[rickcr42]

http://www.passdiy.com/


just out today ,yeah baby !

 

[was ist los?]

Awesome!!

 

[KTpG]

Very nice! I love Pass designs.

 

[rickcr42]

the cool part is that they are all variations on the same theme and you can take what you need from each

my current zen is a zenlite modified from the original zen with the mosfet input buffer from v4 (at least i think it was 4) and the turn on delay from another version

the downside is energy use and heat

the former i just lie to my wife about why the bills are so high , the second is a real pain in the a** and requires large heat sinks and no way around it

another possible downside is ultimate output power

now my speakers are 96dB efficient so i can get away with a 10 watt amp

but sometimes i just want to "let 'er rip" and for that i use my a P-P SS Amp @ 60 watts per side

 

[KTpG]

I have not yet built a Pass amp... but I love the simple design approach.

I am running my receiver for music, currently... 65WPC class AB, I suppose. It sounds pretty good.... and my headphone amp is just opamp based... no discrete SS.

I want something in pure class A and am thinking about using the balanced line stage as a headphone amp (scaled for lower voltage, of course).

 

[rickcr42]

the pass balanced line stage is not optimized for headphone output so would probably be a disappointment , though it IS a very good line stage

but there are plenty of solid state class-A headphone amps out there for DIY

Low Z cans-the Gilmore , the Szekeres ,and finally the Zen headphone Amp-all available at the headwize library .
Plus an Aleph Headphone amp can be found at the www.diyaudio.com site

If having an opamp in the signal path does not bother you i would recommend the SDS opamp/mosfet hybrid ,also available at headwize and can drive any rational impedance cans

a commercial kit option can be the Erno Borbely JFET/MOSFET Class A amp or for straight DIY the hybrid tube/mosfet amp (schematic available at both the headwize and borberly sites) or the chiarra

many options other than the opamp/buffer amps

But as far as the pass designs in general go .i like the simple gain path

one single class A device per polarity

and I use the boz/zen on a daily basis

I KNOW the balzen is better but my boz suits me just fine

 

[KTpG]

If I had low-z cans, it'd be much simpler. But, I have the 580s... so it is harder to use just a single gain stage.

The BLS is a balanced preamp for balanced input, but can also function as a unbalanced-to-balanced converter. Since I have the 580s, I can rewire them to be dual mono and use the BLS to create a balanced output from the unbalanced in. Perhaps not THE best... but it would work fairly well. Another helpful thing is the gain of the BLS being adjustable... so I can make it work for my cans. The only problem is that it probably will not have 0VDC on the output... it will have some offset, no doubt, and will need coupling caps despite being balanced. To avoid using electrolytics, I am thinking about using another SOZ variant as a follower with minimal voltage gain and MUCH lower bias than the actual amp. This way I can use a single film cap on the +/- outputs of the first stage and feed the balanced signal to the output stage, which should have near 0VDC offset on the output as Pass stated. The only problem I see with all of this is that I will have four active devices per channel (not counting CCS if I decide to implement it, which I would really like to). This is far different than the original one device per channel of the Zen. In the end, I'll probably use just the BLS with Cerafine coupling caps on the output. But, I will test everything to see, probably... so perhaps if I ever take the plunge and buy everything, I might have something to report in a year or so. lol

BTW.... I am against opamps now. hehe I tried using my OPA637's in a simple CMOY circuit and got 0.2-0.7VDC on the output of each channel. NO idea why... checked everything multiple times. I threw a decent quality cap on the output to make it headphone-safe... and really, the chips did not sound as well as I had always thought they would. I was not impressed at all and will probably be letting these expensive suckers go (they are the more expensive BP grade, too). Perhaps more testing with them would yield better results... Any thoughts are welcome.

 

[rickcr42]

the output impedance of the box/balzen circuits are not suited to driving 600 ohms so even though the gain would be adequate the output impedance mismatch would most likely not sound very good

it can be done but there are much better driving cicuits

the SOZ is wicked inefficient and most of the energy is wasted as heat

but if you have read the zen 6 pdf it seems help is on the way

as for wanting to eliminate opamps I agree as i have done such myself at every part of the signal pathin my home system

Check out the borbely designs for your 580s ,either the tube/mosfet or jfet/mosfet topology

OR

just optimize a discrete buffer stage as a follower and use your preamp as the gain stage

really a lot of options

have you considered tubes ?

 

[KTpG]

I knew I was forgetting something... the output impedence, that is. heh

Well, I have a PCB for a tube/MOSFET hybrid amp... uses 6DJ8 with IRF530 follower. But, the guy who sent the board to me never sent instructions and he had modified the circuit at the time he made this board, so parts no longer match with board placement and I have no idea what goes where. So, I am awaiting instructions patiently... it has been SEVERAL months and no word yet. Oh well...

I have always loved tubes... but I never can get myself to drop all the money on them. It is true most SS amps can cost as much as a tube amp, but there are so many things in tube amps that cost a lot of money as opposed to just a few things in SS amps that are expensive. I am still looking into all options... I think I may go work with the OPA637's a little so that I'll have an improvement over my current setup, but nothing like I want.

 

[rickcr42]

if you know the original circuit maybe you can tough it out and/or jumper the extra pads ?

also

have you seen this ? (pdf ,right click and save if on dialup)

http://www.borbelyaudio.com/hybrid.pdf

or this

http://www.audiokits.com/products.asp?catid=72

same designs mentioned above and are actually the same but for the front end,one being tubes and the other jfet

 

[rickcr42]

Quote:

BTW.... I am against opamps now.

does that include "discrete' opamps ?

http://www.passdiy.com/pdf/diyopamp.pdf

i see no reason the output could not be optimized to drive loads in the range of 30-600 ohms . At least there is enough info for a running start

 

[KTpG]

I have looked at the discrete opamps.... I am tempted to try one with all MOSFETs, but am afraid it wouldn't work out well. I was hoping for a tried and true design with MOSFETs (since MOSFETs sound the most tubelike of SS components)... but not very many MOSFET designs exist for high-Z cans.

Pass's website is quite useful, though, for info on this kind of stuff.