Ok, in order to let you guys not wait too long, I've been studying a bit more... But I do not want to screw up the amp, so need some extra help here:
By 'resistors that are used to span some traces', I guess you mean the jumpers j2 and j3?
And for the value for the resistor to connect pin 4 and pin 3, 100 ohm would do?
If this is what needs to be done to get it in triode mode, I will try to get this done in the next few days and report my findings!
By 'resistors that are used to span some traces', I guess you mean the jumpers j2 and j3?
And for the value for the resistor to connect pin 4 and pin 3, 100 ohm would do?
If this is what needs to be done to get it in triode mode, I will try to get this done in the next few days and report my findings!
Just did the change to triode with zero fb. So here are my first impressions.
To put things in perspective, first my set up, so that one could compare... All music is lossless, playing with foobar and a Maverickaudio v2 dac. Before the speakers there's an active filter/pre amp, specificly designed for OB speaker. The XO is at 150 hz, 24db. And for both woofers and FR driver there's dipole loss correction. The speakers are OB with 2 Eminence Alpha's and one Tangband W8 1808 each side. The woofers are driven by a SS amp, 220wpc. And off course the Elekit drives the Tangbands.
At first the sound was too bright, sharp even. A bit like the stock tubes in pentode. I found that the Tangband is VERY sensitive for brightness. The 807 in pentode seemed to solve that issue, but the sharpness came back in triode...
When the tubes were warmed up the sharpness seemed to dissapear and in came detail, freshness and a bigger soundstage. Have not listened long enough to tell something about listening fatigue. But so far, so good
At this point I'd say that triode mode brings a more 'audiophile' sound, whatever that may be Certainly intrigueing and asking for some tube rolling, as the 807 is said to be not that great with zero nfb.
Any suggestions for a tube that would sound great for mid and highs?
To put things in perspective, first my set up, so that one could compare... All music is lossless, playing with foobar and a Maverickaudio v2 dac. Before the speakers there's an active filter/pre amp, specificly designed for OB speaker. The XO is at 150 hz, 24db. And for both woofers and FR driver there's dipole loss correction. The speakers are OB with 2 Eminence Alpha's and one Tangband W8 1808 each side. The woofers are driven by a SS amp, 220wpc. And off course the Elekit drives the Tangbands.
At first the sound was too bright, sharp even. A bit like the stock tubes in pentode. I found that the Tangband is VERY sensitive for brightness. The 807 in pentode seemed to solve that issue, but the sharpness came back in triode...
When the tubes were warmed up the sharpness seemed to dissapear and in came detail, freshness and a bigger soundstage. Have not listened long enough to tell something about listening fatigue. But so far, so good
At this point I'd say that triode mode brings a more 'audiophile' sound, whatever that may be
Certainly intrigueing and asking for some tube rolling, as the 807 is said to be not that great with zero nfb. Any suggestions for a tube that would sound great for mid and highs?
Ok, one day later. The 807's with zero feed back are 'too much'. Too tireing to listen to and too forward mid/high. So in went the EH 6l6 tube again. Sharpness gone. Much more detail than in Pentode and overall a nice listening experience, although the big soundstage that the 807 created was not there.
So this morning I've put back the NFB resistorts and again the RCA 807's. Big soundstage, nice detail and not sharp at all. This is a very nice configuration! Triode mode does sound better to me...
But I really think this calls for some more tube rolling. After reading this: Comparing Eight Tubes For Low Power Amplifiers Article Submitted By Mike Zivkovic Of Teresonic I am very interested in the EL3n tube. But like the 6v6, its has limited max voltage. Mr. Jag, do you know if with some changes (like you did for the 6v6) these tubes can be used in this amp? If so, I will figure out how to adapt the socket...
So this morning I've put back the NFB resistorts and again the RCA 807's. Big soundstage, nice detail and not sharp at all. This is a very nice configuration! Triode mode does sound better to me...
