[Spacehead]

PPA style headphone amplifier with buffered ground and left right.

The left and right channels are driven by NJM4556, each dual op amp is configured so that one half is buffer and another is the gain stage. So 2 duals in this amplifier.

Then the ground channel is TLE2426dip+OPA1642+Intersil HA-5002 buffer

Power supply is LM317 configured to 13V. It has Cadj and Cout capacitors.

I am now listening to it, it can drive my Philips SHP2500 to insane volumes so there is enough current output, about 150 mA per channel + 400 mA on ground channel.
Voltage gain is 22K/4.7K+1 = 5.6X
there is no hiss in background.

I intend to sell this amplifier for 60 euros once I get those wires cleaned up and good case for it.

It sounds very close to my PPAv2. Very transparent and powerful.

 

[mrtndoog]

Do you have a circuit, its hard to follow the picture

 

[immtbiker]

This picture looks very similar to a map of the NYC subway system, however, I trust that it runs far more efficiently

 

[Ferrari]

I haven’t post here for a while. This time, not a fully cased up amp but a naked Pimeta with AD797 + quad-stacked BUF634, partly on perf-board, which I have used to teach. (my students seems to like it naked

)

The amp is feeding by a LM317T based 24V PS. The orange capacitors on the PS part are Sikorel (4400µF).

 

[Spacehead]

Quote:

Originally Posted by immtbiker /img/forum/go_quote.gif This picture looks very similar to a map of the NYC subway system, however, I trust that it runs far more efficiently

Yeah there is a lot of wire. I needed to test it quickly so I used wires left over from previous projects.
I have been testing it and I prefer the sound to my PPAv2, maybe because there was involved some precious smd work.

I will post a better picture, sorry about that mess.

 

[Spacehead]

Quote:

Originally Posted by mrtndoog /img/forum/go_quote.gif Do you have a circuit, its hard to follow the picture

No I don't have a schematic but I remember it.

Ground channel
TLE2426->OPA1642->HA-5002<-back to opa1642 with 1K feedback resistor->ground out

left and right is sijosae's work

 

[the_equalizer]

My Millett MiniMAX and Bantam DAC. Lovely sound out of this pair!

 

[Lil' Knight]

Looks very nice. What's the case for the Bantam?

 

[the_equalizer]

Quote:

Originally Posted by Lil' Knight /img/forum/go_quote.gif Looks very nice. What's the case for the Bantam?

Thanks ! The case is nothing special, a cheap ($2.50 USD) plastic enclosure from a local electronics provider.

cheers!

 

[Lil' Knight]

Looks pretty much the same like the Hammond. But $33? I hope it's not in USD.

 

[the_equalizer]

Quote:

Originally Posted by Lil' Knight /img/forum/go_quote.gif Looks pretty much the same like the Hammond. But $33? I hope it's not in USD.

Certainly not ! The price is about $2.50 ~ $2.75 USD.

 

[m11a1]

Your setup looks great equalizer's!

 

[Spacehead]

Super CMOY for op amp testing:

50K Alpha pot set to 0 ohm
2200 uF Panasonic smoothing capacitance
LM317 with Cout and Cadj, set to 24V
Ground channel
Tle2426 -> Various op amps -> OPA633 with heatsink for maximum power output

MKP X2 style input capacitors, with 100 kOhm input impedance = corner frequency 4.8 Hz
SMD and through hole cmoy core
Feedback resistor soldered to pins 6+7 and 1+2 , 12K
R3 3K , gain = 5X
Opamp stabilized with 0.1 uF caps on power pins and Ferrite beads on pins 1 and 7

In the pic AD8620
Currently running ADA4898-1 with singles to dual adapter.

When used with op amps that have the current output, this amplifier can drive 32 ohm headphones to very loud volumes without too much distortion!

There is absolutely no hiss when there is silent signal.

Again this is in testing phase so I will put it neatly when I think it is ready.

 

[pixeljedi]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif I haven’t post here for a while. This time, not a fully cased up amp but a naked Pimeta with AD797 + quad-stacked BUF634, partly on perf-board, which I have used to teach. (my students seems to like it naked )

Now that's what I call a real Stacker!

Excellent work as always Ferrari. I have a few of those protoboards, and I never thought about using them on the bottom like that - I will now

I wouldn't mind seeing a close up pic of those chips stacked.

 

[cfcubed]

Quote:

Originally Posted by Spacehead /img/forum/go_quote.gif Super CMOY for op amp testing: Again this is in testing phase so I will put it neatly when I think it is ready.

I hope this doesn't offend & you said it was a test bed, but I did get a chuckle when I saw that picture.
As if the parts, wire & glue were tossed into a container, shaken up & then the lid opened