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Yet Another SSE Build Thread

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Thanks minerwelder! I had some serious rough spots when I almost threw in the towel. Walking away from it several times really helped me regain the will to persevere.

I am confident at this point that it will stand the test of time - it has a lot of hours on it already - as long as I don't mess with it too much. I am actually hesitant to try ultralinear mode and/or negative feedback, but I really would like to add those as switchable options.
 
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I made some more progress on my amp today.

1) Disassembled everything down to the bare chassis with transformers installed.

2) Drilled and de-burred all the holes for the bolts/nuts/screws that hold my ammeters, voltmeter and VU meters in place - and the holes for my triode/UL switch & CFB switch.

3) Stained the wood.

4) Installed the triode/UL & CFB switches, and all meters properly in the chassis.

5) Re-assembled the amp.

6) Wired up the triode/UL switch.

7) Finally remember to ground my choke housing to the top plate.

It looks much better and has been playing for a couple of hours. The triode/UL switch works. No disasters!

So all that is left is to wire up the CFB switch and install/wire/configure the VU meter controller.
 
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All my listening (since getting the amp up and running again) has been in triode mode up until today. So I am very familiar with how the amp sounds in triode mode.

Switching to UL for the past couple of hours has been a bit of a revelation - but it's not really about the extra power. There's a "crisp" feeling to it. This is actually quite welcome in my system because my speaker drivers are rolled off on the top end. It's going to be really nice to have both options (triode and UL). Very interested to get some CFB going as well, but I think I want to get really used to both modes without CFB so I have a better chance of hearing the difference with CFB enabled.
 
I will be interested in hearing your impressions of how the sound differs in each mode. I have been listening in triode mode since I finished the amp although when testing I did try out UL with CFB for one listening session. I preferred triode without CFB so did not install the switches but keep wondering if I should.


BTW glad to hear you got your SSE up and running again. I was rooting for you reading through your journey from smoke to working amp.
 
Switching to UL for the past couple of hours has been a bit of a revelation - but it's not really about the extra power. There's a "crisp" feeling to it. This is actually quite welcome in my system because my speaker drivers are rolled off on the top end. It's going to be really nice to have both options (triode and UL). Very interested to get some CFB going as well, but I think I want to get really used to both modes without CFB so I have a better chance of hearing the difference with CFB enabled.


Hey glad you're able to listen to your amp again! The whole time I've had my SSE, I've never moved beyond the default triode mode. Have the switches for UL and CFB in the chassis, but not connected. I should do that, now that I have a better listening room and speakers, and should be able to hear the differences.
Enjoy the music!
 
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I will be interested in hearing your impressions of how the sound differs in each mode. I have been listening in triode mode since I finished the amp although when testing I did try out UL with CFB for one listening session. I preferred triode without CFB so did not install the switches but keep wondering if I should.


BTW glad to hear you got your SSE up and running again. I was rooting for you reading through your journey from smoke to working amp.

Thanks spiggs! It seems like the majority of people end up choosing triode mode without CFB. This is just something I've taken mental note of through reading various threads here. I can't say that I have a preference yet. Triode and UL (both without CFB) sound different to me, but I can't say one is better than the other.

Hey glad you're able to listen to your amp again! The whole time I've had my SSE, I've never moved beyond the default triode mode. Have the switches for UL and CFB in the chassis, but not connected. I should do that, now that I have a better listening room and speakers, and should be able to hear the differences.
Enjoy the music!

Thank you, stereo71! I considered manually wiring up the different modes and listening to them to see which I liked and then choosing one mode and wiring it that way. Then I decided I didn't want to be re-wiring things that many times - better to do a more complicated wiring job once and then have all options available permanently. Turns out that wiring up the triode/UL switch was much simpler than I first thought. The CFB switch is more of a challenge to me (personally) because even without the switch, CFB wiring makes my brain go "huh?" It really doesn't help that there is a 50/50 chance of getting it wrong and no easy way to know for sure (from what I gather).

Excellent! You are back up and running with music, no smoke and no smell. Seems that the tranny was the issue, and now you have two. I supposed you could sell one or just build another amp after this one. Enjoy!

Thanks dtaylo3! I actually have 3 transformers if you include the one that fried. As George said, I can use it for something that doesn't require the 5V winding (tube rectifier heater). So I could build another SSE with it and use solid state rectification, for example. I have considered selling the brand new Hammond, but having a fully functioning spare around might be good for peace of mind. Selling stuff is often more hassle than it is worth...
 
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Forgot to mention that I did end up settling on 620ohm bias resistors. With 5AR4 rectifier, the amp settles into a nice groove at ~435V B+ and 59.5mA, so about 22.5W dissipation.

Popping a 5U4-GB in there drops the B+ down to just a bit over 400V with ~56mA current, for ~20W dissipation.
 
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I wired up CFB today. Not switchable yet - I just wanted to get the wiring right to begin with, which I think I did but I am not sure. I went with the reverse polarity wiring. The amp doesn't seem any louder or quieter than it did before, so I have no idea. I also don't know how I would ever be able to tell which wiring makes it louder since it would take at least 10 minutes to disconnect the amp, switch the wiring and then get it connected and running again. The volume level would need to be really different for me to notice which was quieter.

George, I am using Transcendar OPTs. Do you know which way the wiring should go for CFB on them?

One thing I noticed (because I have the B+ voltmeter and current ammeters) is that with CFB enabled there is basically no power supply "sag" at high volume. Without CFB, in either triode or UL mode, both the B+ voltage and the current to the OPTs sag considerably on kick drum, low bass notes, etc. when the volume gets high enough. With CFB, the meters hold steady. I have no idea if this is expected behaviour, but I observed it so I am reporting it.

The sound? Meh. I dunno. I wouldn't say "bland" but maybe "unremarkable" and perhaps a bit "thin" overall, except that bass certainly seems more controlled. This seems to make sense based on my notes above about power sag. With UL + CFB it definitely plays considerably louder before sounding "off". The times I need/want that much SPL are few and far between, but I guess it'll be nice to be able to flip a couple of switches and voila.

I wish I had the equipment and smarts to measure the output, distortion, etc. and provide graphs like George does on his site.
 
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Thanks minerwelder!

Not quite time to kick back and relax yet. I have committed myself to getting this amp 100% done (not 99%) before I can relax. In the past I have slacked off once I got good sound from something and then the project(s) never got finished.

After work today I'll probably finish wiring up the CFB switch, but I am thinking about wiring CFB up to the 4ohm or 16ohm taps to see if I like those any better. CFB is confusing to me, especially the wiring.

The final thing after that is to figure out where and how I will install the 12V transformer for my VU meter control board and then get that all wired up and calibrated.
 
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