diyAB Amp The "Honey Badger" build thread

AndrewT · 2016-02-19 9:18 am

why don't you attach your pics?

Wishborn · 2016-02-19 9:30 am

I did, worked yesterday, now they don't so I shared the album link. I don't know why I suddenly get permission denied, I'll fix it later tonight after work or at lunchbreak

AndrewT · 2016-02-19 9:37 am

Which post did you think you had attached some pics?

I can see you using a remote server that automatically downloads the whole pic file.

Wishborn · 2016-02-19 10:17 am

I see that google bans directlinking, worked last night but I recon they have a filter looking up direct linked photos baning after a amount of reads.
bugger that. I fixed it...

An externally hosted image should be here but it was not working when we last tested it.

Wishborn · 2016-02-20 3:28 pm

Yes, found the problem, Q13 was turned around. Don't know how that happened, but it is fixed now.

Now when biasing this, I turn r17 and DC moves down to around 0 mv.
When turning this dc offset down bias is also moving down and I have to turn a few turns to see some reaction, is this correct behaviour? so for each time I adjust back and forth these moves more or less together?

helitim · 2016-02-20 3:45 pm

Wishborn said:
Q13 was turned around. Don't know how that happened, but it is fixed now.

Glad to hear you figured it out!

helitim · 2016-02-20 3:53 pm

I have just revised my Transistor BOM based on all the recommendations and charts I reviewed while away at work. Below is what I came up with to drive my Statement II's. Does anyone see anything that I may have overlooked?

Q1-Q2 = SS9014DBU
Q3-Q4 =KSC1845FTA
Q5-Q6 = KSA992FTA
Q7-Q8 = KSC1845
Q9 = KSA992FTA
Q10 = KSA1381ESTU
Q11, Q12, Q13 = KSC3503DSTU
Q14/Q15 = MJE15032G/ MJE15033G
Q16-Q21 = MJL4281AG/ MJL4302AG

helitim · 2016-02-21 6:42 pm

Finishing Touches

I have a couple

D) of questions now with my BOM complete...

1) For all the 1/4 watt resistors, I chose Xicon metal film precision 1%. The original BOM had a mix of Carbon and metal film for the 1/4 watters. Choosing 1 brand of high precision MF resistor made the process much quicker, and gives less room for error at 1%. Is this okay?

2) For the 1/2 watters, I stuck with the reccomends, except:
R23 - Xicon 33R 1%, 1/2W metal film
R27 - Xicon 68R 1%, 1/2W metal film
R32,33,53,54 - Xicon 22R .05%, 1/2W Carbon film
R43-48 - Vishay .2R, 1%, 5W Wirewound

Is this Okay? I'm not sure about the metal film and fire ratings, etc for these parts of the circuit.

For the Capacitors:
I stuck with the same type of caps as the recommends, except:
C1 as preciously discussed is the WIMA MKS2 POLY
C5 I chose ECA-2AM470 (Panasonic)...My concern is that the BOM calls for 6mm diameter, but this one is 8mm... anybody know if this will fit OK with everything on the board? I believe this was the recommended unit.

Diodes were straight foward.

For the accessories:
1) Would prefer to use mica insulators for the transistors. Anybody have a source for TO-264 mica insulators?

2) Mouse is sold out of the 2-pin "eurobloc". is there an alternate P/N perhaps I could try?

That's all for now

Thanks,
Tim

AndrewT · 2016-02-22 9:01 am

Xicon 22R .05%, 1/2W Carbon film

Can carbon film achieve and/or maintain this precision over the longer term?

helitim · 2016-02-22 1:57 pm

AndrewT said:
Can carbon film achieve and/or maintain this precision over the longer term?

From what I read, the CF resistors lose accuracy over time. I wasn't sure if metal film was suitable though because of fire rating for that circuit. I wasn't too sure what to do for the 1/2 Watters because they do have more current going through them, and I was thinking of safe operation.

Would you recommend switching to the metal film? I know they are a more reliable resistor from what I read.

yngvejos · 2016-02-22 2:14 pm

I used metal film everywere except for the 0R22 wirewound. It sounds great and I see no reason to use carbon instead.

helitim · 2016-02-23 3:09 am

yngvejos said:
I used metal film everywere except for the 0R22 wirewound. It sounds great and I see no reason to use carbon instead.

