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PostPosted: 29 Jun 2010, 10:06 
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Joined: 19 Jun 2010, 17:08
Posts: 71
Hi,

I've built up the stock unit. Mine has JJ EC82, wima 2.2uF and 470uF Panasonic FC for output caps.

I'm using a Noble 100K for volume control and IRF610. All stock values, instead of POT, I'm using 4.75K resistor.
Do I increase the 4.7K to lower the TP voltage level?

I have a small linear PSU set at 12V, current draw is 400mA. I measure the TP and it reads 7V, not 6V.

Now sitting at 7V, would that cause higher distortion? It sounds good but it starts to distort really bad at slightly lower volumes.
I've tried lowering the PC volume to about 70-80 but still same.

Another thing I wanted to try after the stock build, is to keep the heater at 12V and increase the +B to +24-48V. If I do so,
what value do you suggest for P1?

I'm driving a standard pair of Sony headphones. If I can get the distortion/clipping issue fixed, that would be great.

It's pretty clean, quiet, no humming, no hissing. great little project! Thank you!!! :mrgreen:


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PostPosted: 29 Jun 2010, 15:04 
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Joined: 19 Jun 2010, 17:08
Posts: 71
Hi,

is this headphone amp on ebay: New-G2-Class-Hybrid-Tube-Headphone-Pre-Amplifier-6922-

very similar in design to your NP-100V12?

What do they use to switch between 6V and 12V heaters? something has to dissipate alot of with a 24VDC power supply.


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PostPosted: 29 Jun 2010, 19:28 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
robot797 wrote:
i found a tube

the ecc85
but the distrorcion is very heel erg

and my second build doesnt work at all

all is checked and controlled and it does not woerk

i use a irf520

Robot, the ECC85 has a mu of 50, which is moderately high You will have to increase the value of the anode resistor, and the filaments should be 6.3 volts. If this is the only tube you can source, then wire the filaments in series( using two tubes), and use one triode from tube number 1 and one triode from tube number 2.


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PostPosted: 29 Jun 2010, 19:42 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
Lynxo323 wrote:
I've built up the stock unit. Mine has JJ EC82, wima 2.2uF and 470uF Panasonic FC for output caps.

I'm using a Noble 100K for volume control and IRF610. All stock values, instead of POT, I'm using 4.75K resistor.
Do I increase the 4.7K to lower the TP voltage level?

I have a small linear PSU set at 12V, current draw is 400mA. I measure the TP and it reads 7V, not 6V.

Now sitting at 7V, would that cause higher distortion? It sounds good but it starts to distort really bad at slightly lower volumes.
I've tried lowering the PC volume to about 70-80 but still same.

Another thing I wanted to try after the stock build, is to keep the heater at 12V and increase the +B to +24-48V. If I do so,
what value do you suggest for P1?

I'm driving a standard pair of Sony headphones. If I can get the distortion/clipping issue fixed, that would be great.

It's pretty clean, quiet, no humming, no hissing. great little project! Thank you!!! :mrgreen:

Even with the source voltage at 7v there should not be any distortion, you may be hearing some noise from your power supply. The only way to rule out the power supply is to use a 12 volt battery and see if the distortion ceases.

Increasing the B+ to 24 will need a value of approx 14k ohms for P1, and you will definitely need to heatsink the fets and regulators. I have done similar with another project, I used 18vdc B+ and used an LM7812 and heatsinked it to the chassis.

Image


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PostPosted: 29 Jun 2010, 22:44 
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Joined: 19 Jun 2010, 17:08
Posts: 71
Quote:
Even with the source voltage at 7v there should not be any distortion, you may be hearing some noise from your power supply. The only way to rule out the power supply is to use a 12 volt battery and see if the distortion ceases.

Increasing the B+ to 24 will need a value of approx 14k ohms for P1, and you will definitely need to heatsink the fets and regulators. I have done similar with another project, I used 18vdc B+ and used an LM7812 and heatsinked it to the chassis.

