[FallenAngel]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif I currently use Audio Technica ATH-AD900, which are 32 ohm and quite sensitive. My next phones, if any, will probably be Alessandro (also 32 ohm). 10R it will be.

Consider adding this later, and only if necessary, any resistor will be worse than no resistor so unless you get some kind of hum/hiss (which you shouldn't), why use it, it'll only give you an extra little bit of room on the volume control. I had absolutely no problem with 32 Ohm Grado SR225 with no resistor.

 

[Beefy]

Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif Consider adding this later, and only if necessary, any resistor will be worse than no resistor

People keep saying this...... but you can consistently read on Head-Fi and other places about how much better the ER-4P sounds when you use the 'S' adapter, which puts 73 ohms in series with the drivers. Or how the Beyer DT880 sounds better from the 120 ohm output of the Corda Opera, than the 0 ohm output.

Obviously it is phones/amp dependent, but how can opinions vary so wildly about a thing that is so simple to test?

 

[fordgtlover]

Quote:

Originally Posted by Beefy /img/forum/go_quote.gif People keep saying this...... but you can consistently read on Head-Fi and other places about how much better the ER-4P sounds when you use the 'S' adapter, which puts 73 ohms in series with the drivers. Or how the Beyer DT880 sounds better from the 120 ohm output of the Corda Opera, than the 0 ohm output. Obviously it is phones/amp dependent, but how can opinions vary so wildly about a thing that is so simple to test?

I believe the principle is that there should be as few component in the path as possible - hence the 'no resistor' view.

However, this is always balanced by the 'What's the benefit' question. Where the benefit is of greater value - you have your answer.

So, if adding a resistor does reduce some hum/hiss, and doesn't cause an even greater problem then put it in. If you don't 'need' the resistor then leave it out.

The RB14 resistors in the Max falls in to the category. Some people have some noise that they would like to address, some people add the RB14 to modify (sweeten) the output while many people just jumper it.

We all have different gear and different ears. DIY gives you choices to build things that suits your preferences and your gear

.

 

[tomb]

Quote:

Originally Posted by Migroo /img/forum/go_quote.gif Guys, I bought some 12FK6 tubes from Beezar and I'm going to swap them tonight. I'm expecting to have to re-bias the tubes, but do I have to take the same precautions with the DB bias as I did when setting up the trimmers for the first time? I don't want to risk smoking my DBs! I'm looking forward to the sound of the FK6s as the AE6s sound quite bass heavy on my Senn HD500s - a fault definately with the headphones, not the Max - but swapping the tubes to calm the bass down is a quick fix that I can't resist!! Cheers Chris

You should never have to change the DB bias again. Tubes are different. Every one of them will have a different bias - some worse than others. As long as you don't bump the DB trimmers, though, they should never get out of adjustment. Some people have been known to paint a little fingernail polish on the trimmer screw to mark it and seal it place (assuming you don't want to change it again).

 

[Phil Townsend]

Has anyone tried V Caps?

Tempo Electric : The Great Capacitor Shoot-Out

Phil
Santa Fe

 

[CountChoculaBot]

How much could I expect to pay to get someone to construct a standard build with MOSFET DB's? The BOM says it's all approx. $160... could I expect to pay $200-$250?

 

[Migroo]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif You should never have to change the DB bias again. Tubes are different. Every one of them will have a different bias - some worse than others. As long as you don't bump the DB trimmers, though, they should never get out of adjustment. Some people have been known to paint a little fingernail polish on the trimmer screw to mark it and seal it place (assuming you don't want to change it again).

Hi Tom,

Thanks for clarification. I went ahead and changed the valves - and you were right. PS and Db bias were rock solid. Tube bias was all over the place! Quick adjustment and we're back to half of PS voltage again.

The 12FK6s are great btw

Chris

 

[tomb]

Quote:

Originally Posted by Phil Townsend /img/forum/go_quote.gif Has anyone tried V Caps? Tempo Electric : The Great Capacitor Shoot-Out Phil Santa Fe

The MAX community prefers to use this reference as a baseline (Even though Doug was hard on the K42's.):

Dsavitsk's Notes on Output Coupling Capacitors

In addition, there are a couple of other famous capacitor reviews, but they all disagree on some things one way or another.

That said, the V-Cap and the reference you gave seems to follow the ideal needed for the MAX: neutral and detailed. On the other hand, so many boutique caps add a flavor that results in significant fall-off in the bass and the highs - e.g., Auricaps or Sonicap GEN II's (ironically, we used to recommend both in the early life of the MAX history). The MAX is a tube hybrid: a low voltage tube gain stage combined with a very aggressive, deep Class A fully-discrete output stage. That output stage demands the very best in open neutrality - particularly because we have to slap a giant electrolytic on the end of it, anyway. That's another factor to consider - there are no single cap positions in the MAX: they're all in a bypass mode. Bypassing does not follow hard and fast rules of typical boutique-signal-cap applications. The end result is that caps that vary from the best of a neutral, linear response have a very bad effect in the MAX.

At the same time, the MAX competes at a very low price point compared to its performance. Unfortunately, the V-cap violates that theme by a wide margin. Looking at the V-Cap price list, the 0.22uf is only $89.99!

2X of those exceeds the basic parts cost of the entire MAX!

Are they that much better than a couple of VitaminQ's sold at $3? No way. There are people who rank a good pair of VitQ's as good as the very best (see the same Dsavitsk's reference above). With that potential comparison, it makes it very difficult to justify a difference in cost of that magnitude.


Quote:

Originally Posted by CountChoculaBot How much could I expect to pay to get someone to construct a standard build with MOSFET DB's? The BOM says it's all approx. $160... could I expect to pay $200-$250?

