(AK) classA HA/Preamplifier.

[jonclancy]

Here is a pic of the distribution. Some way out there! But a nice grouping in the 99.9 - 100.2uF range.

[leo]

Mar 1, 2011 0:00:51 GMT @shaun said:

Is the Dact ladder and the Valab shunt? if so I'd try replacing the series resistor on each channel of the valab with something like a Minimelf or other low noise low inductance type.

Hi Leo

how's it going?

as far as i can tell the Mini V and DACT are both series as is the Vlab unless i've missed the shunt R on the Vlab. i may be wrong so feel free to correct me if I've blundered.

yes interesting as the Mini V and Dact both use the same Elma switch but from what i have read have tensioned the springs slightly differently. so any sonic difference would be down to the quality of resistors used and yes i do think that's going to make some difference (did not really believe that resistors made much impact on the sound until i tried some tants on the cathodes of some of my tube amp and heard the noise floor drop) also the construction quality of the boards may impact on the sound i guess to a lesser extent. I've not heard the mini V so can't say how it sounds but that could be interesting to compare at some point. I've read that the goldpoint is pretty darn good though but as Alex said it's a game diminishing returns.

I've schmooched round the net and found some comparisons. some like one and some the other (even read one who preferred the DACT because it was queter to use and did not annoy his wife(spring tension)) so if the mini v uses better resistors then in theory it should sound better.

i fear that my current set up has not the resolving power to clearly show the difference between Vlab and DACT. you may have noticed that i am planning (well mostly groping around in the dark) a PC hi res set up with hopefully a Buffalo at some stage to bump up the SQ maybe.

i did opt for the DACT as long term thing in a kind of fit and forget way. it'll be interesting to try the Vlab again once I've sorted my front end just to see if there is more of a marked difference compared to the DACT or not.

but in my present set up there was no huge jump in SQ from one to the other and the most obvious thing was the improvement to the top end. i did try an Alps Blue which sounded shut in in comparison to the Vlab IMHO.

lets be honest if i could by something with the quality of the Vlab ten years ago for that price I'd be pretty happy (very very happy in fact). so that's moved on quite a bit in a short space of time.

it may be an interesting experiment to shunt the Vlab with a nice resistor to see what that does. shunts of course have there problems but I've had pretty good results from shunting steppers with a nice (box vishay) resistor. then maybe try the Alps shunted with the same resistor just for fun. TBH i just don't like what shunts do to the input impedance and SQ. i have used them but really hard not to as they can sound a bit unnatural to my not so good ears.

i think that if i was going for the best VFM I'd opt for a six position switch (Elma) with maxed out high quality resistors (just for the HA not the PRE) as i don't seem to use much more than that on the switch at the moment.

any way blah blah blah sorry but I'm interested in your thoughts

switches don't even get me started on that

take care

Hi Shaun,

A little knackered but not too bad thanks, hows yourself?

For through hole axial type resistors I usually use something like MRS25's in most places rather than faffing about , all newer metal film and even carbon ones don't seem bad, maybe go for something better in places like IV section of a dac .
With the SMD type resistors some really are not suited for audio and can sound poor, theres quite a variation between types thin and thick films. Some of those cheap attenuators I've seen floating about on ebay use smd types and some are not supplied with details which types are used. If they used poor types and if it was a shunt type then changing the pair of series resistors with something half decent may give a cheap easy improvement. If its a ladder type obviously its not so simple to try.
Just thinking out loud tbh

Agree regarding the Alps blue pots, they tend to sound a little shut in, the last one I tried didn't measure too well either for the channel matching

Regards
Leo

[jonclancy]

I'm hoping to match the following cap pairs on each board. The single caps left on the board will be matched across the stereo pair.

C4/10
C5/11

C6/9
C7/8
C21/22

I think the first two pairs are the most important, but any comment on that welcome!

Cheers

Jon

[Deleted]

Seeing as Tubeshunters prices are similar to Cricklewood, he's a good option if you don't want to buy a job lot and match yourself.

Hi Jon

i used Tubeshunter for my second set of boards and found that they matched pretty close when i measured them.

i was happy with them

take care

[jonclancy]

Hi Shaun,

Yes, Tubehunter's a good option. The rig makes matching pretty quick. Perhaps we could open a swap-shop thread to marry up the orphans. I think Will has some in his stash.

