The 6550 Experience

His guitar slung across his back, his dusty boots is his cadillac.

Moderators: VelvetGeorge, BUG

daveweyer
Senior Member
Posts: 631
Joined: Wed Oct 29, 2014 9:36 pm
Just the numbers in order: 13492

Re: The 6550 Experience

Post by daveweyer » Fri Oct 05, 2018 1:46 am

I liked them.

frenchie
Senior Member
Posts: 1492
Joined: Fri Oct 26, 2007 7:50 am
Location: france

Re: The 6550 Experience

Post by frenchie » Fri Oct 05, 2018 7:38 am

daveweyer wrote:
Thu Oct 04, 2018 9:49 pm
Would you mind if I added a comment?
I can sure see the point of keeping the videos "down home" so they don't look too corporate, and I can sure hear that the amp doesn't sound like Star Spangled Banner, but if Bill wanted that sound, wouldn't he have used a modded fuzzface and a univibe? Isn't it sort of an apples to oranges comparison?
Anyway, I thought that the sound everyone was looking for was BOG. Is that right?
We spend countless months arguing about the REAL specs of the Woodstock amps to finally end up with a hard fought for consensus , and this amp layout is supposed to be the result of all that research made on the back of countless insults , hypocrisy , frustration , and careful laying out ..... It obviously includes your work during the 60s Dave , and the work WE did here in order to brush away with factual proofs any attempt by nasty internet dwellers to make you pass for the occasional lunatic trying to pump up his old ego by pulling out unbacked grandiose claims on forums ....
Bill wants to make money on all of that work , fine in my book , but I think at least he could go through the IMMENSE trouble of exposing it to the world as it is , the Marshall plexi with the REAL Woodstock specs , not a badly tweaked divided by 13 combo played in with mushy Strat pickups and clumsy fingers ...
Or else we could buy a /13 combo and be totally fine with it .....

would you sell a mesa rectifier playing Larry Carlton type jazz on it ?
It may sound relatively good , but it's not the point ...
i may be stupid but when searching for the demo of a mesa amp , the question that is in my head is " will it have the attack and high gain grain I search so hard for ? " , doubt a Larry Carlton oriented demo could bring me that answer clearer than a day without clouds .....

For as long as I don't have a demo of bill's amp full out with proper effects and playing , I won't be able to respond to the question of "do that ultra expensive bespoke amp will actually bring my sound closer to the savage attack and dynamics of voodoo Chile at Woodstock ? closer to a stock plexi ? hmmm ...."
Can't respond to that question right now , because , well the amp is played with sooo much....you know .... "personal taste" ....

The only thing we established with 100% certainty is that the Woodstock amps had 6550 tubes in them , hence the higher B+ voltage and the need for a 45/100 transformer ....
There are NO pictures of the back of BOG's amps so we can't say shit for those gigs , except that the bar stool monitor is a traynor Yorkville YSM1 that Jimi probably fed into the mixer console to refeed it to the amps through the mics in order to tweak his feedback level on the fly from afar , like I would have personally done if my WHOLE career had been oriented around playing with feedback and I had finally been able to find in stores those new weird slanted monitors with a volume knob on the back of them , and said to myself "hmm this feedback shit is pretty wild with 4X4X12 cabinets , why not trying to do that with that puppy alone , hmm I feel I'm onto something "

User avatar
bill bokey
Senior Member
Posts: 471
Joined: Sun Jan 02, 2011 2:54 pm
Just the numbers in order: 13492
Location: France
Contact:

Re: The 6550 Experience

Post by bill bokey » Fri Oct 05, 2018 8:13 am

Just to make things clear, I had nothing to do with the making of that video. I would not have played that strat and I would not have played it that way. When I played the amp in my tiny workshop, it sounded miles better and closer to the real deal than any other Super Lead I modded to Dave's specs.
I asked Tone Factory to make a video of my Mystery Amp and they asked if they could demo the 'West Coast' as well. I was worried it might not sound as good as the clips and videos I previously posted and unfortunately it does not. But I can no longer make videos so it was the only option I had.
A few days ago I demoed the amp to a customer and the tone was spot on. Then he played it with his strats and it sounded very different. As he ordered a 'West Coast' SL, I might have the opportunity to record a few clips of the same amp before the end of the year.

daveweyer
Senior Member
Posts: 631
Joined: Wed Oct 29, 2014 9:36 pm
Just the numbers in order: 13492

