(AK) classA HA/Preamplifier.

[Will]

Ages ago I made a little 15V DC cap pre-former

Hi Jeff,

Sounds interesting, fancy sharing that one? Or is it just a dc supply?

[Deleted]

Feb 3, 2011 21:54:20 GMT Will said:

Ages ago I made a little 15V DC cap pre-former

Hi Jeff,

Sounds interesting, fancy sharing that one? Or is it just a dc supply?

Hi Jeff

x2

take care

[jonclancy]

Jan 29, 2011 0:59:05 GMT XTRProf said:

Btw, what PS boards are you using. They look to have more real estate to fit those big e-caps.

Hey Chong,

Do you think 163,200 uF of PSU caps will be enough?

[Deleted]

Jon,

Kendeils eh, someone's splashing out

Will you have the chance to compare them to a "standard" set up to see how much/what they do to the SQ?

Chris

[jonclancy]

Hi Chris,

Mmm, yes. Pricey but absolutely first rate. Got them in the GB at PFM some time ago. These were bought for my F4/5 project that has been in the wings for some time! However, they could very easily be tried in the Class A for a bit of fun. I think they will be better employed in a future project coming to RG very soon!!

Cheers

Jon

[Deleted]

Feb 4, 2011 15:13:38 GMT jonclancy said:

Hi Chris,

I think they will be better employed in a future project coming to RG very soon!!

Cheers

Jon

Attachments:

[Deleted]

Feb 4, 2011 13:10:02 GMT @shaun said:

Feb 3, 2011 21:54:20 GMT Will said:

Hi Jeff,

Sounds interesting, fancy sharing that one? Or is it just a dc supply?

Hi Jeff

x2

take care

Hint :
You could also try asking Leo.

[Spirit]

Feb 4, 2011 15:13:38 GMT jonclancy said:

I think they will be better employed in a future project coming to RG very soon!!

Class A power amp?!

(my next project!)

[jeffc]

PCBs arrived yesterday, cheers Will

Thick buggers, never seen anything like them, bump into the Titanic and they'd rip it open like a can opener.

Stuffing them now, wondering about all the extra inductance because of the extra wire lengths extending through the holes, pads are a little tiny too so its testing my soldering skills. Not the neatest I've done.

Re the "cap burner", I'll dig up the circuit Alex sent me and snap a pic of how I built it on the little vero boards I have when I get a sec this arvo. Could easily use any one of the 'several' DC supplies I have to do the same, but built one for fun anyway when I was bored one day and in need of a soldering fix. Sad really

Need to take the bride somewhere soon for an outing or suffer the next worse thing to death, , punishment for hiding away in my cave "work room/office" all morning.

cheers.. jeffc

[Deleted]

Stuffing them now, wondering about all the extra inductance because of the extra wire lengths extending through the holes, pads are a little tiny too so its testing my soldering skills.

Hi Jeff
I don't think an extra 1.5mm is going to make any noticable difference at these frequencies.
I got some 2 way PCB screw terminal strips from Altronics in preference to those from Jaycar, as their mounting pins are .5mm longer instead of the usual 3mm. The ends of them are just flush with the copper of the pad. I will not be doing too much for a while as it's 39C here at the moment, and the cool change after 6 days of above 30C isn't predicted to arrive until after noon tomorrow.
It will still hit at least 30C before it arrives though.
Alex

[jeffc]

Yer Alex,

You guys in Sydney a copping shocking heat ATM, we're melting here too and Rocky collapsed after his 1.5 h walk this morning and hasn't moved since. I was dripping wet too with +30C heat and +90% humidity at 6:30am, worse than Cairns. Doesn't make for doing anything, but I only get weekends unlike you folk of leisure. The sea breeze has finally kicked in thank goodness, can breathe again.

