(AK) classA HA/Preamplifier.

[Deleted]

Jan 27, 2011 14:23:49 GMT @cjarchez said:

Hi Will,

For super nonces like myself, is this what you mean?

Chris

Hi Chris

nicely done diagram and is how i have installed mine.

(by the way nonce means something quite different to what you have in mind (hopefully) where i come from.

take care

[Will]

Hi Shaun,

out of interest, what value did the test point value start at, roughly?

Adjusting the LTP is not to important at this stage, but nice to know it's working.

When the amp is fully cased up, listen for an hour, take the lid off, and adjust the LTP testpoints for as close to 0V as you can. Then put the lid back on and listen for another hour or so. Now repeat the adjustment. I found that I only needed to do this three times.

[Deleted]

Jan 27, 2011 16:33:25 GMT Will said:

Hi Shaun,

out of interest, what value did the test point value start at, roughly?

Adjusting the LTP is not to important at this stage, but nice to know it's working.

When the amp is fully cased up, listen for an hour, take the lid off, and adjust the LTP testpoints for as close to 0V as you can. Then put the lid back on and listen for another hour or so. Now repeat the adjustment. I found that I only needed to do this three times.

Hi Will

i think it started of at around 50mV or so over TP1 & TP2. the voltage across the 2.5r was 120mV both boards where pretty much the same but i did center the trimmers before installation.

i was quite surprised how close the measurements where board to board even down to the offset V (unloaded). very nice work indeed:o i did (out of habit) match the stunt transistors.I just could not help myself......... NURSE!!!!!!!

so i have single supply with CL bypassed so i can switch them on latter to hear what difference they make. I'll give it a week or so before switching in the second supply for full dual mono.

yes I'll readjust when i have a spare few hours but the amp is not going to be left switched on unattended until I'm totally sure He's going to behave nicely. the same goes for the special K headphones.

TAKE CARE

[Deleted]

Hi all

I've just whipped the 550 560's out. just to mention something i forgot earlier WATCH THE PIN OUTS of the above: as the orientation is slightly different to the LS's. my 550 560 are CBE so do check with the circuit diagram and make double sure to avoid spoiling the party.

any lucid explanation here would be great.

also i soldered them in to the middle sets of holes just the minimum solder will do (the more put in the more to take out : also solder them in with long legs as it makes them easier to remove (i know some will not have a problem with that). i figured that if it goes pear shaped i would still have the outside holes. as it goes mine came out pretty easy with a little solder sucking to clean up. :)so now to fit the crown Jewell transistors.

take care

[Will]

Some good points to remember when building the pcb's up, Shaun. I suppose there is a fair amount of solder in the pin-hole, especially when the pcb is 3mm thick!

Back on page 25, there is a pin-out of the holes for the LS devices. As Shaun says, the LS devices are pinned differently than 'normal' transistors, so pay careful attention when using the stunt transistors.

rockgrotto.proboards.com/index.cgi?action=downloadattachmentpage&board=m&thread=3977&post=82812

and some links to the datasheets for the LS313 and LS352

www.linearsystems.com/datasheets/LS310-3.pdf
www.datasheetcatalog.org/datasheet/linearsystems/LS350-2.pdf

[Deleted]

Jan 27, 2011 19:00:21 GMT @shaun said:

Hi all

I've just whipped the 550 560's out. just to mention something i forgot earlier WATCH THE PIN OUTS of the above: as the orientation is slightly different to the LS's. my 550 560 are CBE so do check with the circuit diagram and make double sure to avoid spoiling the party.

any lucid explanation here would be great.

also i soldered them in to the middle sets of holes just the minimum solder will do (the more put in the more to take out : also solder them in with long legs as it makes them easier to remove (i know some will not have a problem with that). i figured that if it goes pear shaped i would still have the outside holes. as it goes mine came out pretty easy with a little solder sucking to clean up. :)so now to fit the crown Jewell transistors.

take care

Hi Shaun
The original PCB design took BC550/BC560 directly, but Jon and Will
modified the layout to accept the new dual transistors directly, instead of having to cross leads over.This subject has been previously covered, but due to the length of the thread could be easily missed.
Alex

[Deleted]

Jan 27, 2011 20:37:39 GMT Will said:

Some good points to remember when building the pcb's up, Shaun. I suppose there is a fair amount of solder in the pin-hole, especially when the pcb is 3mm thick!

