# DuoCast vs a real Broadcast



## caiofilipini (Apr 13, 2021)

A while back I built a DuoCast that didn't sound at all close to the Broadcast demos I'd seen. I tried a whole bunch of different germanium transistors, and they made some difference, but overall the pedal was lacking something.

So I bit the bullet and got myself a real Hudson Broadcast Dual. What a sound!

Anyway, I found and fixed an issue with my build (more on that here), so I decided to do a quick shootout against the Hudson:






You'll find this in the video description too, but my initial impressions are that the overall sonic characteristics are all there, even though there are some noticeable gain differences between the two, which likely boils down to the specs of each transistor.

Overall, I think the DuoCast sounds pretty cool!

Hope this is helpful.


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## Dan0h (Apr 13, 2021)

Jealous. I really want to pick up a real one, but I’m afraid it might taint my perfect sound from the one I built. Lol. Awesome side by side.


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## caiofilipini (Apr 13, 2021)

Yeah, I get that. I think I wouldn't have picked one up had my build turned out great from the get go.


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## Harry Klippton (Apr 13, 2021)

I didn't think they sounded that different in your video. At least I couldn't tell while it was playing on my phone while I'm cooking breakfast!


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## caiofilipini (Apr 13, 2021)

Harry Klippton said:


> I didn't think they sounded that different in your video. At least I couldn't tell while it was playing on my phone while I'm cooking breakfast!



Yeah, I tried to dial them in the same ballpark, I guess the main difference is when you try to position the knobs the same in both pedals. Mine seems to have more gain and more volume in the low channel, but less volume in the high channel.

I should also say I set the internal trimmers the same in both. Could probably get them to sound even closer by fine tubing the trimmers to compensate for the differences.


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## Harry Klippton (Apr 13, 2021)

I listened again with headphones and I could hear the gain difference but the overall character of the two was the same. Sorry if you explained this elsewhere but did you try swapping different ge transistors to see if you could get yours closer to the Hudson?


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## giovanni (Apr 13, 2021)

Thanks for sharing the video! There is definitely a difference in the gain structure. The Broadcast seems to have more bite to it, if that makes any sense.


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## fig (Apr 13, 2021)

caiofilipini said:


> Yeah, I tried to dial them in the same ballpark, I guess the main difference is when you try to position the knobs the same in both pedals. Mine seems to have more gain and more volume in the low channel, but less volume in the high channel.
> 
> I should also say I set the internal trimmers the same in both. Could probably get them to sound even closer by fine tubing the trimmers to compensate for the differences.


I'd almost bet the differences are in the biasing (with a bit of wiggle room for minor component variants).
Also, the pots could be a good bit apart on values even at the same rotation.


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## giovanni (Apr 13, 2021)

I agree you shouldn’t rely on the pot position. The tolerance can make two pots with identical specs quite difference. Same goes for trimmers. Using your ears is probably the best way to go.


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## caiofilipini (Apr 13, 2021)

giovanni said:


> Thanks for sharing the video! There is definitely a difference in the gain structure. The Broadcast seems to have more bite to it, if that makes any sense.



Yeah, I definitely hear that as well!


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## caiofilipini (Apr 13, 2021)

fig said:


> I'd almost bet the differences are in the biasing (with a bit of wiggle room for minor component variants).
> Also, the pots could be a good bit apart on values even at the same rotation.



Biasing is not that far off, actually, so I really think it's a combination of hFE differences and component tolerances, especially with the pots.


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## caiofilipini (Apr 13, 2021)

Harry Klippton said:


> I listened again with headphones and I could hear the gain difference but the overall character of the two was the same. Sorry if you explained this elsewhere but did you try swapping different ge transistors to see if you could get yours closer to the Hudson?



I did test a bunch of them when I first built it, but since my BC549C was installed backwards, I'm gonna have to do that again. I tried a couple yesterday, but will try some more when I get a chance.


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## caiofilipini (Apr 13, 2021)

By the way, for those of you who are curious, my Broadcast has an NTE 2N404A in Q2. It is socketed, but I believe it's been soldered to the socket, because I couldn't pull it out.


