HeadWize: DIY Workshop > β22: A discrete, cascoded, fully complementary, pure class A amplifier (part 3)

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DIY Workshop » β22: A discrete, cascoded, fully complementary, pure class A amplifier (part 3)
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amb

Headphone Council

Joined: Apr. 1, 2004
Locale: Sunnyvale, CA. USA
Total Posts: 4408

Message [#60] posted on: 09-12-2008 05:05 AM CST (US).

[Quoting jazzist]
Today I'm very excited as my first β22 backplane arrived :-) (for active ground unbalanced or left channel balanced, there will be another for the right channel balanced/active ground unbalanced).

How about posting some pictures?

jazzist

Member

Joined: May 9, 2008
Locale: N/A
Total Posts: 30

Message [#61] posted on: 09-12-2008 06:27 AM CST (US).

[Quoting amb]
How about posting some pictures?

Sorry, and sorry about the pic, hadn't taken them out of the bubble wrap.

MrMajestic2

Member

Joined: Jun. 5, 2007
Locale: N/A
Total Posts: 90

Message [#62] posted on: 09-12-2008 06:36 AM CST (US).

[Quoting jazzist]
[Quoting amb]
How about posting some pictures?

Sorry, and sorry about the pic, hadn't taken them out of the bubble wrap.
http://mathew.sm...209_UtCwa-M.jpg
http://mathew.sm...te>
Is it just me, or is that pcb black?

n_maher

HeadWize Fanatic

Joined: Dec. 15, 2004
Locale: Portsmouth, NH
Total Posts: 478

Message [#63] posted on: 09-12-2008 10:03 AM CST (US).

[Quoting MrMajestic2]

Is it just me, or is that pcb black?

You can get PCB's masked with all sorts of colors (black, red, blue, green, etc.). Green is the least expensive and the most common.

MrMajestic2

Member

Joined: Jun. 5, 2007
Locale: N/A
Total Posts: 90

Message [#64] posted on: 09-12-2008 11:45 AM CST (US).

[Quoting n_maher]
[Quoting MrMajestic2]

Is it just me, or is that pcb black?
You can get PCB's masked with all sorts of colors (black, red, blue, green, etc.). Green is the least expensive and the most common.

Hehe, yeah, I know that. I just thought that AMBs boards were all green <smile>

jazzist

Member

Joined: May 9, 2008
Locale: N/A
Total Posts: 30

Message [#65] posted on: 09-12-2008 12:35 PM CST (US).

It's my own backplane design, I'll post some better photos probably when the project is a bit further along <smile>

MrMajestic2

Member

Joined: Jun. 5, 2007
Locale: N/A
Total Posts: 90

Message [#66] posted on: 09-12-2008 12:38 PM CST (US).

[Quoting jazzist]
It's my own backplane design, I'll post some better photos probably when the project is a bit further along

Oh very cool, please share info and better pictures <smile> I thought it looks a bit slimmer than AMBs board.

wolf18t

Member

Joined: Mar. 13, 2008
Locale: Quebec, QC, Canada
Total Posts: 14

Message [#67] posted on: 09-17-2008 09:48 PM CST (US).

Hello AMB. I finally put the final touch to my B22!

It's a few months since I started the project but summertime is too short in eastern Canada to let it pass, so I delayed the contruction of my B22 somewhat.

Here's some build information:
- Single Ended, 3 channels with o22 in the same case.
- Late in the project, I added the e12 muting circuit.
- I followed the parts recommendation but have choose many boutique parts suggested like Nichicon Muse KZ and FW and TKD pot;
- Case, pot shaft extension kit and knob from DIY Enclosures LLC
- Encapsulated and shielded transformer from Richard Sumner Technology. I can certify that I have no hum issues with either low or high impedance cans.
- RCA females jacks: Gold over copper DHLABS;
- Most hook-up wires: 22 AWG multistranded silver plated copper wires from ebay seller "navships" - great value!
- Most of the transistor were match following device matching procedure shown in the B22 homepage. Actually all the transistors were matched before I had to replace 1 malfunctionning MOSFET in the left stereo board. Bummer! I didn't keep track the Vgs of my remaining IRFs and was too lazy to unsolder the other MOSFETs to retake their Vgs for rematching.

