Coming out of my *LURKING* hole for good I think : )
Diving into my first *from scratch* build" the Boozhound Triode strapped 6V6 Amp. Should be fun - For now, I'm using an RCA Console for the Iron, all the little bits (vishay, Sprauge & Solen Caps, etc.) are coming from Tube Depot & Mouser. For tubes, I have a pretty wide selection of 6sn7's & 6V6's - mostly old(nos) Military tubes.
Not sure of an enclosure yet, but I'm leaning towards seperate power supply and output chassis to maintain scalability going forward - should make it easy to modify one or the other pretty easily.
Are there any hurdles I should be aware of as a first time builder (besides the obvious - HV, ground issues) ? I'll be starting a blog to document the build (and my other projects) to help others going down this road.
thanks for all the knowledge you guys have supplied me over the last year as I built up to this point.
Mark
Diving into my first *from scratch* build" the Boozhound Triode strapped 6V6 Amp. Should be fun - For now, I'm using an RCA Console for the Iron, all the little bits (vishay, Sprauge & Solen Caps, etc.) are coming from Tube Depot & Mouser. For tubes, I have a pretty wide selection of 6sn7's & 6V6's - mostly old(nos) Military tubes.
Not sure of an enclosure yet, but I'm leaning towards seperate power supply and output chassis to maintain scalability going forward - should make it easy to modify one or the other pretty easily.
Are there any hurdles I should be aware of as a first time builder (besides the obvious - HV, ground issues) ? I'll be starting a blog to document the build (and my other projects) to help others going down this road.
thanks for all the knowledge you guys have supplied me over the last year as I built up to this point.
Mark
Avoid the dreaded hum, the enemy of most of us at one time or another.
Ensure all AC-bearing wire pairs are twisted, especially the heater leads, which cannot be kept away from the vicinity of signal-bearing leads and components.
Shield any long signal-bearing leads.
Use a 'multi-point' grounding scheme and never use the chassis to carry gound currents. Connect ground to chassis at one point only, preferably at the input jack.
I'm not familiar with the Boozhound but another good way of avoiding hum is not to ground the heater circuit directly but to create a centre-tap for the heater supply, with a couple of 100 ohm resistors (or use the physical centre-tap of the 6.3v winding if there is one), and connect that centre-tap to a potential divider between B+ and ground, so that it sits at about +20v; also, connect the centre-tap to ground via a 10uF capacitor.
Ensure all AC-bearing wire pairs are twisted, especially the heater leads, which cannot be kept away from the vicinity of signal-bearing leads and components.
Shield any long signal-bearing leads.
Use a 'multi-point' grounding scheme and never use the chassis to carry gound currents. Connect ground to chassis at one point only, preferably at the input jack.
I'm not familiar with the Boozhound but another good way of avoiding hum is not to ground the heater circuit directly but to create a centre-tap for the heater supply, with a couple of 100 ohm resistors (or use the physical centre-tap of the 6.3v winding if there is one), and connect that centre-tap to a potential divider between B+ and ground, so that it sits at about +20v; also, connect the centre-tap to ground via a 10uF capacitor.
The old Boozehound. What a great site. JSN has a way of putting things that even I can understand. I started to build that amp for my first and got side-tracked on a SET EL-34 circuit. Are you planning on building it exactley as shown, or tweeking? I've got it printed out somewhere. I'll dig it out and follow along. Good luck and welcome to the fold. Jay
thanks Jay
I'm pretty much following it step by step (less chance of f-up). The only thing up in the air is the chassis / case. Probably just oiled Birch plywood, or maybe really but the console to use and strip it like a buffalo - recycle a piece of door, or side panel, cut it down to use as a chassis . . .
Ray: I like how the old industrial tube stuff had a 16 or 14 guage solid gore ground - thingy from one end of the chaasis to the other. I parted out an old variable power supply for caps / variac / etc and still have the tank of a chassis. Icould probably try and duplicate that wiring.
thanks for the heater ground trick - I'll have to try it.
Could I use a VR tube for Heater Voltage, and just string the heaters together in series?
Mark
I'm pretty much following it step by step (less chance of f-up). The only thing up in the air is the chassis / case. Probably just oiled Birch plywood, or maybe really but the console to use and strip it like a buffalo - recycle a piece of door, or side panel, cut it down to use as a chassis . . .
Ray: I like how the old industrial tube stuff had a 16 or 14 guage solid gore ground - thingy from one end of the chaasis to the other. I parted out an old variable power supply for caps / variac / etc and still have the tank of a chassis. Icould probably try and duplicate that wiring.
thanks for the heater ground trick - I'll have to try it.
Could I use a VR tube for Heater Voltage, and just string the heaters together in series?
Mark
I have a question about the Boozhound amp. I was making a parts list, and was looking at the Hammond 125ESE that he references. It has a frequency response lower limit of 150 Hz. Now, I know that's pretty low, but not as low as it shoulc be for full range.
Are there acceptable replacements that would give a lower range? In the 15W output range, there's the P-T 1615, but the specs are different. What changes would have to be made to incorporate the extended frequency? What about going with the P-T 1620 20W OPT? Most likely a different power transformer would be necessary, right?
Are there acceptable replacements that would give a lower range? In the 15W output range, there's the P-T 1615, but the specs are different. What changes would have to be made to incorporate the extended frequency? What about going with the P-T 1620 20W OPT? Most likely a different power transformer would be necessary, right?
You mean a bus-bar. A ground bus-bar is OK, provided you don't connect things to it 'out of sequence.' You want to avoid mixing ground-currents from different stages.
