Salas hotrodded blue DCB1 build

[Salas]

Those will cost the whole blown package.

 

[AndrewT]

In my opinion, DC coupled amplifiers require correction, detection and protection circuits to ensure reliable speaker/s.

That equates to:

DC servo
and
DC detection
and
amplifier shutdown

if the DC wanders away from your preferred maximum output offset.

 

[davym]

And there was me thinking a DC blocking cap was enough

 

[AndrewT]

A post in another Thread said
AC coupled amplifiers are OK.

 

[davym]

In theory then, a DC coupled buffer driving an AC coupled power amplifier fitted with a blocking cap should be a fairly safe combination, especially if the power amplifier has speaker protection built in like the My-Ref FE?

 

[AndrewT]

Yes, in theory and in practice, an AC coupled amplifier prevents input DC from damaging speakers.

 

[BigE]

Using the DCB1 as opposed to the vanilla B1 to feed an AC coupled amp removes *one* set of blocking caps.

So then *generally* we could say that the purpose of a DCB1 is to feed an AC coupled amplifier, and it is recommended that blocking caps are installed to feed a DC coupled amp that has NO DC protection.

Would an input transformer also block DC? Say a transformer to converts a Single ended to Balanced input?

 

[Salas]

Depending on how much DC it could block without reaching saturation I would suppose.

 

[stajo]

A transformer can not pass dc from primary to secondary regardless of saturation or not

 

[davym]

Using the DCB1 as opposed to the vanilla B1 to feed an AC coupled amp removes *one* set of blocking caps.

So then *generally* we could say that the purpose of a DCB1 is to feed an AC coupled amplifier, and it is recommended that blocking caps are installed to feed a DC coupled amp that has NO DC protection.

Would an input transformer also block DC? Say a transformer to converts a Single ended to Balanced input?

That's something I don't really get, would a transformer not potentially negate any possible gain made by going balanced?

 

[stajo]

A 1:1+1 would pass same signal level.

 

[BigE]

Any recommendations?

 

[stajo]

Depends on source, load and signal level but maybe LL1684 could be something for you.
Other Tube Transformers | Product Categories | Lundahl Transformers

 

[Salas]

A transformer can not pass dc from primary to secondary regardless of saturation or not

Yes it can't but we don't want it saturating while blocking also.

 

[stajo]

 

[ypaudio]

Is it possible to use 2SK163 as replacement of 2SK170?

Matched quad 2SK170 and 6 random Toshiba NOS 2SK170

any modification schematic needed?

 

[Salas]

It is possible for comparable Yfs and IDSS JFETs. I don't know the 2SK163 specifics. I thought it was a Mosfet?
If talking about this NEC obscure NOS part that I got this datasheet in my files on the other hand, I see low transconductance vs. K170. It would not be much different in M selection than using a 2SK117BL for instance. No modifications, it will play, just not as great as a K170BL.

 

[ypaudio]

Hi Salas, Thanks for reply.
I search on Google and find 2SK163 is manufactured by NEC. N channel JFET low noise audio amplifier. The datasheet is same with your attachment.
I have to collect some other component and then make a PCB. I will try to build DCB1 with SK163. in local store near my home I can get SK163, but there is no stock SK170. I think it will be interesting

 

[Salas]

Notice they are L or M selection, else avoid. You will need high L or low M IDSS so to have pairs around 9-11mA for having some meaningful gm for DCB1. Where are you located and finding such in a store still?

 

[ypaudio]

ooh I missed with 'L' and 'M' mark, Thanks for notice me. I already buy 10 pcs. I will check the IDSS later.

I live in Indonesia, Solo city. The store doesnt have website, just a small electronic components store