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GB for Salas Folded Simplistic Phono PCB

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LucasAdamson

LucasAdamson

Member
Joined 2009
Your suggestion to read Load the Magnets!!! - [English] was particularly useful Salas, not least because he uses my cartridge as his test case.

I will take your advice when you said:

"For circa 5mV MM cartridge don't populate Q2 or R3.

Use:
91R for R2
5.6K 1W for R13
1.8K for R4,
for 40dB gain and proper overload margin.

Use 100nF C3 only value when with MM.

Choose Q1 between channels from a 10.5-12.5mA range at 5% IDSS pair tolerance."

So make the BOM changes. Use 100pF C2Y straight away as I doubt the RIAA treble will need further taming with MM. That's the simplest way. No variables.

There is no Rload guide per se, just your preferences. Sure thing is you got R1 steady and 4 switched positions paralleling it to take advantage of in various ways. Some examples:


INPUT RESISTORS R1 - Rx1-Rx4

You can use:
100K R1
33K RX1
47K RX2
91K RX3
330K RX4, so to can go 25K 32K 47K 77K with 1, 2, 3, 4, when that DIP switch position is ON alone and 100K when all OFF.

By mixing more than one ON positions you can create many more intermediate values too. Just stick the DMM measuring kOhm across the input when power is down and play. No calculations.

Or use the switch just for CX capacitors. Or use less RX positions and reserve one or two positions for CX. Your TT cable will already have 150pF remember. But read this article first: http://www.tnt-audio.com/sorgenti/lo...magnets_e.html"
Click to expand...

Based on the article findings, I will use:

R1 100K = 100K
Rx1 47K = 32K
Rx2 91K = 48K
Rx3 220K = 68K
Rx4 330K = 77K

Or maybe use Rx1 for an input cap substitute, as they do seem to have as much effect as the resistors.

Many thanks as ever!
 
Tea-Bag

Tea-Bag

Member
Joined 2006
Paid Member
The GB for the Salas board is open for payment up until 11:59PM EST 8/30/2015.

Payment is via PayPal invoice only. You will need to send me your paypal email via private message for me to start this process. Then I will invoice the parts you requested from the spreadsheet. If you reply to this email - cut out some of the existing text, otherwise the message is too big.;)

Customs forms
DO NOT ask for me to fudge up a customs form with really low amount. These are based on reasonable wholesale price.

Shipping

In general boards are a set costs, and mini kits are built into the shipping costs and larger full kits are 10.00-12 to ship. Starting price for shipping is 8.00 for just a small board and can rise from there.

The boards will ship around 2-3 weeks after the GB closes typically. The boards need to be ordered, I don't have them on hand.

Folded Simple Phono Preamp

proto_twin.jpg

Per board cost is $52.00

Link for first post for build guide
http://www.diyaudio.com/forums/grou...-folded-simplistic-phono-pcb.html#post3615620


RAW Supply details -Use before RIAA board as pre power supply.

$15.00 for PCB

IMG_1630.jpg


MiniKit BOM section. This links goes to full details of all the parts included in the kits and there respective positions on the board.
http://www.diyaudio.com/forums/blogs/tea-bag/741-salas-board-minikits-full-kits.html
 
T

tmegaard

Member
Joined 2005
I am building the Salas RIAA. To match the diodes I am using the circuit described in the building guide with a 9V power, 1k5 resistor and test each diode. It says to match triplets to 5,8V +/- 2% and quads to 7,75 +/-1%. With this circuits (which gives approx 5mA test current) I get 1,88-1,90 on all diodes (from the mini kit). That means the suggested voltages will never be reached.

Does it matter? Comments?
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
I had used little stronger than average LEDS as it was my then stash when measuring the prototype hence those numbers. Those were varying much more between samples than yours by the way. Many DIYers had built FSP copies with bit less final voltages for the LED groups since then with no problems as it proved. More important is to match them fairly well.
 
Tea-Bag

Tea-Bag

Member
Joined 2006
Paid Member
tmegaard said:
I am building the Salas RIAA. To match the diodes I am using the circuit described in the building guide with a 9V power, 1k5 resistor and test each diode. It says to match triplets to 5,8V +/- 2% and quads to 7,75 +/-1%. With this circuits (which gives approx 5mA test current) I get 1,88-1,90 on all diodes (from the mini kit). That means the suggested voltages will never be reached.

Does it matter? Comments?
Click to expand...

Can you provide a picture? Later mini kits included matched kingbright units. It may be that your not getting enough juice to them. Not sure if a 1k resistor will make any difference here. I think matching is important both in % and forward voltage.
 
T

tmegaard

Member
Joined 2005
At what current are the later minikits matched? I have a kit with 40 LEDs and they all measure from 1,88-1,90V. I use a dual 30V/3A lab supply and a Fluke 289 multimeter so the test equipment is adequate, but I may increase the current? (by increasing the voltage). I think its best to match them at the current that will occur in the salas circuit, but I don't know that current so I stuck to the 5mA as described in the building guide. My minikit is 2 years old from a group buy here in 2013 or maybe early 2014. If I change the current I may hit the curve at the wrong point. I tested it with 30V supply (close to 20mA) and got Vf at approx 2V. Some guidance will be appreciated.

What do you want a picture of? The test circuit? It is a lab power supply (9V) with one resistor (1k5) in series with the LED and the voltage across the LED is measured very exact. This circuit will give approx 4,7mA current (7,1V/1500ohm). Btw a 1k resistor will increase the current with 50% in this circuit.
 
Last edited:
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
The 2SK117 JFETS that you are going to use feeding those LEDS when on the PCB are the exact current sources, each for a group. The 9V & 1.5K test looks for simulating a 4-5mA state. Since Vf won't change that much when having about there JFETS. If looking to be super exact measure each LED driver K117's IDSS, designate it a place and measure belonging groups of LEDS with different matching CC limit from your lab supply. If its not an accurate down to mA lab PSU model, use the K117s themselves as current sources G +S to LEDS, D to 10Vcc 0.02A CC limit. If by any chance having the popular Rigol DP-382 PSU keep in mind that it shows 1mA off in excess. Scaling 1.1mA as 2mA etc.
 
Tea-Bag

Tea-Bag

Member
Joined 2006
Paid Member
GB ENDING 8-30-2015

LAST day for Group buy. Please pay invoices by 11:59AM EST. If you want to join GB, please PM email address for paypal invoice to be sent to you, and fill out spreadsheet with desired product. I will send an invoice due today. Thanks to all those who have participated!!
 
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