[bwshockley]

Quote:

Kits will be restocked probably by this weekend.  As for the PCB, there's plenty.  They've been in stock and available on the Beezar website for months ... and months.

Could I possibly switch out my Skeleton DAC for a Grub DAC and pay the difference?

 

[bwshockley]

I have another question that came to light last night.  When I first powered on and tuned my MOSFET-MAX I did not have my potentiometer installed, nor did I have any input or outputs installed.  Last night, I was messing around and forgot that I'd placed the pot on the board and I went to check my voltages across the tubes and it was much lower than the initial 13.5vdc.  At first I couldn't figure it out until I realized the pot was in.  Removing it (it was just pressed onto the board) and tubes went back to 13.5vdc.  Of course, turning the pot made a difference too.
 
So, I guess to get to my point, should the 13.5vdc bias be without the pot, or with the pot at "full volume"?  Should the pot even be making a difference to that voltage or is there something wrong?
 
Tonight I should have the last of my parts to at least test out the amp using actual input and headphones.

 

[tomb]

Quote:

Could I possibly switch out my Skeleton DAC for a Grub DAC and pay the difference?

Yes, we will work it out.

 

[tomb]

Quote:

I have another question that came to light last night.  When I first powered on and tuned my MOSFET-MAX I did not have my potentiometer installed, nor did I have any input or outputs installed.  Last night, I was messing around and forgot that I'd placed the pot on the board and I went to check my voltages across the tubes and it was much lower than the initial 13.5vdc.  At first I couldn't figure it out until I realized the pot was in.  Removing it (it was just pressed onto the board) and tubes went back to 13.5vdc.  Of course, turning the pot made a difference too.
 
So, I guess to get to my point, should the 13.5vdc bias be without the pot, or with the pot at "full volume"?  Should the pot even be making a difference to that voltage or is there something wrong?
 
Tonight I should have the last of my parts to at least test out the amp using actual input and headphones.

This used to be a common question in the old days, at least about the volume part (volume setting for biasing tubes).
 
What you have noticed is perfectly normal.  You've noticed that the pot has an impedance that the tubes can see.

  I can't remember anyone attempting to bias the tubes without the pot installed, but there's a first time for everything.  Regardless, bias the tubes with the pot installed and the volume at zero.

 

[bwshockley]

Quote:
]
This used to be a common question in the old days, at least about the volume part (volume setting for biasing tubes).

What you have noticed is perfectly normal.  You've noticed that the pot has an impedance that the tubes can see.   I can't remember anyone attempting to bias the tubes without the pot installed, but there's a first time for everything.  Regardless, bias the tubes with the pot installed and the volume at zero.

Thanks for all the help Tom. I have made the proper adjustments.

Also, tonight I final hear sound through the amp. Some Pink Floyd, Adele, and Foo Fighters. I'm not sure if I'm just biased, but it sounds great. The sound is interesting. This is too much fun!

 

[primer]

Damn it ................. I'm nearly finished populating the MAX and I just realised that I forget the LEDs.  sh#t  sh#t  sh#t
 

 

[tomb]

Quote:

Damn it ................. I'm nearly finished populating the MAX and I just realised that I forget the LEDs.  sh#t  sh#t  sh#t
 

If you drilled out the center pins from the tube sockets, it's not an issue.  You should be able to slip the LEDs right throug the socket to the PCB pads.

 

[primer]

Quote:

If you drilled out the center pins from the tube sockets, it's not an issue.  You should be able to slip the LEDs right throug the socket to the PCB pads.

 


Thanks tomb, managed to desolder the sockets finally.

 

[elctronn]

Please can I use Mosfet Diamond Buffer with symmetrical supply?

Please exist some replacement 2N5486? I can't get it.
 
Thank You.

 

[Avro_Arrow]

You can use a PN4392 in place of the 2N5486

 

[bwshockley]

You can purchase a pair of 2N5486 from amb.org/shop for US $0.50 per pair.  Not sure if you are saying you can't find them or can't receive them, but AMB ships worldwide.

 

[ModMax]

Should the MOSFET-MAX PCB be grounded to the case?  I don't think so, but I want to be sure before moving forward.  Also, I read *somewhere* that it's best if the RCA jacks make contact with the rear panel.  Is this correct?  Thx.

 

[scootsit]

Quote:

Should the MOSFET-MAX PCB be grounded to the case?  I don't think so, but I want to be sure before moving forward.  Also, I read *somewhere* that it's best if the RCA jacks make contact with the rear panel.  Is this correct?  Thx.

Having the case grounded helps block out radio noise. Allowing the RCAs to contact the metal grounds the case to the board, since the outside of the jack is the ground.

 

[tomb]

Quote:

Should the MOSFET-MAX PCB be grounded to the case?  I don't think so, but I want to be sure before moving forward.  Also, I read *somewhere* that it's best if the RCA jacks make contact with the rear panel.  Is this correct?  Thx.

Scootsit has it correct.  Another path for grounding the PCB to the case is through the center standoff - you can scrape off some of the anodizing on the inside of the case so that the standoff makes good electrical contact.  All that said, the MAXes are all very resistant to hum and interference.  Outside of the errant cell phone, I haven't seen or heard of any issue.  We know the onboard linear-regulated power supply is audiophile-quiet. 
 
P.S. the headphone jack and the volume pot also provide potential ground paths for the case, but neither are as consistent as the two paths mentioned above.

 

[ModMax]

Asked tomb this same question by email, but thought I would post it here to in case it helps others or others can offer some advice.
 
Does the following wiring diagram look correct for the MOSFET-MAX power socket to SPST switch and PCB with fuse?