The only thing I want to replace on my B22 is the ugly volume knob. As I receive it from DIY Enclosures his gold color doesn't quite match the front panel champagne color. DIY Enclosures chrome ones are out of stock <frown> Anyone reading this having 50mm chrome polished knob reference or for sale please contact me.

Now some pictures:

Warm up time before final output stage BIAS adjustment...

Top view

For quick changing gain value I socketed R3/R4/C2-C5 on gold plated SIP connnectors

Front view

Some credits on the rear plate... <sticking tongue out>

Installed, plugged and ENJOY <big grin>

Other pictures: http://public.fo...eta-22-headpho/

AMB do you still add picture on your B22 gallery? If so I would like to send you some of my pictures.

amb

Headphone Council

Joined: Apr. 1, 2004
Locale: Sunnyvale, CA. USA
Total Posts: 4408

Message [#68] posted on: 09-17-2008 10:06 PM CST (US).

wolf18t, congratulations on completing your build. The only issue is the fact that the volume pot is right next to the IEC power entry module, but if you don't hear any hum, then that's what matters.

Yes, I always welcome submissions to the website gallery. PM me for details.

Thanks for the credit on the back panel. <cool>

wolf18t

Member

Joined: Mar. 13, 2008
Locale: Quebec, QC, Canada
Total Posts: 14

Message [#69] posted on: 09-18-2008 08:40 PM CST (US).

[Quote]
The only issue is the fact that the volume pot is right next to the IEC power entry module, but if you don't hear any hum, then that's what matters.

I admit I made an error. I drilled the 6mm extension shaft on the front panel before figuring were to put all boards and transfo. My initial plan was to hide the IEC module behind the transfo, but that was much too tight. I was lucky on this one. I guess the earth grounded shielded IEC case saves me.

MrMajestic2

Member

Joined: Jun. 5, 2007
Locale: N/A
Total Posts: 90

Message [#70] posted on: 09-20-2008 12:21 PM CST (US).

If I change the gain using socketed components, does that affect bias?

amb

Headphone Council

Joined: Apr. 1, 2004
Locale: Sunnyvale, CA. USA
Total Posts: 4408

Message [#71] posted on: 09-20-2008 03:01 PM CST (US).

[Quoting MrMajestic2]
If I change the gain using socketed components, does that affect bias?

No it doesn't.

starcat

Member

Joined: Sep. 19, 2008
Locale: N/A
Total Posts: 1

Message [#72] posted on: 09-20-2008 03:54 PM CST (US).

Hello there,

anyone remember this seller on ebay selling silver plated copper wires and which AWG and what lenghts are roughly required for a 4ch version of beta22 with two sigma22 and two torroids in a separate case? Thanks!

MrMajestic2

Member

Joined: Jun. 5, 2007
Locale: N/A
Total Posts: 90

Message [#73] posted on: 09-20-2008 04:03 PM CST (US).

[Quoting starcat]
Hello there,
anyone remember this seller on ebay selling silver plated copper wires and which AWG and what lenghts are roughly required for a 4ch version of beta22 with two sigma22 and two torroids in a separate case? Thanks!

You mean Navships or John's Silver Teflon Wire Shop:
http://stores.e...eflon-Wire-Shop

Cant help you with the length, I never calculated mine. I used AWG 22 for mine.