Re: The 6550 Experience

Post by daveweyer » Fri Oct 05, 2018 2:42 pm

Wow, great discussion. Frenchie I think I get your point, and it looks like Bill does too. it might make sense to Axman as well, since he would also have done the demos differently. It looks as though none of us really know what Bill's amp sounds like because we couldn't tell from the video. I had a feeling there was more to it than the video let on, and those two clips that Axman offered showed a very sweet sounding amp, played mostly clean at lower volumes, something that it would have been nice to hear Bill's amp doing, or trying to do.
And maybe Axman is right, that the amp has too much high end, and should have had the tone caps he listed. Like it was in the West Coast days, we always listened to the amps to decide if the shared (or non shared) cathode should have a tiny bypass cap (technically the shared cathode should act somewhat like a bypassed cathode), or the the bright cap should be smaller, or the input cap to the PI should be smaller. I swear, every amp sounded different, even the same model with consecutive serial numbers.
You just have to listen and make your adjustments according to what you think the ultimate sound should be.
Gotta admit that the clips Axman gave us were pretty sweet sounding, right guitar, right amp, right speakers, right licks for the intended style.
Now as far as that re-amp business goes, it boils down to believers and non believers, since we don't have the visual proof like we got with that article showing the original Hendrix amp with the 6550s I put in there and our sticker on the back.
But life isn't over yet, and we still may get that proof. (I know where an original Hendrix Strat is with that notch in the fret, and one day I hope to get pictures to post here)
One more little thing, the Woodstock amps were the BOG amps, after one more trip to West Coast for "service".

revolver1
Senior Member
Posts: 392
Joined: Thu Jul 28, 2011 1:37 am
Just the numbers in order: 7

Re: The 6550 Experience

Post by revolver1 » Sat Oct 06, 2018 5:07 am

I still think it's a beautifully built amp and although the clip didn't sound exactly like BOG there's still an undeniable Hendrixy quality to it. 6550's all the way.

There's so many variables as discussed before as in what gauge strings, how the guitar is set up, pickup heights, vol and tone on the guitar. It's not the Fillmore and it's not recorded by a sound engineer at the top of his game. Mixed speakers, at least two amps possibly one EL34 one 6550, theres no band or crowd the variables are endless but through all the clips there's definitely that thing to the sound that I've only heard on the records.

Hats off to Dave for sharing.

Just to clarifie did I miss something? Dave i dont recall you saying to put a bright cap on both volume pots of a shared cathode amp? Or did i miss that one?

Also wouldn't the affect of the cap be minimal with the volume on 7?

On another note, picked up a pair of RCA branded Tungsol the other week and the O.T I ordered from Brian has turned up so I'm nearly there.

Since I'm going to have to adjust the bias feed resistor what voltage should I be shooting for? Bearing in mind it's a 50watt.

frenchie
Senior Member
Posts: 1492
Joined: Fri Oct 26, 2007 7:50 am
Location: france

Re: The 6550 Experience

Post by frenchie » Sat Oct 06, 2018 7:31 am

daveweyer wrote:
Fri Oct 05, 2018 2:42 pm
Wow, great discussion. Frenchie I think I get your point, and it looks like Bill does too. it might make sense to Axman as well, since he would also have done the demos differently. It looks as though none of us really know what Bill's amp sounds like because we couldn't tell from the video. I had a feeling there was more to it than the video let on, and those two clips that Axman offered showed a very sweet sounding amp, played mostly clean at lower volumes, something that it would have been nice to hear Bill's amp doing, or trying to do.
And maybe Axman is right, that the amp has too much high end, and should have had the tone caps he listed. Like it was in the West Coast days, we always listened to the amps to decide if the shared (or non shared) cathode should have a tiny bypass cap (technically the shared cathode should act somewhat like a bypassed cathode), or the the bright cap should be smaller, or the input cap to the PI should be smaller. I swear, every amp sounded different, even the same model with consecutive serial numbers.
You just have to listen and make your adjustments according to what you think the ultimate sound should be.
Gotta admit that the clips Axman gave us were pretty sweet sounding, right guitar, right amp, right speakers, right licks for the intended style.
Now as far as that re-amp business goes, it boils down to believers and non believers, since we don't have the visual proof like we got with that article showing the original Hendrix amp with the 6550s I put in there and our sticker on the back.
But life isn't over yet, and we still may get that proof. (I know where an original Hendrix Strat is with that notch in the fret, and one day I hope to get pictures to post here)
One more little thing, the Woodstock amps were the BOG amps, after one more trip to West Coast for "service".

