The Broadcast is a transformer coupled, discrete Class-A germanium pre-amplifier based on the classic broadcast consoles of the 1960s. In the low-gain setting, the Broadcast can cover everything from sparkling clean boost through to transparent overdrive, all with a healthy dose of volume available to push your amp. The Broadcast features a specially selected Triad steel-core transformer and a NOS germanium transistor. Advancing the gain on the Broadcast starts to saturate the transformer and the pedal’s discrete circuitry, giving rise to a gentle and dynamic compression coupled with subtle thickening of the midrange. With the gain switch in the high setting and the trim control wound up, the Broadcast starts to deliver heavier distorted sounds with a warm and fuzzy edge to them. The Broadcast covers a wide range of driven and distorted tones whilst remaining dynamic, responding well to pick attack and the subtle nuances of every player.
Thanks to Tipunk777 for reverse-engineering his own pedal in the Forum section.
There are 2 layouts:
one with a 24V charge pump and one without.
23/12/2016 Layout updated! Changed Gain Switch to On-Off-On and rotated OC71 180 degrees
Added a second layout with charge pump. It's the same as before but on the top of the layout to give more space to the transformer.
Great job with the vero, Alex - thx for sharing. The lower gain tones on the video really shine.
ReplyDeleteBuilt the second layout. Used the wrong transformer. It works and sounds like the video, but my gain and low cut pots aren't doing anything yet. Just finished so haven't looked it over yet.
ReplyDeleteFound a soldering mistake and now low cut works.
ReplyDeleteThanks NDF!
DeleteDo Gain and Low Cut work?
Is it verified than?
Gain still isn't working. It got late so I stopped playing with it. In the schematic in the thread I think the 10 uf attached to gain 1 was 100uf ? Would that change anything?
ReplyDeleteThe 10uF is correct but there may be a mistake somewhere else:
Deletecan you try to disconnect Gain 1 and connect it to row 7, right above Sw1? If it works you should reverse Gain 1 & 2 after.
Please, let me know if it fixes it.
It's all working now. Did the layout change recently? I had been working from a screen cap of it and didn't have the cut on the bottom row.
ReplyDeleteYes Alex changed the layout as there was an error.
DeleteIt sounds pretty cool. Better into a clean amp than a dirty one for me. I used a tm009 for the transformer. Not sure what sort of difference that has made
ReplyDeleteWhere can I find these transistors? Are there alternatives I can use? Ta ~~
ReplyDeletealso should the oc45 be oc75?
ReplyDeleteand should the bs549c be bc549c? a silicon npn?
DeleteYes I think it is bc549c instead, I used a bc549 and an sft 352 pnp germanium transistor. I have a bunch sorted by hfe and I just grabbed one with 70 or 80 hfe.
ReplyDeleteThanks, I'll keep looking around for this pnp... This pedal sounds great!
DeleteI always socket the transistors and try whatever I have, I've found most pedals aren't too picky if you use the right type. I imagine many npn silicons and pnp gemaniums would be fine for this circuit
ReplyDeleteHi NDF!
DeleteDid you make the changes to Gain 1?
YAY!
ReplyDeleteDoes the original have the crarge pump?
ReplyDeletei think there have been 2 different versions, 1 with a charge pump and one without.
Deleteok thanks!
DeleteWhat would be a good hfe for the germanium transistor? 70-150 range? or under that?
ReplyDeleteIs the spdt switch on-on-on?
ReplyDeleteI think the switch is on-on
ReplyDeleteCheers Alex and Tipunk777, I've built the version without the charge pump, and it's working as per expectations, so you can probably tag that layout as verified. Low is pretty subtle, though and I had to make some substitutions of key components because I didn't have exactly the right stuff.
ReplyDeleteSo, the non-charge pump layout works with: 470R substituted for the 450R, 22k level pot instead of 25k, a different 1:1 centre-tapped transformer (which I think is a TM018) and a Russian PNP Ge transistor with a measured gain of about 40 that looks like a grey flying saucer.
Cool. Thanks Strewel!
DeleteCan anyone share how they mounted their transformer - bend the pins? on its side like in the production photo?
