Thanks! BTW, I found the best way to cut the large holes is with a bi-metal hole saw in a drill press, half of the way through from each side. After the five 1-1/8 holes the teeth still seemed to have some edge left. I also found 1/16" G-10 to be plenty stiff enough for the 4-1/2 x 12" board supported as shown by six stand-offs.Bruciep07 wrote:That's a great build Martin! Super clean layout, easy to work on, easy to trace leads, I really want to try something like this now! Huge fan of the tube cut outs by the way, great job!
Non-Traditional Express... another take (updated presence)
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- martin manning
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Re: Non-Traditional Express... another take (updated presence)
Re: Non-Traditional Express... another take (updated presence)
Martin, thanks. Do you "see" the LED flickering on the half cycle? Just curious about that.
- martin manning
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Re: Non-Traditional Express... another take (updated presence)
No, it looks steady.surfsup wrote:Do you "see" the LED flickering on the half cycle?
- martin manning
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Re: Non-Traditional Express... another take (updated presence)
Thanks, Dave. I went with the PI and slope resistor values you ended up with on your PCB Express and I'm really happy with them. I'll wait to see if there is any break-in shift, but I see (or hear) no reason to change anything at this point.Colossal wrote:That looks killer Martin. Beautiful layout. Extremely well thought out!
Re: Non-Traditional Express... another take (updated presence)
Nice Very creative layout.Love to see inovation.
- RJ Guitars
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Re: Non-Traditional Express... another take (updated presence)
Nicely done, you've taken things up a notch in innovation here. I agree that Ken Fischer would be pleased to see innovation coming form the circuits he inspired. In some way it's slightly reassuring that these amps remain on the edge of stability... must mean that the results are not that far from the original. If one doesn't slip over the edge now and then it might seem that we have gone too far in taming the beast.
Did you use two values for the brite caps? I am thinking that I might just go with a 100pF single value in the future. A few folks have mentioned that they use the 500pF setting but I just find that I only try it on that setting long enough to recognize that it's just too extreme for me.
Nice job, lots of great ideas. I will look forward to your "in House" player's reviews on it... I don't have have (like most folks) a real Express to compare my amps to but I was intrigued by his thoughts about it being a different animal.
rj
Did you use two values for the brite caps? I am thinking that I might just go with a 100pF single value in the future. A few folks have mentioned that they use the 500pF setting but I just find that I only try it on that setting long enough to recognize that it's just too extreme for me.
Nice job, lots of great ideas. I will look forward to your "in House" player's reviews on it... I don't have have (like most folks) a real Express to compare my amps to but I was intrigued by his thoughts about it being a different animal.
rj
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- martin manning
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Re: Non-Traditional Express... another take (updated presence)
Definitely standing on your shoulders, though! I think the stability issue is related to the presonance mod. I did put a 22k grid stopper on the input and an 820R on the second stage. Not sure why KF had none... I can't believe there is anything in those frequency ranges that is of any interest.rj wrote:Nicely done, you've taken things up a notch in innovation here. I agree that Ken Fischer would be pleased to see innovation coming form the circuits he inspired. In some way it's slightly reassuring that these amps remain on the edge of stability... must mean that the results are not that far from the original. If one doesn't slip over the edge now and then it might seem that we have gone too far in taming the beast.
I've got a 100pF and a 500pF. I like the dual bright cap feature, and the 500 could be changed to a 300, say, if it is indeed too much to be useful (and it's easy to get to- right on top of the switch!).rj wrote:Did you use two values for the brite caps? I am thinking that I might just go with a 100pF single value in the future. A few folks have mentioned that they use the 500pF setting but I just find that I only try it on that setting long enough to recognize that it's just too extreme for me.
Thanks, and thanks again for the fine chassis and transformers! My in-house player is my son, who can play rings around me any day. I can hear what is working and what isn't in any amp much better when someone who plays well is working it out. I've never heard a real 'wreck in person either. Familiar amps are my Dumble clone and Marshall, plus many Fenders and etc. that have come through. The Express just isn't like any of those. I'm planning on taking it up to the local shop this weekend to have a pro player (who owns an Allyn Meyer Liverpool) give it a whirl.rj wrote:Nice job, lots of great ideas. I will look forward to your "in House" player's reviews on it... I don't have have (like most folks) a real Express to compare my amps to but I was intrigued by his thoughts about it being a different animal.
Its a beauty
Martin, bravo, its a beauty. Bet it rips really well.
Cheers Ange
Cheers Ange
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Re: Non-Traditional Express... another take (updated presence)
Martin,
Beautiful job! So clean. I love the line indicator as well.
btw- my pcb Express is fine with no problems and the Presonance control is wonderful - thank you very much.
Tony
Beautiful job! So clean. I love the line indicator as well.
btw- my pcb Express is fine with no problems and the Presonance control is wonderful - thank you very much.
Tony
"Education is what you're left with after you have forgotten what you have learned" - Enzo
- martin manning
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Re: Non-Traditional Express... another take (updated presence)
Thanks, Ange!
Tony, thanks and you're welcome. It's interesting that you are not having any stability issues, and that's three (yours, Dave's, and Mark's) that have worked fine with the presonance control.
