VOX Beatle Original Transistor Data DIY Style

Shop deals on ebay
shop deals on amazon
Advertise with us
GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
CJ

CJ

Well-known member
GDIY Supporter
Joined
Jun 3, 2004
Messages
15,724
Location
California
that's right, we scored some original transistors, Fets, you name it, for the troublesome Beatle amp,

they were like 8 bones a piece, so knowing what they do can mean realizing a cheaper alternative if you can dig where i'm coming from, or not.

so if you want to upgrade or buy a lot of NOS and sort, you can use this data for the three transistors pictured here>
 

Attachments

  • vox transistors.jpg
    vox transistors.jpg
    94.6 KB · Views: 19
the paint on the transistors means they went thru some sort of matching process, and i imagine the Fets were screened as well,

here are the parts we tested, they comprise the first 4 transistors of the preamp
 

Attachments

  • vox transistor specs (1).jpg
    vox transistor specs (1).jpg
    162.2 KB · Views: 10
FET data,  this guy turned out to have better gain than the data sheet graph, which is why we suspect they were screened, since it is the first stage, we want to get above the noise floor as quick as possible, but wait, no free lunch, more gain = more noise? or not.

here is one of two graphs for the N Ch Fet>
 

Attachments

  • fet loadline.jpg
    fet loadline.jpg
    159.9 KB · Views: 16
here is the circuit where these transistors are used,

that's it. nothing more to see here folks, you are now free to resume your life as you used to know it,  :D

oh, as a side note, some folks like those 2N2925's in their wah wah pedals, so now you know how to match up with the 60's!
 

Attachments

  • Vox normal ch preamp.png
    Vox normal ch preamp.png
    281.4 KB · Views: 27
> anybody know how to translate ma per volts into u-mhos?

Change the mA into uA and the answer is right there.

4.75mA/V is 4,750uA/V so 4,750uMho.  (More than most tubes.)

However in this VOX plan, you don't really need to know. The Q101 Q102 pair is locked in NFB. Gm of the Q101 only matters for the extreme of the Top-Boost.
 

Similar threads

K
Lighter-weight vintage-style Decca Tree
Replies
0
Views
290
k brown
K
F
For Sale DIY Microphones, Preamps, Compressors, Mic transformers, ... (PICS ADDED)
Replies
14
Views
1K
Frank00
F
poctop
D47 Fet New Body Style PCB now available
6 7 8
Replies
150
Views
20K
neowalla
neowalla
rafafredd
For Sale Telefunken V72 original input transformers
Replies
6
Views
3K
andre tchmil
andre tchmil
bosski
Antelope Audio - Townsend Labs Sphere - Mic modelling
Replies
7
Views
1K
bosski
bosski

Latest posts

Back
Top