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Old 5th April 2012, 10:19 AM   #11
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Quote:
Originally Posted by danielwritesbac View Post
Wow, that's compact! It looks great. Have you heard it play yet? I was wondering if it is RF resistant like your other boards?
Yes, If your source doesn't introduce RF strictly, there isn't any issue with RF blocking if we regarding bare amplifier itself. It is dead silent. My conclusion about RF issue that depending my experience is, it is not related with layout that much. It is exclusively related with topology.
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Old 5th April 2012, 01:01 PM   #12
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Quote:
Originally Posted by danielwritesbac View Post
NOS High voltage (more than 40v rails) NPN VAS (4 to 16pF)
2N5858
2N5858 is more likely 2N3019 (80V) but higher fT. Then we may categorize it as "NOS medium voltage"
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Old 5th April 2012, 10:55 PM   #13
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Default Vas, Q5, Q6. . . 4pF to 16pF range

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Originally Posted by forr View Post
Hi,
I am very interested by the Circlophone because having nothing to preset, just like the Quad 405, and because it is a very good way to recycle old devices. It also had good specs and nice reviews. I started to extract the necessary components for my many junk-boxes. However, I did not find any 2N3019 for the Q5-Q6 pair. Being in Tours (France) yesterday, I went to this shop
Radioson where I have been proposed BSW68A (originated form Philips, I think). Looking at the datasheets, they seem adequate for the circuit. What do you think ?
Regards.
On the datasheet, you need to see COB in the range of 4 to 16 pF, like these: 2n3498, 2n3499, 2n3500, 2n3501, 2n3019, 2N3020, 2N1893, 2SC3421, 2SC5171, 2SD667A, a real Hitachi 2SD669, NXP BCP56, a real Philips BC639, a real Philips BD139 (gray case, markings "PHI"), or a BF819 or some low capacitance MosFets.
The 6pF to 12pF selections are near the middle of the range (8pF centerpoint tolerance), for best performance.

Elvee recently mentioned a capacitor trick that I wish I'd known about earlier, since there are lot of medium current ("mini driver" aka "predriver") devices below 4pF COB that I shouldn't have disregarded during my parts search. Apparently, one can increase the device capacitance, for example BF819's 3.9pF to a practically perfect, centerpoint tolerance, 8.6pF, by simply adding a 4.7pF capacitor from collector to base.


Parts Examples. . .
Just for fun, let's look at an all 6pF example with Philips devices:
Philips BC560C (NXP BC860) Input -to- Philips BC639 (NXP BCP56, Philips BD139) VAS -to- Philips BD140 Driver
It is baby bear, mama bear, papa bear, family.
There is small, medium and large, all low capacitance 6pF devices.
Highly expensive, availability at LittleDiode (or ask your favorite hoarders).

How about an all NEC (sometimes Hitachi branded NEC) example:
2SA988 Input -to- 2SD667A (2SD669 is cooler) VAS -to- 2SD647 (SA1220) Driver
That's 2pF small (may be twitchy for layout, extreme gain--must match), 12pF medium, and 26pF large.
Caution: most of today's market is fake and/or dysfunctional reproductions.
Availability: Zilch, except maybe they're in your junk box.

And now for Toshiba:
2SA970-BL Input -to- 2SC3421 VAS -to- 2SA1930 Driver
There's 4pF small, 15pF medium-large, and 26pF large.
This combination can sometimes be found at LittleDiode and Electronics Salon.
2SA1930 can be found many places, including Mouser.

Why not Fairchild (NEC and Philips second source) too?
KSA992, BC560C or BC556C input -to- (KSC1009, TN3019 too hot) ST's 2N3019 VAS -to- KSA1220 Driver
There's 2pF or 6pF small, 12pF medium, and 26pF large.
This combination can be found at Mouser.

For VAS (Q5, Q6) a 2N3019 can be found almost anywhere as there are many makes of this still popular 1 watt NPN transistor. ST brand has close matching (but you might want to HFE match Motorola for QC). The large metal transistor is easier to cool than plastic alternatives.

You can mix and match the above examples, which will make slight differences in sonic signature.

Exceptions (more like "trades"):
Given a really good quality part for VAS and given good layout too (trace length?), then it is possible to use an ordinary ST BD140 or a popular big OnSemi TO220 for driver.
The reverse is also true, since a really good quality low capacitance driver (like authentic gray case Philips BD140 at 6pF) could let you use a slightly higher capacitance VAS.
Reasonable at both locations also works--we've seen this work well with the Toshiba 2SA1358-Y 2SC3421-Y pairs (that Elvee tested for us) when the NPN is 15pF to 16pF and the driver is 26pF to 30pF.