But I really think this calls for some more tube rolling. After reading this: Comparing Eight Tubes For Low Power Amplifiers Article Submitted By Mike Zivkovic Of Teresonic I am very interested in the EL3n tube. But like the 6v6, its has limited max voltage. Mr. Jag, do you know if with some changes (like you did for the 6v6) these tubes can be used in this amp? If so, I will figure out how to adapt the socket...
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If I were to use the 6v6 triode strapped, what would that mean for the convertion of the amp, as the screen is now connected to the plate with a 100ohm resistor? Do I need to replace these with the 27k resistor?
And I'll take it the cathode resistors are R13 and R14?
Thanks so far!
No, you would want to leave the screen connected the way you have it now. I Have mine wired as a pentode amplifier. I expect they will want to draw more current triode wired, so I would probably start with around a 910 ohm cathode resistor, take some measurements and see where you're at, then consider lowering the cathode resistance to get the tubes to around nine watts.
Most nos 6V6 should be okay with the modest voltages in the 879s. I haven't used a lot of new 6V6; I think the JJ would be okay. I've tried several EH6V6 and the ones I had went crackly pretty fast. I won't use any of those again. The JJ and EH are the only new ones I've tried. I have thousands of old tubes, so no real incentive to buy new stuff, except curiosity.
Really, you're outside of what the designer intended, so you're just going to have to experiment and be prepared for the prospect that not all experiments work. Some can cause damage.
Win W5jAG
Edit: i've also used some Shuguang 6v6, I think they would be okay.
Most nos 6V6 should be okay with the modest voltages in the 879s. I haven't used a lot of new 6V6; I think the JJ would be okay. I've tried several EH6V6 and the ones I had went crackly pretty fast. I won't use any of those again. The JJ and EH are the only new ones I've tried. I have thousands of old tubes, so no real incentive to buy new stuff, except curiosity.
Really, you're outside of what the designer intended, so you're just going to have to experiment and be prepared for the prospect that not all experiments work. Some can cause damage.
Win W5jAG
Edit: i've also used some Shuguang 6v6, I think they would be okay.
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Yeah, how cool is that.
Sorry, I'm 7 hours ahead of you on a friday night...
But thanks again! I've read that for your listening you like pentode strapped more. Any reason for that?
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Hmm.. Does it have that grunt over repeat performances? Does it make the speakers squeal in delight? ;-)They say Size does matter and I couldn't agree more...
Then came the 6v6gt from Tung Sol triode strapped in my amp.
BTW, I have the Psvane 12ax7 T2 for about a week now. Nice tube!
I use gold lion kt-66 with Treasure 12AX7. Much better than the 6L6 I used earlier.
G
Sent from Tablet, please excuse brevity and typos...
glad to see people are still playing with this little gem... been wanting to give the Kt-88 a try the shop in tokyo where i bought the kit demo it with kt-88's ,
I been very happy with vintage phillips/ampex/ holland and english made EL34'd and the telefunken standard 12ax7 all the major caps have been changed as well as bypassing the volume pot completely using an external stepped pot. guess the next trick is to build a preamp to go with it. any suggestions?
I been very happy with vintage phillips/ampex/ holland and english made EL34'd and the telefunken standard 12ax7 all the major caps have been changed as well as bypassing the volume pot completely using an external stepped pot. guess the next trick is to build a preamp to go with it. any suggestions?
What do you mean by "triode strapped"?
I had the KT88s on my 879S but moved them over to my new arrival and have just installed a set of Telefunken Black Diamond 6L6GC-TK in their place. Haven't had a chance to warm them up yet.
first vintage tubes i bought after the 12ax7 was a set of vintage tung-sol 6L6gc still have a few pairs of nos spec. will get around to rolling them in again someday, i liked them a lot but my system is really a monitor desk top nice as well never seen a telefunken 6L6's (but i have not looked either) love to hear your report on them.
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