Aleph J illustrated build guide

[tricksters]

I know I only need four "SJ74s", but they are currently not available in the diyaudiostore and I was thinking if I should buy two LSK170 / SJ74 matched quartets, or wait.
This was my perplexity. : D

 

[Zen Mod]

send an e-mail to Store and ask is there any time-frame set, for getting quartets

 

[tricksters]

I have already asked to notify me by e-mail when they were available for sale

 

[Zen Mod]

look at post #6493

 

[tricksters]

Yes, i have read, and i have seen the auction, they are "GR" i think they are fine. 🙂

 

[Zen Mod]

several auctions by punkydawgs

I can't see anything wrong with Toshiba 2SJ74 LAB MATCHED QUAD to 0.03mA / 4mV ("B" "BL" 7-9mA Range) | eBay

 

[tricksters]

They are great too, I think I'll place an order today. Thanks : D

 

[Zen Mod]

Di niente

 

[hanair]

see 4U/300 Modushop case, as reference

and then, even metter - 4U/400

Thanks!

I have a chassis with sides made of 300mm 3U heat sinks. Just wondering if I can make use of those.

What would be the expected steady state temperature after an hour or so on a 4U/300mm?

 

[Zen Mod]

if similar to Modushop heatsinks, expect 55C with 80W of heat

 

[peppennino]

Hi all,
BOM parts from Mouser just ordered! 🙂 It only remains PSU and cabinet(s) and I will start the JZen build!
So...
In order to decide myself, I need your help.

I have two possibilities:
Make a stereo version with 4X33mF, Deluxe 4U and a single 400VA toroid

OR

Two monos with 4X15 (or 22) mF per case, 2x 2515 Chinese cabinets, 2x 200VA toroids.

Just for reference, mono cabs are like those:
2515 cabinets

Is it worth to make two monos? experiences with AJ (dual) monos compared to stereo version?
Toroidy standard versions transformers are good enough for this application?

Many thanks to all

 

[Zen Mod]

make dual mono in Modushop 4U/400

example: SissySIT, another one – Zen Mod Blog

 

[chede]

I second ZenMod's recommendation - have done that for my SissySIT and F4 (in a 5U/400, though).

 

[Chris In Milwaukee]

I second the dual mono option. I used 2X standard PSUs (400VA - probably overkill) in a 5U case since I stacked the PSU board over the transformer. That configuration is quite tall.

 

[hanair]

if similar to Modushop heatsinks, expect 55C with 80W of heat

Since most of the parts are already here, I am going to build my first release into a smaller chassis that has 3U/300mm heat-sinks on either side. I don't think I can run it like that for more than 15 minutes or so. Would it be possible to lower the bias to compensate?

 

[Zen Mod]

lower bias to, say, 1A4 to 1A5, and make Babysitter

then observe temperature again, and increase Iq accordingly

 

[peppennino]

Thanks to all, I'll go for Pesante

 

[hanair]

lower bias to, say, 1A4 to 1A5, and make Babysitter

then observe temperature again, and increase Iq accordingly

Would that be 0.4 to 0.5A or 1.4 to 1.5A? Per channel or per transistor pair?

 

[Zen Mod]

as written
🙂

per channel

 

[hanair]

I am confused because 6L6 wrote in the beginning of this thread that the quiescent current of just over 1A might need a fan for 4U case.

500mV bias = 1.06A = 22.55W/device. This is hot. You could not do this if you build your amp in the 4U chassis without a fan somewhere.

Edit: Is the difference due to "per channel" vs "per transistor pair"?