Got some more seat time with the amp. Sounded quite different, but I found out it is due to trying the 4ohm tap instead of the 8ohm.
4ohm taps give what I interpret as the more traditional tube sound. Bass is there, but takes a back seat while the rest shoves you right inside the sound.
8ohm taps narrow the sound quite a bit but have more bass. Sounds much more congested by comparison. But probably closer to solid state sound.
I wonder if it has to do with the combination of the Faux Pas having 4ohm woofers, and the feedback being pulled from the 8ohm taps.
Fun to have an amp with different personality options though.
Donāt sweat the filament voltage too much. The general rule of thumb is +/- 10%. Thatās 5.68 to 6.93 VAC.
Your build execution of that amp project looks fantastic Drew! Iām glad you are liking how it sounds so far. Both of my lower wattage tube amps are used for nearfield speakers (over workbench at home and on desktop at work). Iād be surprised if Iām even pushing 2 watts out of either of them. I love how they sound.
The only upgrade I might suggest is a higher quality volume pot, like an Alps. PE still sells them at a reasonable price. They are quieter and track way better left to right channel.
Iāve rolled a fair number of tubes and other parts in my tube amps. The driver tube(s) and coupling caps have had the greatest impact. Yeah, different output tubes sound different, but nowhere as different. Nice thing is the driver tube is usually the cheapest tube on the chassis and the coupling caps are very small, like 0.22 - 0.47 uF, so even metal foil caps donāt cost an arm and leg.
@PWRRYD Thanks man! Iām going to have to try hard to not get sucked into this stuff too much (its not cheap) but right now Iām chugging the koolaid . Sounds like my father may be interested, I could tell he was jealous. So I might get to do another kit some time.
What this is getting me going for most right now is more high sensitivity speaker projects!
When I was doing all the ali ordering I got some pots that look identical to Alps. Though, like Alps, they are 50k or 250kohm. The one with the kit is 100kohm. So instead of thinking too hard about it I just used the kit one for the moment. It seems more sensitive before the half way mark than Iām used to. Either the kit one is a linear pot instead of audio taper, or the 250k might do better?
Interesting on the coupling caps. Do metal foil usually make much of a positive difference vs film?
Some folks swear the metal foils sound better, some swear by PIO (paper in oil, specifically Russian miltary surplus), others copper, silver, gold, etc. etc.
What is your source that is feeding the amp? Iām guessing you donāt have a high output impedance tupe amp preamp. So a more normal solid state device would benefit from a lower input impedance volume pot. Generally a 20 kOhm pot is appropriate. Iād swap out the 100k for your 50k.
Ok yeah. Was playing from CD player (SMSL PL100). Or would be from the built-in preamp in the AT turntable. Or a standalone opamp based phono preamp if I get to building one of those.
Are you using .33uf coupling caps? Iām sure I have some vintage paper in oils around here. Shoot me your address and Iāll send you something to try.
Wondering if the 5watt cathode resistor is plenty? Was thinking about swapping for some higher wattage aluminum jacket ones to get the heat farther away from the bypass cap.
Yeah nice and compact. From my seating position it seems plenty quiet reading the disc, though the load/eject is a bit loud (doesnāt matter much to me). Iād say it has the basic features youād need and not much more. The display is good quality, just small. The text size is past my capability to readily make out the track number from the couch ~8-9ft away.
The kit should be ready to make noise with all the included parts, just add solder.. mine did atleast. But as far as sound good, I think investing in better tubes is required. I was skeptical of the electrolytic caps being anywhere close to spec, but who knows; they could be close enough to do fine (I wasnāt risking it). The resistors are probably fine (I used them). It might not come with a power cord, but it uses a typical desktop computer power supply style plug. It doesnāt realy come with much for grounding solutions, which for me was just supplying some ring terminals. I also used my own hookup wire in case the stuff it came with was junk.
If you get the non tube diode version (one with only 3 tubes) then you should be able to upgrade all 3 for under $50 pretty easily.
I read about the tube snobs poopooing the output transformers. Iām sure they arenāt the greatest, but Iām impressed with what Iām able to get out of mine. Could be part of why the 8ohm and 4ohm taps sound so different. But they give you the plug outputs for both so you will always have the choice which ones to plug your speakers into anyway.
I looked on Ebay, and Nobsound also has a 12w x2 class AB version that looks pretty good for $250. Based on your experience, I am tossing around putting one together this winter.
The big problem I see with that 300B kit (and most) is that any half way decent replacement 300B tube, even the Soviet block ones, are now almost $200 each! Couple that with what looks like barely $25 each output transformersā¦.
I think what Drew built is a perfect cost/performance tube kit.
. Sounds like my father may be interested, I could tell he was jealous. So I might get to do another kit some time.