Good bass is certainly possible, even with low-priced EH 300B (Gold-Grid), which are better than many expect.
It's all in the power supply. Choke-input B+, LCLC configured with a large 10H+ first choke, and quality MKP capacitors. And a current driven filament supply, purpose-designed.
With ac-heating, everything sounds relatively muddy and cloudy - and takes the definition out of the music, including the bass.
It's all in the power supply. Choke-input B+, LCLC configured with a large 10H+ first choke, and quality MKP capacitors. And a current driven filament supply, purpose-designed.
With ac-heating, everything sounds relatively muddy and cloudy - and takes the definition out of the music, including the bass.
A good powersuply is one thing but good bass can only be possible with a very good output transformer. Much SE audiotransformers are simply to small to give a very good bass. Second problem the high frequency respons. We want to have both.
An externally hosted image should be here but it was not working when we last tested it.
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Yes, naturally a good OT is needed. I use a Sowter SA08, which has plenty of core to support the bass:
SA08 SINGLE ENDED OUTPUT TRANSFORMER
But even with this OT, one must make a proper effort with the filament and the B+ supplies.
SA08 SINGLE ENDED OUTPUT TRANSFORMER
But even with this OT, one must make a proper effort with the filament and the B+ supplies.
Illustration of the AC and DC heating. Both amplifier uses 300B tubes, one is 300B PP with AC heater, the other is an SE (DC heater). The output power is 1W.
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Actually you can get quite good bass even from a Hammond 125FSE, if you keep the power down. Don't expect it to do unsaturated bass over a few watts, but when kept under that it's surprisingly good, if your amplifier is a good design to start with. And it goes up to 50kHz as well.
The friend I mentioned earlier tried a Lundahl transformer in his design, and stated it could go down to 10Hz at full tilt before saturating. Now, that's quite good for a reasonably priced SE transformer. But still he stated that the perceived quality of the bass was lacking in speed and punch. And that wasn't a fault of the transformer, as I stated earlier he had found out that regardless of OPT (Tango, Lundahl...) he couldn't make a 300B make good bass.
Yes, rectified, smoothed (10000uF), and regulated -if I remember correctly- with one of LDO 5V regulator. The 50Hz and its harmonics due to the poor HV PSU -simple CLC-.
You can see the second pic contains lot of intermodulation spectrums over the base (1kHz) and it's harmonics (+/- 50Hz, +/- 100Hz, +/- 150Hz...).
This pic is the R.C regulated 300B spectrum. This also contains 50Hz and it's harmonics components.
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Hi Rod,
Sorry to jump in the middle. I try to track your postings but could not find details on your proposed current controlled DC heating.
Where can I see some design samples?
Thanks,
Sorry to jump in the middle. I try to track your postings but could not find details on your proposed current controlled DC heating.
Where can I see some design samples?
Thanks,
IMHO Rod's regulators are a prerequisite for a decent dht amplifier. I only use cheap 300b's, Chinese ngg, I couldn't resist @60 quid delivered. Have to say ive never had acceptable bass from them. Lundahl opt and lclc after 500va and 6ax4 bridge rectifier. Gm70 bass through same opt but higher voltage hybrid ps walked over the 300b's. I use 6k for 300b and 11.5k for gm70 as I don't need the power and prioritise damping and distortion. I use sand for <100hz. Now.
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