Cheers

Jon

[Deleted]

Hi Shaun,A little knackered but not too bad thanks, hows yourself?For through hole axial type resistors I usually use something like MRS25's in most places rather than faffing about , all newer metal film and even carbon ones don't seem bad, maybe go for something better in places like IV section of a dac . With the SMD type resistors some really are not suited for audio and can sound poor, theres quite a variation between types thin and thick films. Some of those cheap attenuators I've seen floating about on ebay use smd types and some are not supplied with details which types are used. If they used poor types and if it was a shunt type then changing the pair of series resistors with something half decent may give a cheap easy improvement. If its a ladder type obviously its not so simple to try. Just thinking out loud tbh Agree regarding the Alps blue pots, they tend to sound a little shut in, the last one I tried didn't measure too well either for the channel matchingRegardsLeo

Hi Leo

I'd need to get the trinoculars out to see what resistor types the Vlab uses but it's a series so a shunt would be a possibility. i might try that on the SCHA to see what it does.

i think that DACT are using thin film Vishays but they are not that forthcoming with the type the use.

I'm not that keen on shunts but it may help the Vlab and give some idea of the quality of resistor used by them. ;D

i agree with you that selecting the best place to use the nice resistors is important. i just dint get the splash it all over way that some seem to go for.

i noticed that you said in your post that the small things matter to some.

yup they all add up

we'll be saying the earth is round next

yes things are good here thanks


take care

[Deleted]

Mar 1, 2011 18:11:23 GMT jonclancy said:

Hi Shaun,

Yes, Tubehunter's a good option. The rig makes matching pretty quick. Perhaps we could open a swap-shop thread to marry up the orphans. I think Will has some in his stash.

Cheers

Jon

Hi Jon

that's good thinking let's do it. shall we have a singles bar thread or just post here?

take care

[Will]

So as not to get confusion here, please note that I'm talking of the link between Signal Ground to Chassis Ground ie GND CONNECTOR, which is missing in my PCBA, to BOX CHASSIS. Of course, I will put the other "link" as what I can see everybody was referring to, otherwise there wouldn't be any sound coming from the HP due to open circuit if we follow the traces on the AHA PCB. I will put that link with OCC copper tinned with solder to prevent copper oxidation.Frans is talking the same lingo as me there.

Hi Chong,

I'm sorry about that, I got it completley arse about face, didn't I? I really should not post before I wake up!

[Will]

I'm up for swapping toshies, guys, sounds a good idea. Perhaps if we PM or email? Still find it funny that the ones in my current build are all in the 200 range, whereas to day , they are much lower. Perhaps the silicon you get to day isn't as good as in the old days? ;D

I've another 10 of each to test, thanks to Cricklewood, so will test them and see where I stand.

[Deleted]

Mar 1, 2011 20:00:45 GMT Will said:

I'm up for swapping toshies, guys, sounds a good idea. Perhaps if we PM or email? Still find it funny that the ones in my current build are all in the 200 range, whereas to day , they are much lower. Perhaps the silicon you get to day isn't as good as in the old days? ;D

I've another 10 of each to test, thanks to Cricklewood, so will test them and see where I stand.

Hi Will
Don't forget that you can use the higher HFE BC327-40 and BC337-40 to make up for the reduced gain of the Toshiba devices.
Mine has no stability problems when using that combination.
Regards
Alex

[Will]

Mar 1, 2011 16:36:06 GMT jonclancy said:

I'm hoping to match the following cap pairs on each board. The single caps left on the board will be matched across the stereo pair.

C4/10
C5/11

C6/9
C7/8
C21/22

I think the first two pairs are the most important, but any comment on that welcome!

Cheers

Jon

oooooh, new toy! Nice bit of kit isn't it, and pretty good that we will all be within 1 or 2 'hfe's' when using the DCA.

As for the caps, If I was matching them, that's the pairings that I would go for on each PCB. The electro's and films on the offset corrector c19-c22 aren't as important ( shouldn't have any audible effect), but what the hell, you got the proper kit, so use it

The other thing that impressed me is the relatively narrow spread of values on those FM's, really narrow. There's almost a XKCD comic to be had out of it! What were the worst values to be had?