ReplyDeleteThanks!
I used a different transformer, but I just bent the mounting pins out of the way
ReplyDeleteDoes anyone know if there are more versions of the gain switch? In most videos I have seen online the Pedal has a three position switch. This one seems to be a two position on-on?
ReplyDeleteFor the transformer, could one use pins 2 and 5 for ground, instead of 3 and 4 as in the layout? If it's 1:1, then the windings should be the same, right?
ReplyDelete...or do you only get half the windings with the center taps?
DeleteThe center tap is a wire connected to the center of the winding. You don't really "get half the winding" from the centertap. It has half of the winding on one side of it, and half of the winding on the other side of it.
ReplyDeleteBut to answer your question, if you use the center taps (pins 2 and 5) instead of 3 and 4, it won't work the same as the original.
Built the version with the charge pump. Works nicely, except for the fact that it doesn't make an audible difference if the transformer is installed or not. Bridging the across the top row of where the transformer I'd supposed to go (or not making the cut) doesn't change the sound a bit. Checked it back and forth. Installing a different transformer with different impedances cuts a lot of bass, so it's not an error in the build or layout. Just another mojo myth debunked it seems! I would like to be wrong here. Has anyone made different experiences?
ReplyDeletei own the original 9V Broadcast version in which i later installed an 18V charge pump so it runs on 18V now. upon inspection of your vero layout, one big error that i found is that you have the OC71's emitter and collector reversed. the collector is supposed to connect to a 5K6 resistor to ground and the emitter connects to a 4K7 to the V+.
ReplyDeleteThanks John!
DeleteI've updated it.
right on. i also drew out my 9V original's vero layout. the thing is, they used vero-board with .133" spacing.
DeleteBTW, and LT1054 works fine for the 25V charge pump.
ReplyDeleteCan you tell me why there are two different layouts with charge pumps, both with the same components?
ReplyDeleteplease read the original text. it explains it.
ReplyDeleteSORRY - I downloaded the images before I read the new bit of info about them.
ReplyDeleteSo if the Gain switch is 'on-off-on', it is a 3 position spdt-switch then?
ReplyDeleteYeah, but you could use a 3 position DPDT too though, and just use one side of it.
ReplyDeleteI have a strange problem with the finished build. I have checked my connections but the gain switch ain't working like it should. I get 'low gain' on middle position, 'medium gain' on the left position and 'High gain' on the right.
ReplyDeleteWhat am I missing here?
that sounds correct to me.
ReplyDeleteBut in the demos of 3 position switch-model it goes from left to right? Low-mid-high.
DeleteYou should be able to do the same by using an On-On-On DPDT switch.
DeleteAnyone know of easily accessible, reasonably priced replacements for the OC71? I'm not having any luck finding them.
ReplyDeleteThere are some available on ebay, but you can try any PNP Germanium, with hFE somewhere in the Rangemaster/FF zone, 70-120 Cheap alternative would be AC125 which supposed to be replacement.
DeleteIs it okay to replace one of the 1n5817 with a 1n5818? I just ran out.
ReplyDeleteWhat value of current limiting resistor are people using on the 24v version of this - and has anyone used an on-off-on or an on-on-on switch for the gain level - I'm wondering which is right?
ReplyDeleteVery nice work, thank you all!
ReplyDeleteSomeone can post the voltages on the transistors, mainly on the germanium one?
I have only some AC128...
I finally boxed this up yesterday (my 10th keeper). It sounds great! I've wanted this pedal ever since it came out. Thanks to all the posters and commenters on this site!!
ReplyDeleteHow would I go about adding a second volume pot so there's one for each gain mode? Would it be possible with a 3PDT?
ReplyDeleteI would also love to know this! Really interested in building the dual footswitch version.
DeleteHello,
ReplyDeletei'm trying to make this one but i have one question : what are the small holes I surrounded in green ?
https://drive.google.com/open?id=0B70IAzKXeQTIaVRIVV9RTk1Hemc
I search in the "build guide" and "layout guide" tab but found nothing...
They are link points. Just like the points on the ends of the links. You need to connect to all those circles. Hope this helps!