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## fig (Apr 13, 2021)

caiofilipini said:


> I did test a bunch of them when I first built it, but since my BC549C was installed backwards, I'm gonna have to do that again. I tried a couple yesterday, but will try some more when I get a chance.


Right, that was the one you got from PedalHacker. That was curious to me. If you find out anymore info, plz share.


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## caiofilipini (Apr 13, 2021)

fig said:


> Right, that was the one you got from PedalHacker. That was curious to me. If you find out anymore info, plz share.



Yeah. I can't find a datasheet for Ferranti specifically, but I did notice it's marked BC549C*P*, so maybe that has something to do with it?
Anyway, I feel like I should get some regular BC549C to test in there as well.


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## fig (Apr 13, 2021)

caiofilipini said:


> Yeah. I can't find a datasheet for Ferranti specifically, but I did notice it's marked BC549C*P*, so maybe that has something to do with it?
> Anyway, I feel like I should get some regular BC549C to test in there as well.


I'm pretty sure the pinout is still CBE, but I am far from an EE...so grain of salt.


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## jcrhee (Apr 13, 2021)

caiofilipini said:


> By the way, for those of you who are curious, my Broadcast has an NTE 2N404A in Q2. It is socketed, but I believe it's been soldered to the socket, because I couldn't pull it out.


I think I prefer the NTE 2N404A. The GT sounds more spit-ty. Now to track some of these down. Thanks a lot. 😉


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## caiofilipini (Apr 13, 2021)

I think they sell it directly:






						Item number 2N404A
					

T-PNP GE MEDIUM SPEED SW




					www.ntepartsdirect.com
				




Datasheet says typical hFE is 86, but I guess you'd have to order a few and hope some fall within spec.


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## jcrhee (Apr 13, 2021)

caiofilipini said:


> I think they sell it directly:
> 
> 
> 
> ...


nice. I also found this:





						Transistor - 2N404A
					

Small Bear Electronics DIY Parts




					smallbear-electronics.mybigcommerce.com
				




$7 -- shish...


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## caiofilipini (Apr 13, 2021)

There's also this one:









						Texas Instruments 2N404/404A
					

Small Bear Electronics DIY Parts




					smallbear-electronics.mybigcommerce.com
				




I have a couple of those and they sound pretty good too, but I got a bunch with crazy high hFE too.


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## jcrhee (Apr 13, 2021)

caiofilipini said:


> I think they sell it directly:
> 
> 
> 
> ...


$8 to $9 in shipping -- ouch.


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## TheSin (Apr 13, 2021)

caiofilipini said:


> A while back I built a DuoCast that didn't sound at all close to the Broadcast demos I'd seen. I tried a whole bunch of different germanium transistors, and they made some difference, but overall the pedal was lacking something.
> 
> So I bit the bullet and got myself a real Hudson Broadcast Dual. What a sound!
> 
> ...


Nice! Very close sonically to the real one. Thanks for sharing this!


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## Chuck D. Bones (Apr 13, 2021)

I seriously doubt the gain difference is due to hFE unless you get a tranny with very low hFE.  The R's & C's, mainly the GAIN pot and the two trimmers, set the gain of the circuit.  Like Giovanni said, the tolerance on pots is huge, so that's most likely a contributor.  Some trimmers have a reversed footprint, so don't go by trimpot position.

I've said it before, but I think it bears repeating: don't get hung up on part numbers, especially with Germanium.  There is so much parametric variation within the same part number that you can build two Germanium circuits with the same part numbers and get drastically different results.  The only things that matter are getting hFE and Icbo in the ballpark for the specific circuit.  The boutique pedal builders frequently have to hand-select their Germanium transistors, diodes and FETs.


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## music6000 (Apr 14, 2021)

P


caiofilipini said:


> A while back I built a DuoCast that didn't sound at all close to the Broadcast demos I'd seen. I tried a whole bunch of different germanium transistors, and they made some difference, but overall the pedal was lacking something.
> 
> So I bit the bullet and got myself a real Hudson Broadcast Dual. What a sound!
> 
> ...


Alpha Potentiometers are all over the place, 1M that read as low as 920K, 100K that read as low as 89K and the list goes on!
*TEST everything !*
I've read somewhere that these PCB's are similar to the Pedal they are based on.
It gets down to the type & brand that of components used!


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