very nice rodeo dave!!
I was looking at these as the spec is rather interesting and they look really cool, but for now i'm going with 7r5 mills 5w PCX are taking ages to get their **** together with my order, guess this sale has them run off their feet.The power resistors I used are non-inductive planar 10R 5w thick film resistors (BI Technologies BPC5100J).
Thanks qusp! These resistors really seem to be quite nice. They sink the heat nicely and look swell. They come across pretty brittle though, being deposited on a ceramics plate and all. I'll be very likely using them in future projects again. I wonder how they'd perform directly in the signal path.
Meanwhile I made a quick PSU for the DCB1. It's simply a metal box housing the transformer, a fuse and a thermistor, plus an X2 cap. The transformer is a traditional E-I type with two secondaries with several taps (0-10-12-15V, twice). It's rated 25VA (0.8A per 15V winding) and, if you believe the stamp on it's bottom, was made on August 23rd 1982.
It's dead quiet, gets slightly warm and I have several of them, which is good since I plan on making several DCB1 buffers.
The problem with the oscillating relay apparently was solved by a 470nF cap between C and B (pin 1 and 2) of the BC547 that I am using instead of the BC517. I can't see the relay doing any funny stuff on my scope anymore, and neither anything audibly strange during power-up happens when the buffer is hooked up to my amp.
And since I'm using the DCB1 purely as a buffer without a volume control I paralleled the 221k resistors with 20k underneath the board to get the input impedance within the desirable range.
The orange blob you can see in the picture of the underside of the pcb is a 100nF cap at the output of the 7812 (and it has been there before the final mods so it's not related to the relay stopping to oscillate).
Oh, and for interconnects I'm using RG316/U if someone wants to know.
Meanwhile I made a quick PSU for the DCB1. It's simply a metal box housing the transformer, a fuse and a thermistor, plus an X2 cap. The transformer is a traditional E-I type with two secondaries with several taps (0-10-12-15V, twice). It's rated 25VA (0.8A per 15V winding) and, if you believe the stamp on it's bottom, was made on August 23rd 1982.
It's dead quiet, gets slightly warm and I have several of them, which is good since I plan on making several DCB1 buffers.
The problem with the oscillating relay apparently was solved by a 470nF cap between C and B (pin 1 and 2) of the BC547 that I am using instead of the BC517. I can't see the relay doing any funny stuff on my scope anymore, and neither anything audibly strange during power-up happens when the buffer is hooked up to my amp.
And since I'm using the DCB1 purely as a buffer without a volume control I paralleled the 221k resistors with 20k underneath the board to get the input impedance within the desirable range.
The orange blob you can see in the picture of the underside of the pcb is a 100nF cap at the output of the 7812 (and it has been there before the final mods so it's not related to the relay stopping to oscillate).
Oh, and for interconnects I'm using RG316/U if someone wants to know.
Attachments
The capacitor was the patch before the BC517 was deemed best and made the first BOM. It does the same job on any account. No need to get the Darlington any more if its not easily accessible. Looking like the PSU coming together well in a box. What will be the application? Active crossover?
yeah I need to do the same thing with mine WRT the inputZ, as i'm also just using it as buffer as I run digital volume on my dac. i'll probably end up with TX220Z for the 7.5-10R and TX2575 for the 221K/R, but mills and PRP are as far as I go before finding the best current and deciding if I like this in the chain. got some conrad sinks on order for my balanced build
Hi,
are any of these good enough for the hot rod 10ohm edition for the dcb1 buffer?
Standard Heat Sinks Found
Thanks,
JG
are any of these good enough for the hot rod 10ohm edition for the dcb1 buffer?
Standard Heat Sinks Found
Thanks,
JG
This one says it will rise 20C over ambient with 2W. Looks it will do it for one Mosfet each. Standard Board Level Heat Sinks
Would these be suitable for the DCB1 (when matched):
RED Standard 3mm LEDs Pack of 50. UK on eBay (end time 16-Dec-10 14:14:16 GMT)
Cheers,
- John
RED Standard 3mm LEDs Pack of 50. UK on eBay (end time 16-Dec-10 14:14:16 GMT)
Cheers,
- John
I got them, and just as I thought some of the stuff on board gets in the way.
Should I hack away at the heatsink, or what?
is it too late to bend the FETs outward from the board(ie the legs are already cut short), that would be the best solution (unless there's no room).
Would these be suitable for the DCB1 (when matched):
RED Standard 3mm LEDs Pack of 50. UK on eBay (end time 16-Dec-10 14:14:16 GMT)
Cheers,
- John
These need to be the 20ma dissapation type. I am not sure if these are.
is it too late to bend the FETs outward from the board(ie the legs are already cut short), that would be the best solution (unless there's no room).
I could bend the Fets backwards. I haven't made a decision yet on what to do.
If I do that, I might have to drill another hole in the heatsink. It beats using a dremel to carve away at the heatsink.
These need to be the 20ma dissapation type. I am not sure if these are.
Damn I should have checked that first - I'll email the seller.
I have just asked Spencer for some matched 2SK170BLs for the DCB1. He said he can provide them matched to within 0.2mA idss. Is this tight enough matching for this project?
Thanks,
- John
Would these be suitable for the DCB1 (when matched):
RED Standard 3mm LEDs Pack of 50. UK on eBay (end time 16-Dec-10 14:14:16 GMT)
Cheers,
- John
Yellow & green leds preferred, red a bit too noisy. Avoid blue ones.
Damn I should have checked that first - I'll email the seller.
I have just asked Spencer for some matched 2SK170BLs for the DCB1. He said he can provide them matched to within 0.2mA idss. Is this tight enough matching for this project?
Thanks,
- John
That's pretty good for a quad I guess. It's not going to kill anything to have DC offset <10mv IMO. Better matched better sonically.
Yellow & green leds preferred, red a bit too noisy. Avoid blue ones.
Thanks for that - I guess I'll sell on my red LEDs.
Any preference for the clear, ultra-bright or diffuse types of green LEDs other than appearance?
- John
Last edited:
Any preference for the clear or diffuse types of green LEDs other than appearance?
- John
I thought the IR and Red LEDs were quieter than the shorter wavelength LEDS.Yellow & green leds preferred, red a bit too noisy. Avoid blue ones.
Erm does that mean no for both kinds, or it doesn't matter whether one goes with clear or diffuse?
Putting it another way as I'm finding all this a little confusing, what type/colour am I better off going for:
Green or yellow - clear or 'coloured plastic' type?
1.8 - 2 forward voltage
20mA dissipation
- John
- Home
- Source & Line
- Analog Line Level
- Salas hotrodded blue DCB1 build