DeleteThat was simple indeed...
DeleteThanks to you Riku !
What are the target voltages for biasing the transistors when running at 24v?
ReplyDelete(Also, has anyone had success replacing the OC71 with a SI transistor? I'd be curious to get transistor suggestions for exploring that direction.)
I'm guessing the black dot marked on the transformer is the primary side, right?
ReplyDeleteI would also like to know this..
DeleteYes it's the Primary side
DeleteThanks!
DeleteCheers riku, also any subs for the 15v zener??
ReplyDeletethat sounds correct to me.
ReplyDeleteโกลเด้นสล็อต
บาคาร่า
Built the version without the charge pump. When I plug the power in and play, it seems to work for a second and then just fades out into nothing. If I hit the strings really hard I can hear a crackle but that's about it. Any ideas? This is my first build that hasn't worked first try!
ReplyDeleteWow, thanks for this Alex! I've done plenty of PCB builds but this will be y first on Vero.
ReplyDeleteI'm going to do the smaller 9V version. Could somebody let me know what type of capacitors I need for the yellow boxes and red circle?
Thanks.
Is there a reason the switch is ON-OFF-ON? Surely an ON-ON would work?
ReplyDeleteThanks
Tristan, any luck on your build as of yet? I’m getting ready to source some parts and trying to determine if the charge pump version is worth making over the 9v edition. Especially since there seems to be some whine issues with the 24/25 v version?
ReplyDeleteHi,
ReplyDeleteI never got started... would really like the dual-footswitch version to be honest. Maybe one for the future...
Personally I'd prefer to be able to vary the voltage myself instead of being locked in at 24V
Thanks, works like a charm andere sounds sweet.
ReplyDeleteIk built a dual doorswitch version. Just add a second 3PDT switch. Use the first pole as the switch, the second for the led and the third to switch between two level pots.
Optionally you van add trim pots for the maximum amount of gain in each channel. The 450R resistor between switch 1 and 3 van be replaced with a trimpot for the lowgain channel. Another trimpot could be added for the highgain channel.
He so is the only difference between the dual version and the original that you swap the troggle switch for a footswitch + the internal gaintrimmers per channel and 2 level knobs instead of one?
ReplyDeleteIs there a layout/schematic availabe of the dual version? If not, would any of you be able to make it?
By the way, i'm completely new to building so i don't know how to do any of this myself haha
Also, do you think it would be possible to replace the universal gain knob for a univeraal level knob and the 2 level knobs for 2 gain knobs instead?
Would it sound the same? Like would you only have different controls or would it change the actual sound?
And would there need to change anything in the circuit or is it only a matter of wiring in differently?
Maybe there would be problems with level differences between the channels, i meand that channel 2 would be much louder than channel 1 when you would switch between them with certain settings. Is ther something as an internal level trimmer instead of an internal gaintrimmer? Would this fix that problem?
Sorry for the long post
Just want to build a dual version with a friend of mine so we're just doing some research.
Thanks in advance
I'm going to attempt to build a dual footswitch version, just going through my parts box now to see what I'm missing. But from the Anon post above, it looks like you'd have levels for high and low gain with the pots. There's a guts shot of a Hudson one on Reverb if you do a googler image search, might help.
DeleteWill let you know how it goes.
https://goo.gl/images/Soerhp
DeleteI'm just puzzling over how to fit the ty-141p, it's on it's side and tie-wrapped in - https://goo.gl/images/ciHcP8
Bend the legs.
Deletejust built this and used a russian gt404b transistor (hfe around 80) but it sounds really farty and not very musical in all three switch positions.
ReplyDeletewould this be the transistor, or something else in my build?
Check pinout, cuts and knife strips. What version did you build?
Deletethe 2nd layout. i'll have to pop it out and take a closer look.
DeleteHmm i had problems eith second layout too. Using a seperate voltage board. Dodgy ic? What ic you using?
ReplyDeleteUsing an LT1054 from mouser. I’ll double check voltages/traces/cuts when I’m home next week.
ReplyDeletestupid me... i was using an npn transistor. will try again with a pnp and report back!
