I have a pair of used 6550 in mine which now has about 10 hours on and sounds great, except, one tube is at least 3dB louder than the other. So I'm wondering; do I get another pair of 6550 or KT-66 or 88 or...? My speakers are 97dB sensitive so watts don't matter.
Then what to do about the 5W 560 ohm resistor if I change to another tube? I have the Transcendar OPTS, 5000 ohm, with 320Vdc B+ at the plate and 350 at the OPT.
What are Vp, Vk, Rk, Ik on the "tubes and transformers" page? They don't Google.
Then what to do about the 5W 560 ohm resistor if I change to another tube? I have the Transcendar OPTS, 5000 ohm, with 320Vdc B+ at the plate and 350 at the OPT.
What are Vp, Vk, Rk, Ik on the "tubes and transformers" page? They don't Google.
The answer to that question is greatly a matter of opinion. You can read some banter about it on the 3rd page of this thread, which is my Simple SE build:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=140978&pagenumber=3
While the differences between tube types is fairly subtle on my Dynaco PP amp, they are much more obvious on this amp, especially when it is in triode mode with no CFB. What works best for you will depend on your speakers and the type of music you listen to. I also found that the coupling capacitors make a noticeable difference as well. I started with Russian PIOs but now have Auricaps in there.
I think most will agree that a pair of EL34s resolve the most detail with this amp. I have tried a pair of SED EL34s and a pair of cheap Chinese EL34s (Valve Art). They both sound very similar, but I want to say that the SED may have better bass on my older speakers. On my newer speakers, which are 98dB, I can't really tell the difference.
I think that 6550s and KT88s will all sound similar. This is especially true if you get one of the Russian Reflektor tubes (EH, Sovtek, "Tung-Sol", etc), as I think they have all the same innards. I've also tried the EH KT90s, which are supposedly derived from some Russian sweep tubes, and thought they sounded really good. I've had a pair of SED KT88s in there now and I think they are a bit more well-rounded than the Reflector stuff. They have been in and out but I seem to end up going back to them.
I started with JJ 6L6GCs, as these should be a compromise between the detail of the EL34 and the bass drive capability of the bigger tubes. In my opinion they seem to give up too much detail for very little gain in the bass dept. I imagine KT66 would be similar.
Anyway, those are my feelings. Take them with a grain of salt.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=140978&pagenumber=3
While the differences between tube types is fairly subtle on my Dynaco PP amp, they are much more obvious on this amp, especially when it is in triode mode with no CFB. What works best for you will depend on your speakers and the type of music you listen to. I also found that the coupling capacitors make a noticeable difference as well. I started with Russian PIOs but now have Auricaps in there.
I think most will agree that a pair of EL34s resolve the most detail with this amp. I have tried a pair of SED EL34s and a pair of cheap Chinese EL34s (Valve Art). They both sound very similar, but I want to say that the SED may have better bass on my older speakers. On my newer speakers, which are 98dB, I can't really tell the difference.
I think that 6550s and KT88s will all sound similar. This is especially true if you get one of the Russian Reflektor tubes (EH, Sovtek, "Tung-Sol", etc), as I think they have all the same innards. I've also tried the EH KT90s, which are supposedly derived from some Russian sweep tubes, and thought they sounded really good. I've had a pair of SED KT88s in there now and I think they are a bit more well-rounded than the Reflector stuff. They have been in and out but I seem to end up going back to them.
I started with JJ 6L6GCs, as these should be a compromise between the detail of the EL34 and the bass drive capability of the bigger tubes. In my opinion they seem to give up too much detail for very little gain in the bass dept. I imagine KT66 would be similar.
Anyway, those are my feelings. Take them with a grain of salt.
There was a noticeable increase in detail with switching to the film caps. My speakers are not very strong in the midrange dept, so I didn't notice any difference there. Since they have horns, the loss of detail was actually a benefit for some types of music. I find Auricaps to be a very neutral cap. They are not as expensive as many others (though they are not as cheap as they used to be) but always seem to do well.
I will admit that I didn't give the PIOs a fair shake. It took a long time, like 50-100 hours, for the Dynaco to sound like it does now. It has those same caps in it. I was too impatient and a little frustrated, so I just swapped them. I always intended to put Auricaps in there anyway, I just didn't have the right value on hand when I was breadbaording the amp.
I will admit that I didn't give the PIOs a fair shake. It took a long time, like 50-100 hours, for the Dynaco to sound like it does now. It has those same caps in it. I was too impatient and a little frustrated, so I just swapped them. I always intended to put Auricaps in there anyway, I just didn't have the right value on hand when I was breadbaording the amp.
BillEpstein said:
Which Allied? The 6K7VG or the 6K56VG?
Judging by your measured B+ voltage, I'd wager it's the 6K56VG. With the lower B+, it might be well suited for some 6L6G or maybe even some 6V6 tubes. If you stick with the big tubes, you're probably running them way underbiased. I'm guessing your cathode voltage is somewhere around 30V, and per tube current draw is probably about 50 mA. That puts your overall dissipation at less than 15 watts. Any decent 6550 should be able to handle much more than that.
Oh yeah...the bias resistor. 560 is a high value to use for a 320V B+, even for an EL34. I use that same resistance on mine for the EL34, but my B+ is 460V. Something more like 390 or 360 ohms will put some current through those things and get them sounding good. That is even more the case for your 6550s. They will do much better with more current and that may be why one sounds so much weaker than the other. Try 270 or 240 ohms to kick the current up.
