Hi Ammel,
That one is the line stage. This one here is particularly configured for driving any kind of headphones, including the low-ohm ones.
Okay, what is the gain of the line stage circuit and which 2 resistors set the gain?
Also, can you post a more legible schematic. All the fonts on your schematic seem to be very faint and not bold enough.
Thanks.
To see the schematic in more detail, please press "maximize" in the bottom left corner of the image.
Hi Valery,
Okay, that's easy enough.
Is the post 126 circuit Class A?
Have you actually built and listened to the circuit or just simulated it?
Thanks.
I've got boards but they include a PGA2310 volume control and a pre-buffer. I'm using this for test equipment, so the design is tailored for my application. They are compact surface mount boards.
If you want to use surface mount devices I can modify the layout to something you can use, or if you want to use through hole devices I think I have some layouts for input boards that can be easily modified to suit your needs.
If you want to use surface mount devices I can modify the layout to something you can use, or if you want to use through hole devices I think I have some layouts for input boards that can be easily modified to suit your needs.
I just had a closer look at Valery's schematic, and he's added an extra pair of devices after the VAS in these. That would make them VHex+ boards without the output devices installed. I have those in stock too.
My version of simple "blameless" pre-amp. Not tested!
Maybe it better to add DC Offset adjustment.
THD at 20kHz should be 0.002978%, sorry.
Maybe it better to add DC Offset adjustment.
THD at 20kHz should be 0.002978%, sorry.
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Yes, it's class A unless you use it with some too low-ohm load, it's not designed for.
All these options are based on VHex amplifier, built and tested many times.
Are they through-hole or SM?
I would like a through-hole board with all the C3503s and A1381s(that need fastening to a single heatsink) close to the back edge of the board and eliminate the portion of the board with the VHex+ output devices and their components.
Perhaps I can take the board you have, load it into Sprint and remove the components that aren't needed, which should decrease the size of the board some.
The VHex board is a mix of through hole and SMD. All transistors are through hole. The layout is excellent for a 2U chassis design, but to modify for a preamp design would be harder than starting over. Adding a pair of transistors to the Ampliwire layout would be much easier, and it's completely through hole. My files are all drawn in Diptrace, but you can import the Gerbers in Sprint and modify them if you like.
I would like to get a Gerber of Ampliwire - looks nice.
I have another idea for a preamp/head amp. I have a bunch of JK VSSA thru hole PCBs. Replace the the outputs (2sk1058/2sj162 latFETs) with IRF610/9610 with a twist of legs 2 and 3 and stand them up with small local heatsinks. Could probably run 24v rails without other modifications.
I have another idea for a preamp/head amp. I have a bunch of JK VSSA thru hole PCBs. Replace the the outputs (2sk1058/2sj162 latFETs) with IRF610/9610 with a twist of legs 2 and 3 and stand them up with small local heatsinks. Could probably run 24v rails without other modifications.
on Reichelt there are original 2SK170 - 2SJ74 (Toshiba) but the price is to fall to the ***, they are really expensive.😱
Here's the Gerber files for the Ampliwire input board. It should be easily modified to match Valery's preamp schematic.
Hi Gnobuddy, there are a few shortcomings and component issues but the design that you have been slating is that of David Hafler. It was a pre-amp, never intended to drive speakers of any kind and was highly acclaimed as one of the better sounding products by any standard. Even John Curl may be old enough to know David whom also had a few power amps under his belt, David was by no means a poor designer, you may have the wrong cat by the balls.😡
For the record, if you are referring to the complementary differential input stage transconductance amps, I invented this circuit, first in 1968 with bipolar, and then in 1972 with jfets. Others also independently invented the comp-differential bipolar input stage at about the same time, but David Hafler was not one of them. David Hafler was a great business man, but he usually used the work of other designers. The transconductance amp (without a follower output stage, is ideal for relatively high impedance loads. It is simple, fast, can be very linear, without adding much negative feedback, stable (more stable with cap loads than an op amp design (with follower output stage) and it has an intrinsically higher open loop bandwidth. I first used the jfet input stage version with the 'Wall of Sound' Grateful Dead sound system (1973) and as the line amp for the Mark Levinson JC-2 preamp (1974) with great success, and I still use the same topology today in just about everything that I make.