[Beefy]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Just an update on the MOSFET-MAX V1.2 - I came to the conclusion that I hate Muse KZ caps. I replaced the KZ's on the outputs today with a pair of Silmic's at 1000uf 35V (big caps, but there was room!). It sounds wonderful. I even backed it down from 150ma bias in the buffer down to 125ma. It still sounds wonderful.

What did I tell ya, eh?

 

[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Thanks, Jeff! Sorry about the comments on the KZ's. I just never tried them before, believe it or not. There must be some bad combination that results from their "hard etched sound" that combines badly with Millett tubes - or perhaps the VitQ's that we use for output bypasses. The MOSFETs definitely contribute to this, because they do seem very fast. To be specific, no on the 1000uf - the KZ's I tried were 470uf 50V. Keep in mind this is only in the CA7 positions - the direct output couplers. Sound quality means everything at that spot. To sum up again, I used the following: PS - 2 x 2000uf 50V Panasonic FC CA4/CA5 Decouplers - 3300uf 35V Panasonic FC CA2 - 1000uf 25V Elna RFS Silmic II CA7 - 1000uf 35V Elna RFS Silmic II Wima MKP10 bypasses all around, except 0.22uf 100V 196P-series Sprague VitaminQ at CA8 MOSFETS are Z24/9Z34 with Toshiba JFETs 2SJ74 and 2SK170 at Q2/Q3 buffer signal input positions. Thanks for the comments on the board! Yes, we are getting very close. The PS tests just as good as the MiniMAX, the sound is great with the combo I'm using now. The only thing left is to test the BantamDAC mounting and the input-relay switching. I'll try to get to it this weekend, but you know how things go - I've got the Starving Student I've got to release for sale on Beezar, too.

Now socket the DB transistor positions, add 3/8" spacers under the sinks and screw mount them! Then you can swap DBs till your hearts content like I plan to do! Might have to invest in permanent voltage meters for the bias current test points too.

Off to eBay...

Laying out the chassis for the new V1.2 boards in the NABUs. My top cover art will allow both tubes to be visible or have clearance if I need it. Tom, how tall are your tube top tips measured from the top of the PCB? Just want to make sure I have the height I need to allow me to put screening in the chassis to cover the openings.

 

[tomb]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif Now socket the DB transistor positions, add 3/8" spacers under the sinks and screw mount them! Then you can swap DBs till your hearts content like I plan to do! Might have to invest in permanent voltage meters for the bias current test points too. Off to eBay... Laying out the chassis for the new V1.2 boards in the NABUs. My top cover art will allow both tubes to be visible or have clearance if I need it. Tom, how tall are your tube top tips measured from the top of the PCB? Just want to make sure I have the height I need to allow me to put screening in the chassis to cover the openings.

Standard tube height from the base is 1-7/8", but there's the socket height to consider - probably about 5/8". So, I'd say approx. 2-1/2" ... this will vary according to the tubes, but should be about maximum.

 

[TimJo]

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Originally Posted by tomb /img/forum/go_quote.gif The Starving Student PCB version blew out another one of my BantamDACs.

What happened?

 

[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Standard tube height from the base is 1-7/8", but there's the socket height to consider - probably about 5/8". So, I'd say approx. 2-1/2" ... this will vary according to the tubes, but should be about maximum.

Thanks. I saw the tube drawing, but wasn't sure of the maximum height installed with the sockets.

 

[tomb]

Quote:

Originally Posted by TimJo /img/forum/go_quote.gif What happened?

Talk to Ludoo.

It's a common recurring problem, unfortunately. There is something in the grounded cathode/MOSFETs on the SSMH that cause a voltage/ground issue to develop on the RCA inputs. It's enough to fry an Alien/BantamDAC under the right scenario. This time, the DAC had been plugged in to the USB for hours - so the DAC's output caps were plenty charged. The SSMH was on, because some of us suspected the offset occurred on power up (PS "stuttering"). I think I missed the socket on one channel and accidentally touched the center pin to the outside of the RCA jacks on the SSMH (negative ground). That was enough - that channel is dead.

I'd talk about the suspicions of what causes it more, but it should probably be discussed in the SSMH thread, not here. Before anyone asks, let me say I've not had issue one with MAX/MiniMAX and Bantams/Aliens - nor have I heard of an issue, either.

