[NeilR]

ppl,

Good to see you join this discussion since you are one of the buffer mavens.

I guess I could add 2 more comp pairs, for a total of 4 and then I would be entitled to call it a "Dyna(something)"

I should have added that I primarily listen with HD-650's and I doubt they need more current than even one comp pair (ala ppa) provides. I also have Ety ER-4s's, which are 100R and might use a little more current but even those are not exactly "ultra low impedance".

 

[ppl]

I was actualy Kidding that you needed more current gain IMHO anny buffer that can maintain low DC offset while driving a 32 ohm load with a 10K yes that a 10,0000 Ohm input resistor between the source and Buffer input is not going to load down the tube. somewhare xtreme4099 posted my recomended resistor changes to the PPA V2. Ill look for the link

Ok I found the link with resistor values changed. http://www6.head-fi.org/forums/showp...0&postcount=11

Note from that thread these are the new resistor values for the PPA-V2 Buffer sections

“”””””Resistor changes as follows :

R11 change from 1K to 220 ohm

R34 R24 - 2 ohms are changed to 1 or 1.1ohm “””””””””””””

xtreme4099 forgot to include R21 & R22 and R31 & R32 from 220 ohms to 120 ohms.

 

[NeilR]

ppl,

This is the land of the extreme. Sometimes it is tough to tell when someone is kidding about something like this

I will add your post to my PPA notes. Thanks for the input!

Regards,
Neil

 

[nikongod]

did anyone ever get the 139/140 output transistors?

it was mentioned above.

 

[NeilR]

Quote:

Originally Posted by nikongod did anyone ever get the 139/140 output transistors? it was mentioned above.

I bought some but haven't used them yet.

Regards,
Neil

 

[nikongod]

looks like i will be first.

sweet.

 

[NeilR]

If you ever want to try the BD137/8 transistors, PM me. I am getting a bunch from Steinchen.

 

[nikongod]

DBB is built with the 139/140 transistors on the output, all else as described in the "standard parts guide" thingy.

voltage offset (measured with 1 end of dmm on tube, other on "buffer side" of the 22ohm resistor) is 0mV (yes, lower than my meter measures) on one side, and 2mV on the other. yea. 0.000?V and 0.002V. i matched all transistors as close as possible with my cheap DMM (has transistor tester) and got 2 VERY good pairs for the ones that it was said were most important, and not as good pairs (still not that bad, about 30 off) for the others. the output transistors were the first 4 that fell out of the package

i wonder how bad it would be with VERY far spaced pairs of input transistors from the same "gain/hfe family: a good far spread.

 

[nikongod]

update:
on the board i use most of the time i did not bias appropriately.

i adjusted the bias to about 22mA and 0mfgwtfbbq!!!111
i may try 25mA bias later.

that is all.