I got mine on eBay. The ones I have look a lot like these: 300B Ceramic Socket. I think I just searched for 300B ceramic sockets.
"ux4 socket ceramic" returns this (among other things): Another ceramic socket.
Note the socket pins are intended to poke through the big hole in the board and then connect with short wires to the pads on the board.
~Tom
"ux4 socket ceramic" returns this (among other things): Another ceramic socket.
Note the socket pins are intended to poke through the big hole in the board and then connect with short wires to the pads on the board.
~Tom
Last edited:
Hi tomchr, I have a Tubelab SSE witch 6P3S-E (Good and cheap) but my PT (300-0-300) only produces 350 B+.
I have to buy a more powerful one and was thinking of buying the ClassicTone and your 300B-PSU and the Maida regulator boards, that would be an almost universal PSU.
That would allow me to run any tube, also tempts me your 300B but this tube is very expensive though 6N6P is very cheap, I have never heard a DHT so do not wait.
The SSE sounds great but I can not run more powerful tubes, my girlfriend gave me a pair of KT90's for Christmas and I was thinking about a 460-470 B+.
Your PSU+Maida can provide this voltage?
I have to buy a more powerful one and was thinking of buying the ClassicTone and your 300B-PSU and the Maida regulator boards, that would be an almost universal PSU.
That would allow me to run any tube, also tempts me your 300B but this tube is very expensive though 6N6P is very cheap, I have never heard a DHT so do not wait.
The SSE sounds great but I can not run more powerful tubes, my girlfriend gave me a pair of KT90's for Christmas and I was thinking about a 460-470 B+.
Your PSU+Maida can provide this voltage?
No need for an excuse. Your English is fine.
Yep. I like the 0-330-380 secondary on the ClassicTone for that reason. It gives you many options for B+ voltages without dissipating ridiculous amounts of power in the 21st Century Maida Regulator. And if for some reason you want lower B+ voltages, you could always grab a different transformer and hook it to the 300B PSU board.
You may want to take a look at this thread: http://www.diyaudio.com/forums/tubes-valves/183329-one-more-4p1l-se.html
The 4P1L is pretty inexpensive (<$5/each on eBay) and is supposed to be really good. You won't get as much power as you would with a 300B, but maybe with many in parallel... Or just get more efficient speakers.
I wouldn't run higher than 500 V RMS into the PSU board. That would result in about 650 V out (700 V at no load). So that's the limit there.
With the ClassicTone transformer, you'll get about 520 V out at nominal mains voltage. So roughly 490~550 V with +/-5 % mains variation (this is pretty tight, actually). The 21st Century Maida Regulator requires about 15 V across the regulator in order to regulate. So you're fine there.
But if the mains variation gets to +/-10 %, you'll run out of headroom. As far as I know, both the EU and the US operate at +/-5 % mains, so it should be alright, but I generally design for +/-10 % mains variation.
Another option is to lower the B+ voltage to 450 V. Then you can support +/-10 % mains variation with the ClassicTone transformer I specify.
~Tom
Last edited:
I'd say the maximum B+ you can get with the ClassicTone 40-18069, my PSU board, and the 21st Century Maida Regulator for +/-5 % mains variation is roughly:
520 * 0.95 - 15 = 479 V.
That's assuming about 225 mA of steady-state load (like my 300B amp). If you push the transformer closer to the limit, I wouldn't count on more than 470~475 V.
520 * 0.95 - 15 = 479 V.
That's assuming about 225 mA of steady-state load (like my 300B amp). If you push the transformer closer to the limit, I wouldn't count on more than 470~475 V.
The plot thickens... 
I promised pictures of how the ferrite bead mounts to the gate of Q1. See attached.
1) Gather materials: FQP3P50, machine screw (M3x8 or #4x3/8 is probably ideal), lock washer, nut, thermal goop, heat sink.
2) Using pliers, bend the leads on the FQP3P50 to a 90 degree angle such that the mounting hole and the pins line up with the respective holes on the board footprint. Apply a thin coat of thermal compound to the FQP3P50 and drape the ferrite bead onto the gate lead.
3) It requires a bit of skill and patience, but it is possible to get the FQP3P50 onto the heatsink and the combo aligned with the footprint on the board without losing the ferrite bead. Tighten the screw until the lock washer bites into the board. Cut and solder the leads.
Note: For the ultimate gory detail in the picture, right click on it and open it in a new tab.
~Tom
I promised pictures of how the ferrite bead mounts to the gate of Q1. See attached.
1) Gather materials: FQP3P50, machine screw (M3x8 or #4x3/8 is probably ideal), lock washer, nut, thermal goop, heat sink.
2) Using pliers, bend the leads on the FQP3P50 to a 90 degree angle such that the mounting hole and the pins line up with the respective holes on the board footprint. Apply a thin coat of thermal compound to the FQP3P50 and drape the ferrite bead onto the gate lead.
3) It requires a bit of skill and patience, but it is possible to get the FQP3P50 onto the heatsink and the combo aligned with the footprint on the board without losing the ferrite bead. Tighten the screw until the lock washer bites into the board. Cut and solder the leads.
