Salas hotrodded blue DCB1 build

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I am using PRP Audio grade Metal Film resistors, which cost 30c each. The price/quality ratio for these is unsurpassed, period.

I think it's pretty ridiculous to spend that kind of money on resistors before you've let the circuit settle in - like using $30 silver/gold film caps in a power supply or gold wiring.

For me, such resistors would be a potential tweak for a year or so down the road, if I felt the need. That way you can hear for yourself if you've wasted you're money or not.

I agree with your comments re PRP. However, after listening to Kiwame, PRP, Takman Rex, Caddock MK132 and TX2575, I vote for these in this circuit.
 
well at least we (Tea Bag) got the most expensive part - relays
my basic Idea Is to switch shunt pair of resistors conected to 2 NO contacts of one tq2 relay
rotary switch will power only one shunt pair at the time
the only problem Is that for each step will need two tq2 relays - unbalanced and four when go balanced
 
This is the question I was asking before. From what I understand the configuration you propose is good if you need to keep the impedance constant. But if you have the buffer you do not really need, and you can have a shunt configuration, that let you use half of the relays. Am I correct ? Mostly if you use two buffers, one before and one after. The source and the amp will never know what is in the middle.

D.
 
this Is what am talking The relay-switched attenuator volume control

It Is shunt type - the signal pass at only 2 resistors at the time and relay contacts
and gives constant Impedance
all other volume controls I have seen pass signal through many resistors / relays and are not of Interest to me
the only problem here are count of relays - but In practice we only listen to not more than 16 step of attenuation
 
what is the effect on the source if the load impedance varies?
How much can it vary for no audible effect. Must the load impedance stay exactly the same for
constant Zin Is good for source
to hold true.

Let's take an example.
Rin =100k for power amp
R of pot = 20k
Rs = 200r
Capacitance of cables 100pF

At maximum volume (minimum attenuation) the load is 16k667
At minimum volume (maximum attenuation = -60dB to -100dB) the load is ~20k

What effect does this change in load impedance have on the source?
Is it audible?

which arguments have swayed you towards an attenuator with a varying output impedance?
What makes that version attractive to you?
 
Vishay Z-Foils. TX2575. I dont think you'll regret the investment, especially if there is something else in their first to try.

Direct from texas instruments I get them for for about 10.00 each before shipping and handling. That may be another $10.00 for that. Maybe more for asia shipping. Anyone can order from there I think, even just 1 resistor.

Use caddock for 220k, 1M anything else IMO.

yep excellent resistors, but I would also let the circuit settle a bit before trying them, although you really cant go wrong with them IMO. they are 10 each for their plain vanilla 0.1% overall value match but also go up in price as the value goes up, for a 500k will cost more, for 0.05% is about 14 and for 0.005% is like 19. then you can pay for them to be matched to the same degree as a relative match to each other in pairs or quads. they also sell the Zfoil power resistors at up to 5W rating and numerous other exotic types of precision R's.

another vote for PRP here tho, fantastic resistors at a great value plus they look sweet in red

caps on the other hand I would definitely wait to see if the system needs tuning one way or another.
 
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Matching is irrelevant here, its for instrumentation applications and fighter jets. Don't pay for such in the DCB1. It does not have differential ultra low noise sensors or something. The audio part resistors just terminate impedances and buffer cables. Influential but for material properties, not value accuracy. Ask for their worse tolerance possible and best quote.
 
Haha, of course its irrelevant Saias; I mentioned it more out of interest. I wasnt suggesting the highest degree, even if we could get the components and signal from before this point perfectly matched, it would be overwhelmed by a touch more solder in a joint here, or a couple cm of wire in the cable there. but since when has it been totally about audio quality, if I get them i'll get the 0.01% global and relative in quads because I can and because it makes me feel better :D the highest degree match global and relative in quads is insanely priced, but i'll go the next one down because I have a mental problem. 0.1% is the lowest
 
0.1% accuracy to an arbitrary and subjective value is in the "Mundorf unobtanium plated fairy wings in virgin's blood capacitor" league. You might as well have you're circuit board remade in Gold. Silly.

Experimenting with different values of PRPs might give you more mileage. Sorry, I'm in the PRP fan club now. So good! So cheap!
 
0.1% accuracy to an arbitrary and subjective value is in the "Mundorf unobtanium plated fairy wings in virgin's blood capacitor" league. You might as well have you're circuit board remade in Gold. Silly.

Experimenting with different values of PRPs might give you more mileage. Sorry, I'm in the PRP fan club now. So good! So cheap!

i'm wondering if you read my post at all, it seems to be your native tongue. in order to get less than 0.1% Zfoils, I would have to pay them a custom fee, do you suggest that I do this? paying them more to give me less seems a bit strange does it not? 0.1% is the lowest and cheapest matching they come with. now THAT would be silly. also you might be able to see my recommendation for and love of PRP a couple posts up.

I doubt that their tooling is even capable of it, they are laser trimmed. I suppose I could put 220 through a random number generator and specify 219.7, 220.8, 219.2 and 220.3 in order to simulate a 1% degree of matching :D
 
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Sorry Qusp, I wasn't referring to you at all - I read already that you agreed with Salas, so I knew that you were not personally chasing that degree of tolerance. There are people, however, that build a circuit without trying to understand it much, and then just throw money at it's shortcomings.

I'm a novice, but it has become quite clear to me that there is a lot of snake-oil around, and boutique parts are often a big part of that - not always, but often. Most of what we hear is design and implementation anyway. Experimenting with resistor values, as opposed to "value" is really the wise form of modding, in my opinion.

Anyway, no offence intended whatsoever. :)