Back on page 25, there is a pin-out of the holes for the LS devices. As Shaun says, the LS devices are pinned differently than 'normal' transistors, so pay careful attention when using the stunt transistors.

rockgrotto.proboards.com/index.cgi?action=downloadattachmentpage&board=m&thread=3977&post=82812

and some links to the datasheets for the LS313 and LS352

www.linearsystems.com/datasheets/LS310-3.pdf
www.datasheetcatalog.org/datasheet/linearsystems/LS350-2.pdf

Hi Will

yes solder did flow down some of the outside holes. i just used a quick flick of solder to get em set in and a damed good sucking (so to speak) to get the b****rs out again. i heated one side of the board and sucked from t'other and it seemed to work fine just a bit fiddly.

LS's are in and the patient seems to be doing fine so far so tomorrow it's the full set up.

Take care

[Deleted]

Jan 27, 2011 20:41:50 GMT @sandyk said:

Jan 27, 2011 19:00:21 GMT @shaun said:

Hi all

I've just whipped the 550 560's out. just to mention something i forgot earlier WATCH THE PIN OUTS of the above: as the orientation is slightly different to the LS's. my 550 560 are CBE so do check with the circuit diagram and make double sure to avoid spoiling the party.

any lucid explanation here would be great.

also i soldered them in to the middle sets of holes just the minimum solder will do (the more put in the more to take out : also solder them in with long legs as it makes them easier to remove (i know some will not have a problem with that). i figured that if it goes pear shaped i would still have the outside holes. as it goes mine came out pretty easy with a little solder sucking to clean up. :)so now to fit the crown Jewell transistors.

take care

Hi Sean
The original PCB design took BC550/BC560 directly, but Jon and Will
modified the layout to accept the new dual transistors directly, instead of having to cross leads over.This subject has been previously covered, but due to the length of the thread could be easily missed.
Alex

Hi Alex

How's it going?

yes i did find the explanation earlier in this thread but being new to transistors i also nearly forgot. maybe the advantage of newness is i always seem to be checking and rechecking things.

LS's are in amd the patient lives. so failing any disasters good to go to the setup tommorow.

take care

[Deleted]

Hi Shaun
Updated schematic is attached. I think all of the guys here in this thread are able to check the pinouts of the alternative/test transistors from downloaded data sheets.
Regards
Alex

[Deleted]

i have single supply with CL bypassed so i can switch them on latter to hear what difference they make. I'll give it a week or so before switching in the second supply for full dual mono.

Hi Shaun
I found mine sounds far better with the CLs in circuit, not like in the Jaycar HA. I would recommend that both JLHs use the CLs .
When you go to dual mono, you could if you wished, increase the emitter resistors of the CL transistors to 1.2 or 1.5 ohms, as the current through each JLH will then be half of that when using a single JLH.
Alex

[Deleted]

Jan 27, 2011 21:36:27 GMT @sandyk said:

i have single supply with CL bypassed so i can switch them on latter to hear what difference they make. I'll give it a week or so before switching in the second supply for full dual mono.

Hi Sean
I found mine sounds far better with the CLs in circuit, not like in the Jaycar HA. I would recommend that both JLHs use the CLs .
When you go to dual mono, you could if you wished, increase the emitter resistors of the CL transistors to 1.2 or 1.5 ohms, as the current through each JLH will then be half of that when using a single JLH.
Alex

Hi Alex

Yes the CL is definitely going on tomorrow but i did want to have a quick listen without just to see what it did to the sound.
its just a case of snipping a few wire links and it's in. i think another sign of newness is if it works think hard before hassling it.so the Caps in the JLH have had about a month of continuous burn in (forming) so should be good to go. I'll CL her tomorrow and have another measure around the TP's and see if anythings changes.

take care

[Will]

Attached a big version of the circuit the pcbs were created from. It might be useful to refer to both diagrams.

Attachments:

[Deleted]

Jan 27, 2011 21:41:40 GMT @shaun said:

Jan 27, 2011 21:36:27 GMT @sandyk said:

Hi Sean
I found mine sounds far better with the CLs in circuit, not like in the Jaycar HA. I would recommend that both JLHs use the CLs .
When you go to dual mono, you could if you wished, increase the emitter resistors of the CL transistors to 1.2 or 1.5 ohms, as the current through each JLH will then be half of that when using a single JLH.
Alex

Hi Alex

Yes the CL is definitely going on tomorrow but i did want to have a quick listen without just to see what it did to the sound.
its just a case of snipping a few wire links and it's in. i think another sign of newness is if it works think hard before hassling it.so the Caps in the JLH have had about a month of continuous burn in (forming) so should be good to go. I'll CL her tomorrow and have another measure around the TP's and see if anythings changes.