Thanks, I will stick to metal film.

Anybody have an opinion on KOA or Yageo ? The Xicon doesn't drop below 21c a piece until you order 200. 3-5c per piece for 100 of KOA or Yageo. Not that I need 100 of each, just thinking of future projects...

AndrewT · 2016-02-23 9:20 am

In the UK, we have metal film 500mW and 600mW 1% 100ppm/C at around 2p when bought by the hundred. That's about $3/100

helitim · 2016-02-23 1:37 pm

AndrewT said:
In the UK, we have metal film 500mW and 600mW 1% 100ppm/C at around 2p when bought by the hundred. That's about $3/100

I wish prices were that good here!

helitim · 2016-02-23 2:26 pm

Andrew T: I found some 600mW 1% metal films for 3c per piece/ 100. Not sure if I can get all sizes, but probably most needed. Aside from awkward mounting, do you think there would be fitting issues?

AndrewT · 2016-02-23 3:43 pm

Our Vishay/Philips/Royal 600mW are just suitable for a 0.4", or 10mm, pin pitch or larger.
But 0.45" allows a bigger bending radius of the lead out.
Check the body length.

AndrewT · 2016-02-23 3:45 pm

Our Vishay/Philips/Royal 600mW are just suitable for a 0.4", or 10mm, pin pitch or larger.
But 0.45" allows a bigger bending radius of the lead out.
Check the body length.

They are usually available in E24 range from 10r to 1M

janusz · 2016-02-24 12:58 am

I use low inductance 5W KOA in the output circuits where values of 0.1 to 0.33 ohm and higher wattage ratings are needed. In zoebel I use caddocks.

In PAs, as I said before, I use 1W 1% metal film resistors except where low noise and inductance make sense. I use Dale resistors there.

cheers,

helitim · 2016-02-24 1:27 pm

AndrewT said:
Our Vishay/Philips/Royal 600mW are just suitable for a 0.4", or 10mm, pin pitch or larger.
But 0.45" allows a bigger bending radius of the lead out.
Check the body length.

They are usually available in E24 range from 10r to 1M

I measured a few 1/4 resistor pitch pads on the badger PCB. The are roughly 8-9mm (5/16). I can get 6.8mm or smaller 1/2 Watters. Would this leave enough room for lead bending in your opinion?

janusz said:
I use low inductance 5W KOA in the output circuits where values of 0.1 to 0.33 ohm and higher wattage ratings are needed. In zoebel I use caddocks.

In PAs, as I said before, I use 1W 1% metal film resistors except where low noise and inductance make sense. I use Dale resistors there.

cheers,

Thanks Jaunsez

AndrewT · 2016-02-24 1:32 pm

helitim said:
I measured a few 1/4 resistor pitch pads on the badger PCB. The are roughly 8-9mm (5/16). I can get 6.8mm or smaller 1/2 Watters. Would this leave enough room for lead bending in your opinion? ............

8 to 9mm is well below 0.4" (I did not realise the Badger PCB had them that small !)
Our 600mW resistors would not fit that pin pitch. It would require the lead out to be bent very sharply at the exit from the body putting excessive strain on the bent wire (risk of fatigue failure due to work hardening) and risking cracking of the coating.

If the wire lead out is welded to the end cap, then there will be a (weld) heat affected zone and one should not place a bend inside this heat affected zone.
If some other attachment method is used then for reliability reasons I would be wary of bending very close to the attachment.

I cannot see any bending specification in either Vishay, nor Tru-Ohm datasheets. The body length is stated as 6mm to 6.5mm for the 600mW resistors.

Precision resistors from Holco had very specific bending instructions. They could not be fitted to narrow pitch pin pads and as a result had to be stood on end for most assembly. Holco H8 are 8mm body length and if the minimum radius were 2mm and to start 1mm from the body, then minimum pin pitch would be 14mm. That's why we generally see them stood on end.

diyAB Amp The "Honey Badger" build thread

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