Bryston 4B SST clone

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#863
Hello

I have order that Bryston 4B SST clone

I have only have a power transformer to give +50 v -50 v DC

So, that clone amp will not have a supply of +85 v -85 v , but only +50 v -50 v DC

I do not mind to have less output power, I know that the bias will be lower, but is there others change to do in some parts values ?

Thank

Bye

Gaetan
 
#864
chalky said:
bobina if you look back to post #369 you'll see I detail all of the changes I made to the parts you mentioned. I made the changes because the PN100A/PN200A are obsolete. I know, so are the BC560C but I have a large stash of them, as do many other people. If you want current production devices then use the KSC1845/KSA992 pair ( with a bit of lead dressing ). I changed the resistor values so that the quiescent current of the VAS transistors Q5/Q6 was cut from 12mA to 6mA. At the original current Q5/Q6 were dissipating 400mW and ran pretty hot - now they run cool. To cut the loading on Q5/Q6 now that the standing current was reduced I used output devices with potentially 4x the hfe of the MJE172/MJE182. I've redrawn the schematic with my revised parts values and attached it to this post.
Click to expand...
Hello chalky

Looking at your BrystonSmallInp.pdf schematic.

You did replaced the cfp vas by a standard vas and the Vbe multiplier by D3 D4 R14 for the bias.

Wy did you take out the cfp vas and the Vbe multiplier ?

Is it because cfp are less stable ?

Any others reasons for those changes ?

Thank you

Bye

Gaetan
 
Last edited:
#865
Hello chalky

I forgot to say that my Bryston 4B SST clone do have cfp vas, I found out that there is other version of this clone with no cfp vas but with a standard vas.

Thank

Bye

Gaetan
 

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#866
I think you're talking at cross purposes here. My modifications were to the input board, not the power amplifier board. The schematic you've shown is for a simple push pull vas, not a complementary feedback pair push pull vas, in the power amplifier board. If the latter were true then both the upper and lower vas would be comprised of two, rather than one, transistors.
On a different topic I notice that some of the more recent dual input boards have servos to null out the output offset voltage. This is only necessary because the non-optimal choice of input and feedback resistors leads to an output offset voltage. The output offset voltage of the (older) input boards which adhered more closely to the original Bryston design is negligible and doesn't require an output offset servo.
 
#870
Hello guys,
this is Danny from Italy.
I read all 44 page and then I decided to purchase PCBs for 4B SST on Ebay and I've got all papers but as I'm very newbie I can't decifer which component I need, I'm trying to source from RS componets and DigiKey but it's very difficult because for e.g. a capacitor 22p on the input board, there are almost 7 different variations of the same component and I don't know which one to choose.
It's almost the same for all other components.
I don't know if I'm asking too much but do you have a order list or a compiled and saved BOM list for Rs Components or Digikey or other store in Europe ready to be ordered so it could be easier for me to start?
Thanks in advance for your help and patience.
D
 
#871
If you are a beginner, you should start by buying the kit with the parts included. After that you can upgrade buy buyong better capacitor like simlic, muse or wima etc
Be sure you ordre original ON output transistor at Digikey if you want to avoid troobles.
Antek in NJ makes good toroidal transformers. If you use the components from the kit it will sound very good. Good luck and be patient!
I'm doing my 12th upgraded kits of 3Bsst2 and 4Bsst and they sound very good.
 
#872
Thank you Bengtx600, even if I have built a Whammy and some Neve clone preamps successfully, I'm still considering myself "a hungry newbie" and, with lot of enthusiasm, but without all sourced parts, it is a nightmare for me to find it out.
I will take your suggestion considering to buy a complete kit with parts included and then upgrade like you are doing.

At this time I have two Class D Hypex NC400 monoblock amplifiers, they are really good, but I miss very much the punch and presence of class A sound, I would like to compare them both in my room, I can't afford original Bryston of course that's why this could be a nice solution.
An other idea would be to try the F5T from Mr Pass but some parts (like chassis and heatsinks) are not available here in diyAudio shop unfortunately and I have some doubt to find it all, it's a shame!
Any suggestions on my case will be very appreciated... 🙂 THANKS!!!
 
#873
I order Pass casing on AliExpress ( DIY Talent Audio Supermarket Store) and you can ask for a blank back panel and also give them the pdf file so they can make all 20 holes tapped tp 3 mm or 4-40. It don't cost much, I can say it's very a good price.
You can get most of the parts on AliExpress, capacitors, resistors, capacitors, black screws, casing, etc.
I also buy nice power supply (Bridge/ 20 000uf capacitors), elna audio gold. Again don't buy your MJL output on Ali, buy them at Digikey.
I clone Bryston since 45 years, In the past I have to do everything, from boards to casing.... And they still works fine.
 
#874
Bengtx60 thank you so much for all the infos, AliExpress seller saved.
I've found all 3 Bryston pcb's on Ebay with components except for MJL21193 and MJL21194 founded on mouser in a new final G version (MJL21193G and MJL21194G) because the other are obsolete.
Last two questions if you don't mind: as you are very experienced after 45 years of fun (and maybe some damnations, too) on Bryston amps, do you have a suggestion for main rectifier capacitors with max diameter of 40mm (12 pieces as you know)?
Also for the tranny, the Antek AN-6450 is correct? This one here.
Thank you again for your time and your help!
 
#875
You can use two AN-5450, AN-6450, or one AN-10450. You can also or to can easily use two AN-5455, AN-6455, or one AN-10455, AN-10458 (Two 500VA is Ok, or one 1000VA is Ok also) Up to 58Vac max. More you put voltage more tight must be the transistor matching.
Softstart 115V on amazon, DC Blocker on Aliexpress, very important because of toroidal saturation.
For the supply I use two set of ''Golden 4*10000UF 100V Schottky Rectifier Filter Power Board'' on ebay.
 
#876
Thank you again! I did not imagine all others things to buy.
For your electrical info I almost forgot: I’m from Italy, so here we are at 230 Volts.
Can you please double-check if those below are correct?

Softstart 230 15A

DC blocker 25A

Rectifier Schottky

I also bought a rectifier for 4B on ebay along with other main pcbs, this last one is wrong and I don’t need it?

Thanks again for your suggestion and your time.
 
#877
The big board they are selling in the kit for the power supply didn't fit in my casing, so I bought two of these on ebay. They are very good.
Golden 4*10000UF 100V Schottky Rectifier Filter Power Board from Emma Technology Company
Yes, this DC Boloker works very well, I install these already.

Softstart for Audio , on Amazon

30A 6600W Soft Start Protection Module, AC 100V‑250V Start Protection Board for Class A Amplifier Module​


I hope that help.
Ben
 
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