Hi
does anyone have a schematic of a preamp based on germanium transistors which provide more high db before it begin to distort and add more feedback to the sound?
thanx
does anyone have a schematic of a preamp based on germanium transistors which provide more high db before it begin to distort and add more feedback to the sound?
thanx
What are you after?
The above statement is too vague for anyone to help.
I've got an old Mullard application book from the 1960s that shows the OC71 being used in a number of applications.
The above statement is too vague for anyone to help.
I've got an old Mullard application book from the 1960s that shows the OC71 being used in a number of applications.
1. find simple schematic with npn transistors only.
2. replace npn with pnp's
3. reverse all polarised components ( electrlytics)
4. reverse supply voltage
5. you're done.
😀
2. replace npn with pnp's
3. reverse all polarised components ( electrlytics)
4. reverse supply voltage
5. you're done.
😀
i'm after a mic/instrument preamp that use a pnp germanium transistors , which the volume could go up to higher db before it begins to distort , and produce a headroom , i'm not sure if i add interstage transformer would add a headroom to the sound ?! , also to have a feedback knob which add amp feedback to the sound , the use is for electric guitar and acoustic miced guitar
I understand why you would have to change these things if you swap
NPN/PNP. but how dose this get him to what he is after?
I asking cause I don't know. I'm not being a butt.
I can't see why you want to design a new circuit with PNP Germanium Onobtanium devices.
AFAIK Germanium went the same way as Gallium Arsenic for transistors. They only hold their own in Authentic Restoration Projects.
It's pretty easy to build a pre-amp with modern silicon transistors that will give you as much headroom as you want before clipping.
AFAIK Germanium went the same way as Gallium Arsenic for transistors. They only hold their own in Authentic Restoration Projects.
It's pretty easy to build a pre-amp with modern silicon transistors that will give you as much headroom as you want before clipping.
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the reason is the sound , each transistor would provide you a kind of tone , the purpose again is for electric guitar and acoustic guitar , the sound from silicon is different from a germanium one , i know it easy to go with silicon that isnt my intend
There is a thread on here regarding a renowned FUZZ PEDAL which started its life with Germanium transistors. It might take some finding.
It's not difficult to produce a pre-amp, its basic electronic theory. The problems occur with power amps and load lines. What sort of Vcc are you intending on using and what sort of Pk-Pk output are you after ?
Germanium transistors are horrible when it comes to distortion so all the arguments about capacitor choice become largely irrelevant.
Their frequency response is also very poor when compared with their silcon brothers.
It's not difficult to produce a pre-amp, its basic electronic theory. The problems occur with power amps and load lines. What sort of Vcc are you intending on using and what sort of Pk-Pk output are you after ?
Germanium transistors are horrible when it comes to distortion so all the arguments about capacitor choice become largely irrelevant.
Their frequency response is also very poor when compared with their silcon brothers.
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thanx KatieandDad for your time , with more search on the gallium arsenide , there is the GaAs Fet / Mesfet as well i dont know how they sound like or if there is circuits based on them but i'm keeping my research 😉
The secret fuzz-pedal germanium transistor with the cult following in the US is OC44 -
There... that posting guarantees the price of such unobtanium is now doubled.
Read more in the museum of retrotech The Douglas Self Site
'Don't think this has anything at all to do with preamps though.
There... that posting guarantees the price of such unobtanium is now doubled.
Read more in the museum of retrotech The Douglas Self Site
'Don't think this has anything at all to do with preamps though.
The few remaining OC44 ought to be reserved for use in repairing antique AM radio frequency changers.
Frequency changers, you say? That title in AM rings a distant bell but I know it was used in vacuum tube days to describe a heterodyne mixer for shortwave use. Would that refer to UK Low band dual or shortwave equipped receivers? Just mixer/oscillator tubes in general?
OC44 was used in early AM (medium wave and long wave) superhet transistor radios, as a self-oscillating mixer (also known as frequency changer). OC45 was used as the IF amplifier. These early transistors only worked up to a few MHz.
Ah..so the term still applied in solid state times. It didn't here and only a few manufacturers used that 40 series Mullard? part numbers.
Well, a mixer/oscillator would tend to be good for all sorts of distortion so perhaps it could make a "special" fruity kind of audio distortion like a Dalek or chipmunk on vocals perhaps?
Well, a mixer/oscillator would tend to be good for all sorts of distortion so perhaps it could make a "special" fruity kind of audio distortion like a Dalek or chipmunk on vocals perhaps?
I've done a couple of distortion pedals with Ge transistors, and they certainly seem to sound different when overdriven. The OT is looking for something which is not clean, so possibly it makes sense to build something with Ge transistors. Chandler does so for studio equipment (eq, mike preamp), and seem to do fine.
There are a lot of interesting transistors, OC44 is pretty expensive, but there are a ton of others available more cheaply, depending on your location. There's stuff from russia, but also the AC*** series which are in a lot of stuff from the 60's and 70's.
Leakage is something to watch out for, so measure transistors before using them. I would just breadboard the circuit and work out biasing, then put it on perf.
On the ProdigyPro forum, member Kubarth has done a Ge mike preamp for studio use and it uses only one or two Ge stages for colour, the rest is "contemporary".
The reason for swapping out npn for pnp is that Ge transistors are commonly available in pnp but npn's are rare (and not as good).
If you are willing to buy on ebay, there's a guy in the UK is selling NOS military Ge pnp's, I bought a couple of batches from him and they are all low leakage, type is cv7355, IIRC
jerluwoo, that seems like an interesting schematic, think I'll give it a try, thanks!
There are a lot of interesting transistors, OC44 is pretty expensive, but there are a ton of others available more cheaply, depending on your location. There's stuff from russia, but also the AC*** series which are in a lot of stuff from the 60's and 70's.
Leakage is something to watch out for, so measure transistors before using them. I would just breadboard the circuit and work out biasing, then put it on perf.
On the ProdigyPro forum, member Kubarth has done a Ge mike preamp for studio use and it uses only one or two Ge stages for colour, the rest is "contemporary".
The reason for swapping out npn for pnp is that Ge transistors are commonly available in pnp but npn's are rare (and not as good).
If you are willing to buy on ebay, there's a guy in the UK is selling NOS military Ge pnp's, I bought a couple of batches from him and they are all low leakage, type is cv7355, IIRC
jerluwoo, that seems like an interesting schematic, think I'll give it a try, thanks!
OC44s are still frequently available here in the UK.
10 CV 7003 transistors new old stock oc44 | eBay
10 CV 7003 transistors new old stock oc44 | eBay
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