My terminal blocks only poke through 0.5-1.0 mm too but the case is so tight in width I might have to solder +V and -V supply wiring directly to the underside of the PCB anyway. I'm leaving these til' last. Thanks for the tip on where to get others.

cheers..jeffc

[Deleted]

Hi Jeff

Still 40.3C here at the moment, which is a slight improvement on the 40.9C it was an hour ago.
I had a few spare Jaycar terminal blocks and they were quite a bit below when I tried inserting them.
That't why I got some from Altronics this morning.
Despite these minor problems, the PCBs should look very imposing when completed !
Alex

P.S.
Temp is now back to 40.9 at 4.50PM DST.

[Will]

Feb 5, 2011 1:50:42 GMT Spirit said:

Feb 4, 2011 15:13:38 GMT jonclancy said:

I think they will be better employed in a future project coming to RG very soon!!

Class A power amp?!

(my next project!)

Yep, that's the one, in 15W guise. It'll be a while yet, and I'll post details in a separate thread, so that it doesn't confuse matters here.

[Will]

Hi Jeff,

Thanks for the feedback on the PCB's. I've seen a few 3mm PCB's, and they have coped fine with the components I've used, so a bit odd that you guys are finding them short. The JLH's we did were 3mm, as is a ArjenHelder TA2020 pcb I have.
I'll look into the solder mask on the PCB, as I think it's that which is perhaps constricting the pads. Having said that, I've the pads are again similar in size to other pcb's I bought in the past (pimeta, mini3).

How far do you think you are from having sound? Sounds like you are of to a flying start!



edited for spelling: pdd=odd!

[XTRProf]

Feb 4, 2011 13:59:46 GMT jonclancy said:

Jan 29, 2011 0:59:05 GMT XTRProf said:

Btw, what PS boards are you using. They look to have more real estate to fit those big e-caps.

Hey Chong,

Do you think 163,200 uF of PSU caps will be enough?

Wow, I almost dropped off my chair when I saw this. I love it, man! Oh hail, the next king here! You have me thoroughly beaten down right there! Great!

Yeah, do let us know the sound. I'm expecting the biggest bass whallop in the richter scale ...............

[XTRProf]

Jan 28, 2011 10:13:27 GMT XTRProf said:

Jan 28, 2011 10:00:15 GMT Will said:

No need for anything decent in a pair of stunt phones. Just follow these simple rules.

1. Goto shops.
2. Find cheapest headphones (not in-ear types)
3. Buy them.

There you go. All you are looking for is something to make sounds, and if you suddenly get 32Vdc on the output during testing, you've not wasted your money.

Agreed .......... But the Superlux is also very cheap and sounds good from reviews even if used permanently later.

Had been digging around during the spring cleaning for the CNY and found this:




Ohmage measured



so just perfect for the "Suicide Mission HP". Ok, Rambo go to work after the HA build or you be fired as well!

[Deleted]

Feb 5, 2011 10:15:19 GMT Will said:

Hi Jeff,

Thanks for the feedback on the PCB's. I've seen a few 3mm PCB's, and they have coped fine with the components I've used, so a bit pdd that you guys are finding them short. The JLH's we did were 3mm, as is a ArjenHelder TA2020 pcb I have.
I'll look into the solder mask on the PCB, as I think it's that which is perhaps constricting the pads. Having said that, I've the pads are again similar in size to other pcb's I bought in the past (pimeta, mini3).

How far do you think you are from having sound? Sounds like you are of to a flying start!

Hi Will

I've built up 4 of these boards now and managed just fine. I'm waiting on some matched 1930/5171 from tubeshunter to finish the second pair. i will check the match on those and report back. ;D

I'm not used to building on circuit boards but found the ones you produced for the Class A very nice to work on. so the lead lengths end up a bit longer due to the thickness of the boards 8-)we are not building phono stages here are we?

I've found that for small solder pads it helps to used a bit with a finer tip.

take care

[Will]

PCB layout, just in case it's needed

Red traces on top, blue on the bottom.

