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Geshelli Lab Erish coming soon

JustAnandaDourEyedDude said:
This causes a question to pop up in my mind that I have had from time to time but never asked for fear of sounding ignorant. When an amp is driving a reactive headphone or speaker, does any energy get returned to caps in the output circuit of the amp at any time, or is it all stored in the load so that the power output from the amp is always positive or zero? Does this depend on whether the reactance of the load is due to inductance in a crossover network or just due to mechanical inertia in the drivers? I have a confused picture in my mind, because I am not familiar with the electro-mechanics of such a situation. Basically, I am asking whether the interface between amplifier and load is designed to be one-way only for transfer of electrical energy, or can energy be transferred from the load to the amp during transients, though of course the average power is transferred from the amp to the load? Perhaps the amp itself has negligible electrical inertia, and it responds practically instantaneously to changing demands in the load and so energy is never absorbed by the amp even at high audio frequencies? I guess this is off-topic for the thread, but on the other hand, two experts in amp design are posting here. :)
Click to expand...

Back EMF will be dissipated in 'heat' in the output devices. With headphones the generated 'power' (if any) is very, very small.
 
solderdude said:
Back EMF will be dissipated in 'heat' in the output devices. With headphones the generated 'power' (if any) is very, very small.
Click to expand...

Ah, okay, I understand. The conversion in both directions is pretty inefficient, so the back emf is extremely small. The energy stays as kinetic or elastic flexural energy in the drivers and some of it dissipates via internal friction or internal electrical resistance as heat leading to damping of driver oscillation, its just their mass inertia that can cause their motion (and thus the acoustics) to be out of phase with the amplifier's output. Thanks for clarifying!
 
Yes, the generated current is what increases the impedance of the headphone.
For the same voltage (an amplifier is a voltage source) less current is needed (the back EMF current is opposite in direction to the supplied current to subtract) thus voltage efficiency remains the same while power efficiency rises. This is because the driver loves to vibrate on those frequencies by itself. It just requires less power.
The headphones with hardly any impedance rises are mechanically damped well enough and do not need electrical damping at all.
Heavy woofers in speakers generate lots more currents because of their higher mass.
Most of the energy will be dissipated in the Ohmic losses (inductor and wiring), the higher the output R of the amp the more percentage of 'heat' will be dissipated in the amps output devices.
 
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solderdude said:
Yes, the generated current is what increases the impedance of the headphone.
For the same voltage less current is needed (voltage efficiency remains the same, power efficiency rises) because the driver loves to vibrate on those frequencies by itself. It just requires less power.
The headphones with hardly any impedance rises are mechanically damped well enough and do not need electrical damping at all.
Heavy woofers in speakers generate lots more currents because of their higher mass.
Most of the energy will be dissipated in the Ohmic losses (inductor and wiring), the higher the output R of the amp the more percentage of 'heat' will be dissipated in the amps output devices.
Click to expand...

I see, electrical damping of the motion of heavy woofers, with ohmic losses split between speaker inductance/wiring and amp output resistance. Cool details. Thank you. Been a few decades since I studied electrical/electronics for a semester or two. ;)
 
Reading this thread is making me wonder what kind of amp design would result from a collaboration between Geno Geshelli (or is it Bisceglia? I’ve seen both in print) and John Yang. Both seem to have different design philosophies but are able to obtain spectacular results from very modest costs. Impressive. But I guess that’s like hypothesizing what kind of drink Coke and Pepsi would produce together.
 
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ssips said:
Can we expect a review for this?
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Billy Budapest said:
Reading this thread is making me wonder what kind of amp design would result from a collaboration between Geno Geshelli (or is it Bisceglia? I’ve seen both in print) and John Yang. Both seem to have different design philosophies but are able to obtain spectacular results from very modest costs. Impressive. But I guess that’s like hypothesizing what kind of drink Coke and Pepsi would produce together.
Click to expand...

I would expect both around the same time. 12th of Never :(
 
Billy Budapest said:
Reading this thread is making me wonder what kind of amp design would result from a collaboration between Geno Geshelli (or is it Bisceglia? I’ve seen both in print) and John Yang. Both seem to have different design philosophies but are able to obtain spectacular results from very modest costs. Impressive. But I guess that’s like hypothesizing what kind of drink Coke and Pepsi would produce together.
Click to expand...

Both use opamps / IC's with low distortion.
Both have the power supply separated from the audio path (low leakage).
Both have high enough output voltage for driving high impedance headphones and can supply enough current for low impedance headphones.
Both use inexpensive components and keep the price low (easier for John/Topping)
Both measure and tinker with board layouts.
The above almost ensures good measurements.
Jason can do a similar thing also for a low price.
There is no magic here, just decent engineering, measurements and the ability to market directly (Geshelli, Schitt) or work for a brand that markets it (John)

Where they differ....
Geshelli uses power limited DCDC converters, John does not (AC transformer just like Schiit)
Looks: Geshelli goes for a DIY-type look and Schiit and Topping go for a more 'classic' and fully closed/shielded look.

Suppose they could wind up exchanging ideas and would 'marry' their design the electronics used would not be much different from what is used now.
What would become an argument is power supply.
A middle ground could be that both use the same circuit and even layout but the DCDC converter used may be a 6W type and would be powered by a transformer or a low leakage DCDC wallwart.
One would build it in a 'DIY-ish' looking enclosure and Topping in a classic enclosure that will be difficult to take apart.
 
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solderdude said:
Both use opamps / IC's with low distortion.
Both have the power supply separated from the audio path (low leakage).
Both have high enough output voltage for driving high impedance headphones and can supply enough current for low impedance headphones.
Both use inexpensive components and keep the price low (easier for John/Topping)
Both measure and tinker with board layouts.
The above almost ensures good measurements.
Jason can do a similar thing also for a low price.
There is no magic here, just decent engineering, measurements and the ability to market directly (Geshelli, Schitt) or work for a brand that markets it (John)

Where they differ....
Geshelli uses power limited DCDC converters, John does not (AC transformer just like Schiit)
Looks: Geshelli goes for a DIY-type look and Schiit and Topping go for a more 'classic' and fully closed/shielded look.

Suppose they could wind up exchanging ideas and would 'marry' their design the electronics used would not be much different from what is used now.
What would become an argument is power supply.
A middle ground could be that both use the same circuit and even layout but the DCDC converter used may be a 6W type and would be powered by a transformer or a low leakage DCDC wallwart.
One would build it in a 'DIY-ish' looking enclosure and Topping in a classic enclosure that will be difficult to take apart.
Click to expand...
My question was more of a meeting-of-the-minds hypothetical. John expressed some surprise when learning of the current source topology Geno stated he used. They could both learn valuable things from each other, I bet.
 
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I suspect that there is no current source topology used at all. I think someone on the web misunderstood.
I think current feedback opamps are used. Just like some Schiit amps also use current feedback topology.
The output impedance is very low and a voltage source.

I think both John and Geno are very down to earth guys. Perhaps John is the most 'audiophile' oriented and Geno just wants to build and market something that is build properly. In both cases the guys measure and thus end up with low distortion designs.
They certainly aren't the only ones making well measuring and affordable gear.
 
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Billy Budapest said:
My question was more of a meeting-of-the-minds hypothetical. John expressed some surprise when learning of the current source topology Geno stated he used. They could both learn valuable thing from each other, I bet.
Click to expand...
Big egos in small boxes :cool:
 
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It’s like saying Microsoft and Apple should collaborate ;)
 
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