captainbeefheart Posted February 2, 2022 Share Posted February 2, 2022 Another idea is to add another bottle for 6 total, each channel gets a whole 6SN7 and tie both triodes in parallel, run it at 20mA with a low value cathode resistor. 1 Link to comment Share on other sites More sharing options...
captainbeefheart Posted February 2, 2022 Share Posted February 2, 2022 For a hoot I tried an EL84 triode strapped as the follower circuit instead of the 6SN7, it does gain some power. 17.3 watts output at 5% THD. Not a huge ordeal, just need to make the power supply a little more beefy for the extra current. FWIW These models aren't great at accuracy for grid current A2 mode. It's ballpark enough and extremely accurate for non grid current operation but from what I have measured in reality is always much better. It will most likely be 20 watts or more at 5% THD. 1 Link to comment Share on other sites More sharing options...
Curious_George Posted February 2, 2022 Share Posted February 2, 2022 37 minutes ago, captainbeefheart said: For a hoot I tried an EL84 triode strapped as the follower circuit instead of the 6SN7, it does gain some power. 17.3 watts output at 5% THD. Not a huge ordeal, just need to make the power supply a little more beefy for the extra current. FWIW These models aren't great at accuracy for grid current A2 mode. It's ballpark enough and extremely accurate for non grid current operation but from what I have measured in reality is always much better. It will most likely be 20 watts or more at 5% THD. The EL84 follower would be a great alternate build for some members. I’d keep it as an alternative. 1 Link to comment Share on other sites More sharing options...
Curious_George Posted February 2, 2022 Share Posted February 2, 2022 1 hour ago, captainbeefheart said: Another idea is to add another bottle for 6 total, each channel gets a whole 6SN7 and tie both triodes in parallel, run it at 20mA with a low value cathode resistor. What about a 6BX7? Link to comment Share on other sites More sharing options...
captainbeefheart Posted February 2, 2022 Share Posted February 2, 2022 12 hours ago, Curious_George said: What about a 6BX7? I will have to check to see if I have some around to try. The 6BX7 is great for common cathode stage with the output at the plate due to the very low plate impedance, like with a Williamson circuit driving the power tubes. For a follower stage it doesn't gain much in regard to transconductance vs 6SN7 which will determine cathode impedance. I have several very high gm tubes that I have experimented with followers but some have stability issues. One such tube is a 12HL7 which doubles the gm of a 6BQ5 at 21mA/V or 21,000uMhos. That can give us a follower stage with an output impedance of 47 ohms!! The 6BQ5 works pretty good with an output impedance around 100 ohms, it is still in production which is also a bonus. When I build this circuit I will be able to see the grid drive performance better vs simulation as the models don't really work great for grid current. If the 6BQ5 is much better vs 6SN7 parallel which will have similar gm I will go with it. Link to comment Share on other sites More sharing options...
CWelsh Posted February 2, 2022 Share Posted February 2, 2022 The anticipation builds! Love it!!! Link to comment Share on other sites More sharing options...
Curious_George Posted February 2, 2022 Share Posted February 2, 2022 1 hour ago, captainbeefheart said: I will have to check to see if I have some around to try. The 6BX7 is great for common cathode stage with the output at the plate due to the very low plate impedance, like with a Williamson circuit driving the power tubes. For a follower stage it doesn't gain much in regard to transconductance vs 6SN7 which will determine cathode impedance. I have several very high gm tubes that I have experimented with followers but some have stability issues. One such tube is a 12HL7 which doubles the gm of a 6BQ5 at 21mA/V or 21,000uMhos. That can give us a follower stage with an output impedance of 47 ohms!! The 6BQ5 works pretty good with an output impedance around 100 ohms, it is still in production which is also a bonus. When I build this circuit I will be able to see the grid drive performance better vs simulation as the models don't really work great for grid current. If the 6BQ5 is much better vs 6SN7 parallel which will have similar gm I will go with it. You're right, I forgot about the necessity to use tubes that are in production. In order to keep the cost down, the 6SN7 is probably the best choice in your circuit. It is a great all around tube! Link to comment Share on other sites More sharing options...