Thanks for your help. Do I need to lower the source voltage to 6V? the distortion is only when I turn the volume up higher, maybe it's clipping? Unfortunately I don't have
a 12V battery.

Do you like the sound better with the +18V and LM7812?

I bought a pair of Sony MDR-XD200 and using that with this headphone amp. Do you know which headphones can't be heard outside of the headphones?
I was listening in the middle of the night and took the headphones off, wow, I did not realize how loud they could be heard. they sound like small pc speakers.


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PostPosted: 29 Jun 2010, 22:45 
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Joined: 19 Jun 2010, 17:08
Posts: 71
Quote:
Increasing the B+ to 24 will need a value of approx 14k ohms for P1, and you will definitely need to heatsink the fets and regulators. I have done similar with another project, I used 18vdc B+ and used an LM7812 and heatsinked it to the chassis.

What value should I use for P1 for 18V supply. My psu can go up to 18V so I will try that first. I should have some 7812's laying around.

thanks! :D


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PostPosted: 29 Jun 2010, 22:51 
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Joined: 19 Jun 2010, 17:08
Posts: 71
Quote:
I have done similar with another project, I used 18vdc B+ and used an LM7812 and heatsinked it to the chassis.

from your photo, it looks like a Pass B1 buffer(?) is it a preamp that you built?


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PostPosted: 30 Jun 2010, 10:32 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
Lynx,

You should not be hearing any distortion even at 7 volts, I would check the wiring of the volume pot. From your reading of 7v 400mA that sound about right. Also recheck the values of R1 (100k) and R5 (1K) you may have them switched.

For 18v power supply I used a 10k ohm resistor, and yes that is a Nelson Pass B1 :thumbsup: I built it for my bedroom setup, with an RIAA for turntable and NP100 for headphones at night. It sits in an old gutted Dynaco chassis.

As far as headphones, you will hear music outside especially if they are "open air". You can try some "closed back" like Denon AH-D1001 or Audio Technica ATH-M50. If those are out of budget you can also go with one of my favorite budget cans the Sennheiser HD-202 for about $26. I bought the Sennheisers for my kids and also use them for while running a soundboard at Church. They do a great job at blocking out noise both in and out. My kids like the extra Bass, that most closed back headphones have.


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PostPosted: 30 Jun 2010, 10:46 
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Joined: 19 Jun 2010, 17:08
Posts: 71
Quote:
You should not be hearing any distortion even at 7 volts, I would check the wiring of the volume pot. From your reading of 7v 400mA that sound about right. Also recheck the values of R1 (100k) and R5 (1K) you may have them switched.

For 18v power supply I used a 10k ohm resistor, and yes that is a Nelson Pass B1 :thumbsup: I built it for my bedroom setup, with an RIAA for turntable and NP100 for headphones at night. It sits in an old gutted Dynaco chassis.

As far as headphones, you will hear music outside especially if they are "open air". You can try some "closed back" like Denon AH-D1001 or Audio Technica ATH-M50. If those are out of budget you can also go with one of my favorite budget cans the Sennheiser HD-202 for about $26. I bought the Sennheisers for my kids and also use them for while running a soundboard at Church. They do a great job at blocking out noise both in and out. My kids like the extra Bass, that most closed back headphones have.

I will double check again, pretty sure R1 and R5 is correct. I will bypass the pot and give it a try.

I've built a B1, it's nice sounding :mrgreen:

Thanks for the tip on the HD-202, was going to get that first but went cheap with the sony.

I'm wiring P2P, how much length of wire could I get away with when connect the output of the tube to
the gate of the FET? since there is no gate resistor, I'm concerned it might oscillate.


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PostPosted: 30 Jun 2010, 20:55 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
Lynxo323 wrote:
I'm wiring P2P, how much length of wire could I get away with when connect the output of the tube to the gate of the FET? since there is no gate resistor, I'm concerned it might oscillate.

I have used wires up to 6 inches without issue (point to point), as long as the grounds are good, you should be in good shape.


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