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6550 power tubes in an Ampeg V-4B?

#61
agedhorse said:
Tung Sol 7027A is a good tube.

Also note that there were different versions of the 7027, I'm talking about the A version which IIRC uses a slightly thicker plate. The A version is pretty similar but not identical to the 6L6GC, but then again there are quite a few variants of the 6L6 as well.
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I found the specs are 35W, so it is similar to the original. Nice to know that.
 
#64
Sunnampeg said:
Hi, thanks, this is nice, but I had to change the original Power transformer since I'm in the UK, with a TAD (clone replacement 230v ahaha), I do not know if I could run the 6550s,i will re-ask my tech at the next retubing.
anyway, back in the day when i ve asked my tech how much the6550 s would have booset the output he said that itw would not be more than 10w maybe 15w, so 110 maybe 115w, but was safer running the 7581A and also 7581A would have given me more headroom and boost the output at110w so i went for the 7581A and infact he measured the output and everything he said it was right.
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I run reissue 7581A's in my V4B. The headroom is good. It's worth knowing if your new transformer has a higher heater current capacity. Even if you never run 6550A. I see the 6550A as good if you want a long service life and more headroom with a colder bias, not about more power.
 
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#65
beans-on-toast said:
I run reissue 7581A's in my V4B. The headroom is good. It's worth knowing if your new transformer has a higher heater current capacity. Even if you never run 6550A. I see the 6550A as good if you want a long service life and more headroom with a colder bias, not about more power.
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True, it makes sense, I will try to fit 6550s at the next retubing. I've heard that the 7581As are cleaner, but 6550s pull outa bit more low end, they could have said me a lie, but probably they did not, output tubes can change a bit the EQ of your amp..for instance, the Sunn 2000s with the 6550 has more distortion and a little less low end with the KT88 ahs more low end and less drive more headroom, almost completely clean
 
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#66
Sunnampeg said:
The original 7027A had 35W plate dissipation, and the regular 7027, if I'm not wrong, 30W. Is the new Tungsol 7027A a tube with the same plate dissipation of 35W?? I'm not able to find the specs for the Tungsol 7027A.
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The Tung Sol tube has a plate dissipation rating of 35W according to my IEM data sheet.
 
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#69
Sunnampeg said:
True, it makes sense, I will try to fit 6550s at the next retubing. I've heard that the 7581As are cleaner, but 6550s pull outa bit more low end, they could have said me a lie, but probably they did not, output tubes can change a bit the EQ of your amp..for instance, the Sunn 2000s with the 6550 has more distortion and a little less low end with the KT88 ahs more low end and less drive more headroom, almost completely clean
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Can anyone say "Zombie?" My last post on this thread was 19 years ago. Are you looking for clean, or are you looking for color? I've got almost every flavor of octal power tube lying around, and still prefer 6550 for bass in the tube amps I've used or serviced.
 
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#70
mthoople said:
Can anyone say "Zombie?" My last post on this thread was 19 years ago. Are you looking for clean, or are you looking for color? I've got almost every flavor of octal power tube lying around, and still prefer 6550 for bass in the tube amps I've used or serviced.
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hi i think that the 6L6 for bass lacks aggressive low end, or even better, it is soft low end , and not enough headroom, and smaller sound stage, now i ve never tried the 7581a or the 6550 on the v4b ,what i need is little more low end little bigger soundstage presence and a couple of notches of clean volume, but the amp is on the tech bench he ll pull out the almost new 6550s from my Sunn2000s put it in the v4b with cold bias i think, and put some new JJ kt88 in the Sunn2000s
 
#71
Sunnampeg said:
,what i need is little more low end little bigger soundstage presence and a couple of notches of clean volume
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IMHO the way to achieve these goals is with an SVT.

The power supply and transformers in the V4b are not set up to fully leverage the higher capacity of 6550 tubes. Running 6550s may make a small difference to the tone and OD characteristics, but it will most likely be subtle. It's possible you may get some extra powerl, but I would expect < 1dB of volume.
 
