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Building a symmetrical psu B1 buffer
Building a symmetrical psu B1 buffer
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Old 10th April 2010, 07:11 AM   #1281
ra7 is offline ra7  United States
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Building a symmetrical psu B1 buffer
hey, where are you guys sourcing your pots from?
I'm having a hard time getting alps rk27 @ 20k for a reasonable price.
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Old 10th April 2010, 10:08 AM   #1282
regiregi22 is offline regiregi22  Europe
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Quote:
Originally Posted by ra7 View Post
hey, where are you guys sourcing your pots from?
I'm having a hard time getting alps rk27 @ 20k for a reasonable price.
yeah, they are really expensive out there. I boughtm ebay an stteped attenuator and soldered all the resistors by my self. It was a bargain, but now I understand why. It fails sooo much times, really bad contacts and suddenly on channel stops sounding. Be aware with extremely cheap products.
I am waiting for a Lightspeed to arrive, it cost a bit more than a good pot to implement, but seems to sound far better that pots.
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Old 10th April 2010, 12:12 PM   #1283
woodturner-fran is offline woodturner-fran  Ireland
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look for seller "gigaworks" on ebay for what looks like a cheap POS stepped pot - but it actually sounds very good and is a drop in replacement for the alps.

About 10-15USD

Fran
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Old 10th April 2010, 02:03 PM   #1284
sutantoroy is offline sutantoroy  Indonesia
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Building a symmetrical psu B1 buffer
Quote:
Originally Posted by vgeorge View Post
What temperature did you have on the fets?
I have 2 other shunts and an F5 running hotter than this and survived previous Greek summer with no AC!
Not measuring the nominal, but quite hot that i cant touch it continuosly more than 5 seconds before failed. At the end, the transistor isnt going hot again just warm, then i measured the resistance between the pins, there is thing i said before.
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Old 10th April 2010, 04:32 PM   #1285
vgeorge is offline vgeorge  Greece
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Building a symmetrical psu B1 buffer
Well, I can touch it more than 5 seconds.
Were the fets well insulated from the heatsinks, if you used one common for them?
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Old 10th April 2010, 05:31 PM   #1286
ra7 is offline ra7  United States
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Building a symmetrical psu B1 buffer
Thanks guys!
I bought the gigaworks pot. Let's hope it's good.
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Old 11th April 2010, 08:16 PM   #1287
william2001 is offline william2001  United States
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Alright, "without pics it didn't happen...", so let's try this.

Some highlights:
- LDR attenuator (can I say Lightspeed?), powered by Salas mini-shunt (4.86V)
- 2 buffers, (1 hypnotize, 1 mesmerize). Flexibility for my bi-amped system (drive PLLXO's, sum to mono, etc.) Have a single powered sub running at the moment but plan to build cabinets for my Seas Excel W26's eventually (crossover at line level below 300 hz).
- 4 inputs, simple intuitive LED indicator on front to show selection, pic shows "input 3" is selected. Controls work great, volume typically stays in the 10:00 to 12:00 range at my listening levels. Orange LED indicates center of the LDR range for long life.
- Aluminum mesh top gives a glimpse of the beast within. Looks awesome at night.
- Increased CCS to just under 100mA (20 ohm, 2 watt at R1), heatsinks only warm, could be increased more, no other "mods" yet.
- SOUND?! Incredibly dynamic and transparent, as advertised. I'm all for "simple as possible" but can find no drawbacks to replacing my "passive pre" with this, only enormous improvement in all areas. Actually shocked at how much better everything sounds. Even sounds fantastic at low volume settings. I can very easily route the output of the attenuator straight to the ouputs bypassing the buffers completely if I wanted (everything on connectors), but have no reason to.

Thank you Salas, CRT, georgehifi (Lightspeed), Tea-bag, udailey, and all others that made this possible. This is one wicked preamp....
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Old 11th April 2010, 08:24 PM   #1288
william2001 is offline william2001  United States
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the back... 4 in, 2 out
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Old 11th April 2010, 08:30 PM   #1289
william2001 is offline william2001  United States
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inside...
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Old 11th April 2010, 09:12 PM   #1290
woodturner-fran is offline woodturner-fran  Ireland
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Lovely build william2001!!


Well done

Fran
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