yep - damn cool
Yeah - my nephew is heavy into guitar playing, so the next project for the summer will be a guitar head with at least a tone control. Maybe push-pull 6bq5 or something . . . I have some old Stromberg Carlson PA amps just waiting for a noble use.
Here's the gallery again:
I mistakenly posted my edit / upload web address (DOH!)
Tonight we'll be wiring up the heaters and the rest of the power supply. Because everything is a little tight, we may use some copper shielding inside to help in noise reduction.
I'll post more progress soon !
Yeah - my nephew is heavy into guitar playing, so the next project for the summer will be a guitar head with at least a tone control. Maybe push-pull 6bq5 or something . . . I have some old Stromberg Carlson PA amps just waiting for a noble use.
Here's the gallery again:
I mistakenly posted my edit / upload web address (DOH!)
Tonight we'll be wiring up the heaters and the rest of the power supply. Because everything is a little tight, we may use some copper shielding inside to help in noise reduction.
I'll post more progress soon !
I would suggest omiting the copper shielding. It likely won't help much. To shield magnetic fields you need iron or mumetal or something.
Just twist the heater wiring, and try to run the low level signal wiring away from everything else - or at least not parallel with the heater or B+ wiring.
Your photo of the unmodified console amp shows just how much of a rat's nest you can get away with. And that is actually better in many ways than the military style bundled and tied wiring you see in some test equipment and stuff. That is a neat assembly method - they would lay the wiring harness out on a jig, tie it together, then drop it into a chassis and solder it up.
jsn
Just twist the heater wiring, and try to run the low level signal wiring away from everything else - or at least not parallel with the heater or B+ wiring.
Your photo of the unmodified console amp shows just how much of a rat's nest you can get away with. And that is actually better in many ways than the military style bundled and tied wiring you see in some test equipment and stuff. That is a neat assembly method - they would lay the wiring harness out on a jig, tie it together, then drop it into a chassis and solder it up.
jsn
thanks fro the tips
that will make things easier
another interesting thing about the console wiring, is that they appear to use rca-like wiring for signal leads: signal wire core, surrounded by the ground wire, wrapped in a black outer coating . . might try to re-use them in the *Franken-Booze*.
that will make things easier
another interesting thing about the console wiring, is that they appear to use rca-like wiring for signal leads: signal wire core, surrounded by the ground wire, wrapped in a black outer coating . . might try to re-use them in the *Franken-Booze*.
finished the heater wiring tonight . .
took ray moth's advice and twisted the + and - all the way to the PT. My nephew soldered the *pi* filter this morning - everything is going slow and steady. We're going to work a bus bar into the grounding scheme, which will make things cleaner under the hood.
I should be able to post a picture or two tomorrow (*might* need help with the OPT wiring - I think I have it down though)
thanks for all the help so far guys
took ray moth's advice and twisted the + and - all the way to the PT. My nephew soldered the *pi* filter this morning - everything is going slow and steady. We're going to work a bus bar into the grounding scheme, which will make things cleaner under the hood.
I should be able to post a picture or two tomorrow (*might* need help with the OPT wiring - I think I have it down though)
thanks for all the help so far guys
a couple wiring questions . . .
So, my nephew and I are about 80 % done with the wiring - heater wires first, then power supply, B+, OPT, etc . . .
Made a few silly mistakes, like while wiring up the 6SN7 (mixed up the plate s and cathodes, and didn't notice till *after* the solder was cooled (DOH!)) That's why I ALWAYS double check my work! ! Easy fix
Now for the questions:
1) The OPT's have the standard color coding, but I have a yellow wire coming off that doesn't have a home. Would this be a screen tap or something from the factory 6V6 wiring? Since I'm going triode, do I just leave this disconnected ?
2) Volume Pot: (Granted, I wrapped up last night's wiring around 1:00 AM so this could be a no branier . . . ) How to figure out what connects where? I have three connections on (each side of) the pot: one for ground, one for the incoming signal, and one for the connection to 6SN7 grid . . . no labels
thanks for any help !
So, my nephew and I are about 80 % done with the wiring - heater wires first, then power supply, B+, OPT, etc . . .
Made a few silly mistakes, like while wiring up the 6SN7 (mixed up the plate s and cathodes, and didn't notice till *after* the solder was cooled (DOH!)) That's why I ALWAYS double check my work! ! Easy fix
Now for the questions:
1) The OPT's have the standard color coding, but I have a yellow wire coming off that doesn't have a home. Would this be a screen tap or something from the factory 6V6 wiring? Since I'm going triode, do I just leave this disconnected ?