[Will]

Mar 1, 2011 20:19:08 GMT @sandyk said:

Mar 1, 2011 20:00:45 GMT Will said:

I'm up for swapping toshies, guys, sounds a good idea. Perhaps if we PM or email? Still find it funny that the ones in my current build are all in the 200 range, whereas to day , they are much lower. Perhaps the silicon you get to day isn't as good as in the old days? ;D

I've another 10 of each to test, thanks to Cricklewood, so will test them and see where I stand.

Hi Will
Don't forget that you can use the higher HFE BC327-40 and BC337-40 to make up for the reduced gain of the Toshiba devices.
Mine has no stability problems when using that combination.
Regards
Alex

On the case, Alex

[jonclancy]

Mar 1, 2011 20:20:50 GMT Will said:

Mar 1, 2011 16:36:06 GMT jonclancy said:

I'm hoping to match the following cap pairs on each board. The single caps left on the board will be matched across the stereo pair.

C4/10
C5/11

C6/9
C7/8
C21/22

I think the first two pairs are the most important, but any comment on that welcome!

Cheers

Jon

oooooh, new toy! Nice bit of kit isn't it, and pretty good that we will all be within 1 or 2 'hfe's' when using the DCA.

As for the caps, If I was matching them, that's the pairings that I would go for on each PCB. The electro's and films on the offset corrector c19-c22 aren't as important ( shouldn't have any audible effect), but what the hell, you got the proper kit, so use it

The other thing that impressed me is the relatively narrow spread of values on those FM's, really narrow. There's almost a XKCD comic to be had out of it! What were the worst values to be had?

Hi Will,

Thanks for the confirmation - I was holding off until someone checked my work!! The FM range from 99.02uF (a pair on the left of the photo) to 100.5uF on the right. Actually, the far right cap is a rogue 106.6 - still within the datasheet limits, but one I won't be using in a critical location!

These meters are BRILLIANT! Thanks very much for the loan of yours (which I will be returning very soon). Possibly the best bit of electronics kit I have bought for a long time, and I know I'll be using these LOTS!

I'll get these caps and terminal blocks soldered in ASAP and then have a think about the transistors. Got around 330 Hfe for some I trial measured (cant remember which).

Cheers

Jon

[Deleted]

Hey Jon !
Why don't you use the furthest apart samples, have a good listen, then change over to closer matched ones, and report back the differences heard ? (after allowing time for them to "acclimatise ")




Only stirring !
Regards
Alex

P.S.
I do NOT recommend changing electros with this thick , but beautiful,PCB ! You may end up in deep doo doo !

[jonclancy]

Nae probs - just use my SMD tweezers that are hotter than the sun itself! Caps just drop out in .3 sec!

But, can't be bothered with all of that!

[Deleted]

Mar 1, 2011 20:00:45 GMT Will said:

I'm up for swapping toshies, guys, sounds a good idea. Perhaps if we PM or email? Still find it funny that the ones in my current build are all in the 200 range, whereas to day , they are much lower. Perhaps the silicon you get to day isn't as good as in the old days? ;D

I've another 10 of each to test, thanks to Cricklewood, so will test them and see where I stand.

Hi Will

All but two of the 31 I've had from three sources have all been well under 200. no worries from me on that though

i just thank god and Mike that i bought the atlas it just made things much easier and less of a chore.

I'll sort out my singles and PM or email what do people think?

take care

[Deleted]

Mar 2, 2011 0:17:23 GMT jonclancy said:

Nae probs - just use my SMD tweezers that are hotter than the sun itself! Caps just drop out in .3 sec!

But, can't be bothered with all of that!

Jon
Interesting method. I must get back my SMD tweezers that I loaned a friend.
Using normal methods, due to the PCB thickness, you may still need to wiggle the caps a bit. I had trouble removing some of the short pin terminal blocks when replacing them, due to a tight fit.
I found a little bit of copper on one of the removed one's pins.
Alex

[XTRProf]

Mar 1, 2011 16:12:47 GMT jonclancy said:

Here is a pic of the distribution. Some way out there! But a nice grouping in the 99.9 - 100.2uF range.