Attachments:

[Deleted]

Hi All

I've just received my matched 5171/1930 from Tubeshunter on ebay.

they are advertised as matched hfe to within 3% and when checked with my atlas DCA55 i found following:

5751 - hfe 149 and 150
1930 - hfe 140 and 150

so Tubeshunter gets the thumbs up from me.

oh yes and they are the genuine stylized t version so all good

take care

[Deleted]

Hi Shaun
The only hold up with me now, is waiting for some more 2SA1930 to arrive from RS. I had around 20 x 2SC5171, but only 2 x 2SA1930 left.
I could have used those , but wanted a closer match.
Regards
Alex

[Deleted]

Feb 8, 2011 10:14:42 GMT @sandyk said:

Hi Shaun
The only hold up with me now, is waiting for some more 2SA1930 to arrive from RS. I had around 20 x 2SC5171, but only 2 x 2SA1930 left.
I could have used those , but wanted a closer match.
Regards
Alex

Hi Alex

i bought 25 of each to get four dead on matches so i have lots of pairs but no quads. good news for the JLH but no cigar for the ClassA. I thought I'd try some of those ebay tubeshunter ones Will mentioned some time ago in this thread and fair doooo's they measured pretty well.

I'm glad you are up Alex.

IT'S QUADS

I now have all four boards up and running.

the Pre Boards have a 68r load so it will be interesting to compare that to the 120r load for the HA with K701. what really got me was how close the first start up V's where on all four boards (great work).

for the Pre I'm using OPA0134 for the offset IC (i had a spare pair from neco portable)and it measures just as well as the 744 which i used for the HA.

so it's going supa dooopa.

thanks again Alex

[Deleted]

Attached is a component layout for Will's PCB, as well as a schematic showing voltage measurements to assist fault finding.
The voltages shown are approximate, and from my own Class A HA which differs ONLY in using modified SC designed PCBs.
The readings were taken with the cover off, (as you would expect!)
so the amplifier was not fully warmed up.
Alex

P.S.
Please advise me if you spot any errors or omissions in the layout diagram or schematic.
The TPa and TPb voltages shown are WRT -20V rail.



URL=http://img825.imageshack.us/i/therockgrottoclassahapr.jpg/][/URL]

[jonclancy]

Just got my MyRefs up and running in the chassis last night. Sounding great, but more importantly allows me to tidy up the workroom and start to fit all the MATCHED resistors to my Class A boards. Wow!! I'd forgotton how much I would appreciate 0.1% resistors if they were reasonably priced!!!

Here's an interesting tip for you stepped attenuator users that I caught in the LS thread over at DIYA. I think it might have some relevance to Class A builds.

www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp-80.html#post2463689

Cheers

Jon

[Deleted]

Feb 10, 2011 11:42:29 GMT jonclancy said:

Just got my MyRefs up and running in the chassis last night. Sounding great, but more importantly allows me to tidy up the workroom and start to fit all the MATCHED resistors to my Class A boards. Wow!! I'd forgotton how much I would appreciate 0.1% resistors if they were reasonably priced!!!

Here's an interesting tip for you stepped attenuator users that I caught in the LS thread over at DIYA. I think it might have some relevance to Class A builds.

www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp-80.html#post2463689

Cheers

Jon

Hi Jon

I'll give the blue tack a try on the back of my cheapy stepper. I have my stepper located at the back of the chassis on an aluminum extension shaft. good tip for Ali shafts is to use heat shrink on them as I've found that it reduces that ringing sound when changing volume. I've used blue tack on the stepper mounting plate but never really thought of damping the switch body so worth a go.

i used 0.1 for the 100r and 150r emitter resistors but i can't comment any change in sound as i used them from the start. I'm pretty sure that the technical reasons for using them in that location are sound and make sense.

i was thinking of using them for the 10K feedbacks but have not got around to trying that yet.

thanks for the tip

take care.

[jonclancy]

Hi Shaun,

Agreed about the 0.1% emitter resistors. I have some (somewhere) in my bombsite room that Will sent me. I'll have more of a rummage around, as I have cleared up the desk and have the PCBs cleaned and ready to start stuffing!!

We were thinking about doing something a bit trick for the feedback resistors. Z Foils have been mooted. but 10K might be a bit on the pricey side.

Good luck with the damping - I'll be interested to hear how you get on. I might just have to get one of those Valab steppers to validate my own comparisons here!

Cheers

Jon