Note: For the ultimate gory detail in the picture, right click on it and open it in a new tab.
~Tom
Attachments
The noise level of the 300B amp? That's roughly 1 uV/rt(Hz) noise spectral density. I seem to recall that integrating up to about 300 uV RMS (80 kHz bandwidth).
I'd say the 300B amp is a bit overkill for headphone use, but each to their own, I guess.
The supply is as quiet as it gets. The B+ measures 20 uV RMS hum+noise at the output of the 21st Century Maida Regulator.
~Tom
I'd say the 300B amp is a bit overkill for headphone use, but each to their own, I guess.
The supply is as quiet as it gets. The B+ measures 20 uV RMS hum+noise at the output of the 21st Century Maida Regulator.
~Tom
On my Switchmode Filament Supply thread, the following question came up. I figured the answer would be more useful in this thread, so I'm porting the question over.
The general rule of thumb is that you get lower distortion with the higher primary impedances at the expense of lower output power.
I think most people tend to gravitate towards 3.3 kOhm for slightly higher output power at slightly higher THD and 5 kOhm for slightly lower output power and slightly lower THD.
Personally, I use 5 kOhm and have tried emulating the effects of using different primary impedances by changing the load resistor. I found that I got the best performance at 400 V, 85 mA, 5 kOhm primary. I seem to recall getting about the same amount of output power at clipping regardless of primary impedance. But at the lower primary impedances, the THD at low power (typical listening levels) was quite a bit higher. Basically, my amp is optimized for 5 kOhm primary impedance, and after experimenting with different primary impedances I didn't see any reason to change this.
I have tried the Edcor CXSE25-8-5K ($80/each) and Electra-Print custom wound transformers (spec: 300B, 20 W, 100 mA, 5 kOhm, 4 & 8 ohm secondary, copper). The Edcor transformers are quite good but the Electra-Print are amazing. I wouldn't say the difference is "night and day" but I like the tone of the E-P better and they do seem to resolve more detail in the highs while providing firmer bass. But they're also 3x the cost of the Edcors. If you're on a budget, get the Edcor. At $80/each, it's very hard to beat on performance/price.
~Tom
The general rule of thumb is that you get lower distortion with the higher primary impedances at the expense of lower output power.
I think most people tend to gravitate towards 3.3 kOhm for slightly higher output power at slightly higher THD and 5 kOhm for slightly lower output power and slightly lower THD.
Personally, I use 5 kOhm and have tried emulating the effects of using different primary impedances by changing the load resistor. I found that I got the best performance at 400 V, 85 mA, 5 kOhm primary. I seem to recall getting about the same amount of output power at clipping regardless of primary impedance. But at the lower primary impedances, the THD at low power (typical listening levels) was quite a bit higher. Basically, my amp is optimized for 5 kOhm primary impedance, and after experimenting with different primary impedances I didn't see any reason to change this.
I have tried the Edcor CXSE25-8-5K ($80/each) and Electra-Print custom wound transformers (spec: 300B, 20 W, 100 mA, 5 kOhm, 4 & 8 ohm secondary, copper). The Edcor transformers are quite good but the Electra-Print are amazing. I wouldn't say the difference is "night and day" but I like the tone of the E-P better and they do seem to resolve more detail in the highs while providing firmer bass. But they're also 3x the cost of the Edcors. If you're on a budget, get the Edcor. At $80/each, it's very hard to beat on performance/price.
~Tom
Last edited:
I agree. If you're building with 300Bs, you're already aiming high. Save up some more cash. Get good OPTs. Don't put a 3-cylinder engine in a Ferrari.
~Tom
Tom,
Thank you for complete replies in both threads.
You answered in all questions I was looking answer from somebody who has experience on building 300B amp and circuits around it, perfect.
As per transformers you are suggesting, I search in the sites and found very good reviews and customers are satisfied with them. In my location where I live, it's a bit problematic to receive transformers from overseas and customs here is pain..
In my neighboring country, are few companies which produce output transformers, among them is trafomatic.com and they offer dual C core outputs and standard ones.
I will see how much will cost and I might order pair of them.
thanks
bekim
Thank you for complete replies in both threads.
You answered in all questions I was looking answer from somebody who has experience on building 300B amp and circuits around it, perfect.
As per transformers you are suggesting, I search in the sites and found very good reviews and customers are satisfied with them. In my location where I live, it's a bit problematic to receive transformers from overseas and customs here is pain..
In my neighboring country, are few companies which produce output transformers, among them is trafomatic.com and they offer dual C core outputs and standard ones.
I will see how much will cost and I might order pair of them.
thanks
bekim
I know - too many questions
Ok, I can find mostly two types of output transformers (OT): EI and double C core. Now, more than half of people are suggesting EI core towards double C core, in terms of sound quality; warm sound, natural vocals, etc..etc..
I contact through email this guy who makes OT in poland - ogonowski.eu, and he recommends EI rather than C core..
What you say..? I know there isn't perfect part for certain job, but just your experience. I appreciate that.
thanks
bekim
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.