ReplyDeleteRussian got 402 with hfe around 70 seems perfect! Layout #2 verified. Nothing else to see here. Move along...
ReplyDeleteI finished the second layout a few days ago. It sounds great, and works just like many of the demos I've seen. However, mine has a steady and rapid ticking that gets louder with more gain. I've put buffers before and after with no change. Any ideas what could be causing this?
ReplyDeleteI built the second layout with an OC71. Unfortunately, I have to troubleshoot now. At one point I had sound but no gain or level... I;ve gone through checking to make sure everything is as it should be now I have no sound... I'm getting the 24v through the pedal to the OC71. But after that I have drastic voltage drops. I'm not sure if this is what is suppose to happen. any help would be appreciated... I will update if I'm able to figure anything out
ReplyDeleteUpdate: After reflowing solder, cutting tracks checking with an audio probe I found out I had a faulty potentiometer. now I have sound going through the pedal, but the gain switch and the gain pot are not working. When I turn the gain pot I hear a crackle but the sound is otherwise unchanged. I accidentally touched the gain 1 solder on the enclosure and that caused the gain to show up, but I'm not sure what this means otherwise. any advice would be great.
DeleteHmm.. no expert here, but check the following:
ReplyDelete- if you touched the solder on the pot enclosure, you likely shorted it to ground and therefore took it out of the current flow path (?).
- check that pot again or replace it. Instead of just reflowing solder, remove it and clean the solder lug surface, do the same for the wire connections on the tag board. Make sure you have good mechanical connections before you solder.
- triple check your layout, did you perhaps miss the double link joint (the white dot with blue-ish outline) on the same row as the switch 3 connection?
- are your capacitors adequately rated for 24 V? The electrolytics should be rated for > 30 V, 25 v won’t cut it for this layout.
Hey Daniel, thank you for the reply. I have 35v caps in the build as per the build sheet. I'll have to check the continuity in in the double link joint to make sure that it is connected properly. I will also look over the layout yet again.
DeleteI'm not sure if solder quality plays a role in this, but I just bought a new solder iron kit from amazon, and I used the solder that came with the kit. It left many 'grey' solder joints.
Did you change the solder you were using mid-build? Probably shouldn't do that, especially if the solder is a different mixture (leaded vs lead-free vs 60/40 vs 65/35, etc.).
DeleteA grey solder joint is undesirable and may cause issues. I would recommend you clean off any grey solder by heating and using the solder sucker. I too use one of those cheapo blue soldering irons from an Amazon all-in-one kit, with much success too, although the tips are crap and go South quickly.
Clean your solder joints, follow the general guidelines of good soldering (clean tip after 1-2 joints have been made, tin tip, keep tip hot (350 C), apply heat to joints, wait a sec, apply solder, remove solder strand from joint, keep tip on joint for ~ 1 sec, etc.)
As a note, I made the third layout and added a daughter board for switchable 9/18 V power. I obviously built them separately and this circuit still sounds great at 9 V. If success continues to elude your build, build the third one, get it working then add the daughter board (search under the charge pump section on this website, I used the NE555 layout with the SPDT 9V/18V switch).
I decided to build the 9v version last night. I finished it off this morning and... I'm having a similar issue. The gain circuit still isn't working. my transistor voltages are off of what the should be but I'm not sure how to fix that.
DeleteOc 71
C= 8.7
B= 8.7
E= .2 !!!
BC549C
C= 8.7
B= 3.2
E= 2.7
anyways I'm going to take another look over my placement and values. After that I'm not sure what I'll do
Hmm.. 0.2 does seem strange/low, but I am no expert at this stuff. The bigger thing to me is that C=B on the OC71... Are you links and cuts correct?
DeleteI will measure my voltages when I get home tonight and report back to you.
My dumb recommendations:
- Check your OC71 pinouts. Flip it around if needed.
- Do you have another PNP? Swap out with the OC71 to see if issues persist
- Print out or save to excel the layout images and zoooom in. For example is that 10R resistor coming off the Voltage rail really 10R for you, etc.