#72
Hi, yes, I know, in fact, I own an Svt vintage reissue 2007, but what I want from the V4b is just the same amplitude, a little more low end, and 1 or 2 notches of headroom. i still want the v4b grind now it start to break up at 11;30 IF could start 12:30 or 13;00 o'clock I'm fine, or also just a litle more low end i would be happy, i also like it like it is but i want to try to improve in little details, i own the head from few years, i only want to try those( famous)mods, i m sure there will be very little change, and of course the SVT is the SVT, in terms of power probably gain 10 watts, which won`t make difference, anyway i m curious to try , i may prefer it with 6550
 
#73
Sunnampeg said:
Hi, yes, I know, in fact, I own an Svt vintage reissue 2007, but what I want from the V4b is just the same amplitude, a little more low end, and 1 or 2 notches of headroom. i still want the v4b grind now it start to break up at 11;30 IF could start 12:30 or 13;00 o'clock I'm fine, or also just a litle more low end i would be happy, i also like it like it is but i want to try to improve in little details, i own the head from few years, i only want to try those( famous)mods, i m sure there will be very little change, and of course the SVT is the SVT, in terms of power probably gain 10 watts, which won`t make difference, anyway i m curious to try , i may prefer it with 6550
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One difference between the voicing of the V4B and SVT is the SVT has a gentle broadband boost centered around 400hz. The V4B is closer to flat.

I don't have any problem with your experiment. In fact I recently replaced a sextet of EL34B in one of my Sadowsky SA200s with KT88. The change in tone was so subtle that I can't really say for sure how it changed. I don't have any way of measuring the power and distortion, but my perception is the amp may have been slightly louder with EL34B.

If your are value conscious, the level of extra performance you will get from 6550 will be hard to justify. A quad of 6L6GC is about $114 vs $240 for a quad of 6550. The 6550s may sound slightly different. Whether they sound better or worse in up to you.

Good luck and let us know how it turns out.
 
#74
Wasnex said:
One difference between the voicing of the V4B and SVT is the SVT has a gentle broadband boost centered around 400hz. The V4B is closer to flat.

I don't have any problem with your experiment. In fact I recently replaced a sextet of EL34B in one of my Sadowsky SA200s with KT88. The change in tone was so subtle that I can't really say for sure how it changed. I don't have any way of measuring the power and distortion, but my perception is the amp may have been slightly louder with EL34B.

If your are value conscious, the level of extra performance you will get from 6550 will be hard to justify. A quad of 6L6GC is about $114 vs $240 for a quad of 6550. The 6550s may sound slightly different. Whether they sound better or worse in up to you.

Good luck and let us know how it turns out.
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I will let you know very soon, 10 days max, and the v4b will be back home. Just noticed Sunn2000s with kt88 JJ has slightly lower and a bit more low end, which is good, but it heats up quicker than before, but my tech, Andy, says it is o,k he repaired amps for Entwiste, Page, Gilmour.
 
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#75
agedhorse said:
The Tung Sol tube has a plate dissipation rating of 35W according to my IEM data sheet.
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so experiment done and i likethe sound of the 6550s they are more aggressive a nd bold slight;y bigger sounding, but the only disappointment is i was expecting more headroom compared to the 6L6 Tad and instead i ve got LESS headroom which i almost do not believe what i hear, but this is the truth,, weird but this is my experience, could be the bieas to high ..the tech regulated in front of me ..also since i ve not the original power transformers, because i m in the UK, i ve to replace with a v4b PT replacement, that is slightly larger,, so very very little space between the PT and the 6550s,, plus al lot of heat.. I'm sadly surprised with the (less headroom outcome) i think I'm going to put 7581A or simply 6L6 TAD for the moment. I've to say 6550s Sovtek are not famous for clean headroom.
 
#76
Sunnampeg said:
so experiment done and i likethe sound of the 6550s they are more aggressive a nd bold slight;y bigger sounding, but the only disappointment is i was expecting more headroom compared to the 6L6 Tad and instead i ve got LESS headroom which i almost do not believe what i hear, but this is the truth,, weird but this is my experience, could be the bieas to high ..the tech regulated in front of me ..also since i ve not the original power transformers, because i m in the UK, i ve to replace with a v4b PT replacement, that is slightly larger,, so very very little space between the PT and the 6550s,, plus al lot of heat.. I'm sadly surprised with the (less headroom outcome) i think I'm going to put 7581A or simply 6L6 TAD for the moment. I've to say 6550s Sovtek are not famous for clean headroom.
Click to expand...

The vintage V4B performs well with 6550’s set at a cooler bias. Have the tech set the power tube bias at 55-60% max plate dissipation rather than the typical 70%. Try the amp and see how it sounds.
 
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