2) Volume Pot: (Granted, I wrapped up last night's wiring around 1:00 AM so this could be a no branier . . . ) How to figure out what connects where? I have three connections on (each side of) the pot: one for ground, one for the incoming signal, and one for the connection to 6SN7 grid . . . no labels
thanks for any help !
Some weeks ago I rebuilt my 6v6 pentode into a 6v6set based on the Boozhound site and this thread. I am very pleased with the change in sound. The driver is now an ecc83 but have two e80cc (one reserve) on the shelve as replacement. Attached is the setup I will try. Photo's will follow later.
Are there any more experiences? Perhaps a different bias or cathode with/without cap... etc
Jeroen
Are there any more experiences? Perhaps a different bias or cathode with/without cap... etc
Jeroen
Attachments
I'm a big slacker : (
well, my nephew left in late August, and all my amp does successfully is blow fuses (DOH!) . . . the GOOD news is one of the diyaudio faithfuls who's in my general area will be helping sort out the circuit.
I've been distracted by the usual things: family, work, and LIFE
I figure by the new year, this baby will be making music
As for my tube choices, I stumbled across a coule NIB/NOS Sylvania 6SN7GT's which I'm using for the driver . . .
Glad your project is going smooth Jeroen !
well, my nephew left in late August, and all my amp does successfully is blow fuses (DOH!) . . . the GOOD news is one of the diyaudio faithfuls who's in my general area will be helping sort out the circuit.
I've been distracted by the usual things: family, work, and LIFE
I figure by the new year, this baby will be making music
As for my tube choices, I stumbled across a coule NIB/NOS Sylvania 6SN7GT's which I'm using for the driver . . .
Glad your project is going smooth Jeroen !
I have a quick question about this amp. I'm not too familiar with audio amplifiers, though I have built my fair share of voltage followers, buffers and solid state amplifiers (when I did my Physics MSc.). I skimmed the boozhound article fairly well, but I'm missing how he jumps from the 2 stage amplifier he describes at first to the amplifier with two outputs. Basically, I'm missing why there is no second 6SN7 stage for the seemingly stereo amplifier he builds. I see he uses a stereo potentiometer as well, so I'm a little lost on this point. I suppose it is possible that I've missed something.
Thanks.
Thanks.
hey geoff,
the ^sn7 is a dual triode, so one half for "L" one half for "R" . . .
I wish I could say I've done more on this little guy, but have been distracted by a little SE EL84 Sylvania console amp, and magnavox PP EL84 console amp . . .
Also, I believe my powertransformer (and possiblely OPT's) which I pulled from a RCA console were of questionable releability . . . soooooo . . . I removed the PT, and have a few others I plan on using. This is until I can actually afford the Hammond units, as thats what Mr. Boozehound spec'ed
the ^sn7 is a dual triode, so one half for "L" one half for "R" . . .
I wish I could say I've done more on this little guy, but have been distracted by a little SE EL84 Sylvania console amp, and magnavox PP EL84 console amp . . .
Also, I believe my powertransformer (and possiblely OPT's) which I pulled from a RCA console were of questionable releability . . . soooooo . . . I removed the PT, and have a few others I plan on using. This is until I can actually afford the Hammond units, as thats what Mr. Boozehound spec'ed
I would hold off on the Hammond OP. Many of the tranny’s from consoles sound very good, quit likely better then the 125. Use what you have and if the amp is a keeper, move up to the MQ Robin Hoods. This would be a big step up in performance.
As to blowing fuses. Test the power transformer. If you are using a tube rectifier, remove it, remove all the tubs while we are at it and see if you can power up. If so check for a large AC voltage, across pins 4 and 6.(this is for many common rectifiers I forget what you are using) Be careful, this could be as much as 800 volts or so, AC. Best to plug the Leeds into the tube socket with the power off. Next check for 5 or 6 VAC from pin 2 to 8
If your OK so far Power off and connect your black meter lead to the power supply ground. Probably the Neg- terminal of the first power supply cap. Power up and go back to pin 4 with the red lead. You should see about ½ the high voltage, the same at pin 6
Post back and we’ll take it from there…John
As to blowing fuses. Test the power transformer. If you are using a tube rectifier, remove it, remove all the tubs while we are at it and see if you can power up. If so check for a large AC voltage, across pins 4 and 6.(this is for many common rectifiers I forget what you are using) Be careful, this could be as much as 800 volts or so, AC. Best to plug the Leeds into the tube socket with the power off. Next check for 5 or 6 VAC from pin 2 to 8
If your OK so far Power off and connect your black meter lead to the power supply ground. Probably the Neg- terminal of the first power supply cap. Power up and go back to pin 4 with the red lead. You should see about ½ the high voltage, the same at pin 6
Post back and we’ll take it from there…John
I'm building the same amp. Looks very simple and fun, just what I need for a first time tube attempt. I winged it a bit with some of the parts just to be a real cheapskate and bought a hammont P-T31 OPT from Antique electronic supply. It's specs are:
TRANSFORMER, OUTPUT, 8 WATT, SINGLE ENDED
Specifications
Power: 8 watts
Primary: 5K ohm single-ended
Secondary: 8 ohm
Mounting centers: 2.375", U-bracket
Weight: 0.7 lbs.
