That's a very subjective question, but...
Ultralinear is a way of connecting a pentode in a 'triode-ish' way. It is also a form of local feedback. It will sound different.
You will have less power, as it is less efficient. It does, however, have more power than triode-strapping the screen.
Try it, and tell us your impressions. You could also try it triode-strapped, it too is quite simple. I would like to read about your results!
Ultralinear is a way of connecting a pentode in a 'triode-ish' way. It is also a form of local feedback. It will sound different.
You will have less power, as it is less efficient. It does, however, have more power than triode-strapping the screen.
Try it, and tell us your impressions. You could also try it triode-strapped, it too is quite simple. I would like to read about your results!
A totally unrelated question. I've included a bleeder resistor for the testing stages. The resistor is tied from the B+ on the large cap to ground. Can I leave the resistor in place or do people normally remove them? (Not sure if it affects performance?)
If keeping the resistor - what is a good value?
Thanks for all the help.
If keeping the resistor - what is a good value?
Thanks for all the help.
Bleeders are a good safety measure. I leave them in (but I also always check with a meter before touching anything). The ideal size depends on the size of the cap you are bleeding down.
I hope you are enjoying the amp. I sure like mine!
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
I hope you are enjoying the amp. I sure like mine!
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
Done!
Well, the amp is done!
I ended up using a 5H Hammond choke (158Q), Antek power transformer (275-0-275v for 292v on B+) and Edcor GXSE 15w transformers. Fostex 206en speakers are almost dead-quiet in spite of their high efficiency. I am using 47uf on the first cap and 100+100uf on the second cap. (Similar to RH84 schematic.)
Overall this is a noticeable improvement over my old Miniwatt N3. More bass response and the music is more 'energetic'. Better detail as well. Response is from a tad below 30hz up to about 19khz.
BTW - I am using a 100k resistor for the bleeder resistor.
Well, the amp is done!
I ended up using a 5H Hammond choke (158Q), Antek power transformer (275-0-275v for 292v on B+) and Edcor GXSE 15w transformers. Fostex 206en speakers are almost dead-quiet in spite of their high efficiency. I am using 47uf on the first cap and 100+100uf on the second cap. (Similar to RH84 schematic.)
Overall this is a noticeable improvement over my old Miniwatt N3. More bass response and the music is more 'energetic'. Better detail as well. Response is from a tad below 30hz up to about 19khz.
BTW - I am using a 100k resistor for the bleeder resistor.
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Wow, that is snug! Tube amps can be darn quiet. My RH84 versions are quieter than any chip amp or class-t I've tried, and noise is obnoxious on high-efficiency speakers!
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
Nice build! I love small chassis (chassi?) asthetically.
Very happy to hear that it's up and working well.
A suggestion, but emphatic -- don't make any changes (Transformer hookups, specifically) until the unit is all good and broken-in. Then fiddle as much as you want, but only make one change at a time. That way you can understand what the changes actually sound like.
Very happy to hear that it's up and working well.
A suggestion, but emphatic -- don't make any changes (Transformer hookups, specifically) until the unit is all good and broken-in. Then fiddle as much as you want, but only make one change at a time. That way you can understand what the changes actually sound like.
To change the design to run in triode mode, do I just need to run the screen resistor (2k2) to the anode. With a smaller value, maybe 470R?
That should be about right. You might also consider removing the 100K Rfb as well.
If I can ask a quick question about the RH84....
To change the design to run in triode mode, do I just need to run the screen resistor (2k2) to the anode. With a smaller value, maybe 470R?
Thanks
The closer you get to a direct connection between screen and plate, the more it will be like 'true' triode connection. As I understand it, the low-value resistor (100 ohms?) is to forestall potential oscillation problems.
For comparison, a Champ 6V6 (pentode-connected) has the screen connected via a 25k resistor (RC filter) to the B+.
Will try this amp for a first not-kit build also - it has a seductively simple schematic and looks like I might be able to do it without blowing myself up. Question: I've built PCB amps in the past but would like to try hard-wiring. How does one go about it, just try to replicate the schematic with wires and components, or should I use a tag board? (I'm sure this question has been asked before the but the search on this forum baffles me.) Finally, can this amp be used without a preamp - and if I do put a pot or stepped attenuator what value would be optimal? Thanks in advance for helping a beginner.
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