♫♪ My little cheap Circlophone© ♫♪

[Elvee]

Originally Posted by danielwritesbac

I have a few more curiosities. . .
The 2N5551 actually does not work consistently across all builds for Q12/Q13 (HFE and noise differences), and as a result, there is some variety of troubles, like suddenly blown output devices, extra heat, or just a sonic signature difficulty. Is there, by any chance, a better commonplace device "just like" BC546B that could manage Q12/Q13 with up to 40+40vdc rails?

The 2SC(or KSC)1845 is a perfect substitute, commonly available and suitable for up to +/-60V supplies

And, there's two more curiosities from the prototype photos. . .
Those two big yellow 22uF caps? Are they inbound of the Shottky's or is it simply 22uF//100uF per rail?

No they are 2.2µF rail decouplings (mylar), but this was an early prototype, and I don't recommend doing it: they resonate with the supply leads and cause ringing.
Good electrolytics like in the schematic are preferable, they provide decoupling and damping

That ST-BD140 driver pictured has the extension obscured by the mounting screw and I was wondering if it is BD140-10 or BD140-16, since whichever device was actually used during measuring is a nice point of reference

Neither, they are unsorted, suffixless.

[Elvee]

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.

[pdp11]

this is an interesting unusual desing,
I have bookmarked this thread, I hope i found the time for an deeper analisys.

P.

[danielwritesbac]

Originally Posted by pdp11

this is an interesting unusual desing,
I have bookmarked this thread, I hope i found the time for an deeper analisys.
P.

Today I have done more upgrades to the Circlophone Builder's Thread so it can be faster to read.

The information is presented tight and compact.
It also has example schematics, a verified parts shopping feature, many pcb layouts, a perfboard method, a build/art gallery, and accessories.
Circlophone has a live sound characteristic.
There are many available parts and perhaps you already have most of them.

[danielwritesbac]

Originally Posted by Elvee

. . .
1/ 2SD1047 1.76
2/ MJ(L)21194 1.6
3/ MJ(W)21196 1.45
4/ MJ15022,4 1.2
5/ BD249C 1.04
6/ MJ15003 0.94
7/ MJ15015 0.55
8/ MJE3055 0.46
9/ TIP41 0.43
10/ 2N3055 0.35
. . .

What do you think of these?
MJ802G 30a,
MJW1820G 30a,
MJE13009G
FJA13009TU

While I was working on it, some of the program code on the builder's thread found those devices automatically. So, temporarily, I have constricted the search to omit them, because I do not know if they are suitable.

[Elvee]

I didn't find data on the MJW1820.

Here is the figure of merit for the others:

MJ802 0.71
MJE/FJA13009 1.2
But the absolute value of the Hfe for the 13009 is very low, and this will put severe stress on the drivers.

[danielwritesbac]

Originally Posted by Elvee

I didn't find data on the MJW1820.
Here is the figure of merit for the others:
MJ802 0.71
MJE/FJA13009 1.2
But the absolute value of the Hfe for the 13009 is very low, and this will put severe stress on the drivers.

Good news for the MJ802. Thanks.
MJW1820? Sorry for the typo. It is MJW18020G, a 250w plastic.

The links below open datasheets.
Here are the stragglers:
MJW18020G 30a, 250w HFE14
MJE18008G 8a, 125w, HFE14
FJP13007H1TU 8a, 80w, HFE15

[Elvee]

Originally Posted by danielwritesbac

G
Here are the stragglers:

MJW18020G 30a, 250w HFE14: 2.36
The 2.36 figure is excellent, but unfortunately since it is a high voltage transistor, the useful Hfe is low, around ~30, and this will demand hefty drivers.

These two have a really too low gain (<10) to be of any use:
MJE18008G 8a, 125w, HFE14
FJP13007H1TU 8a, 80w, HFE15

[Piersma]

An extremely rugged multi emitter transistor, also excellent for the Circlophone: the Sanken 2SC2922

[Elvee]

Originally Posted by Piersma

An extremely rugged multi emitter transistor, also excellent for the Circlophone: the Sanken 2SC2922

Indeed: its figure of merit is 6.

With this transistor, a good layout, good bypassing and optimum compensation is compulsory: with the 50MHz Ft, any imperfection will result in oscillations.