BillEpstein said:
Vp=plate voltage (determined by B+ voltage and current)
Vk=cathode voltage (determined by cathode R Value and cathode current)
Rk=cathode resistor value
Ik=cathode current (same as anode current for triode mode)
Risking a sweeping generalization, EL34's have great midrange/vocals, and 6550/KT88 give up a little mids for better bass and more punch/attack.
As already mentioned, you may need more PS power to drive 6550's/KT88's than EL34's.
Ah...good point on the transformer, Ty. Yeah, I wouldn't push it too much then with the big tubes. I think you should look at EL34s or some good 6V6GTs that can handle high, out-of-spec plate voltages. Some guitar amps are like this and generally destroy cheap current-production stuff. Things are better now, but the only tube I know for sure can handle it is the EH 6V6GT. The Russian "Tung-Sol" should also be fine, probably because it is the same frickin tube.
You should be able to bias either of those as hot as you dare on that transformer.
You should be able to bias either of those as hot as you dare on that transformer.
Tou guys are a huge help
Yes, the lower power Allied, I really didn't pay enough attention to the tubes I'd be running, D'OH!
I have a tranny with 560, 720 and 840CTs but only 100mA; no headroom at all. Even under-biased, I like the sound well enough to invest in a bigger transformer.
One more thing: how come there's no resistor in place of the volume pot when wiring w/o?
Yes, the lower power Allied, I really didn't pay enough attention to the tubes I'd be running, D'OH!
I have a tranny with 560, 720 and 840CTs but only 100mA; no headroom at all. Even under-biased, I like the sound well enough to invest in a bigger transformer.
One more thing: how come there's no resistor in place of the volume pot when wiring w/o?
I just ordered the bigger Allied power tranny as I solved the tube imbalance problem. It was the effin' PEC volume pot. This is the 4th of 4 PECs I've had go bad; either noisy or way out of balance or both.
You'd think you could trust Canadians for quality
It's really a shame too, because they sound so good when right. It's back to TKD and another $40 bucks for me.
You'd think you could trust Canadians for quality
It's really a shame too, because they sound so good when right. It's back to TKD and another $40 bucks for me.
If you have any 6V6 tubes give them a try. They sound real nice in triode with a 5K to 6K load. You only get about 2 watts so that may not go to far if you have inefficient speakers. I have a Simple SE with the small Allied. I have fed it 6V6's 6K6's and abunch more that I don't remember right now (I am 1100 miles away from home).
The 6K56VG is rated for 120 mA on 50Hz and is probably good for about 140 to 150 mA on 60Hz. I have one in a Tubelab SE, which I often stuff with 300B's biased at 60 mA each. That sucks about 170 mA from the transformer. Yes it gets real toasty, but it has been alive for about 5 years now. It is actually the only Hammond / Allied transformer that I have ever had to replace due to failure. The original got full of water in a hurricane, and it still worked for about a month before it fried.
The 6K56VG is rated for 120 mA on 50Hz and is probably good for about 140 to 150 mA on 60Hz. I have one in a Tubelab SE, which I often stuff with 300B's biased at 60 mA each. That sucks about 170 mA from the transformer. Yes it gets real toasty, but it has been alive for about 5 years now. It is actually the only Hammond / Allied transformer that I have ever had to replace due to failure. The original got full of water in a hurricane, and it still worked for about a month before it fried.
It's all sordid out now with 431vDC plate and 450vDC output, 41 volts bias; all with a Boogie Woogie Mullard 5AR4, Telefunken 12AT7 (a Paramour leftover) and the Svetlana 6550s.
The PEC pot is gone; the Simple is now a main amplifier, fed by a passive pre with my last remaining 100K PEC and a Greyhill switch. Other components are HW-19 IV with SAMA, dampered SME III/Benz Ace Low or Marantz 8001 SACD and Pi 4 speakers with the new crossover.
Compared to my parafed, direct-coupled, SE'd 45 amp with Magnequest chokes, OPTs and other goodies for a total of about $1200 in parts, the $300 Simple has a warmer tone and weightier bass.
The 45 does nuance better but the 3X more powerful Simple unravels the complex a mite clearer.
The 45 goes higher and reveals more, both beauty and warts in the upper treble; you should hear Emma Kirkby thrill the high notes in Haydns "With verdure clad". Who says compression drivers don't go high? OTOH, Alison Krauss is never shrill with the Simple.
There's also a bit more needle-in-da-groove noise so perhaps the Transcendars have a peak or three or maybe it's the 6550s.
Now I have two fine amplifiers. Life's a b-tch? Says who?
The PEC pot is gone; the Simple is now a main amplifier, fed by a passive pre with my last remaining 100K PEC and a Greyhill switch. Other components are HW-19 IV with SAMA, dampered SME III/Benz Ace Low or Marantz 8001 SACD and Pi 4 speakers with the new crossover.
Compared to my parafed, direct-coupled, SE'd 45 amp with Magnequest chokes, OPTs and other goodies for a total of about $1200 in parts, the $300 Simple has a warmer tone and weightier bass.
The 45 does nuance better but the 3X more powerful Simple unravels the complex a mite clearer.
The 45 goes higher and reveals more, both beauty and warts in the upper treble; you should hear Emma Kirkby thrill the high notes in Haydns "With verdure clad". Who says compression drivers don't go high? OTOH, Alison Krauss is never shrill with the Simple.
There's also a bit more needle-in-da-groove noise so perhaps the Transcendars have a peak or three or maybe it's the 6550s.
Now I have two fine amplifiers. Life's a b-tch? Says who?
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