I put a meter on the leads yesterday and read 230R and a fraction of an ohm on the other end. Can this be right?
TRANSFORMER, OUTPUT, 8 WATT, SINGLE ENDED
Specifications
Power: 8 watts
Primary: 5K ohm single-ended
Secondary: 8 ohm
Mounting centers: 2.375", U-bracket
Weight: 0.7 lbs.
I put a meter on the leads yesterday and read 230R and a fraction of an ohm on the other end. Can this be right?
serse said:
No, not hazardous but could be and often is, noisy.
Every conductor has resistance and the ground line is a "signal path". If there is a resistance, then a noise voltage can be developed across it, which is why we ground at the input socket. Another issue is that multiple grounding creates an earth loop, this is asking for trouble (usually hum + noise, rather than "noise" per se).
7N7
I've seen and used grounding schemes that parallel 2 large rectifier diodes with a higher power 5R or so resistor. The diodes are in opposing polarity. This setup goes between signal/power ground and earth. The idea is that it isolates the earth from ground via the resistor unless potential between the two is greater than breakover for the diodes (.7v or so). At that point they conduct, bypassing the resistor and, usually, blowing the fuse. It works well.
Ah, Found the answer.
http://www.radioremembered.org/outimp.htm
I guess the impedence is NOT the dc impedence of the coil but the reflected AC impedence of the secondary as seen by the primary.
I thought I'd have to order other OPT's. Well, as soon as I can sit down at this thing for an hour or so, I'll have a working amp.
Next question is, what small bookshelf speakers are a good "plug and play" match for this amp.
http://www.radioremembered.org/outimp.htm
I guess the impedence is NOT the dc impedence of the coil but the reflected AC impedence of the secondary as seen by the primary.
I thought I'd have to order other OPT's. Well, as soon as I can sit down at this thing for an hour or so, I'll have a working amp.Next question is, what small bookshelf speakers are a good "plug and play" match for this amp.
Proud to display my work.
The chassis is a cigar box tarted up a bit with a couple coats of varnish. I went really cheapo on this project so the power transformer is a 270EX. I guess I should have known it's a bit underpowered.
Trying to drive my Joseph audio RM25si speakers is almost futile. they have an 88dB sensitivity and I suspect that may be overstated.
A link for the curious:
http://www.josephaudio.com/specs.rm25simk2.html
I'm buiding a pair of Buschhorns this weekend with a nice little 4.5" driver from MTM. They should sound alot better. I tried listening to the amp on my headphones and, if I could get that sound out of a pair of speakers, I would be very happy.
Finally and certainly not least, a heartfelt thank you to JSN. Yours was the most informative, newbie friendly, and encouraging article I have found on the topic. Being a big fan of Nelson Pass, I would suggest that your article is the vacuum tube equivalent of Nelson's Zen article.
http://i125.photobucket.com/albums/p70/dinui/IMG_2352.jpg
http://i125.photobucket.com/albums/p70/dinui/IMG_2339.jpg
The chassis is a cigar box tarted up a bit with a couple coats of varnish. I went really cheapo on this project so the power transformer is a 270EX. I guess I should have known it's a bit underpowered.
Trying to drive my Joseph audio RM25si speakers is almost futile. they have an 88dB sensitivity and I suspect that may be overstated.
A link for the curious:
http://www.josephaudio.com/specs.rm25simk2.html
I'm buiding a pair of Buschhorns this weekend with a nice little 4.5" driver from MTM. They should sound alot better. I tried listening to the amp on my headphones and, if I could get that sound out of a pair of speakers, I would be very happy.
Finally and certainly not least, a heartfelt thank you to JSN. Yours was the most informative, newbie friendly, and encouraging article I have found on the topic. Being a big fan of Nelson Pass, I would suggest that your article is the vacuum tube equivalent of Nelson's Zen article.
http://i125.photobucket.com/albums/p70/dinui/IMG_2352.jpg
http://i125.photobucket.com/albums/p70/dinui/IMG_2339.jpg
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