Well, that parts cost is true in an absolute sense. However, one has to consider that up until a couple of months ago, you had to order from up to four different sources to get those parts. If you count the shipping on also adding a boutique capacitor or upgraded output transistors - then that's even more. So, that's an unlisted shipping cost potential of $30-$40, or more. So to consider a fair cost to the seller, you're closer to $200 for the basic parts cost.

Add to that some miscellaneous items such as the Volume knob, RCA jacks, wiring, case hardware, etc., and I'd say the $250 is a bottom theoretical purchase price for a finished amp. $275 is more like it as a starting point for a commissioned build, and I think that's what Nate Maher used for a brand new one he built. I know we don't count labor (

) in the Head-Fi For Sale forums, but heck - it's worth $100 to someone just to drill all the holes in that case lid!

Bottom line, yes - a DIYer would compare the parts cost to other DIY amps at $160. Buying a completely built one is a different process of adding up costs, however.

 

[Kenneth S]

Hi Tom,

How goes the integration of the Alien DAC with the Max coming along? Any luck? I am planning to begin on the MOSFET Max build and also planning to finish up the first Alien build and hook it up to the other one. Clue me in, I get electronic noise when i push the pot up to abt the 12 - 2 o'clock position. Is this something that can be fixed with a magnetic filter on the cables? How much change will the DAC make to the problem?

 

[Phil Townsend]

Thanks Tom...
I guess the first job is to build The Max...
I'll pop over and order the board.

Phil
Santa Fe

 

[tomb]

Quote:

Originally Posted by Kenneth S /img/forum/go_quote.gif Hi Tom, How goes the integration of the Alien DAC with the Max coming along? Any luck? I am planning to begin on the MOSFET Max build and also planning to finish up the first Alien build and hook it up to the other one. Clue me in, I get electronic noise when i push the pot up to abt the 12 - 2 o'clock position. Is this something that can be fixed with a magnetic filter on the cables? How much change will the DAC make to the problem?

Believe it or not, static in the pot is more than likely caused by the tubes. I never considered it until Negatron suggested it awhile back. These RK27's are very resistant to pot noise in the normal course of soldering. I flushed one out one time, only to loose some of the important grease around the shaft (no longer a blue velvet). Turned out, it was the tubes - both the left and right would do it to some degree, so switching them had no luck. The tubes weren't that bad, either - sounded OK to me, but not among the best I've had. It was something in the pins and how they connected to the plates or even just slight corrosion on the pins and their contact with the sockets.

You might try:
1. Switching the Left and Right tubes with each other and see if the scratchiness changes.
2. Try a different set of tubes - 12FK6's don't seem as susceptible with their lower gain.
3. Use a toothbrush and some 91% rubbing alcohol (99cents a quart at Walmart) on the pins to see if that changes things.

I keep trying to work on the Alien DAC MAX - I have the Alien running - fine and FLAT (slightly less than 3/8" thick at its thickest).

So, it will work, it's just documenting all of it. It's tops on my list, so hopefully it will not be much longer.

EDIT: That remedy is for a scratchy pot, maybe. If you're having constant noise at the 12-2 o'clock position, it's probably something else.

 

[mik000000]

I have been through (most) of this thread, but can find no discussion of th relative merits of MOSFET buffers vs Diamond buffers. I understand the MOSFET version is more difficult to build and adjust. Is there a sonic difference?

 

[denden88]

i'm having some problems with completing my max

. when i power it on, the LEDs come on and the tubes glow but when i plug in my headphones all i hear is hum. and for some reason i can only bias the left side. the right side seems to stay exactly the same, no matter what i do. also when i first turned it on before adjusting the powersupply voltage, the resistor in RB2R slot smoked up a bit. here are the voltages i'm getting:

V+ to GND: 24.7v
TA2L to GND: -13.1v
TB1L to TA2L: -67.5mv
TB2L to TA2L: -67.5mv

TA2R to GND: -8.35v (can't regulate)
TB1R to TA2R: -1.12v (can't regulate)
TB2R to TA2R: 1.12v (can't regulate)

i'll take some pictures when i figure out where my camera is

edit: the resistor that smoked up reads 9ohms

 

[tomb]

Quote:

Originally Posted by mik000000 /img/forum/go_quote.gif I have been through (most) of this thread, but can find no discussion of th relative merits of MOSFET buffers vs Diamond buffers. I understand the MOSFET version is more difficult to build and adjust. Is there a sonic difference?

We'll have to wait until someone's built all of them. That would probably be me since I've done six and counting - all with different BJT's. However, stuffing an Alien DAC into one of my existing MAXes comes first. I have the parts ready for two MOSFET MAXes using AMB's JFET mod. Colin is working on one, too - he can compare it to his 2SC3421/2SA1359/ES-VitQ MAX.

 

[tomb]

Quote:

Originally Posted by denden88 /img/forum/go_quote.gif i'm having some problems with completing my max . when i power it on, the LEDs come on and the tubes glow but when i plug in my headphones all i hear is hum. and for some reason i can only bias the left side. the right side seems to stay exactly the same, no matter what i do. also when i first turned it on before adjusting the powersupply voltage, the resistor in RB2R slot smoked up a bit. here are the voltages i'm getting: V+ to GND: 24.7v TA2L to GND: -13.1v TB1L to TA2L: -67.5mv TB2L to TA2L: -67.5mv TA2R to GND: -8.35v (can't regulate) TB1R to TA2R: -1.12v (can't regulate) TB2R to TA2R: 1.12v (can't regulate) i'll take some pictures when i figure out where my camera is edit: the resistor that smoked up reads 9ohms

Others have smoked that resistor and if memory serves, it was always an output transistor reversed or out of position. Give us those pics when you can.