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I really wanted this to work for me, but I tried this tube in a spud amp and found it harsh sounding. I used grid stoppers and decoupled heater winding to gnd - usual precautions to have no oscillations. I didn't see any r.f. hash on the CRO either. If I did something wrong then I don't know what it was ?
http://www.diyaudio.com/forums/tubes-valves/280167-yukon-gold-spud-amp.html
it's easy to make a Spud amp but to make it better than a conventional two stage amp is not the same story . but it"s possible
these are my finding:
first thing due to the gain of the tube the power supply must be very silent same as you would build for a Line stage . PIO or oil motor cap will help in for the last cap of your filter.
2: elevating AC heater or DC heater will help smoothing things too.
3: use the better output transformer you can get
as you will do for a 2A3 or 300B .
4: prefer a grid choke than a grid resistor ( the low dcr of the choke will help to keep the bias stable when you will push the tube)
5: don't push the tube to it"s max you will have more power but harsh sounding.
6: prefer battery grid bias or schootky bias to resistor cathode bias.
if it does"t work for you than build a 2A3 amp more difficult too make a bad one
these are my finding:
first thing due to the gain of the tube the power supply must be very silent same as you would build for a Line stage . PIO or oil motor cap will help in for the last cap of your filter.
2: elevating AC heater or DC heater will help smoothing things too.
3: use the better output transformer you can get
as you will do for a 2A3 or 300B .
4: prefer a grid choke than a grid resistor ( the low dcr of the choke will help to keep the bias stable when you will push the tube)
5: don't push the tube to it"s max you will have more power but harsh sounding.
6: prefer battery grid bias or schootky bias to resistor cathode bias.
if it does"t work for you than build a 2A3 amp more difficult too make a bad one
Many thanks Johann!
I´m suprised that SiC diodes are available at CONRAD in Germany ;-)
I will try them out!
cheers
Peter
I really wanted this to work for me, but I tried this tube in a spud amp and found it harsh sounding. I used grid stoppers and decoupled heater winding to gnd - usual precautions to have no oscillations. I didn't see any r.f. hash on the CRO either. If I did something wrong then I don't know what it was ?
http://www.diyaudio.com/forums/tubes-valves/280167-yukon-gold-spud-amp.html
do you have tried Triode Vs pentode mode on your spud amp ?
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Joined 2009
Paid Member
4 related articles on SPUD amplifier....Perhaps, the last article doesn't count as SPUD...
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A Purist' Wet Dream - diyparadise
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Great tube great amp great job I love it love spuds and am overwhelmed and impressed with simplicity and simple things they make stuff more pure and enjoyable I build spuds every day and have a breadboard in my bedroom tomorrow I plan on building a 4 parallel ecc85 spud and one of these days use one of those dht low voltage pentodes as a spud love the way a ecc81 opens up and may do something with it also use the 6sn7gta a lot but feel it doesn't have the atmospheric warmth I desire plan on building a parafeed or normal opt preamp out of it as Sakuma said powerful lungs make powerful vocals and I guess this pre would be a powerful pair of lungs for some nice spud but parafeed or straight opt
When you respect the 150V heater-cathode voltage (by lifting the heaters at least 50V) you could put the anode at 200V. A 270R cathode resistor will give you circa 3 to 4V bias voltage and current through the tube will be 12 to 14 mA.
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I built the amp from the schematics from post #2. I used 5K output transformers because I did not have any 2.5K transformers. 4 ohm Braun L200 speakers and a Bottlehead Quickie preamp are used. I have twenty hours on it so far and it sounds great, not too bad for a low parts count amp with $4 tubes. Output is a little more than a watt.
Looks nice! I've never tried to build a spud amp but I do have some 6E5Ps around that I've never done anything with, so perhaps I'll try this one sometime.
I don't mean to nitpic and it's really just a philosophical question but, if you're using a preamp that has gain, is it still considered a spud amp just because the input tubes are in a different chassis?
I said I've never tried to build a spud, but I inadvertently did build one. I modded a little Voice of Music SE 6BQ5 amp that normally uses a 12AX7 input tube that's mounted on a separate chassis. I eliminated the connection to the 12AX7, along with the global NFB, so that I could use the amp section with whatever preamp I wanted.
I left it in pentode to maximize the power output and added local NFB. I have no way to measure the power output but I assume it's probably in the 3 to 4 watt range. Whatever it is, it's enough for me.
What surprised me is that the amp works very nicely with no preamp - either a passive preamp (simple volume control) or using the volume control on my computer to stream to the amp using an Airport Express.
Volume level is a bit lower than it is when using a preamp with gain but it sounds wonderful.