I did some testing, changing the 10k resistor in the presonance circuit to 15k and then to 4k7, putting the bottom cover on each time just to be sure that some stray emf wasn't a factor. With the cover off, there is a marked increase in the level of 60Hz hum. Changing the resistor didn't seem to make much difference to the oscillation- I could still get a squeal by diming all the controls and then turning the presonance to the left, so I went back to the original 10k.
I noticed at one point that putting my finger near the volume pot wiper when the cover was off could start some oscillation. I thought about a larger grid stopper on V1B, and then decided to try a few different tubes first. Strangely enough a quiet tube improved things. I'm not sure I understand why fiddling with the global feedback in the power amp would start an oscillation in the preamp... the whole thing is just right on the edge, I guess. At this point it's sounding great and is stable at any reasonable setting of the knobs, so I guess it's going to stay the way it is for now.
Tony, thanks and you're welcome. It's interesting that you are not having any stability issues, and that's three (yours, Dave's, and Mark's) that have worked fine with the presonance control.
I did some testing, changing the 10k resistor in the presonance circuit to 15k and then to 4k7, putting the bottom cover on each time just to be sure that some stray emf wasn't a factor. With the cover off, there is a marked increase in the level of 60Hz hum. Changing the resistor didn't seem to make much difference to the oscillation- I could still get a squeal by diming all the controls and then turning the presonance to the left, so I went back to the original 10k.
I noticed at one point that putting my finger near the volume pot wiper when the cover was off could start some oscillation. I thought about a larger grid stopper on V1B, and then decided to try a few different tubes first. Strangely enough a quiet tube improved things. I'm not sure I understand why fiddling with the global feedback in the power amp would start an oscillation in the preamp... the whole thing is just right on the edge, I guess. At this point it's sounding great and is stable at any reasonable setting of the knobs, so I guess it's going to stay the way it is for now.
Re: Non-Traditional Express... another take (updated presence)
Hey Martin,martin manning wrote:Thanks, Dave. I went with the PI and slope resistor values you ended up with on your PCB Express and I'm really happy with them. I'll wait to see if there is any break-in shift, but I see (or hear) no reason to change anything at this point.Colossal wrote:That looks killer Martin. Beautiful layout. Extremely well thought out!
Very cool about the modified PI values and slope! I'll be interested to hear what your resident musician thinks about the amp. I was experimenting to get a little more crunch/grind working at lower volumes (sans fizz). I find with most non-master tube amps that aside from the extreme volume when the amp is opened up (in order to get to the gain levels needed to excite the amp properly), you really hear the feedback kicking in and it emphasizes a midrange frequency that is a bit much for me. Plus the extreme volume is just not practical. I do like mids (a lot!) but just not quite at the frequencies when the amp is wide open. I have been avoiding attenuation as much as possible but for home use of course, something's got to give.
Re: Non-Traditional Express... another take (updated presence)
Hey, that's not a pcb !!
At first I thought swiss cheese ?
But it didn't take long looking at it for that layout to grow on me.
I'm still studying the TW designs before I start something myself, but you are drawing me toward the less traditional layout.
Kudos
rd
At first I thought swiss cheese ?
But it didn't take long looking at it for that layout to grow on me.
I'm still studying the TW designs before I start something myself, but you are drawing me toward the less traditional layout.
Kudos
rd
- martin manning
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Re: Non-Traditional Express... another take (updated presence)
rd- Flea clips and perf-board? Caps glued together like cordwood? Flimsy chassis? With all due respect, that's not my cup of tea. It was really quick work to fab the single eyelet board and get on with it. I'll add an under board view to the first post so you can see what that looks like without having to squint through the rest of the layout.
- martin manning
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Re: Non-Traditional Express... another take (updated presence)
I put a couple of new pics in the opening post of this thread to show off some beautiful faceplates from BNP Lasers. The artwork was done in PowerPoint and saved to a .pdf format, which BNP then imported into their standard package (CorelDraw). This worked easily, but sometimes it doesn't depending upon the MS Office SW version, I'm told. Definitly worth a shot if you are interested in some high quality faceplates. The ones shown are in matte black/gray. Super service too!
On the operational side, I've been running the stage three input attenuator at -3dB, and it seems to give a little more control of the distortion and volume relationship, so I think that is a useful mod. The 500pF bright cap is a bit much, so that probably will go down to 300pF. I also tried 6L6 and 6V6 power tubes, and had no trouble biasing them as required. EL34's sound best in this thing, IMO.
On the operational side, I've been running the stage three input attenuator at -3dB, and it seems to give a little more control of the distortion and volume relationship, so I think that is a useful mod. The 500pF bright cap is a bit much, so that probably will go down to 300pF. I also tried 6L6 and 6V6 power tubes, and had no trouble biasing them as required. EL34's sound best in this thing, IMO.
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Re: Non-Traditional Express... another take (updated presence)
Wow - that is totally excellent! Well thought out and nicely executed... nice final look as well. I love it that these amps keep that exterior Trainwreck look and hopefully sound like a Wreck, but have moved the innovation level along. I think Ken would have enjoyed this effort... rj
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