Found some Mullard OC81D Transistors...

[Rapidrory]

Ok, first a little backstory:

Almost 2 years ago I inherited my grandfather's collection of radio equipment components. This was basically an entire garage full of a wide range of electronic components that he had horded over the last 70 years. Amongst these there was several hundred valves (including many vintage audio valves), boxes of germanium transistors, hundreds of old style resistors and capacitors of every type, classic op amps and a wide range of diecast boxes, knobs, potentiometers, audio jacks, etc.. Basically a classic guitar effect maker's gold mine.

Whilst browsing online I came across the Tone Bender Professional MKII, which used the 'legendary' OC81D transistors to achieve it's effect... so I went through my boxes of germanium transistors and found 2 Mullard OC81Ds, 2 Mullard OC81s, and 2 OC81somethings as the last part of the number is missing.

Having done a bit more research, it seems that the OC81Ds are particularly rare, but I can't find out how much they're actually worth. The guy who I make pedals for (I don't actually own a guitar, I just love electronics and stompboxes are great little projects) is currently looking for a fuzz pedal, so if I can find a third OC81D I'm tempted to make a replica Tone Bender Professional MKII, including all period passive components etc.

So my question is, does anyone know how much a set of 3 OC81Ds would be worth? I haven't actually checked they work yet, but they're unused so hopefully. I'm trying to decide whether to sell them or make an exact replica of the pedal (circuit wise at least).

[UKToecutter]

Here's an auction for 5 of them
http://www.ebay.co.uk/itm/5-of-OC81D-germanium-transistors-black-glass-case-/381094386507?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item58bafedb4b

Also Littlediode has them at £8.98 each

[Rapidrory]

Well then, I'll build the fuzz pedal instead

[jbgron]

The new production black glass OC81Ds by DSI are low gain and not really usable in a Tone Bender.

http://www.diystompboxes.com/smfforum/index.php?topic=82702.0

Vintage Mullard OC81Ds are a lot more expensive, if you can find them.

[Electric Warrior]

You may also want to check your stash of parts for OC75s. The MKII originally used these.

[Rapidrory]

Got OC71s and OC45s; no OC75s that I can see on my brief search sadly.

Any suggestions for other designs that need vintage germanium transistors/ other vintage components? I've used one as a booster in a valvecaster before (which sounded beautiful), but would like to try a few other circuits if there are some good ones...

[newfish]

Given the amount of leakage most Ge devices have, I'd suggest that part numbers are not the most important factor.

Breadboarding a Tone bender circuit, and auditioning your OC45 / 71 devices may well yield a great sounding pedal.

FWIW, I've had great 'Fuzz Face' results with OC45 devices in the past.

[Electric Warrior]

Given the amount of leakage most Ge devices have, I'd suggest that part numbers are not the most important factor.

Breadboarding a Tone bender circuit, and auditioning your OC45 / 71 devices may well yield a great sounding pedal.

FWIW, I've had great 'Fuzz Face' results with OC45 devices in the past.

The amount of leakage can vary considerably. OC75s leak a lot, which is what makes them work great in a MKII. Low leakage devices are usually problematic. Sola Sound used Impex S3-1Ts sometime, which hardly leak anything and are either very low or very high gain. For some bizarre reason they work great. I tried similar setups, but they would neither sound right nor behave well.

OC81Ds may or may not leak a little less than OC75s(I've heard varying reports about this). Vintage units with OC81Ds mostly had a different bias setup than OC75 units. They all sound rather similar in comparison:

Your OC81Ds will probably work rather well. Too bad you only have two. It's always nice to have a couple of extra ones to select a great sounding set.

[Arcane Analog]

Here's an auction for 5 of them
http://www.ebay.co.uk/itm/5-of-OC81D-germanium-transistors-black-glass-case-/381094386507?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item58bafedb4b

The transistors in your link are not Mullard devices. They are DSI and are relatively new production devices that do not share the same characteristics as the Mullard branded devices. In my experience, these are relatively worthless for MKIIs. You can purchase much better devices for a lot less.

[Rapidrory]

I'm not trying to purchase them, I just want to know roughly how much original Mullard OC81Ds are worth

[Scruffie]

You say you have some non 'D' suffix OC81, I actually had quite a few mullard OC81D & OC81 when I build my MkII and when auditioning actually found that the standard 81s were great (I can't remember the numbers of the exact ones I used but I do have the measurements from most of what I had at the time, I ended up with an 81D in the second transistor position and 81s in the other 2 spots.

OC81D
65hFe Just Over 300uA

OC81D
118hFe Under 500uA

OC81D
112hFe Just Over 400uA

OC81D
106hFe Just Over 400uA

OC81
66hFe About 250uA

OC81
108hFe Just Over 300uA

OC81
88hFe Just Over 300uA

OC81
55hFe Just Under 550uA

OC81
56hFe Under 600uA

OC81
37hFe Just Under 250uA

OC81
192hFe Almost 1mA

OC44
211hFe Under 150uA

OC45
153hFe Under 100uA

OC45
28hFe

OC44
149hFe Under 100uA


I also built a great MkII with 2 x OC45 and an OC44 in the second transistors spot (which I stupidly sold... hoping the guy will sell it back to me one day), I had more 45 than I have readings for above though.

So really... just audition all the mullards you have in a breadboard circuit

[Scruffie]

I'm not trying to purchase them, I just want to know roughly how much original Mullard OC81Ds are worth

Depending on how good they are... could be £5-20 each from memory of what i've seen them go for.

[Arcane Analog]

I'm not trying to purchase them, I just want to know roughly how much original Mullard OC81Ds are worth

Who was suggesting that you were trying to purchase transistors?