 

[tomb]

Success!! The MOSFET-MAX V1.2 prototype now lives with an onboard BantamDAC and operating switching relay between the DAC and RCA inputs. The operation is seamless, no switching noise, nada - it works flawlessly
!

Today I spent some time building another BantamDAC and hooking it up to check the final feature in the MAX V1.2 PCB - the onboard Bantam with relay switching between RCA inputs and the Bantam. Pics below.

Note the Bantam with output leads plugged into a 6p terminal block (2x3's in this case). The three leads on the right are from RCA jacks. The 2p terminal block is connected to a DPDT switch. I haven't populated the LED because I'm going to use the other two poles on the switch to activate the LED when the switch is thrown. This will all be wired to the front panel.

Cetoole has some tweaks we've discussed to add to the board, but we're essentially ready to go to production.

 

[zkool448]

Congrats tomb

What sets this MAX V1.2 apart to me is the built-in DAC feature - a nice, convenient option IMO.

[size=xx-small]* Let me know when you're fully done with that proto board, I'd be happy to take that off your hands[/size]

 

[tomb]

Quote:

Originally Posted by zkool448 /img/forum/go_quote.gif Congrats tomb What sets this MAX V1.2 apart to me is the built-in DAC feature - a nice, convenient option IMO. [size=xx-small]* Let me know when you're fully done with that proto board, I'd be happy to take that off your hands[/size]

Thanks! It's been a long time coming (more of that one-man band thing and too much to do). I can't wait to case it up. The MOSFET buffer is really something else with the Elna Silmic caps, too.

EDIT: I suppose my HF-1's will be passe', soon.

 

[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Success!! The MOSFET-MAX V1.2 prototype now lives with an onboard BantamDAC and operating switching relay between the DAC and RCA inputs. The operation is seamless, no switching noise, nada - it works flawlessly ! Today I spent some time building another BantamDAC and hooking it up to check the final feature in the MAX V1.2 PCB - the onboard Bantam with relay switching between RCA inputs and the Bantam. Pics below. Note the Bantam with output leads plugged into a 6p terminal block (2x3's in this case). The three leads on the right are from RCA jacks. The 2p terminal block is connected to a DPDT switch. I haven't populated the LED because I'm going to use the other two poles on the switch to activate the LED when the switch is thrown. This will all be wired to the front panel. Cetoole has some tweaks we've discussed to add to the board, but we're essentially ready to go to production.

Woohoo! Can you do us a huge favor for those of us who have full parts count for V1.0 MAXes that are waiting for the V1.2 release? When it's in production, can you do a small BOM for only the new or changed parts calling out exactly what has changed and what new parts we'll need to order for the V1.2 build?

It's nice to see I can use my Darwin I/O control and bypass a DPDT, although I did drill holes in the rear for them in two chassis as a precaution.

I have pics of my V1.0 board mocked up in it's NABU chassis that will be my console amp so it also has the AudioSector Gainclone boards in it. With 1/4" PCB standoffs and 3/8" spacers between the PCB and 2-1/2" DB heatsinks, I still have 1/4" of clearance between the top of the DB heatsink and the chassis top! So it's a full 3" of available clearance from the top of the PCB! Tubes and everything else will remain safely under cover.

I have pics, but need to upload them to photobucket...

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Thanks! It's been a long time coming (more of that one-man band thing and too much to do). I can't wait to case it up. The MOSFET buffer is really something else with the Elna Silmic caps, too. EDIT: I suppose my HF-1's will be passe', soon.

Why do you say that? They look great next to the V1.2 MAX. I have Silmics and Cerafines, but was planning to use the Cerafines in my MOSFET-MAX. Muse ESs are going in V1.0 with the console amp. Maybe my V1.2 BJT MAX needs the Silmics?

You might be able to talk me into prepping a NABU case for you too (but I'll need to order more...).

I have the layout pretty standardized now (including access to the DB heatsink mounting screws from below to allow fast swaps of DB with socketed boards). I also figured out how to maximize utility and aesthetics by reusing or cutting out the existing holes in the chassis so only the old TO-3 V-reg holes are visible if they aren't used (using mine for the Darwin and phono stage regs so they're closed).

OT, but the Aikido 24V was much more challenging to prep since it's so much bigger. Almost as many cooling holes in that PCB as the new MAX too!