[Edited by MrMajestic2 on 09-20-2008 at 04:03 PM.]

amb

Headphone Council

Joined: Apr. 1, 2004
Locale: Sunnyvale, CA. USA
Total Posts: 4408

Message [#74] posted on: 09-20-2008 05:10 PM CST (US).

wolf18t, I just noticed that your headphone jack might not be isolated. If that's true, you would have a short circuit between the ground channel amp's output and the chassis.

wolf18t

Member

Joined: Mar. 13, 2008
Locale: Quebec, QC, Canada
Total Posts: 14

Message [#75] posted on: 09-21-2008 07:58 PM CST (US).

[Quote]
wolf18t, I just noticed that your headphone jack might not be isolated. If that's true, you would have a short circuit between the ground channel amp's output and the chassis.

AMB, You made my heart spin! <shocked>

I've just check again and the signal ground connector of the switchcraft is isolated from the chassis and earth ground <cool> . BTW I used the Switchcraft NL112B which is specified as insulated.

Thanks for worrying. For my curiosity, what made you think from the pictures it was not isolated?

amb

Headphone Council

Joined: Apr. 1, 2004
Locale: Sunnyvale, CA. USA
Total Posts: 4408

Message [#76] posted on: 09-21-2008 08:03 PM CST (US).

[Quoting wolf18t]
Thanks for worrying. For my curiosity, what made you think from the pictures it was not isolated?

The jack's mounting nut contacts the front panel. If the jack's threaded collar is not plastic, then it's connected to the sleeve contact of the jack, and thus will short to the chassis. I couldn't tell whether your jack has a metal collar or plastic. In either case, you have to also be careful that the headphone plug's sleeve connection doesn't touch the mounting nut when it's inserted into the jack, or you'd create a short.

wolf18t

Member

Joined: Mar. 13, 2008
Locale: Quebec, QC, Canada
Total Posts: 14

Message [#77] posted on: 09-21-2008 08:29 PM CST (US).

[Quoting starcat]
Hello there,
anyone remember this seller on ebay selling silver plated copper wires and which AWG and what lenghts are roughly required for a 4ch version of beta22 with two sigma22 and two torroids in a separate case? Thanks!

IIRC it is recommended to use bigger wire than 22AWG for the umbilical cable between your separate o22 power supply and b22 amplifer chassis. And IMHO you won't have a gain using silver plated wires when not in the audio signal path. I've just used ordinary stranded copper 18 AWG wires in my build.

The wires I've got from Navships were in 50 feet in lenght. I ordered the 3 basic strereo colors (red/white/black). Even if you order only one color, you can build many b22 with 50'!

wolf18t

Member

Joined: Mar. 13, 2008
Locale: Quebec, QC, Canada
Total Posts: 14

Message [#78] posted on: 09-21-2008 08:36 PM CST (US).

[Quoting amb]

In either case, you have to also be careful that the headphone plug's sleeve connection doesn't touch the mounting nut when it's inserted into the jack, or you'd create a short.

Thanks for the warning, AMB. I'll be careful to this fact.

lcp

Member

Joined: Nov. 12, 2006
Locale: N/A
Total Posts: 33

Message [#79] posted on: 09-23-2008 01:36 AM CST (US).

Hi Amb,

In addition to my Sigma22 problem, I have problem from B22 as well. One B22 board has -3.7V at the output. I have checked the diode property of all npn, pnp, mosfet etc. It seems Ok when comparing with the normal working board. I found D9 was broken during check. According to the 24V checklist, I found 0V at the check point between Q1&Q5 while it was OK at Q3&Q7. I have swapped Q1, Q3 and Q5 but problem was not fixed.

amb

Headphone Council

Joined: Apr. 1, 2004
Locale: Sunnyvale, CA. USA
Total Posts: 4408

Message [#80] posted on: 09-23-2008 01:46 AM CST (US).

lcp, did you check to see if there are other voltage anomalies against the troubleshooting pdf file? When you "swapped" Q1, Q3 and Q5, did you replace them with new parts? Is CR1 installed in the correct orientation? Is there 12V across D1? What are the voltages across R9 through R12?

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