Re - Small Special Build
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Re - Small Special Build
Has anyone built this version of the Small Special? I was going to build a scaled back version, 6aq5 or el84 , but I have Iron on hand for the 6L6 so Im going to build it as shown here. I see some difference in the schematic vs the layout so I guess im looking for some direction, suggestions and or experience with this one. . Joe
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Re: Re - Small Special Build
Just from a cursory glance, I'd build the more robust filter section from the schematic rather than the one on the layout. I suspect the layout version might be a little light for 50 watts.
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Stevem
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Re: Re - Small Special Build
The red yellow from the PT needs to go right to the negative of the first filter and then to the chassis .
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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dorrisant
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Re: Re - Small Special Build
Great circuit...
Look here: https://ampgarage.com/forum/viewtopic.p ... 755824a97f
Also, look for posts from Smokebreak and Synchu... I was using his layout.
Look here: https://ampgarage.com/forum/viewtopic.p ... 755824a97f
Also, look for posts from Smokebreak and Synchu... I was using his layout.
"Education is what you're left with after you have forgotten what you have learned" - Enzo
Re: Re - Small Special Build
I have a question that im sure someone can help me to understand. On the layout above what is happening with the negative feedback? It is different than the schematic, there are many differences, but why is a 5 watt resistor required there? I dont recall ever seeing such a value in a negative feedback. 100r seems very low and 5watts seems very high?
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Re: Re - Small Special Build
Seems like a typo. Should be 3.3K to match the schematic. 5w is not necessary there. 1 or 2 watts will be fine.joe6v6 wrote: ↑Wed Aug 20, 2025 1:40 am I have a question that im sure someone can help me to understand. On the layout above what is happening with the negative feedback? It is different than the schematic, there are many differences, but why is a 5 watt resistor required there? I dont recall ever seeing such a value in a negative feedback. 100r seems very low and 5watts seems very high?
-Dan
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Stevem
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Re: Re - Small Special Build
I agree with reply #1 and would like to add these notes.
6L6 tubes do not have a pin one so there’s no need to wire the tube socket up as such unless you plan to pop EL34s in there in which case the 470 ohm screen resistors should be changed out for 1k resistors.
In the schematic the feed back is being drawn off of all the 3 taps on the OT, which to me is darn wrong!
I would take the feed off of only the 8 ohm tap into a 15k resistor for starters and see how you like it.
No need these days to use 3 diodes on each leg of the V+ .
Go with 2 UF4008 on each leg which will be plenty of reverse voltage handling and sound better also.
Since your building from scratch you want to put the coupling caps that feed the next down stream gain stage right on that tube socket .
This is very important to do in particular with the PI caps that feed pin 5 of each 6l6.
Long grid wires are an invite to oscillating that you might not even know is taking place without a scope, and even without that problem it leads to poor tone.
Also in terms of the PI coupling caps I would start off with .022uf caps and see if that provides enough low end for you at low volumes of less then 4.
Any amp will sound it’s best when the tone control pots are wide open and this helps in this regard.
With these Fender type tone circuits and the .1uf coupling caps in the PI section as you play the amp with the volume above 5 you will find that on your neck pickup or even you solo pickup that you have to back the Bass control way down so as to not have loss of definition in single notes being played, no less chords .
6L6 tubes do not have a pin one so there’s no need to wire the tube socket up as such unless you plan to pop EL34s in there in which case the 470 ohm screen resistors should be changed out for 1k resistors.
In the schematic the feed back is being drawn off of all the 3 taps on the OT, which to me is darn wrong!
I would take the feed off of only the 8 ohm tap into a 15k resistor for starters and see how you like it.
No need these days to use 3 diodes on each leg of the V+ .
Go with 2 UF4008 on each leg which will be plenty of reverse voltage handling and sound better also.
Since your building from scratch you want to put the coupling caps that feed the next down stream gain stage right on that tube socket .
This is very important to do in particular with the PI caps that feed pin 5 of each 6l6.
Long grid wires are an invite to oscillating that you might not even know is taking place without a scope, and even without that problem it leads to poor tone.
Also in terms of the PI coupling caps I would start off with .022uf caps and see if that provides enough low end for you at low volumes of less then 4.
Any amp will sound it’s best when the tone control pots are wide open and this helps in this regard.
With these Fender type tone circuits and the .1uf coupling caps in the PI section as you play the amp with the volume above 5 you will find that on your neck pickup or even you solo pickup that you have to back the Bass control way down so as to not have loss of definition in single notes being played, no less chords .
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Re - Small Special Build
are the 47k/51k plate resistors intended for 12at7 or 12ax7 in the phase inverter?
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Re: Re - Small Special Build
This is what I was thinking but I saw the post above by Dorrisant and in his pictures you can see his was built just like the layout, which, I think, would add a ton of negative feedback. , But his amp sounds nice- theres a clip of it in there somewhere. I am going to use the value on the schematic and maybe add that accent switch. thanks ; JoeSeems like a typo. Should be 3.3K to match the schematic. 5w is not necessary there. 1 or 2 watts will be fine.
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dorrisant
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Re: Re - Small Special Build
I changed my NFB resistor from metal oxide to carbon comp... Kept the value at 100R. It sounded better, smoother, but was still very rowdy. I was surprised at the ease of breakup with this amount of NFB, but it is what it is.
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joe6v6
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Re: Re - Small Special Build
I got the Small Special in operation today. Fired right up with no issues. I havent plugged it into a proper speaker cabinet yet, just a 12" speaker that hangs on the wall in my shop. but it sounded real nice even thru that. I wound up using a 1k5 nfb resistor with a 50k pot so it is variable & I also put a switch to turn the nfb off. I wont really be able to feel it out until its in is cabinet. I have an empty combo cab that I built the chassis to fit into. I have to get a speaker for it. I also added a tone stack lift that works nice and lets it break up real good even at low volume. A few pictures & I will report back after I put it into service. . Joe
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