Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bnwitt on September 07, 2017, 07:42:08 am
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I have begun the Sluckey Vox AC15 amp build layout drawing and I have a couple of questions for those who have built the amp.
1. Do the Top Cut and brilliance control supply enough tone control for the amp?
2. Did you install the SPST brilliance switch or the rotary multi switch brilliance?
3. Did you install the SPDT standby switch with the 250Ω 10 watt resistor? Benefit?
4. Did you install the Tremolo cap change switch? Useful?
I am very interested in making the most versatile version of this amplifier possible as I will be building more than one of them. One for me and others for local players. Any feedback is appreciated.
thank you in advance,
Barry
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I did find this YouTube video of the AC15's tone. I don't know which year this one is though.
https://www.youtube.com/watch?v=CpbRmCZ9e0c (https://www.youtube.com/watch?v=CpbRmCZ9e0c)
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1. Do the Top Cut and brilliance control supply enough tone control for the amp?
2. Did you install the SPST brilliance switch or the rotary multi switch brilliance?
I'll combine these two items because they are so closely related. The Top Cut pot and 6 position Brilliance switch give plenty of tone control. I highly recommend this mod. I felt the original on/off Brilliance switch was useless. I think Ed Chambley even uses a 12 position switch for even more tone control. BTW, Ed has built several of these for pickers. He can probably provide a lot of valuable user feedback about this amp.
3. Did you install the SPDT standby switch with the 250Ω 10 watt resistor? Benefit?
I installed it and then replaced with a standard standby switch. This was a "golly gee" idea for another use for the progressive on/standby/play switch that Doug sells. No real world benefits. In fact any kind of standby switch on a 15 watt amp seems ridiculous to me. I suppose it could be useful in a studio.
4. Did you install the Tremolo cap change switch? Useful?
I did. My fast/slow switch increases the speed range of the tremolo. Mainly provides a slower speed range. I find that useful. My push/pull speed switch is actually on the back of the Depth pot (just like the bright switch on the volume pot on your AB763).
Actually, I consider all the Trem mods (except the LED) to be necessities. The original circuit provided a 3 position speed switch on the front panel. That's it! And there is no intensity control! That's just lazy and cheap in my opinion. Any quality amp with tremolo must have a speed and intensity control.
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... any kind of standby switch on a 15 watt amp seems ridiculous to me. I suppose it could be useful in a studio.
I completely agree. I might use that control panel space for something else. Steve, I know you put a lot of work into this design and have had some time to experiment with the amp so I value your insight on making this a great tone machine. Ed, If you would give me some feedback on your experiences on Steve's amp and your implementation I would appreciate it too. I hope to get these amps onto some recordings in the San Diego area.
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I leave the cap off the board and use a rotary switch. This gives me 12 cap values and the ability to allow the passing lower frequencies. For me, I configured a head with a single 12 celestion blue and a cab that has removable portions, 3. When closed back it has a 3 inch port. Bass is solid.
I simply built and kept the plate voltage right on 300. No switching. I install an additional pot on the tremolo instead of the resistor. Reason is I have a lot of good strong tubes, but one I built would not get a good swampy tremolo. This is on back and can be adjusted to user taste, but also allow to swing from a weaker tube. When I do this I use a locking pot with a screwdriver slot. A lot of guys door not care for tremolo until you show them how to get it slow and light for texture.
Initially I was hitting 350 plate, but the amp did not break up the way I remembered. When I was much younger I had an original 63 and remembered I could get nice overdrive tone without being loud, even with the 100 spl blue.
I am not knocking classictone, but their ot for this amp is 6k and dulls the tone compared to 7.6 to 8. I have a Mercury on mine, but I used 3 ot,s tweed deluxe new sensor Doug was blowing out some with some dings and bends. I simply straightened them. They sound great. I used a 8k from a Baldwin and while I really liked the low end, it was too clean.
I use 2 inputs with a switch on builds, on mine I finally wired the channels together as I always play it this way. Adds loads of versatility and puts the trem vibrato on the normal ef86 channel.
The ef86 nos Tesla drives better than a screen Mullard with the screen. It is fine too. If you have the cash to get some amperex el84 I highly recommend. The RCA pan getters are the best bang for the buck IMO. Wire the tremolo to run as the delay is irritating.
I added reverb to 2. Waste of time to me. It just doesn't sound right to my ears. Overdriven reverb not my thing.
That is it for now, if I think of something else I will chime in. I will say this, I have a friend that owns nice music store and took one to him. He wants 4 more and I have built him 3. Each one sold in less than a week. Expect the vibrato to be weaker than the tremolo.
Please ignore typos, I am typing on a screen and spell correction will change mullard to Millard.
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Mine was an AC30/4 but basically the same amp plus two tubes and a different set of transformers. I used the switchable tremolo cap option, and also the potentiometer for the speed instead of fixed 3 speeds or whatever it was. Otherwise it's pretty much stock. I may do some of those mods at some point though, we'll see :)
~Phil
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Thanks for the information fellows.