[SpringHalo]

Quote:

'Editing' the PCB layout for a different tube might seem simple but, as you just discovered, it's usually not. You might want to consider building tube socket adapters, which are certainly feasible, and use the same PCB layout.  There was talk about that in the thread some 2 years ago, I think. Search the thread for 'adapter' or some such thing.
 
cheers!

 


Quote:

Indeed I built the prototype 17EW8 version, but it was a point-to-point build, not 'editing' the beezar PCB. As you very well said it has the same pinout as the 12AU7 so it CAN be used as a drop-in replacement for the 12AU7, but the heater voltage will not be optimum. As you pointed out too, some simple modifications (to the MOSFET biasing resistors) can put that voltage around the 17 volts that make the 17EW8 happiest.
 
Said modifications can be found earlier in the thread (a year ago, I think?? Time flies !)
 
cheers!
 

I have gone through most of this thread, from page ~150 to present. I must have skimmed over the speak of an adapter for the PCB. I think I've come up with a few edits to the PCB, but right now they're just drawings. I rotated the 9-pin to a certain direction, but I'm worried that the tad bit of clutter around the tubes could cause unnessecary inductance. I've read your post about using the 17EW8, and that's what I'm basing the pinouts on. Much appreciated. I'll upload the sketches in a few minutes.
 
R1 would probably be moved further up to bridge at a -45 degree angle over the line connecting pin 4 and C3
 

 

 

[videoman5]

Not up on my tubes; can I use a 12AU6 instead of a 12AU7?

 

[livewire]

Quote:

Not up on my tubes; can I use a 12AU6 instead of a 12AU7?

Nope. Different animals.


 

 

[the_equalizer]

Quote:

Not up on my tubes; can I use a 12AU6 instead of a 12AU7?

As livewire showed, you can't. But you can use a 12AX7, 12AT7, 12AV7 hence why we like refering to the mod as the 12A_7 mod. I personally have only tried 12AU7 and 12AX7 but know from others who have built the amp that 12AT7 and 12AV7 also work.
 
The difference between all those tubes? The gain they will provide, as well as differences in distortion, hence a slightly different 'tone'.  Ah, there'll also be a difference in cost. I believe the 12AV7, being more rare, will be more expensive than the very common 12AX7
 
 
 
cheers!

 

[videoman5]

As livewire showed, you can't. But you can use a 12AX7, 12AT7, 12AV7 hence why we like refering to the mod as the 12A_7 mod. I personally have only tried 12AU7 and 12AX7 but know from others who have built the amp that 12AT7 and 12AV7 also work.
 
The difference between all those tubes? The gain they will provide, as well as differences in distortion, hence a slightly different 'tone'.  Ah, there'll also be a difference in cost. I believe the 12AV7, being more rare, will be more expensive than the very common 12AX7
 
 
 
cheers!

Would a 12SR7 work? I can get them super-cheap.

 

[the_equalizer]

Quote:

Would a 12SR7 work? I can get them super-cheap.

They certainly do. But it's a different type of tube (a single triode), that requires a different socket (octal). Search the thread for '12SR7'. It was user 'Logistic' who developed and built the 12SR7 version.
 

EDIT:  Ok, took a bit of searching but here's Logistic's original post.
 
cheers!

 

[SpringHalo]

After doing some searching [Actually looking at the first page in the DIY forums] I found this thread, which I'll probably use for my design. I just asked a friend, and he said he has a few 12AT7s and sockets, as well as etching resources to help, so I'm in business.

I'll probably post a build thread once I order the parts.
 

 

[the_equalizer]

Quote:

After doing some searching [Actually looking at the first page in the DIY forums] I found this thread, which I'll probably use for my design. I just asked a friend, and he said he has a few 12AT7s and sockets, as well as etching resources to help, so I'm in business.

I'll probably post a build thread once I order the parts.
 

Yes, he's also started a build log thread. He's already populated the PCB and done basic voltage testing. 
 
In this very thread, someone else has built a PCB 12AU7 SSMH I just can't remember the user name.

 

[Ikarios]

Be careful with using the 12AX/AT7 tubes - they are useable alongside the 12AU7, but the gain is very high and may make the amp unuseable beyond the first few degrees of the pot. With my 12AU7s I could barely use the first third of the volume pot before getting unreasonably loud with most headphones.
 
Head-Fi user "TestSubject" has done a stripboard version of the 12AU7, it's pretty nice. I don't know what progress he has made and if he has found a fully complete board layout yet, though.

 

[zammykoo]

Quote:

Yes, he's also started a build log thread. He's already populated the PCB and done basic voltage testing. 
 
In this very thread, someone else has built a PCB 12AU7 SSMH I just can't remember the user name.