Hi Jon,

Just being nosy as usual, what caps are those? Panasonic, BG or whatever .......... I really love your matching of the caps as we are talking of highend methodology now.

[XTRProf]

Mar 1, 2011 19:54:53 GMT Will said:

So as not to get confusion here, please note that I'm talking of the link between Signal Ground to Chassis Ground ie GND CONNECTOR, which is missing in my PCBA, to BOX CHASSIS. Of course, I will put the other "link" as what I can see everybody was referring to, otherwise there wouldn't be any sound coming from the HP due to open circuit if we follow the traces on the AHA PCB. I will put that link with OCC copper tinned with solder to prevent copper oxidation.Frans is talking the same lingo as me there.

Hi Chong,

I'm sorry about that, I got it completley arse about face, didn't I? I really should not post before I wake up!

Actually, no problem. Just keep the comments coming whether right, righter or wrong, wronger. Free speech is all for me as I really like constructive comments to get feebacks to see how I'm doing. That's what great forums are all about out of concen for each other. Really no problem and so don't have it as your bedtime nightmare .........

[XTRProf]

Mar 1, 2011 18:25:29 GMT @shaun said:

Mar 1, 2011 18:11:23 GMT jonclancy said:

Hi Shaun,

Yes, Tubehunter's a good option. The rig makes matching pretty quick. Perhaps we could open a swap-shop thread to marry up the orphans. I think Will has some in his stash.

Cheers

Jon

Hi Jon

that's good thinking let's do it. shall we have a singles bar thread or just post here?

take care

Excellent and should be in another dedicated thread since many parts have to be bought in bulk. I'm all for that thread in the parts section.

[XTRProf]

Really just in case if I can't find 0.1uf film caps in Singapore, can I subsitute those for 0.15uf film caps. I remember I can get it from one of the diy shops in Singapore. I know for sure that C4, C6, C9, C10, C18, C19 and C20 can. But I'm not too sure for C3 though.

Thanks for any feedback.

[Deleted]

Mar 2, 2011 7:59:41 GMT XTRProf said:

Really just in case if I can't find 0.1uf film caps in Singapore, can I subsitute those for 0.15uf film caps. I remember I can get it from one of the diy shops in Singapore. I know for sure that C4, C6, C9, C10, C18, C19 and C20 can. But I'm not too sure for C3 though.

Thanks for any feedback.

Chong
150nF should be fine at all locations, but 100nF should normally be easier to obtain than 150nF as they are far more commonly used. Alex

[Deleted]

Re the tosh swaps, I found the correct box!
So I'll kick things off with the balance of my "Audio Wind" pieces.



Note I'm using a standard meter, and had a bit of a game getting a constant reading.

[jonclancy]

Nice work, Chris.

Mine were mostly lower Hfe as mentioned earlier.

Here is the Transistor Lonely Hearts Club I've started in the DIY Resources section.

rockgrotto.proboards.com/index.cgi?action=display&board=barry&thread=6456

Chong, these are all Panasonic FM Low ESR caps.

Alex, the smd tweezers run so hot that they just melt smd parts to a blob. I think they are at a fixed (turbo) temperature!! But they are great for desoldering as I don't bend leads when I stuff a board, rather use a bit of insulating tape to hold the part in place while I solder. With the tweezers and a suitably wide "tip" (I made mine from copper plate, but will one day invest in the proper item), you can literally pull out a DIP 8 in an instant!

Progressing well on the board stuffing, but realise I don't have the 7XL15, but can get some in a week or so from RS. I think I'm going to settle on the 20K Valab, as it is similar value to my other attenuators if I want to do any meaningful comparisons.

Cheers

Jon

[Deleted]

Mar 2, 2011 12:58:47 GMT @cjarchez said:

Re the tosh swaps, I found the correct box!
So I'll kick things off with the balance of my "Audio Wind" pieces.



Note I'm using a standard meter, and had a bit of a game getting a constant reading.

Guys
Let's not get carried away here.Chris has a few more than adequate matches here. They would still be only around 2% different which is fine in the output stage.You will more than likely have trouble getting their driver transistors that close in HFE. (BC327 and BC337)
Alex