I noticed that on the new Leach Superamp I just finished the DC offset jumps around during the playing of music. There is no input cap. The amp seems to work just fine with great bass.
Thanks
Thanks
Hi Valery
Your ideas seem to me very interesting, especially about VAS stage, may I suggest that you try the 2SC1775/2SA872 for the IPS stage, and the 2SA1360/2SC3423 for the VAS or as a low power Driver stage.
As a drivers the 2SD669/2SB649 and as you post earlier the Sanken's for output.
I made a lot of simulations on different circuits and this combination *give me *the best results.
Best regards
Your ideas seem to me very interesting, especially about VAS stage, may I suggest that you try the 2SC1775/2SA872 for the IPS stage, and the 2SA1360/2SC3423 for the VAS or as a low power Driver stage.
As a drivers the 2SD669/2SB649 and as you post earlier the Sanken's for output.
I made a lot of simulations on different circuits and this combination *give me *the best results.
Best regards
Heres an old Maplin amplifier circuit from the 1980's.
It was 225WRMS into 4 ohms.
I used one on a mobile disco for many years.
With 4 off Fane 50WRMS speakers it sounded good and was very loud.
It was 225WRMS into 4 ohms.
I used one on a mobile disco for many years.
With 4 off Fane 50WRMS speakers it sounded good and was very loud.
An externally hosted image should be here but it was not working when we last tested it.
Hi Guys,
Hopefully you see this sometime in the morning. Seems I need a little nudge in the right direction. Is the schematic in post 21 the correct one? If so are D2/D4 15v? Should I use BC550/560 or BC546/556 for the small transistors?
Thanks, Terry
Hopefully you see this sometime in the morning. Seems I need a little nudge in the right direction. Is the schematic in post 21 the correct one? If so are D2/D4 15v? Should I use BC550/560 or BC546/556 for the small transistors?
Thanks, Terry
D2/4 are 15V. I drew it up wit BC550/560 but either choice would likely be fine at 15V. The two TO-92 in the VAS section are 2n5401/5551 for the higher voltage.
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Absolutely correct. Q7, Q8 can also be either (550/560 or 546/556) as with +/-50V rails they only see some 35V c-e as a maximum.
Hi Antonio,
Thank you for the info, but 2SA1360/2SC3423 are rather rare in my area, and 2SC1775/2SA872 are nice low noise Hitachi devices, but simply impossible to get here (even Mouser doesn't sell them).
However, in case you've got the SPICE models for 2SA1360/2SC3423 - could you please share them? It would be interesting to try some simulations.
Cheers,
Valery
Nice print on the component side. How did you do that?
Toner transferred from paper printed by laser printers?
Toner transferred from paper printed by laser printers?
Yes, but I use shelving paper as the medium to get a clean transfer. I really do need to make a short video of the procedure some day. It would help a lot of folks.
Blessings, Terry
Valery, how good is thermal stability of the circuit, especially thermal stability of VAS idle current?
Very valid question. I did not test this particular one, but I have heavily tested my other symmetric circuit - >THIS ONE<
It took some tens of seconds to settle, but then it stayed constant (keeping the OPS bias stable) - no problem.
We have provided a local heatsink for the VAS TO-126's. At 5-7mA VAS current it's not going to be a problem anyway, if someone is going to run it at, say, 15mA (e.g. for driving the MOSFETs directly) - it will take a bit longer to settle and it will run warmer for sure, but I don't expect any thermo stability issues.
Off course Valery, here they are:
.model 2sc3423 npn IS=14f BF=130 VAF=50 IKF=300m BR=5.61 VAR=500 RB=10 RE=0.01 RC=0.8 CJE=5p VJE=0.7 MJE=0.5 TF=795.77p XTF=7 VTF=6 ITF=50m CJC=4.4p VJC=0.6 MJC=0.286 XCJC=0.5 TR=4n XTB=1.5 EG=1.11 XTI=3 FC=0.5
.MODEL 2SA1360 PNP IS=116.73f BF=147.48 VAF=100 IKF=78.684m ISE=297.72f NE=1.5511 BR=.77363 VAR=100 IKR=1.0217 ISC=26.92n NC=2.9970 NK=.49889 RC=4.5038 CJE=4.0176p MJE=.33333 CJC=6.287p VJC=.35 MJC=.26272 TF=344.39p XTF=84.382 VTF=7.0050 ITF=.11443 TR=10n
greetings
Hi Valery,
I'm almost finished. I have been meaning to ask this for a while. I see all the time folks using .1uF as the value for the decoupling caps. I order them 50 at a time but am constantly running out of them. Anything magical about that value? I have a bag full of .22uF caps. Can I use those in place of the .1u for decoupling?
Thanks, Terry
I'm almost finished. I have been meaning to ask this for a while. I see all the time folks using .1uF as the value for the decoupling caps. I order them 50 at a time but am constantly running out of them. Anything magical about that value? I have a bag full of .22uF caps. Can I use those in place of the .1u for decoupling?
Thanks, Terry
H.Ott says that you should use the highest value available in the package size you choose.
He was specifically referring to SMD, but in my opinion the same philosophy applies to through hole.
On that basis, if the 220nF is physically the same size and lead spacing as the 100nF, then buy/use the 220nF.
