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NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread
http://diyaudioprojects.com/Forum/viewtopic.php?f=10&t=1799
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Author:  KrammeAcoustics [ 30 Nov 2010, 12:56 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

koogar wrote:
Had some good success today Kramme with a rectified AC transformer i thought i would try regulating it twice using two LM317's (one extra before my on-board LM317 PSU) the supply was silent :)

I used a 16 VAC 1A wallwart rectified it was 24.56v DC using the extra LM317 i regulated it to 17v then passed it on to my on-board PSU LM317 which regulated it down to 12.6

I originally tried it with a 24 VAC transformer but after rectification the heatsink i had installed got a little hot on the first lm317.

At the moment both regulators run cool at 40 degrees C each which is also a bonus.


PS: I dont mean to hijack Rogers thread with alot of talk regarding the PSU's but i still think its valid to people building this amp as not everyone has a lot of different PSU's to try and often we have to find solutions for things we have lying around

Hi Koogar

I'm glad to hear you've got success :thumbsup:

I think you've added some good info about double regulated PS to this thread. :idea: Are you using a powerresistor, to draw some current in the first lead of regulation ? Could you show us some schematics of what you've done ?

Hope i'm right, when i'm saying Rogers most likely will see your comment as valid. He use to be very open to new and constructive inputs from all of us hijackers. :mrgreen:

I see this forumthread, not only as a "how to do it", but also a thread of development. When this is said, offcourse this is Rogers baby, but i still think, we all love to nurse Rogers baby. :P

santik wrote:
ok, let just say I like the sound of this tube A and also the sound of tube B; can we do 2 tubes as preamp? parallel to each other?

inputs to the gates of both tubes and the plates of both tubes to MOSFET. possible? logical?

I think the tubes are basically one way, like a diode. isn't it?

Hi santik

I've also tried that ( in parallel ), but the only thing happening, were more hissing and distortion, no profit at all.
Possible = yes, logical = yes, but i think it won't bring anything useful to this construction. Anyway it could be fun to hear your experiences. Are you intending to try it ?

When you're saying tubes = one way = diode, i guess you're thinking of a rectifiertube (?), which also exists. But the tube for this construction is a triodetube.
Purpose:
A triode is a voltage-controlled device, in that a voltage that is applied as an input to the grid can be used to modulate the rate of electron flow between anode and cathode. The relationship between this input voltage and the output current is determined by a transconductance function. Control grid current is practically negligible in most circuits.
Text found here: http://en.wikipedia.org/wiki/Vacuum_tube

Note: The triodetube in the NP-100v12 also works as a phaseinverter.

Author:  SmittyHalibut [ 30 Nov 2010, 18:15 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

santik wrote:
both will go though a line of parallel capacitors.
using a Switch Mode Power Supply will have less hum and hissing compared to Regulated Power Supply?

The switching PS will just create ripple at a (much) higher frequency, which is a lot easier to filter.

Author:  SmittyHalibut [ 30 Nov 2010, 18:21 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

KrammeAcoustics wrote:
I've tried both, regulated PS, SMPS and RC filtered PS, for the NP-100v12. I think they all got both some good and bad behaviors. But if it comes to a choice of taste:
1. RC filtered PS ( in my ears, it's possible to create good sound )
2. SMPS ( no hum at all, but in my ears, boring sound )
3. Regulated PS ( i've tried LM7812 ...but like SMPS, i think it's boring sound )

When it comes to all, it's a matter of taste. Some people also like the sound of chokes in a PS, because they add something to the sound ( NOTE: i don't mean a choke is needed for this build. It's just to mention, that taste are individual from one person to another ).

One wouldn't think that the power supply would flavor the sound, but the ability to provide current when it's needed without dipping voltage is actually something that would matter significantly.

If I had to guess, the reason your RC filter sounds better to you is because of all the added C providing instantaneous current without dipping the voltage when your amp needs it. If you added a similarly ridiculously large capacitor at the output of your switcher or linear, for the ability to dump huge amounts of current into the circuit in an instance not for filtering hum, I bet you'd start to get some of that good sound with switchers and linears.

Chokes would make this effect worse. A chokes resist changes in current flow, so when you get a bass kick, the amp will starve for current which has the effect of dipping the voltage (read: distortion.) I think a choke would be a horrible idea. (Purely theoretical; I have never listened to an amp with a choke on the power line so I may be wrong here.)