V in = 9.36
ReplyDeleteOc71
E 6.9
B 6.77
C 2.84
Bc
C 2.49
B 2.54
E 6.77
Sorry
DeleteBC
C 6.77
B 2.54
E 2.49
thanks, I've checked the voltage from the 9v source. when I trace it up to the OC71 the only place where I notice the voltage getting lowered, besides the ground rail which is 0, is after the 330n cap. I do not have a great understanding on the effects that resistors and capacitors have on a signal but I figured that a resistor would lower the voltage. Anyways I think I'm going to swap out some of the parts and see how it goes from there
ReplyDeleteI replaced all of the capacitors and resistors and it works as it should. I guess third tries the charm. I Haven't played it long, but so far it sounds really good. I look forward to trying it over the next few days
DeleteThis comment has been removed by the author.
ReplyDeleteAny idea how to use this as a microphone Amplifier? I think there is an issue with symmetric/ non-symmetric. But I have no idea how to build this. Would very much like to build a germanium mic preamp. Your help is very welcome! Thanks.
ReplyDeleteHow would I convert this into a dual broadcast? I understand for the dual the gain switch is moved to a stomp, 2 internal trimmers are added to control maximum gain for each side and a pot is added to control the volume of the gain channel. I have no idea where to make these adjustments. Anyone have any clues?
ReplyDelete
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Finished build this week. I should have spaced the board out a bit, as plenty of room in a 1590BB. Components ended up a bit cramped. I copied the original's appearance to challenge my level of finish (changed the name). Didn't work 1st time, turned out OC71 wasn't in properly (I used half a 6-pin DIL socket). Noticeable difference for each of the 3 switch positions. I can't hear much difference on low cut after 12 o'clock. Overall really pleased, already on my board.
ReplyDeletePedal shot:
https://drive.google.com/file/d/1UtqwD7hnjW6uyNKJXIXVhMhn_aDM-nyl/view?usp=sharing
Gut shot:
https://drive.google.com/file/d/1d_MFWvo_IxS5Xa5JHxSFmeIotT5UwFPv/view?usp=sharing
WoW! Awesome finish!
DeleteWhat is the label material?
Thanks for sharing valuable Information, I really very impressive on your blog. I hope you continue on blogging job.
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Hi. I have a quick question. I've built some pedals from kits before, but have never built using veroboard. So I think I'm okay to give it a go, and I mostly understand what I'm seeing with the layout. One this one there's one symbol that I don't get. Looking at the 3rd layout, what's the little circle on the two bottom-most links, the little blue circle with a white inside dot? As I type this, I realise it's such a newbie question - but I just can't find the answer anywhere. I bet it's obvious and when someone gives a reply I'll be wondering why I didn't know that! Anyway, thanks in advance.
ReplyDeleteNo dumb questions! That blue/white circle indicates a shared hole for two links. In other words the link that starts from the bottom and the link that starts from the top both terminate at the blue/white hole. So you will have three electrically continuous rows (until you get a cut that is). Don’t hesitate to reply if that wasn’t clear enough.
ReplyDeleteThank you! And yes, that's absolutely clear. I'm going to give this one a go. I had an actual Broadcast a little while back, but it didn't work out for me. Great pedal though. But I've changed up my amp since then, so I'd like to try one again, and so I'll attempt a build.
Delete2 questions about this build –
ReplyDelete1) Is it possible to add a switch for 9V/24V operation? Or do I need to commit to one or the other? If it's switchable, where does the switching fit into the layout?
2) There seems to be a lot of questions about the 3-position SPDT switch, on/off/on vs on/on/on – what is the best toggle to use?
1. Yes. Use the regular 9v layout and build a separate charge pump board (you can find a few layouts on this website). Use and SPDT on/on switch, connect the broadcast's power wire to SPDT lug 2. Thn connect SPDT lugs 1 and 3 to 9v and 24v, respectively.
Delete2. Use whichever switch you have. Make sure it is latching. An SPDT on/on would probably be best.
Thanks! Very helpful
Deletewhat should I do to have only two positions with the gain switch as on the original?
ReplyDeleteSwitch and wiring?
Thank you
Simply use an on-on SPDT switch with the above circuit!
DeleteThank you very much for the answer.
