The BA-3 as preamp build guide

[Dudeisms]

one can always expect help here , be it question about component selection , or little math

I tend to have strong opinion about chip regs (mostly series regs) versus proper shunt regs

no comparison , when shunt reg ........ I mean - entire PSU, inclusive shunt regs - executed properly

ZM... I have seen you make reference to a “proper shunt reg, with proper implementation”...

What would be proper shunt and what entails proper implementation?

 

[Dudeisms]

I would read the SuperReg article and thread and see if you are up for it.

Super Regulator

You will need a separate cap bank and rectifiers in front of the super reg. The Super Reg board has no cap bank and rectifier diodes on board.

or you could spend $15 on Amazon and have it up and running in no time with lm317/337.

I understand the separate rectifiers ( lol recognize those squares in people posts)... but capacitor bank I don’t think I have seen an example of

 

[Zen Mod]

ZM... I have seen you make reference to a “proper shunt reg, with proper implementation”...

What would be proper shunt and what entails proper implementation?

generally , I prefer regs with error amplifier ,to ones being set as sort of reference followers

also , I'm heavy biased there ..... during the years , tried most best known , and even if I was satisfied with some of them , wasn't satisfied due to feeling that pure cloning isn't enough

so , back to biased - Shunty and Good Gemini are my cup of tea ; Good Gemini, as later - even if simpler , made with even greater care of phase behavior and pcb routing , which is of same importance as electrical design

if you want simplest possible but with good performance , look at reg in PSM LS article

 

[marconi118]

is-it possible to use FQP13N10 and FQP7P06 for output stage?

400pF gate capacitance and 6S Yfs

 

[silasmellor]

Hey guys, i made an oops in ordering and ordered RN60s for R13 instead of proper 3W resistors... I've got some 100R 3W lying around i could plop in instead, but that would lover the gain a lot. Any chance i can compensate somewhere else in the circuit without compromising things?

 

[MASantos]

Hey guys, i made an oops in ordering and ordered RN60s for R13 instead of proper 3W resistors... I've got some 100R 3W lying around i could plop in instead, but that would lover the gain a lot. Any chance i can compensate somewhere else in the circuit without compromising things?

If you have 6 of those you could get 300ohm.

 

[silasmellor]

Hey MAsantos, I unfortunately only have 2. I ordered some panasonic 330 ohm 3ws which should be here Tuesday. I am curious about the BA-3 / F6 combo, does the ba-3 drive the f6 to clipping? Is there any need to lower gain?

 

[wdecho]

Leave alone. Should drive any amplifier to clipping except maybe the F4 that does not have a front end.

 

[Manolo47]

Received first batch of parts for my build....

From Digikey. Ordered all resistors, mosfets, vr's, etc. The bill of materials specifies all resistors as 1/4w except one, which is 3w. But, these resistors are very very small, compared to what is in the board photos in the threads... are you guys using 1/2w or bigger resistors?

 

[KevinHeem]

these resistors are very very small, compared to what is in the board photos in the threads... are you guys using 1/2w or bigger resistors?

A lot of people are using Dale/Vishay RN60D resistors which are conservatively rated at 1/4 watt. They are bigger in size and probably good to a 1/2 Watt. That's more than likely what you're seeing in the photo's.

 

[MASantos]

Leave alone. Should drive any amplifier to clipping except maybe the F4 that does not have a front end.

It drives the F4 to clipping, no sweat.

 

[silasmellor]

Understood, but isn't it more desirable to have enough gain but shy of clipping?

 

[6L6]

Not really. That's what the volume knob is for.

What you want to avoid is too much gain, for example where you have less than 90deg of knob movement before it's painfully loud...

 

[silasmellor]

Ok, i will build it and decide then. Thanks.

 

[Todd Mills]

BA3 Preamp

I thought I was almost done but I decided to swap out the Auricaps for a pair of Stealthcaps. They are considerably bigger and I have some space issues but it should be okay to solder the output wires and ground etc from below the board. The pads should be able to take the solder. Has anyone soldered from below the board and are there any issues with doing so? Also the cap wires are about an inch long? Is this going to cause me any problems that anyone can foresee?

Thanks

 

[Hikari1]

I thought I was almost done but I decided to swap out the Auricaps for a pair of Stealthcaps. They are considerably bigger and I have some space issues but it should be okay to solder the output wires and ground etc from below the board. The pads should be able to take the solder. Has anyone soldered from below the board and are there any issues with doing so? Also the cap wires are about an inch long? Is this going to cause me any problems that anyone can foresee?

Thanks

Wires to bottom of board is no problem. Cap wires are no problem...you need to be able to measure DC offset before the cap so the length of bare wire is good for that.

 

[Manolo47]

MOSFET heatsinks wattage capacity...

Would a 10w aluminum one fit the bill?

 

[KevinHeem]

Would a 10w aluminum one fit the bill?

These are the HEATSINKS I used. Can't tell you if the 10W would work.

 

[silasmellor]

In the process of biasing the right channel now. I notice there is a bit of offset after the cap (10uf mundorf evo oil), between 10-30 mv. Nothing reconnected to output at the moment. Is this acceptable?

 

[Zen Mod]

put bleeder resistor

100K will do