Amp Camp Pre+Headphone Amp - ACP+

[Zen Mod]

put 2 or 3 in parallel

 

[Antoinel]

Class A biased. Iq = Imax. Thank you.

Does anyone think pursuing a front end with the more available and cheaper 2SK170/LSK170 devices worth it, despite H2 being Positive phase?

Hello Samuel Jayaraj. Reverse the speaker leads in your suggested amp to get H2 negative phase.

Best
Anton

 

[EUVL]

> I'm curious to know: how much would you pay "punkydawgs" or "fetaudio" another seller, to do the work for you? You pay him money and he sends you two little ziptop envelopes, each envelope contains 1 JFET and 1 resistor. Each envelope creates a 10.0 mA (± 5%) current source?

E-103 Semitec | Mouser


Patrick

 

[indra1]

How many J113 do you need to get a "10mA sample"?
I consider buying 1000 pcs J112 as these has min. Idss = 5.0 mA so greater chance to get a 10-12 mA sample than with J113 which has min. Idss = 2.0 mA?

You can read Understanding the J113 JFET - diyAudio for some idea.

 

[Mark Johnson]

> I'm curious to know: how much would you pay "punkydawgs" or "fetaudio" another seller, to do the work for you? You pay him money and he sends you two little ziptop envelopes, each envelope contains 1 JFET and 1 resistor. Each envelope creates a 10.0 mA (± 5%) current source?

E-103 Semitec | Mouser

E103 datasheet guarantees (8mA <= Current <= 12mA) which is a ±20% tolerance. Finicky DIYers demand better.

 

[EUVL]

https://www.onsemi.com/pub/Collateral/AND8109-D.PDF
3-pins, one resistor, as on the PCB.
But resistor value can be pre-calculated.

+/-4%.


Patrick

 

[EUVL]

See also :
https://www.audioxpress.com/assets/upload/files/Sources_101_P2.pdf


Patrick

 

[MEPER]

You can read Understanding the J113 JFET - diyAudio for some idea.

What seems a bit strange to me is that it seems that to reach Id = 0 a typical value for Vgs is -1.5V for J113. 10mA in 125 ohm gives a Vgs = -1.25V? …..if that value gives Id = 10mA for NP's J113 it is a bit away from typical value?

So....have to finetune this when building the amp....

Will look at J112 with this in mind.....
If I get 1000 (to get them at low price) the J112 may be the most "all purpose" of them for preamp use?

 

[Samuel Jayaraj]

Please help me understand, how. H2 Negative Or Positive Phase is relative to the fundamental, isn't it? Hence, by changing absolute phase at the speaker won't change H2 phase relative to the fundamental, would it?

Hello Samuel Jayaraj. Reverse the speaker leads in your suggested amp to get H2 negative phase.

Best
Anton

 

[MEPER]

Please help me understand, how. H2 Negative Or Positive Phase is relative to the fundamental, isn't it? Hence, by changing absolute phase at the speaker won't change H2 phase relative to the fundamental, would it?

Yes, and I think that what NP says you should just accept without thinking too much about it.

 

[indra1]

...If I get 1000 (to get them at low price) the J112 may be the most "all purpose" of them for preamp use?

I'd expect IDSS spread from 15 - 50 ma most will be 25 - 40 ma.

 

[MEPER]

I'd expect IDSS spread from 15 - 50 ma most will be 25 - 40 ma.

Ok....if Idss is that high then it must be J113. Probably not many are in the 2 mA range but around 10 - 15 mA. Then J113 would be best buy…..for Pass forum builds…..

 

[indra1]

... around 10 - 15 mA...

As seen on the blog post, IDSS of J113 bought by rjm are mostly 20 - 28 ma, but the lot you buy will be different. Hopefully most will still be usable for 10 ma CCS.

 

[MEPER]

A test rig should be made so the JFET can be easy inserted for Idss sorting. Then a box with a lot of small rooms to put them in after measurements. No doubt that it should be J113.

 

[Samuel Jayaraj]

Yes, and I think that what NP says you should just accept without thinking too much about it.

What? I can't sleep tonight.

 

[Zen Mod]

interesting,how thread about new Papatoy transformed in JFet CCS Fetish happening

 

[indra1]

What? I can't sleep tonight.

Welcome new member. Sleep is overrated anyway.

 

[planet10]

Here's a dumb question if the circuit produces 1 watt at 32ohms how many watts will it produce for an 8ohm load? I'm definitely going to try it out with my old Fortes.

In theory 8/32 * 1 = 0.25 watt.

I couldn’t find an impedance curve but what i could find was that it is a typical Klipsch with wildly swinging impedance. A more important question is what the outpu timpedance of the ACP+ is.

dave

 

[EUVL]

The circuit as published is capable of ~+/-10V and 300mA output before clipping.

For 32R, it is current limited at ~1.4W.
For 8R, it is also current limited at 0.36W.
For 100R load, it is voltage limited, at ~0.5W.


Patrick

 

[Nelson Pass]

How is the J113 selected for the CCS of the input stage?
When I read the datasheet J113 has a min. Idss = 2.0 mA. Those can't be used as a 10 mA CCS? …..you need one with a bit higher than 10 mA Idss? …..are there many of those among J113 in a batch?
J112 has min. Idss = 5.0 mA so some of those could also be used?

Forget those minimum numbers on the data sheets. The lowest Idss I
have seen on J113 is about 6 mA after testing thousands, and that was
only from a couple lot codes. Most of them have Idss in the 20-30 range,
and the J111 is a lot higher than those.