Curious_George Posted February 3, 2022 Share Posted February 3, 2022 What is the input sensitivity? Looks like you will be able to use this connected directly to a source. Link to comment Share on other sites More sharing options...
captainbeefheart Posted February 3, 2022 Share Posted February 3, 2022 15 hours ago, Curious_George said: What is the input sensitivity? Looks like you will be able to use this connected directly to a source. Gain is +20db, with 1Vrms input you will reach 12.5 watts output. Another reason why I was going to conservatively rate the amplifier as a 12 watt amplifier, that and distortion is at 1% at 12 watts. People can enjoy the amplifier directly from a source without a preamplifier. From experience with real world grid current drive vs simulation it's tough for me to tell the exact output at 5% THD but I am willing to bet it will be at least 20 watts. It's my experience that the majority of sources will be at least 1Vrms or 1.4Vpeak which means those will never clip the amp, and of course many sources especially today's high end CD players or DAC's use higher rail voltages for the opamps, usually at least +/- 5V easily outputting 2Vrms and of course if you use a preamp on average they can swing even greater output pushing the amps boundaries to maximum of around 20 watts. 1.26Vrms will get you to 20 watts which should be doable from most sources. 2 Link to comment Share on other sites More sharing options...
Area 51 Posted February 5, 2022 Share Posted February 5, 2022 On 1/25/2022 at 1:24 PM, captainbeefheart said: This is a Klipsch community and I know we do not need much power to get great sound, regardless spending $200 I think is easier to sell to the wife compared to $350 Yes. Most of us have efficient Klipsch speakers. I think you're on to something. I find it very interesting. Especially at $200. Sounds like fun. Link to comment Share on other sites More sharing options...
Area 51 Posted February 5, 2022 Share Posted February 5, 2022 On 1/26/2022 at 9:51 AM, Marvel said: they are lower powered This is a fascinating subject. Since most of us own Klipsch speakers how much power do we really need? Link to comment Share on other sites More sharing options...
Area 51 Posted February 5, 2022 Share Posted February 5, 2022 On 1/26/2022 at 11:23 AM, captainbeefheart said: This would be an assembled amp sold to only forum members. Where do I sign? Link to comment Share on other sites More sharing options...
hanksjim1 Posted June 8, 2022 Share Posted June 8, 2022 I was following his tube amp build and have sent a few messages to him without reply...anyone have a contact address for him? 1 Link to comment Share on other sites More sharing options...
Marvel Posted June 8, 2022 Share Posted June 8, 2022 Maybe he got chased off. Or he's on vacation somewhere and having more fun than being on here. It's only been a week and a half... Link to comment Share on other sites More sharing options...
hanksjim1 Posted June 8, 2022 Share Posted June 8, 2022 14 minutes ago, Marvel said: Or he's on vacation somewhere and having more fun than being on here. no way more fun than here!...LOL Link to comment Share on other sites More sharing options...
KT88 Posted June 9, 2022 Share Posted June 9, 2022 I quoted him two weeks ago in a post like this @captainbeefheartand no response, I hope he is not bored about the forum and also healthy and lively. 4 Link to comment Share on other sites More sharing options...
michaelwjones Posted June 9, 2022 Share Posted June 9, 2022 Y 2 hours ago, KT88 said: I quoted him two weeks ago in a post like this @captainbeefheartand no response, I hope he is not bored about the forum and also healthy and lively. You are not alone; I've not had responses from him either. Link to comment Share on other sites More sharing options...
CWelsh Posted June 9, 2022 Share Posted June 9, 2022 @Shakeydeal and @Westcoastdrums were both having custom amps built by him. Maybe they know something. I seem to remember him saying something about a health scare a couple of months back. I may be remembering something incorrectly, though. 1 Link to comment Share on other sites More sharing options...
billybob Posted June 9, 2022 Share Posted June 9, 2022 17 minutes ago, CWelsh said: @Shakeydeal and @Westcoastdrums were both having custom amps built by him. Maybe they know something. I seem to remember him saying something about a health scare a couple of months back. I may be remembering something incorrectly, though. True... Link to comment Share on other sites More sharing options...
Shakeydeal Posted June 9, 2022 Share Posted June 9, 2022 He did have some health issues a while back, I think he’s ok now. I really don’t have a lot of information other than that. Link to comment Share on other sites More sharing options...
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