The F6 build of the century :) (I want to learn everything)

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#41
6L6 and others who have heard some of the pass designs: which one is your favouite sounding of the bunch? for a mid range guy like me who is attracted to these designs because of the promise of a warmish sound that some have described as tubish, which one do you suggest. Honestly I just chose F6 because its a latest but i could go with whichever is better recommended.
 
#43
alright great. i'm ordering the case right now. it's Dissipante 4U

Heatsinks:Universal Mounting Specification (UMS)
UMS heatsink depth (Match your chassis depth):300mm chassis
Number of chassis to upgrade to UMS heatsinks:Upgrade 1 chassis to UMS heatsinks [Add $59.00]
Customization:I would like my panels customized

Quantity 1 / 300mm w/Steel Covers / 4mm Black

for 240. so this UMS stuff is a 60 dollar option. i have no clue what it is and what it does. like i looked at all the pictures and read the description and it lityerally just saying buy this it makes your life easier. lol

what the deal with that?/
 
#44
Get the 4U deluxe. (with the UMS, the perf baseplate, more vents, etc...)

Get the Back Panel parts kit.

Now you will have all the hardware necessary, and the only hole you'll need to drill is 1, to enlarge a baseplate hole big enough to take the transformer bolt.

It saves a ton of time, work, and aggravation.

If you get a non-UMS chassis, you will have to drill and tap every hole to mount the PCBs, transformer, PSU, mosfet, etc...
 
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#45
Q1,2 IRFP240 (These do not have to be matched, but of course, it doesn’t hurt.)
Q2 2SK170BL or LSK170B
Q3 2SJ74BL or LSJ74B
(This circuit will benefit from the input Jfets having a similar Idss, but don’t obsess about getting matches down to 3 decimal points — within 10% is more than good enough.)
Click to expand...

im not clear which one of these are the output transistors and how many of each, i have looked them up on bdent.com and they look so luch smaller than the output JFETs that i see in the pictures in the illustrated guide.
 
#46
The IRFP240 are the power (output) mosfet.

The K170/J74 are the input (small-signal) Jfet.

B&D do sell genuine Toshiba, but they are not actually matched as required for our requirements - if you buy a 'matched pair' from them it's just a J ad K from the same Idss grade.

The Jfet matched pairs in the diyAudio store are perfect for this amp. (By design..)

Linear Systems Matched JFET pairs (Grade B) – diyAudio Store (BETA)

Also remember that for all practical purposes, any K170 or J74 on Ebay from asia are fakes. There's a guy in Israel who has some that are, from all accounts, genuine.
 
#47
i have access to oscilloscope and some other precision measuring devices in the physics lab in my college. if i buy a few on them (the power JFETs) what is process of matching? exactly what do you guys call matched? in other words what do i need to measure?
 
#48
I assume you are asking about matching the input jfets, in which case, you need
to measure the jfet's Idss:

http://www.diyaudio.com/forums/pass-labs/228897-jfet-matching-sorting.html

http://ken-gilbert.com/images/pdf/erno_borbely_on_jfets.pdf

The measurement itself conceptually is not difficult; the problem is finding
a sufficient number of parts to match with.

To give you a data point, the 2sk170BL and 2sj74BL I have are quite widely
spread out in the 6.5 - 11.5 mA range. So a small number of parts is unlikely
to give adequate matching.
 
#49
86 dB speakers, OK??

All,

Dadbeth sent me a PM, and in it he indicated he wanted to use the Pass F6 design with his Bogdan Audio Creations Piccolo speakers (nice 'speakers, by the way!).

The Piccolo has 86dB sensitivity. I'm not familiar with F6 power levels, nor the Bogdan designs.......

Will the F6 (or for that matter, the F5) be able to drive the Bogdan's to typical room-level volume? (This might be a critical consideration for Dadbeth to ponder, before he picks a final map design).

Inputs? Comments? Thoughts??
 
#50
The F6 has similar power and current as the F5... so if they have a reasonably smooth impedance curve they will likely be fine.

There's not going to be headbanging noise levels (so no real-life J58 SPL... 🙂 ) but I bet everything will work nicely.
 
#51
This is the back of the speaker:

UEuJ3Xi.jpg


he himself told me that he has been using Vintage tube during shows with this speaker. So I have chosen F6 specifically for this application. tubes for me are out of question as I have no desire to deal with their maintenance. i am definitely not a basshead, even though I do listen to a good bit of rock and metal (I love Iron maiden, tool, led zeppelin) so the bass needs to be there but i dont want anytihng to shake or vibrate 😀

i am planning on suplementing the lower frequencies with a subwoofer after im done taking care of the amp (after F6 is working and everything)

I have done some research on Rythmik subs. they have a dual 8 inch model that they say can be crossed over as high as 250hz specifically designed to reinforce mid bass I dont know about going that high in cross over. before seeing that subwoofer i never in my life considered crossing over a sub over 100hz. ever. but it's an option and its there and I welcome all advice.
 
#54
A quote from Rythmik site: "Customers should note signals above 80hz can be localized and therefore placement is important if FM8 is used above 80hz". So I am pretty sure they will recommend you use 2 subwoofers set up as stereo for anything crossed over above 100 Hz. Talk with them. As their site also says, you will have to work on getting a seamless transition. I am not sure of the Piccolo low rolloff. Is it a vented box (4th order rolloff) or 2nd order (12db/octave)? I use the normal 12" F12 subwoofer and it works great with my speakers. However, they are a sealed box (12 db/octave rolloff) and they go deeper than the Piccolo. I also am using a 12 db active high pass to my main amp (a Aleph J). For your setup, the F6 should sound superb and you should be very happy with it. You probably will have to work a little on the integration. That probably will be no more than a cap of correct value in series (before) with the input of the F6. Read all the Rythmik site and then talk with them for recommendations.
 
#55
thank you all for great advice and insight and Jim has really helped me out. I learned a lot already. following the discussion about subwoofers, im not clear how it would be interated in this system. i mean my DAC and this amp neither have sub out. and there is the case of integrating two subwoofers in case i need to reinforce the midbass region. how would that be done?
 
#57
Dadbeh: I would suggest to do this one step at a time and not get ahead of yourself. First build the F6 just the way that 6L6 build guide shows. Do not change anything yet. You do not know enough YET to improve on the given design. Then spend some time experimenting with speaker placement and enjoy the beautiful music coming out of your speakers. After a good while, if you feel you need more deep bass (on most music you probably won't) then first write to Bogdan Audio Creations. From what I have heard, Mr. Petrescu is a real artist that takes pride in his work and he would know the most about his excellent speakers. If you decide to try a subwoofer, first read all that Rythmik has on their site about integrating a subwoofer (have you read that yet?) Also, read what Nelson Pass wrote in his manuals with the B4 and B5 about integration. I think you might start with one of the F12G Rythmik subs and see how that works. You might not need to cross over above 100 Hz. It might blend nicely with just a splitter out from preamp. I suspect that Mr. Petrescu is much more honest with his rating of 65 Hz than most speaker companies, but talk with him first when the time comes.
 
#58
I would second propitious' opinion. First build the F6, then listen, optimize the speaker's placement, and then listen more.
From there you'll habe already learned a lot. You don't need at least 200W from an amp, and speaker placement is imensely important.

After this you can think about any kind of changes. And if you then still want a sub: there are also lots of diy-subs, and other manufacturers. And, as already said, ask the manufacturer of your speakers. His statement of 65Hz seem really to me so much more honest in comparison to all the marketing blub of other companies.
 
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