Οκ tell us more
what is the bias of this circuit and what determine the bias
i dlike to know more as a picture remindes the operation og QSC but never seen that before done with mosfets
i like symmetric circuits but i am not shure about that ( or was it akg ? )
what is the bias of this circuit and what determine the bias
i dlike to know more as a picture remindes the operation og QSC but never seen that before done with mosfets
i like symmetric circuits but i am not shure about that ( or was it akg ? )
Ok, well, it's chain dependent.
Four zeners D1,D2,D3,D4 and four emitter resistances R9,R10,R11,R12 defines current through Q17,Q18,Q19,Q20.
In couple with R1,R5 current the whole chain creates strictly dependent current through R33 which can be easily swapped with a simple LED (red, no high-voltage-drop ones).
The whole chain are excited by opamp's output current.
This curcuit are worth to try.
Ask what you want to know about.
Yes.
In the OPS gates even 3904/3906 or bc550/560 based on accessibility in EU and preferred bias current.
5 mA are well enough, but there are no limit in the sky.
😉
In first stage Hitachis are well known performers and now produced elsewhere from Rochester and up to ISC and unnamed chineese. 3503/1381 could become bottleneck, i'ld prefer something with higher Ic.
TTC011/TTA006, KSA1220/KSC2690, 2SC3421/2SA1358, 2SC4793/2SA1837, 2SC5171/2SA1930.
Of course. There are even at least three differently routed boards. But unfortunately all of them for TO-3P cased k1058/j162
One idea will be to use a P101 circuit that will be easy
I wonder though is it possible to operate a p101 in high bias
I wonder though is it possible to operate a p101 in high bias
Aaargh...
Just check how perfect an attached pcb.
Again, they don't need high bias.
You're trying to use scalpel to crack bones.
If we want to fight the influence of parasitic capacitances, BesPavs circuit seems better. However P101 has less silicon junctions.
P101 are ugly even by topology.
First - dominant pole compensation, C3 at the original schematic. Putting itbetween two high-impedance points in the actual device you just drop out at least 40 dB of feedback depth at high audio frequencies resulting in poor transistor-named sounding and proportional THD rise.
Second - straight VAS loading to OPS gates adds its part to slowdown brilliant latfets in such a cheme.
Third - due to low transconductance such a latfets need up to +10 V at gate-source junction. P101 are very bad in OPS devices SOA perspective. It meant you add second pair for keeping inside SOA, but even increasing OPS input capacitance and double fallback in speed.
So, no, p101 did not deserve a try.
Bespav
You may have misinterpreted my sarcastic statement…because I do not recommend the P101 for an hi-end system.
I remember that it has a very slow slew rate too.
Fab
You may have misinterpreted my sarcastic statement…because I do not recommend the P101 for an hi-end system.
I remember that it has a very slow slew rate too.
Fab
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over the years, i've seen people comment about about speed of amps with lateral mosfet ops. if you have that concern, it might be worthwhile to look at some spectral designs - they are high speed designs that (i think) used lateral mosfets in their ops.
ok, my memory was not quite as bad as i thought. here's an internal shot of a dma-50 power amp:
Spectral Audio DMA-50 Megahertz Stereo Amplifier – SkyFi Audio
ok, my memory was not quite as bad as i thought. here's an internal shot of a dma-50 power amp:
Spectral Audio DMA-50 Megahertz Stereo Amplifier – SkyFi Audio
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I presume so, but I don't have any.
However, the designer, Demian Martin, is a member here and might have some useful info.
However, the designer, Demian Martin, is a member here and might have some useful info.
Based on informations can be gathered from the web, it seems that it’s all about the speed here. Complementer symmetric topology, cascoded jfet input, cascoded bjt VAS and VFET (not lateral) output.
Yes, you're right. LATFTs were used in the vintage models. The newer models are built with VFETs according to Spectral’s website.
"Our breakthrough topology time aligns high-current vertical fet output devices for rapid, pistonic signal launch. The output section is comprised of eight individual V-fet amplifier modules paralleled to achieve a minimum 200 watt RMS / per channel with 60 amp capability. With this “Focused Array” arrangement of parallel fet amplifiers, full rated power is delivered with total load stability at an unprecedented 1 MHz." - DMA-250
"Our breakthrough topology time aligns high-current vertical fet output devices for rapid, pistonic signal launch. The output section is comprised of eight individual V-fet amplifier modules paralleled to achieve a minimum 200 watt RMS / per channel with 60 amp capability. With this “Focused Array” arrangement of parallel fet amplifiers, full rated power is delivered with total load stability at an unprecedented 1 MHz." - DMA-250
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