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Old 23rd July 2008, 09:46 PM   #271
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Default Re: 25V caps

Quote:
Originally posted by Diomedian


I wasn't thinking and ordered a 24V regulated wall wart, and 25V 15000uF caps for the power supply. Would anyone think it's a bad idea running the caps this close to their limit?


I'd suggest checking the voltage of the wall wart. There's no guarantee that it will actually be 24V.

Grey
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Old 23rd July 2008, 11:15 PM   #272
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Dear ZenMod,

Quote:
jack pot , bingo, right thing , just go for it etc
Why do you think it is necessary to do this?
Doesn't the TVC "buffers" itself?

Regards,
M
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Old 24th July 2008, 07:28 AM   #273
h_a is offline h_a  Europe
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Quote:
I'd suggest checking the voltage of the wall wart.
Seconded. If it's really regulated you're fine. If it's not electronically regulated, or even not regulated at all, you get an unloaded voltage that can be 20%+ higher than the specified voltage.

Regularly people forget that the specified voltage is valid only at full load and wonder why they got such a much higher voltage with a lighter load

Have fun, Hannes
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Old 24th July 2008, 12:41 PM   #274
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Default Re: Re: 25V caps

Quote:
Originally posted by GRollins



I'd suggest checking the voltage of the wall wart. There's no guarantee that it will actually be 24V.

Grey

That's a good point - I've checked, and it seems to put out 30V. The supply is also rated for 400mA, and since this circuit draws nowhere near that, I guess it isn't suitable...

Is it possible to tell if it's not actually regulated or if it just uses some sort of weak regulation (I'm not sure what Hannes means by "not electronically regulated")? I paid $11 for it, but if I can send it back, I will (grr - took me an hour and a half on a city bus each way to reach the shop). Anyone have a pointer to a useable model so I know what to look for?

thanks,
-d
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Old 24th July 2008, 01:42 PM   #275
h_a is offline h_a  Europe
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Sorry to cause confusion!

I meant electronic regulation. I do not know wether marketing people already use the weak transformer regulation as marketing gimmick.

If your unit outputs just one jota more than 24V, than it's not electronically regulated.* You can build one on your own if you wish, by adding a voltage regulator and a couple of small caps. At least this would allow you to use the wall wart. But I'm sorry I didn't read the older posts, so maybe I missed something and this is no option for you.

Have fun, Hannes

*always apply at least a light load as voltage regulators require a minimum output current.
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Old 24th July 2008, 06:46 PM   #276
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As long as your power supply filter cap is rated that high, 30V will work fine.
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Old 24th July 2008, 07:32 PM   #277
Tolu is offline Tolu  Germany
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Quote:
Originally posted by supernet



Great


What are your listening experiences with them? Have you done any comparison with passive preamp solution?
Since I am a member of this forum I have the strong suspicion that everybody is just tinkering and discussing the pros and cons of a method and writing books of technical opinions but ... does anybody listens the stuff in a critical way?

It remembers me a lot when I was a little boy and had a model railway. Always building and never playing!

So, dear members: don't discuss like hell theories, talk about the sound!
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Old 24th July 2008, 07:49 PM   #278
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Default Regulation

Quote:
Originally posted by h_a
You can build one on your own if you wish, by adding a voltage regulator and a couple of small caps.
Great idea - I don't know why I didn't think of that, regulate it myself. I could have saved a lot of bother and just bopped (or shimmied, as the situation demanded) down to the Radioshack and bought any old DC wall wart. A 7824 is a lot cheaper than bus fare (since I ordered from Digikey anyway)! hehe

Anyway, I'm assuming the value of the caps aren't too critical? I've found parts suppliers reference schematics that have used 0.33uF and 0.1uF caps upstream and downstream from the regulator (respectively), and other schematics that have used huge caps. They're there to smooth out DC ripples, is that right? And since I have these giant 15000uF caps right afterwards, the regulator caps aren't so important?

Also, as I'll be dropping a few volts across the regulator, I suppose I should drop it only to 20-24V so as not to generate too much heat - would a heatsink be required?

thanks again,
-d
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Old 24th July 2008, 07:53 PM   #279
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Quote:
Originally posted by Tolu

So, dear members: don't discuss like hell theories, talk about the sound!
My B1 is currently sitting in pieces in a box, but when I rattle the box around it gives amazing, lifelike sound - especially the 2sk170s - they sound like water rushing over sand on the beach. Unfortunately though, I'd have to say the sound is most influenced by the power supply and signal path capacitors (they're just huge).

;-)

-d
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Old 24th July 2008, 09:01 PM   #280
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Hi, a newbie here,

I have just built my first amp (a p2p LM3886 chipamp) and as part of the experiments and listening tests I have realized the importance of keeping the cable from pot to amp short and using low capacitance cable. So basically I have experienced the problems caused by impedance when using "passive preamps" which is what the B1 addresses. At the same time I also learned that as some people claim, the LM3886 sounds better when gain is kept not too high at around 20db and a preamp is used to compensate.

Then I read about Mr Pass' B1 Buffer Preamp and liked its principle and simplicity. So I would appreciate your opinion/ experiences bout the B1-chipamp combination.

By the way I am running the chipamp as an integrated amp with a couple of 10 K log pots and a 20 db gain and am generally happy volume wise (the pot get close to 7 or 8 o'clock but I would not go higher as it would be too loud. My speakers are Jordan full range drivers with BSC, so sensitivity is around 86.

Thanks in advance.

Antonio
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