 

[tomb]

Quote:

Originally Posted by BoilermakerFan /img/forum/go_quote.gif Woohoo! Can you do us a huge favor for those of us who have full parts count for V1.0 MAXes that are waiting for the V1.2 release? When it's in production, can you do a small BOM for only the new or changed parts calling out exactly what has changed and what new parts we'll need to order for the V1.2 build?

Yep - I'll work on it!

<snip>

Quote:

Why do you say that? They look great next to the V1.2 MAX.

The new Grado HF-2 is being sold to Head-Fi members as we speak (at TTVJ) and will be unveiled at CanJam.

Quote:

I have Silmics and Cerafines, but was planning to use the Cerafines in my MOSFET-MAX. Muse ESs are going in V1.0 with the console amp. Maybe my V1.2 BJT MAX needs the Silmics?

Cerafines are probably just as good, although I still haven't had the pleasure.

ES's will always be the first choice for 1" heights and the MiniMAX.

Quote:

You might be able to talk me into prepping a NABU case for you too (but I'll need to order more...). I have the layout pretty standardized now (including access to the DB heatsink mounting screws from below to allow fast swaps of DB with socketed boards). I also figured out how to maximize utility and aesthetics by reusing or cutting out the existing holes in the chassis so only the old TO-3 V-reg holes are visible if they aren't used (using mine for the Darwin and phono stage regs so they're closed). OT, but the Aikido 24V was much more challenging to prep since it's so much bigger. Almost as many cooling holes in that PCB as the new MAX too!

The production version will have even larger holes under the center sinks - that's one of the tweaks we're making.

 

[GRUN]

hi TomB

I finished building my miniMAX few weeks ago.

I feel MAX sound is warm and bouncing!
It looks like the sound of RS-1 if it compares it.
This is just my favorite sound. thanks!

 

[BoilermakerFan]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Yep - I'll work on it! <snip> The new Grado HF-2 is being sold to Head-Fi members as we speak (at TTVJ) and will be unveiled at CanJam. Cerafines are probably just as good, although I still haven't had the pleasure. ES's will always be the first choice for 1" heights and the MiniMAX. The production version will have even larger holes under the center sinks - that's one of the tweaks we're making.

Uh oh, must resist pre-order...

Well, the Cerafines are definitely going in my MOSFET-MAX, and since the KZs have been "difficult" in the MAX, I'll probably use the Silmics in the V1.2 BJT. I need the bass punch of the ES for my console as I'll have no EQ in it.

I should have enough air flow with the holes I have drilled, plus the big 5/16" holes under the DB mounting screws...

 

[BoilermakerFan]

Pics of the mock up of the V1.0 BJT build as promised...

Below you can see the location of the gainclone amp boards at the rear with their corresponding PSU cards still attached to the front. That's the Darwin I/O selector to the far right. I need a smaller PCB card for my phono stage to fit it in between the MAX and Darwin. The little bits outside the case to the left with the red center leads are my vintage, salvaged Garrard mid-fi BJT pairs that will demo'd in the MAX just to hear them. Holes across the front from left to right are, 3/4" for power, four original holes above the center line for LEDs mounted to a PCB which is being repopulated (and stealthed behind the wood front), two hoes for 1/4" jacks, two holes for the Darwin selector switches, and the ALPS pot. The rectangular hole next to the gainclone is the hole for an L-Con USB jack. This chassis has been my guinea pig metal. It's going in the console, to be buried in the guts and out of sight later so some parts will be removed or only installed temporarily. The IEC power input will not be used and instead PowerCon will feed in the 24Vac from a separate chassis housing the toroid.

Trying to show the 1/4" of clearance to the top, even with the 2-1/2" heat sinks sitting on 3/8" spacers. I still need to drill a couple of wiring holes in the divider once I know all of the sizes and quantity.

A bigger side view, the double gang ALPS will be replaced with a single since the OptiVols only need a single gang to control both channels.

After all the metal work is done on the 5 chassis, they'll be sent out for blasting, then head over to the body shop for paint in either black or navy blue. Then I'll label everything on the back with dry transfer lettering before dropping the chassis off again for 3 coats of clear at the body shop. The tops are going receive designs cut in the tops before being blasted and painted.

 

[tomb]

Gotta love those gold heat sinks.

Looks like quite an ambitious project you have - it'll be neat seeing it finished!