take care

Hi Shaun
In my case, (but not necessarily with all builds), it sounded a little "closed in", like the bandwidth had been reduced, or it was on the verge of instability, when the CL wasn't in circuit.
That's part of the reason I suggested that the VAS BC549c shouldn't have an HFE too much above 500.
Regards
Alex

[Deleted]

Jan 27, 2011 22:58:26 GMT @sandyk said:

Jan 27, 2011 21:41:40 GMT @shaun said:

Hi Alex

Yes the CL is definitely going on tomorrow but i did want to have a quick listen without just to see what it did to the sound.
its just a case of snipping a few wire links and it's in. i think another sign of newness is if it works think hard before hassling it.so the Caps in the JLH have had about a month of continuous burn in (forming) so should be good to go. I'll CL her tomorrow and have another measure around the TP's and see if anythings changes.

take care

Hi Shaun
In my case, (but not necessarily with all builds), it sounded a little "closed in", like the bandwidth had been reduced, or it was on the verge of instability, when the CL wasn't in circuit.
That's part of the reason I suggested that the VAS BC549c shouldn't have an HFE too much above 500.
Regards
Alex

Hi Alex

point taken with the CL.

i have them built in but bypassed for the cap forming part of the PSU build. so just a case of snipping the links and it's done.

i must say those JLH and Signal boards just look great built up. works of art in every sense.

take care

[XTRProf]

Jan 27, 2011 12:58:49 GMT @shaun said:

Hi All

DC offset unloaded 16mV
DC offset loaded uV (yup so low my multimeter runs out of resolution)
TP1-2 set to 200uV ish(again so low my multimeter runs out of thinking power)
100ma set

well done Alex and Will

stunt transistors in

NO HUM, a smidgen of hiss

even on the crap forlorn hope headphones it sounds great

i think it's time for the nice transistors

so halfway there just the pre to do now

come on you lot

Wow, Shaun, you clearly as good as already won the century sprint! We "retardards" still hopping and panting to the finish line.

[Deleted]

Wow, Shaun, you clearly as good as already won the century sprint! We "retardards" still hopping and panting to the finish line.

Hi Chong

No no no it's not a race. it's just the way i like to work. if it takes too long i loose focus and miss things. so took a day off (boss was OK with that ) and got stuck in. i did use the waiting for the boards time to get the components sorted, build the PSU / JLH and do some hacking at a case. so just Will's lovely signal boards to do.

Mr Chong i took a quick listen last night (ended up a three hour session)_and would at this point say that the sound is fantastic. so just one or two more quick hops and you are in for a real treat.

just out of interest what headphones will you be using? i plugged the K701 in last night and they worked very well with this amp (i did hear the stunt phones muttering about never being given the Chance to play anymore as they went back to there box).

take care

[XTRProf]

Jan 28, 2011 9:28:38 GMT @shaun said:

Mr Chong i took a quick listen last night (ended up a three hour session)_and would at this point say that the sound is fantastic. so just one or two more quick hops and you are in for a real treat.

Yup, it should be good without even hearing yet. It will be same for me when everything is working fine. CDs after CDs, SACDs/DVDAs after SACDs/DVDAs or Vinyls after Vinyls and so forth.

Btw, have you compared it to any tube HA in your arsenal yet? Oops........., again ducked quickly for cover, lucky me for being army trained, as Alex is coming ..........

Jan 28, 2011 9:28:38 GMT @shaun said:

just out of interest what headphones will you be using? i plugged the K701 in last night and they worked very well with this amp (i did hear the stunt phones muttering about never being given the Chance to play anymore as they went back to there box).

take care

Still looking for one cheap TEST HP so as not to be broken hearted if things go awry. Most probably a Superlux HD668B or Koss Portapro Limited Edition. Come to the worst, my Philips digital wireless SHD6800 as it has an switch for high output HA. Most unlikely for the last option. Highend not likely so fast and still considering the options carefully.

[Deleted]

Shaun
What kind of diet are you feeding it ?
It was also specifically designed to play back much higher resolution files without HF rolloff, so the higher the quality of the source material, the better it will sound.At least that has been my finding, even with 24/192 material , or 24/96 DLs. An attenuator instead of a normal Blue Alps will further extend the bandwidth.
Just remember to use a 100pF Input filter cap with 20-25K volume controls and 47pF for 50K volume controls.
Alex

[Will]

Still looking for one cheap TEST HP so as not to be broken hearted if things go awry. Most probably a Superlux HD668B or Koss Portapro Limited Edition. Come to the worst, my Philips digital wireless SHD6800 as it has an switch for high output HA. Most unlikely for the last option. Highend not likely so fast and still considering the options carefully.