DeleteBut I have another "problem", I used a NTK275 with a 85 Hfe, and I do not get a fuzzy sound, I should take a transistor with more gain I think?
So my build doesn't sound great with the transistors I have on hand, kind of farty with no sustain. Gain knob doesn't do much, selector switch works, low cut seems to work, level works. The hFe for my transistors range in the 300 on average... not sure if that plays a huge factor in this pedal or not.
ReplyDeleteI selected a few on Mouser by hFe alone (as that's all I really had to go on), but before I buy I'd like some input as I don't know what I'm looking at.
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=1e9f473790
Just starting to build this and I noticed the TY-141P transformer has a gap of 3 holes in the middle vs the 2 on the layout. Does anything think there will be any problems with it taking up another hole gap, so the secondary pins will be soldered 3 from the right instead of 4 from the right? I am using the bottom layout and plan to use a charge pump daughter board later. Thanks!
ReplyDeleteJon q - I would try a few different PNP germaniums in place of the OC71 to see if that makes a difference. The BC549C is a high gain transistor, the BC108 or BC109 should be a satisfactory replacement. If your gain knob doesn't do much then there is likely a wiring or component issue on your build. Double check it all.
ReplyDeleteMoterrac - My transformer has the same setup. Having to solder one column further to the right will have no impact. One thing my transformer required was that I had to solder my pins every other row (not every subsequent row as shown on the layout). I am sure yours will require the same. Be mindful to have that 5k6 resistor and grounding link follow the 3rd transformer pin and add the additional cuts needed to maintain continuity/discontinuity.
Hi Brazdj, thanks for getting back to me! After fiddling around with I came to the same conclusion; I lowered the 5k6, added a few more cuts and lowered the ground jumper on the right to the bottom row, now the transformer fits perfectly with minor fiddling!
DeleteThanks!
All working first time even with the adjustments. Very good sounding pedal -think i'm going to hit the benson preamp next. Thanks Alex!
DeleteThanks. I ordered an OC71 and put a BC108 in there. Fixed my issue, sounds amazing. Not super high gain by any means, but as an OD it sounds pretty tasty. It has breakup unlike any of my other dirt pedals...
DeleteIs the OC71 driving the gain? If I swap out the 108 will I get a gain boost?
how did you wire the second foot-switch? I've been trying to figure that out
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteI couldn't get hold of 35 V capacitors, should I only build the 9v version or will these be ok with the charge pump version
ReplyDeleteI build the non chargepump version and used the GT2307 and tested, with succes a AC116 in remplacement of the OC71.
ReplyDeleteGreat pedal and good layout :)
I build the non chargepump version and used the GT2307 and tested, with succes a AC116 in remplacement of the OC71.
ReplyDeleteGreat pedal and good layout :)
I build the non chargepump version with GT2307 to replace the OC71. Also tested it with a AC116, sounded the same.
ReplyDeletegreat pedal good layout :)
Hello! I build it and it works.. i am just wondering about this 1nF cap.. should it be ACROSS gain pot 1 and 2? Is there a mistake in this layout? Cheers for any reply!
ReplyDeleteCan I use a silicon transistor in place of the oc71?
ReplyDeleteYou can, but most likely you will get oscillation if the hfe is above 200. I actually flipped a 5087 backwards and I get no oscillation, but it doesn’t get super compressed and gated at high gain settings. I am going to hunt for a low gain silicon PNP below 100 and try it the right way.
DeleteC4 and C11 need to be swapped each other.
ReplyDelete- C4 from silicon emitter is 10uf
- c11 at the bottom row is 100uf
It seems that way, bit it doesn't seem to make any difference to the circuit.
DeleteAnd to be fair, there's a hudson in the forum that was traces and has the capacitors in the eay as in this layout. So i don't think it probably matters either way by looks.
DeleteBuilt this guy up tonight using a 2N404 transistor and my gain really isn't doing anything. Everything else seems to work okay. Ideas? I used the middle layout
ReplyDeleteHey everyone, I built this guy up today (middle layout) with a 2n404 but my gain pot really doesn't seem to do anything. Any ideas?
ReplyDelete