The best way is to run the bus-bar from the input socket at one end (which should also be its only connection to the chassis), to the negative terminal of the power supply's reservoir capacitor at the other end. In between, there should be a series of tightly-grouped grounding connections for each stage of the amplifier.
No reason at all not to shield the AC-bearing leads as you suggest, and that's what some people do. The only snag is that it might not be very practical with short leads, such as the leads going from one heater to the next, but with long leads it's a good idea.
Hey guys.
Thanks for all the interest in that site. I'm psyched.
I'm currently in Seattle for a show in some friends' space. I am giving them this amp. So it is a cool coincidence.
http://designcommission.com/pedalreloaded/
Anyway, it has been a while since I built this thing, but I am totally happy to help. I'll sub to this thread to keep in touch.
My one piece of advice would be to use a beefier power transformer. The Hammond gets pretty warm.
jsn
Thanks for all the interest in that site. I'm psyched.
I'm currently in Seattle for a show in some friends' space. I am giving them this amp. So it is a cool coincidence.
http://designcommission.com/pedalreloaded/
Anyway, it has been a while since I built this thing, but I am totally happy to help. I'll sub to this thread to keep in touch.
My one piece of advice would be to use a beefier power transformer. The Hammond gets pretty warm.
jsn
yeah! - Boozhound Hotrod Thread
hey JSN - nice to meet Mr. Boozhound
I'm planning on using the iron from an old RCA 6v6 console, and since it's only running the amp, and not a whole tuner / preamp / amp setup, I *think* it'll sound decent with the first iteration. Later on, I'll swap in different transformers to mess with (fix) voltage, impedence, and FR if need be.
BUS-BAR - that's the ticket. I might even just cut it out and transplant right into "Franken-Booze" v1.0
Just waiting on the Hammond choke spec'ed in the recipe - BTW - could I use a different value choke (on-hand), and expect big variations in performance?
hey JSN - nice to meet Mr. Boozhound
I'm planning on using the iron from an old RCA 6v6 console, and since it's only running the amp, and not a whole tuner / preamp / amp setup, I *think* it'll sound decent with the first iteration. Later on, I'll swap in different transformers to mess with (fix) voltage, impedence, and FR if need be.
BUS-BAR - that's the ticket. I might even just cut it out and transplant right into "Franken-Booze" v1.0
Just waiting on the Hammond choke spec'ed in the recipe - BTW - could I use a different value choke (on-hand), and expect big variations in performance?
Power transformer and choke: I don't recall off hand what the B+ voltage was for that amp, but if you have a power transformer from a console using 6v6 tues, it should be close enough. There are a couple tricks you can use to get different voltages out of the same transformer. choke-input, cap input, and using a small first cap in the power supply. The choke can be pretty much anything, as long at it is rated for enough current. More henries means more filtering, and less resistance means less voltage drop, but it isn't critical.
Output transformers: You can use pretty much anything with a primary impedance of around 5k. If you are shopping, I would recommend the Magnequest Robin Hood series.
I'm travelling, but when I get home I will get familar with the schematic again, to be able to answer questions and talk in voltages and stuff rather than generalities.
jsn
Output transformers: You can use pretty much anything with a primary impedance of around 5k. If you are shopping, I would recommend the Magnequest Robin Hood series.
I'm travelling, but when I get home I will get familar with the schematic again, to be able to answer questions and talk in voltages and stuff rather than generalities.
jsn
My suggestion for grounding, noise, etc. is not to worry too much about shielding stuff. This is a low gain power amp, not a phono stage or something, so noise is not *that* much of an issue.
I have been building mic preamps using a bus bar and I really like it. Very clean, and easy to do. And of course sounds fine - very quiet. Have a look at the project for the aikido mic pre for photos.
jsn
I have been building mic preamps using a bus bar and I really like it. Very clean, and easy to do. And of course sounds fine - very quiet. Have a look at the project for the aikido mic pre for photos.
jsn
I'm going to trust you that the Magnequest RH OPT's will work with the 6V6's in your plan, or would a replacement with the 300B's (recommended on the site) yield better results, though at much higher cost? Or at the nominal ~15W power output, and all the characteristics of your planned amp, are the 6V6's just fine for a first timer?
Given the DIY nature of this hobby, it shouldn't be an issue to start with the 6V6 model (basically what you built) with either the Robin Hood OPT's or the cheaper Hammond P-t 1615 or P-T 1620 OPT's, and recycle parts for future project, right? Given that, perhaps the RH is a better investment? Do you think the RH series will provide a vastly cleaner sound from the 6V6 over the Hammond units? We're looking at about $200 vs. $80-$90 for the pairs.
I know, lot's of n00b questions...sorry about that.
Given the DIY nature of this hobby, it shouldn't be an issue to start with the 6V6 model (basically what you built) with either the Robin Hood OPT's or the cheaper Hammond P-t 1615 or P-T 1620 OPT's, and recycle parts for future project, right? Given that, perhaps the RH is a better investment? Do you think the RH series will provide a vastly cleaner sound from the 6V6 over the Hammond units? We're looking at about $200 vs. $80-$90 for the pairs.
I know, lot's of n00b questions...sorry about that.
Well the Hammonds are definitely more versatile, and darn good for what they cost. I just like the price of the RHs and the specs are right. The seem like the best bang for the buck - even if they cost more bucks. You want the 60mA version, btw.
But you will have fun and enjoy the results either way. Maybe using the Hammonds will give you an upgrade path for the future. Hey man, it's your amp, so you should use whatever parts you want!
jsn
But you will have fun and enjoy the results either way. Maybe using the Hammonds will give you an upgrade path for the future. Hey man, it's your amp, so you should use whatever parts you want!
jsn
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