Author:  koogar [ 01 Dec 2010, 08:44 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

KrammeAcoustics wrote:
I think you've added some good info about double regulated PS to this thread. :idea: Are you using a powerresistor, to draw some current in the first lead of regulation ? Could you show us some schematics of what you've done ?

No Power resistor Kramme

Readings from the Wall Wart were as below

16 VAC 1A Wall Wart (minimum you can use)
---------------------------
19 VAC
17.8 VAC under load

After rectification
24.5 DC
20.5 DC underload

i just plugged a spare LM317 PSU board i had kicking around into my amps onboard LM317 PSU it basicly looks like this if you include both into a schematic ( see download link).

http://alturl.com/89xqb

koogar

Author:  santik [ 06 Dec 2010, 04:03 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

SmittyHalibut wrote:
santik wrote:
both will go though a line of parallel capacitors.
using a Switch Mode Power Supply will have less hum and hissing compared to Regulated Power Supply?

The switching PS will just create ripple at a (much) higher frequency, which is a lot easier to filter.

so,
"both will go though a line of parallel capacitors.
using a Switch Mode Power Supply will have less hum and hissing compared to Regulated Power Supply?"

SMPS will be more quieter after filtering?

Regulated Power Supply, not as quiet as SMPS after filtering?

Author:  gofast [ 06 Dec 2010, 14:57 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

i've just built this amp and the sound quality is very good, but ps hum is very bad. tried both types of several wall warts. 12v gives mid hum, 18v computer switched ps gives higher hum with lots of rf interference.

will battery completely eliminate these hum?

can someone post a RC filter circuit that successfully eliminated the hum? do i use (IN-resistor in series-capacitor to ground-OUT)? what value do i start with?

Author:  obalys [ 07 Dec 2010, 11:39 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

I have problem with my amp. With 20K trim potentiometers I can drop one channel voltage below 5.5V, and other channel is 8V and it doesn't change. Power supply 12V regulated, transistors IRF510, tube Tungsram ECC82. I thought that IRF is bad and solder another - nothing changed. 8V on output cap and it doesn't react to trim pot resistance. Trim pot is good, I desolder it and check. Both tube heaters is working.
Where is the problem hide? :bawling:

Author:  koogar [ 07 Dec 2010, 19:13 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

Managed to get the POT VU/ INPUT board done today came out rather well :mrgreen:


Image

Image


koog

Author:  Gio [ 08 Dec 2010, 13:43 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

obalys wrote:
I have problem with my amp. With 20K trim potentiometers I can drop one channel voltage below 5.5V, and other channel is 8V and it doesn't change.

With some tubes the pot needs to be as high as 50k. I will be updating this on the project page shortly - DONE: http://diyaudioprojects.com/Solid/12AU7 ... 7-Headamp/

This is some info in this post: viewtopic.php?p=20345#p20345

koogar wrote:
Managed to get the POT VU/ INPUT board done today came out rather well

Great work! :thumbsup:
Cheers

Author:  gofast [ 08 Dec 2010, 14:59 ]
Post subject:  Re: NP-100v12 - 12AU7 / IRF510 HeadAmp Support Thread

i tried to build the RC filter circuit using the instruction on page number 45 of this thread.

here's what i did in two different times with two different wall warts.

Image
with 20vdc output wall wart, i connected 54ohm-4700uf-10ohm-4700uf as the picture shows and was able to drop the voltage close to 13v, but the problem was the cap and the resistor got really hot. i've seen power resistors getting too hot to even touch, but not the capacitors this hot. anyways, the rubber part of the capacitor started to balloon up so i had to disconnect it.

on the second time, i connected 18vdc output wall wart to 10ohm-4700uf and to the power input, and it acted really funny, at first, the voltage went up to almost 14vdc and then it went down slowly to 6.5vdc, and then it went back up to 12.7vdc, and after about 5 minutes, i heard a noise of some liquid shooting out of the 'lytic cap. i disconnected it quickly. the cap's blown and some liquid came out. i'm not sure if the cap is completely blown from the inside but the black rubber around the lead popped out.

when the voltage stayed around 12.7, the audio was great with almost no hum.

did i make a wrong connection somewhere? are these caps (from radio shack - 470uf 35v) defective or not have suitable rating? i've used exact parts described in page 45. what do you think is the problem here? can anyone reply and help? please?

thank you in advance for any help!

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