IIRC, I think it was Fred_fred2004 who built the 12AU7 SSMH based on dsavitsk's pcb design

 

[SpringHalo]

Quote:

Be careful with using the 12AX/AT7 tubes - they are useable alongside the 12AU7, but the gain is very high and may make the amp unuseable beyond the first few degrees of the pot. With my 12AU7s I could barely use the first third of the volume pot before getting unreasonably loud with most headphones.

In attempt to increase the sensitivity of the pot, could I change R16/R17 from 50k to 100k. Or would that still be not enough? I'm using ATH-M50 36ohm (rated for 32ohm, but I recently measured 36.).
 
The caps that I got from a friend are all rated at 50v, which include C1/C6, which I think 1000uf should be fine (increases the lower frequency response? Or is that C3/C5?) He also has C3/C5 , which are 470uf @50v. Are C2/C4, C3a/C5a able to be substituted by .22uf/50v film caps? Is there a point for them being rated for 250v?

 

[tomb]

Quote:

In attempt to increase the sensitivity of the pot, could I change R16/R17 from 50k to 100k. Or would that still be not enough? I'm using ATH-M50 36ohm (rated for 32ohm, but I recently measured 36.).
 
The caps that I got from a friend are all rated at 50v, which include C1/C6, which I think 1000uf should be fine (increases the lower frequency response? Or is that C3/C5?) He also has C3/C5 , which are 470uf @50v. Are C2/C4, C3a/C5a able to be substituted by .22uf/50v film caps? Is there a point for them being rated for 250v?

You could go to 200K - 250K on the input resistors without a problem, IMHO.  There's no reason why you can't experiment with it.  Try it in increments of 50K or 100K as you go up in your resistance.
 
If you are using the Cisco power supply, the caps should be rated at 63V, minimum, IMHO - 50V is too close with a 48V power supply.
 
C3 and C5 are the output electrolytic capacitors.  You will notice a bass improvement going to 1000uf if you are using low impedance (32 ohms or less) phones.  Grados and all higher-impedance phones are OK with the 470uf's, though, because while Grados are 32ohms, they tend to peak at 50Hz, not 20Hz.  At least, that's been my experience with several different amp designs.  All of this has to do with the physics of the RC circuit formed by the output caps and the impedance of the phones.  It forms a high-pass frequency filter and unless the cap is big enough (in uf's) compared to the headphones' impedance, bass-filtering will occur.
 
The only reason the film caps are rated for 250V is because the wonderfully performing Wima MKP10 simply come that way.  The Wima's have more or less been a bypassing standard all the way back to the original Millett Hybrid.  They also matched what I already carry at Beezar for the MAX/MiniMAX/MOSFET-MAX, so it was an easy choice.  They were picked for sound quality, not for the voltage rating.

 
 

 

[SpringHalo]

 
Quote:

You could go to 200K - 250K on the input resistors without a problem, IMHO.  There's no reason why you can't experiment with it.  Try it in increments of 50K or 100K as you go up in your resistance.
 
If you are using the Cisco power supply, the caps should be rated at 63V, minimum, IMHO - 50V is too close with a 48V power supply.
 
C3 and C5 are the output electrolytic capacitors.  You will notice a bass improvement going to 1000uf if you are using low impedance (32 ohms or less) phones.  Grados and all higher-impedance phones are OK with the 470uf's, though, because while Grados are 32ohms, they tend to peak at 50Hz, not 20Hz.  At least, that's been my experience with several different amp designs.  All of this has to do with the physics of the RC circuit formed by the output caps and the impedance of the phones.  It forms a high-pass frequency filter and unless the cap is big enough (in uf's) compared to the headphones' impedance, bass-filtering will occur.
 
The only reason the film caps are rated for 250V is because the wonderfully performing Wima MKP10 simply come that way.  The Wima's have more or less been a bypassing standard all the way back to the original Millett Hybrid.  They also matched what I already carry at Beezar for the MAX/MiniMAX/MOSFET-MAX, so it was an easy choice.  They were picked for sound quality, not for the voltage rating.

 

So I should just buy all new caps? I'm also planning on getting parts for a grubDAC, so I could grab a couple caps while I'm at it, (though they're also on mouser IIRC.. Probably ordering later today. Should I get a 100K potentiometer or just stick with the 50K?
 
Thanks!
 
 

 

[Fred_fred2004]

Quote:

IIRC, I think it was Fred_fred2004 who built the 12AU7 SSMH based on dsavitsk's pcb design

No sorry not me I used Dsavitsk's circuit but the layout was a single sided toner transfer effort of my own
 
 
 

 

[zammykoo]

Quote:

No sorry not me I used Dsavitsk's circuit but the layout was a single sided toner transfer effort of my own
 
 
 

Oops my apologies, now I remember that's your single sided pcb