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.

[XTRProf]

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

Still looking for one cheap TEST HP so as not to be broken hearted if things go awry. Most probably a Superlux HD668B or Koss Portapro Limited Edition. Come to the worst, my Philips digital wireless SHD6800 as it has an switch for high output HA. Most unlikely for the last option. Highend not likely so fast and still considering the options carefully.

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.

[Deleted]

ShaunWhat kind of diet are you feeding it ?

Hi Alex

Just good old fashion vinyl.(Notts Analogue Spacedeck with heavy graphite mod and psu. airbairing parallel tracking tone arm, Lyra Dorian, WAD phono 2 with Nick Gorham shunt psu mod but I'm thinking of trying to find a good SS phono so any ideas welcome) 8-)so not the super deluxe but still a very good setup IMHO.

on the digital side not so good (Squeezebox duet with QNAS server and Cambridge Audio dacmagic or Audio note DAC2.1.
yup i need to sort the digital side of things out. i am finding that the Audio note is keeping the stunt phones company in the unused box. the Cambridge is much more to my liking so I'll be planing a goooood dac before long i suspect. i was a bit slow with computer audio (i still marvel at the fact that i can build with people from all over the world) but agree that the potential for improvement with higher res files is real and valid. I'm going to be picking someones brain on a good computer for audio so look out for the dumb questions.

Hi Chong

all i have in the way of tube HA is a little dot MK11 MK11 and it's just pants (mullard front end and 6n30p drivers) just crap IMHO.

. i will be looking at building something better but that's some way off and the quality of the Class A just makes me wonder about the effort of building another HA. it realy is that good

take care

[Deleted]

An attenuator instead of a normal Blue Alps will further extend the bandwidth.Just remember to use a 100pF Input filter cap with 20-25K volume controls and 47pF for 50K volume controls. Alex

Hi Alex

yes good points. i have one of those ebay cheapy DACT alike switchers from Velab and i must say it sounds a whole lot better than i was expecting . i do think that the Goldpoint or DACT looks good for the money so I'll think on that. Alps blue's are OK for the money but lack the extension,clarity and balance of a good switch pot IMHO. i have not used a tracked pot for years (the extra detail and top end sparkle was always welcome with my tube stuff).not to mention the relatively poor tracking balance. with a good switcher you just know that its going to be better in most ways.

i have used the Dale Vishay switcher which uses the same switch. can i tell the difference sound wise? er no but my wallet can i have used a few of those D/V's and they have all had the bouncezilla (switch loosing contact with the contact momentarily it's poor English but you know what i mean ) not so with the VL. well done to them.

so the Velab (vintage audio lab) gets a thumbs up from me. it's good value for money. build quality is OK but you can tell the difference just in the action between the cheapy and a good switch (VL feels a little sloppy but still OK and usable) but no bounce with the VL so well done to them. anyone on a tight budget should try one. I've just ordered another for the pre

it's just IMHO so i may be wrong

so i have a 50k switcher but used 100pf for the input filter so will need to have a look at that once things settle down.

on another subject ish

i did use an Alps Blue to get the SCHA up and running (what i had to hand) but he did not last long and has been replaced with the VL stepper. much much better. I'm using the SCHA without input caps as i found that (i did try plenty of expensive caps) all the caps i tried made the sound worse. just could not bring myself to use them in the end. SCHA is being measured up for a nicer suit. he has been a good boy and deserves a pampering.

take care

[Will]

Just in case, here is the layout of the PCB. Red traces on the top, blue traces under.

Attachments:

[jonclancy]

I've come to the conclusion that I will be a few more weeks with mine.

Got this on the bench at the moment... good news is that it will be playing music soon. Not so good news is that the AMB switchery circuits have yet to be built and tested, so that white-ring LED stainless Bulgin switch will be purely for show for the time being.



Cheers

Jon

[Deleted]

Jan 28, 2011 15:04:14 GMT jonclancy said:

I've come to the conclusion that I will be a few more weeks with mine.

Got this on the bench at the moment... good news is that it will be playing music soon. Not so good news is that the AMB switchery circuits have yet to be built and tested, so that white-ring LED stainless Bulgin switch will be purely for show for the time being.



Cheers

Jon

Hi Jon

Very nice work makes mine look pretty dull

take care