krell ksa5 klone

[jose]

You can find original LKS170 on DIYAudio store. 

 

[muskyhuntr]

That does not appear to be one of AMB's Sigma 22's.  Could be part of your problem is here.

Me

[Southman]

I solved the Hummmmm sound issue after made grounding correctly.

As i checked my volume control have problem, so i have not install it now. and next time i will change the signal cable to OCC copper and the 2SK366 to 2N5564, hope this changing will get positive effect. 

The amp's sound are petty good, high resolution  and very clear, but the sound hearing cold. Maybe the R-type transformer or 2SK366 input transistor affected the sound, so i don't know why. Anyone have idea for this issue, i want the sound warn.

About the sigma22 PSU information, as i asked the seller and got that the circuit is same as AMB sigma22 but the PCB layout is not. So it is not a factor to caused the Hummmmm sound. But i Thank you very much for your concern and gave me idea.

 

Revise, the transformer is dual 25.4vac, not 27vac. the PSU  voltage regulation are from 25.4vac to 22.0vdc. I think it have a little bit high after understand your comment.

 

[Southman]

By the way, i found a capacitor ESR very low compare with Nichicon FW 1000uf/35V, 

but it is for 50V The following are my testing results.

 

 Nichicon FW 1000uf/35V

Aishi RS 1000uf/50V 

[Southman]

I replaced the input transistor to 5N5564 (second hand) then got the the amazing result. Beside, i replaced the volume control to step volume control.

The sound hearing clear, warmth and have good feeling of spaciousness, the dynamic very high and strong.

The treble are very smooth and bright, the bass are taut and rich, the alto are got high transparency and clarity.   

The cables looks in disarray, next time try to tidy it up.

[Mullet]

I'm finally about to build my KSA-5 Klone. I shelved the boards for like 5 years - can't believe I waited that long. Thus far with eBay and a cart full of goodies from Mouser I've gotten the price down to a reasonable ≈$215 including I/O jacks, standoffs, etc. The kits offered on eBay are cheaper. I've been tempted to buy the kits, but fear the parts are cheap and cheerful.

After reading through most of the thread... a question or two...

For the 2Ω resistors - can I use this? - 667-ERX-3SJ2R0

Or are 1% resistors necessary throughout amp?

Thx,

Mullet

 

[jose]

You can try with 71-cpf3-f-2

Yes 1% is right.

Edited December 16, 2019 by jose

[Mullet]

Thanks!

Anyone have experience with these iron transformer covers from eBay? Do they really work? I'm thinking of using one in my Klone.

https://www.ebay.com/itm/1pcs-toroidal-transformer-circular-cover-the-105-51mm-balck-metal-Metal/264373072892

[Craig Sawyers]

Do you have a hum problem you are trying to cure?

[Mullet]

Not on this particular amp. But I do have it on another amp and I was thinking of taking precautionary measures on this one. I'm thinking of going single chassis.

[Craig Sawyers]

Toroidal transformers are not completely symmetrical, because of the wire exits. The usual way of reducing hum induced by the asymmetry is to leave the leads long (or solder on temporary extension wires), loosen the chassis fixing and rotate the transformer to minimise or reduce below audibility the hum. Then tighten up the fixing bolt and tidy up the wiring.

Also make sure that the primary, and secondary wires are twisted. Open wire loops can induce hum and buzz in signal circuits through simple transformer action.

[Mullet]

Interesting. So basically turn the transformer until it's facing a different direction and thus reducing the hum. In this case it seems there is a possibility of having to permanently extend wires to get enough length.

[jose]

The number of problems that disappear with just a 1/4 turn of a toroid is impressive.

[rumina]

these cover are mostly cosmetic but i like to use them, the only shield a tad vs grain orientated metal or mu metal.

place the trafo near the big transistors with heatsink and you have a silent amp like in this pic (the 3th i made).

my first version had some inducted hum because the trafo was on the other side near the small transistors.

good luck with your build :-).

 

 

Edited December 25, 2019 by rumina

[thuytn]

I happen to have some KSA5 alternative supply. I wonder what parts need to be changed to get it output +/-18v (Dynalo) and +/-30v (Dynahi) respectively? Would the 2x18V and 2x30V transformers work here? I tried to find a link to the schematics but all seem to be dead now.

 

[Pars]

Usually the Stax topic is where you find the links (since Kevin retired from Northwestern University).

docs:  https://drive.google.com/drive/folders/0B7egryukiT7_TFlEQlBRejdVdDQ

gerbers (for PCBs): https://drive.google.com/drive/folders/0B_iJFfZStuVhSE5nOHBVdTByR1k

The TO-3 transistors used for that might be problematic to find. This might help: https://www.diyaudio.com/forums/solid-state/106973-krell-484081-484002-output-transistors-remplaces-codes-help.html

Not sure if there is a BOM floating around anywhere for that version of the PSU.

EDIT: Ahhh, right above, Rumina is using that PSU version for his KSA clone. Looks like MJ15024 and MJ15025.

Edited December 27, 2019 by Pars

[thuytn]

Thanks, Pars. I managed to find the schematics in that folder. 

Those TO-3 transistors are not a problem, I have many of them left from projects in the past.

[Mullet]

So I ended up figuring out what my hum issue was after moving trafo orientation. BTW this is for an EHHA Rev A. It turns out that my RK27 was going bad. After readjusting everything, I noticed that I was still getting leakage even though my pot was fully turned down. I could hear a small amount of audio coming through. I replaced the pot and now we're back in business.

With regard to my Klone, are those silicone / mica insulator kits for all the F15030/1 parts required? I'm counting 10 on the main amp board and possibly 2 on the alt. psu board.

[Mullet]

For the alternate power supply shown a few posts above, what hardware is requiered for the TO-3 transistors? I'm looking at kits on eBay and they come with more parts than I think I'd need. I'm thinking all that is needed is: 2x plastic washers, 2x screws, and 2x nuts. The kits come with 2 sets of metal washers and a metal tab for soldering. I'm thinking I wouldn't need these extra parts. See attached picture.

[Mullet]

Quick question when matching transistors...

on same channel - L or R... do you match PNP to NPN with similar or same HFE? or do you match NPN to NPN or PNP to PNP?

[Pars]

Matching PNP to NPN isn't easy usually, but try to get them as close as you can. And match NPN-NPN and PNP-PNP.

[Mullet]

Thanks!

[paroxod4]

Hello, is it possible to use BF256C field-effect transistors from PHILIPS at the input?

[paroxod4]

2SK389 / LSK389 or 2x2SK170BL everywhere Chinese fake, BF256C-original.

[Mullet]

I'm no expert, but I'd just use the suggested parts. You're thinking of using these instead of LSK389 or 2N5564? I know this is generally not advised, but I got the 2N5564 on eBay from seller Top Chips. I've recently fully powered up and tested the amp prior to casing things up and the amp plays music. So the parts are legit? I have no way of telling. My guess is the amp wouldn't work at all if the parts were fake.

On another note, you do have to watch out with eBay - I tried to skimp on paying $12 x4 for the OPA445 and bought them on eBay. When trying them out in the PSU no voltage or close to none. I ended up having to go to Mouser with my tail between my legs and bought 'em there. Boom success!