[jdkJake]

BTW, if you do want to try out the Grado sound, the SR60 is a good place to start at a low price. You can always work your way up the chain if you like their sound (as finances and desire allow).
 
There are also a lot of them available in the used forum at varying prices and condition.
 
jk

 

[tomb]

Grados are wonderful with the MOSFET-MAX.  Of course, you haven't really heard an AKG K701 until you've heard one with a MOSFET-MAX.  I am fully admitting my bias, of course.

 

[jdkJake]

Grados are wonderful with the MOSFET-MAX.  Of course, you haven't really heard an AKG K701 until you've heard one with a MOSFET-MAX.  I am fully admitting my bias, of course.

That's an interesting combination. Everyone complains how the 701/702 is light in bass. I suspect the MOSFET-MAX would help that situation considerably.

I might have to try that combination. Just have to find a pair of 701's.


jk

 

[MASantos]

I drive my pair of 701's with the revH millett hybrid with the discrete diamond buffer, the predecessor of the the Millett MAX, and it really makes the 701 shine! I thinking of building a MAX to improve the 701's even more! I don't think you can go wrong with one of these!

 

[jdkJake]

Interesting. The 701/702 are pretty fairly priced right now.

TomB/MASantos, what tubes are you running your K701's with?

MASantos, what BJT pair did you go with?

jk

 

[BoilermakerFan]

I'd throw K601s and vintage K401s on the list as well.  K401s were my favorite of the 401, 601, 701.  Just not a fan of the more peaked highs on the 701s.  The 12AE6 tubes can help that, but I thought the 401s had the best sound sig.  Only reason I sold them is because my SR-Lambdas had the same sound sig, but much faster transient response though they were a little brighter than the K401s but not peaky or overly analytical like the 701s.

 

[MASantos]

The Bjt's are the MJE243 and 253, and I'm running FK's, but I never really did extensive tube rolling though. 

 

[TBomb06]

Well, I had a feeling this would end up happening, but I ordered the parts for a MOSFET Max today . After reading how awesome the MOSFET version is with Grados, I figured I might as well go ahead and do it and get it over with. I'll probably end up casing up the BJT version I have (which sounds pretty awesome as it is) and giving it to my dad to use with the SR-60's I bought him a couple of years ago. I'm pumped to get all my parts in and start building...I've already been through my spare parts from my last build and matched my transistors I can't wait to hear how this thing will sound!

 

[jdkJake]

Excellent.

I most interested to hear what you think of the new PCB as well as the MOSFETs.

I suspect you will not be disappointed!

jk

 

[TBomb06]

Quote:

Excellent.

I most interested to hear what you think of the new PCB as well as the MOSFETs.

I suspect you will not be disappointed!

jk

I suspect I will not be either
 
I do have a question regarding the input switching. Is the 2 position terminal for wiring up a selector switch to choose between the 2 sources? Is that the only way to select between the 2 sources? I don't really know that I'll ever use more than one source at a time, but I decided to go ahead and build it up with the capability just in case.
 
EDIT: Nevermind, found the answer to that one.
 
Also, on the BOM it lists 6 2N5087 for QB4L/R and QB6L/R, and 6 2N5088 for QB5L/R and QB7L/R. From looking at the schematic and the layout, there are only 4 of each that I see. Did I miss something?
 
Oh, and on the MOSFET Max sit, it says QB2 and QB3 should be reversed compared to the silk screen on the board. Is that due to the different type of transistor used for the MOSFET version compared to the BJT?
 
EDIT: Found the answer to that one too.
 
Ok...I think that's it for now...

 

[jdkJake]

Looks like you figured most of it out.

I currently have the selector "open" which defaults to a single input. I believe it is the right-most input when facing the front of the amp. The selector is a simple shorting circuit, so, it is easy to implement as required. Just as easy for single input is attaching to the terminal block by the alps.

I never noticed the mismatch in the number of small transistors. I just bought and used the matched set from beezar and never paid any mind to it. I will have to re-check when I get home (currently on the road). Interesting observation though.

jk

 

[TBomb06]

Cool, thanks for the input. One other question has to do with the upsized CA7 caps. I used the Muse ES's in my first amp, and loved the sound. Unfortunately, they don't make the 1000uF ES's in anything bigger than a 25V (I know I might could get by using this if I had to). What has everyone been using for the 1000uF 35V cap? I've thought about using the Elna Silmic II but I don't know anything about how it would sound. Would the Muse KZs be comparable to the ES? I'll be using Vitamin-Qs for the CA7 bypass caps. I'm still planning to use the ESs for CA2.

 

[Aalelan]

Speaking of CA7,  I read that this is the biggest spot affect for bass.  Could one use Nichicon HE 2200uf in this spot, if so would you have to make any tweaks downstream?
 
I could not sleep last night and was just thinking, I'm still learning and may ask crazy things sometimes.

 

[tomb]

 
Quote:

Cool, thanks for the input. One other question has to do with the upsized CA7 caps. I used the Muse ES's in my first amp, and loved the sound. Unfortunately, they don't make the 1000uF ES's in anything bigger than a 25V (I know I might could get by using this if I had to). What has everyone been using for the 1000uF 35V cap? I've thought about using the Elna Silmic II but I don't know anything about how it would sound. Would the Muse KZs be comparable to the ES? I'll be using Vitamin-Qs for the CA7 bypass caps. I'm still planning to use the ESs for CA2.

If you're building a MOSFET-MAX, you're already using 1-1/2" tall heat sinks and locating the PCB in the bottom slot of the recommended Hammond case.  This allows you to alleviate the only issue with Elna RFS Silmic II's: their very-large size.  IMHO, there's no reason to use anything else than an Elna RFS Silmic II, as long as the rating is sufficient and there's sufficient room.  They are as good as Black Gate NX's without the break-in and the high cost (now add rarity!).  What's not to like?
 
Use the 1000uf Elna RFS Silmic II at 16V, 25V, or 35V for CA2 L/R - all available and stocked at DigiKey.  Use the 1000uf Elna RFS Silmic II at 35V for CA7 L/R.  Handmade Electronics also stocks some of those sizes.
 
Stay away from KZ's - their natural "etchiness" combines badly with the detail of the MOSFET diamond buffer and borders on constant sibilance. (I speak from experience.

)
 

 

[tomb]

Quote:

Speaking of CA7,  I read that this is the biggest spot affect for bass.  Could one use Nichicon HE 2200uf in this spot, if so would you have to make any tweaks downstream?
 
I could not sleep last night and was just thinking, I'm still learning and may ask crazy things sometimes.

Actually, the CA2 and CA9 position have the most to do with preserving bass from the basic input signal/source.  It's a question of keeping all there is, or taking some away.  This can happen with the wrong bypass cap at CA9 (don't use Vitamin Q's, there, for instance), or if CA2 is too small (<1000uf).  Either the ES 1000uf 16V or the Elna RFS Silmic II at 1000uf and one of the voltage ratings listed in the previous post is best.  For CA9, you should just use Wima MKP10's.
 
As far as bass at CA7, it's strictly controlled by the RC-circuit cutoff frequency formed with CA7, RB14, and the impedance of the headphones.  1000uf should take care of everything down to 4 ohms, assuming you use a 22R at RB14.