the boards with parts I have available. If we are looking at the board horizontally on top right IRFP240 it looks as if there is an insertion hole missing for one end of the 470r resistor.

Also, the BOM states that there are 4 sk170 matched, where on the board do they go?

Concerning that 470R resistor, the pad is there. However, it is positioned on its end instead of mounting flat against the board. This was done as a compromise for the board layout.

The matched 2SK170's are in a row near the muting relay marked 4x 2SK170BL. You will want to keep the the matched FET's together with one set on each side. They are arranged so one set will have the flat side pointing to one side and the other set reversed from that. I believe that if you have a set of FET's where one has a slightly higher Ids than the other (eg. 7.7 & 7.8 Ids) then you place the higher Ids (7.8) in the middle of that row. The signal FET (7.7) is on the end of the row.
 
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I believe that if you have a set of FET's where one has a slightly higher Ids than the other (eg. 7.7 & 7.8 Ids) then you place the higher Ids (7.8) in the middle of that row. The signal FET (7.7) is on the end of the row.
there was an earlier poster who claimed that he got better sound by running the amplifying FET at a bias above it's Idss.

I disagreed then and still do now.
A jFET follower will tolerate some higher current running during signal induced high Vgs, read Curl. But there is a big downside to using a high bias at above Idss and then applying the signal induced Vgs sending current even higher.

I would much rather run the bias at 95% of Idss rather than set bias to 105% of Idss
What the B1, as proposed by Pass, does is run the FET follower at very near but not above 100% Idss.
 
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Also, the BOM states that there are 4 sk170 matched, where on the board do they go?

Middle ones are to be the (very slightly) lower IDSS ones between matched pairs. Example.

Please make all assembly questions to the building thread so we keep them together in a known place.

P.S. The new board & its circuit we talk about for people bumping here to understand, are in the pictures below:
 

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diyAudio Chief Moderator
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To understand, your question is about opinions in parts quality decisions? If yes, the members will surely have comments.

*Here I upload the general BOM guide too so it can be found in this thread as well.
 

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The BOM has too many "Your Choice"

Much confusion between "Hot Rod" and no Hot Rod build, where the Matched jfets are mounted vs unmatched.

The board has too many holes and not labeled as most boards, Building Uriah's

MyRefC or Pass B1 I had no confusion. This Blue Board may not be confusing to most but it is to me.

A Build Manual with pictures would really help.
 
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The your choice stuff is about parts ''quality'' not values. We can't recommend pricey parts to everybody. It works without electrical differences from generic to ''Rolex''.

There are options between high CCS, low CCS, reg only, full buffer. Matched fets are the quad behind the relay.

Big diodes and big 10W 10R resistors and big heatsinks make it hotrod. Small diodes, 47/47R small resistors, mini heatsinks make it regular.

Tea had a blog I think showing the prototype constructed.

Blue DCB1 is not a kit, its a better board for a very extensively discussed project. Has its options, and its very easy to figure. All builders are happy to explain specifics.
 
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I think a point of confusion that will come up is the diodes,
mount only TO-220 or the smaller MUR-120 type. I personally would recommend the TO-220's regardless. About any TO-220 diode will work if being used for a buffer. MUR-860, MSR-860, IXYS has several types that I like.

We also have the addition of the 1R resistors in the supply, which is not on the BOM.
I don't believe they are necessary, and can be jumpered if the offset in power supply is reasonable. Salas can add to this I hope.
 
The only part that threw me off was the 470r resistor that is to be standing. If I had looked underneath the board and looked at the trace it would have made sense.

Salas, I am going for the hot rod version of the build. You just stated in your post above to use 10watt, is the 5watt still applicable?
 
Mouser is out of the MUR120 rectifier diodes (will be in stock by the end of this year!?). Would it be okay to substitute a "fast" rather than "ultrafast" diode with the same ratings? They have plenty of the fast 200V 1amp versions: their part number: 863-1N4935RLG.

Or, if someone can recommend another supplier (in the USA) who might have the little buggers in stock?

Thanx,

Neil
 
Mouser is out of the MUR120 rectifier diodes (will be in stock by the end of this year!?). Would it be okay to substitute a "fast" rather than "ultrafast" diode with the same ratings? They have plenty of the fast 200V 1amp versions: their part number: 863-1N4935RLG.

Or, if someone can recommend another supplier (in the USA) who might have the little buggers in stock?

Thanx,

Neil

Why not use MUR860?
 
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We also have the addition of the 1R resistors in the supply, which is not on the BOM.
I don't believe they are necessary, and can be jumpered if the offset in power supply is reasonable. Salas can add to this I hope.

They are handy resistors so to measure Vdrop across them and translate directly to mA. Having them fitted may be useful indicators in some trimming Vout cases. Not strictly necessary.