Last edited by danielwritesbac; 5th April 2012 at 11:11 PM.
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Old 6th April 2012, 01:22 AM   #14
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Default Easter egg!

In honor of the Easter holiday, I have hyperlinked a heck of a lot and included a link to an authentic stock of gray case Philips BD140 PNP drivers. . . somewhere on this thread. . . And, there's a lot of other classic and recent devices to find. As always, high performance classics are in short supply, so if you miss them, just ask your friends here on diyaudio.com, since trading devices and supplies is fairly commonplace. This forum also has a commercial sector that is worth mentioning. NOS (discontinued) devices aren't vital to Circlophone at all; however, some people do like to use the classic devices for fun.
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Old 7th April 2012, 11:17 AM   #15
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What size heatsinks are people using?
I have a couple 260 x 100 x 40 high fins, use one or both?

Getting nearer, boards populated apart from BD140's + heatsinks.
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Old 7th April 2012, 03:50 PM   #16
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Quote:
Originally Posted by TonedeafDIY View Post
What size heatsinks are people using?
The dissipation is mostly comparable to that of more conventional class AB amplifiers.
There are one or two minor differences: the quiescent power is typically 2 to 3 times larger than a normal AB amp, , but that is partly compensated by a better efficiency at high power.

Quote:
I have a couple 260 x 100 x 40 high fins, use one or both?
For a 60W/ch amplifier used domestically, one is enough.
If you build a higher power version, and you listen to heavily compressed music at high volume, you should use one per channel
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. .Circlophone your life !!!! . .
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Old 8th April 2012, 08:58 AM   #17
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Quote:
Originally Posted by TonedeafDIY View Post
What size heatsinks are people using?
I have a couple 260 x 100 x 40 high fins, use one or both?
Getting nearer, boards populated apart from BD140's + heatsinks.
With the sole clue being the voltage range of BD140. . .
I guess 120w to 140w worth of class AB amplifier per each heatsink (much depending on other factors like thermal interface speed, quality of thermal materials, significant amplifier enclosure ventilation, added mounting brackets, etc. . .).
So, 1 heatsink for stereo amp with 8 ohm speakers or 2 heatsinks if 4 ohm speakers.
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Old 14th April 2012, 09:14 AM   #18
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Quote:
Originally Posted by Elvee View Post
I have just tested the 2SA1930/2SC5171 pair as drivers and VAS.
The samples kindly provided by Daniel are authentic, and they perform remarkably well in the Circlophone.
The all-plastic construction makes mounting on a heatsink very easy, and the case has a low enough thermal resistance of its own for the VAS to be left without heatsink.
In summary, an excellent choice: high availability, good performances and ease of use: a dream.
Did you, subjectively, like the little toshiba pair better or the big toshiba pair? Oh, I meant the audio quality?

I wish I could have been there to see the look on your face while you were pin bending and soldering great big TO220NIS sized parts into the VAS. Thank you for testing.

I guess that the 2SA1930/2SC5171 have one oddity in that they work better after warming up, but that is not a problem here.
Toshiba is also carried inexpensively by Mouser so this is very convenient. I would also like to thank Electronics Salon and Zoe_Tsang for commitment to authentic parts.

Last edited by danielwritesbac; 14th April 2012 at 09:20 AM.
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Old 14th April 2012, 10:12 AM   #19
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Quote:
Originally Posted by danielwritesbac View Post
Did you, subjectively, like the little toshiba pair better or the big toshiba pair? Oh, I meant the audio quality?
I think Elvee is preferring to leave listening impressions to the builders. And he already stated that he had tiny ears.

Since that I'm not such a skilled and equipped person for accurate measuring, capable builders (like Elvee) may help us to provide part combinations for oscillation free builds, especially without that 10nf. I know that if a Circlophone is healthy, it is already sounding very beautiful. Hope you get my idea.
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Old 14th April 2012, 11:11 AM   #20
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Quote:
Originally Posted by terranigma View Post
. . .tiny ears.. . .
Tin ears is a regional colloquialism, meaning that one does not have perfect pitch; however, when returned into the original context (containing polite satire) it may mean that ears do not substitute for measuring. It probably means that just one set of ears do not substitute for measuring. The preference of leaving the published listening impressions to others is because a larger sample makes better data.

Last edited by danielwritesbac; 14th April 2012 at 11:25 AM.
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