By the way .....like with all things Jimi Hendrix tied , when historically accurate elements are actually found and proven , shit gets WEIRD , the old website page of trainer yorkville that was depicting the date of production and whole data sheet about the 1969 trainer Yorkville YSM1 monitor that Jimi Hendrix used during the Fillmore east concerts on the bar stool , has been put down ( yes the page I linked to in the old thread of 8 years ago about Jimi Hendrix and his spare use of jbl speakers ) .....
Impossible to reach it now , and wayback machine hasn't recorded that page ....
We're not FUCKED per say because lots of metro amp members actually went to see that page at the time we discussed that issue , and posted that indeed that that page CLEARLY showed the monitor , so I guess I'm totally out of the woods concerning any possibility of fucktards attempting to say I'm lying and that that monitor wasn't a trainer Yorkville ysm1 , but you guys should really contact both the CIA and the Hendrix estate to calm them down just a notch about trying to bury historical elements about his tone :lol: ..... for fucks sake why do they do that shit ? insanity ... we weren't even trying to post a receipt of mike Jeffries buying 8 boxes off barbiturates dated to the morning of the 18th of september 1970 ...why do they do that ?

User avatar
axeman
Senior Member
Posts: 2416
Joined: Wed Apr 02, 2008 1:21 pm
Just the numbers in order: 7
Location: Los Angeles
Contact:

Re: The 6550 Experience

Post by axeman » Sat Oct 06, 2018 12:19 pm

It’s not brain surgery, the 4700pf cap does not go well with a shared cathode amp, also replace the cathode capacitor. Not every Marshall amp was great sounding right out of the barn. 3 guys pumped them out with urgency and sacrificed quality for time. If it’s built correctly and the components are good, it’s going to sound good. Check out this amp, it’s my first build and I’m using orange drop caps with a tube screamer.

https://m.youtube.com/watch?v=Man1Jm50GTc

daveweyer
Senior Member
Posts: 631
Joined: Wed Oct 29, 2014 9:36 pm
Just the numbers in order: 13492

Re: The 6550 Experience

Post by daveweyer » Thu Oct 11, 2018 11:04 pm

I expected everyone would be all over this. Anyway, I liked it. Nice first build.

User avatar
axeman
Senior Member
Posts: 2416
Joined: Wed Apr 02, 2008 1:21 pm
Just the numbers in order: 7
Location: Los Angeles
Contact:

Re: The 6550 Experience

Post by axeman » Fri Oct 12, 2018 1:58 am

Thanks it haves mustards now and sounds really nice

revolver1
Senior Member
Posts: 392
Joined: Thu Jul 28, 2011 1:37 am
Just the numbers in order: 7

Re: The 6550 Experience

Post by revolver1 » Fri Oct 26, 2018 8:57 am

Chaps, I could use some advice... Bear in mind this is a 50w 1987.

I went with a Classic Tone PT that give's a guidance of 456vdc on the plates with SS rectification. I have wall voltage of 230va.c. but the PT only has 220v and 240v primary taps. I had it on the 220v tap but yesterday I re-wired it all to the 240v tap.

With no tubes installed my voltages are;

Heaters: 6.52vac. I have some resistors coming to get this down to 6.3vac so no prob.

The rectifier is kicking out 474vdc but I tested it again this morning and was seeing 487vdc, (fluctuations in wall voltage I think).

The thing is the build instructions say to get the plate voltage measurement at the HT fuse and I'm seeing 487vdc. The PT is speced for 456vdc so surely if I'm using 230v on the 240v tap I should see less than 456vdc?

Does it make a difference, will the voltage come down when the valves are installed?

And my last question my bias range is -58.5vdc to -39.9vdc. Will -58.5vdc be cool enough when I first install the tubes?

I have a 150k on the bias input and a 47k on the bias range resistor. Should I change the range resistor to achieve a higher negative figure? With the high voltage I'm a little nervous of smoking the valves right off.

I have a set of NOS RCA branded Tungsol 6550's but I'm going to use Tungsol new sensor for testing rather than risking blowing the NOS set but obviously they are not as robust.

revolver1
Senior Member
Posts: 392
Joined: Thu Jul 28, 2011 1:37 am
Just the numbers in order: 7

Re: The 6550 Experience

Post by revolver1 » Fri Oct 26, 2018 2:05 pm

OK, so I've replaced the 47k bias range resistor and now I'm seeing -66vdc to -48vdc for the bias range. Do you think this will be enough to get to 25ma?

daveweyer
Senior Member
Posts: 631
Joined: Wed Oct 29, 2014 9:36 pm
Just the numbers in order: 13492

Re: The 6550 Experience

Post by daveweyer » Fri Oct 26, 2018 2:10 pm

The voltage will come down when the tubes are installed. You won't need heater resistors because the voltage will be on the low side. Your B+ voltage will also be on the low side. With a bias voltage of -56 volts you will have fairly low current in the tubes, but it is a good idea to use replaceable tubes to start up, just in case something goes wrong. You have about 2 minutes to disconnect the power if the 6550s are running at zero bias, they should be turning red by then.
I ran Jimi's tubes at 15 to 18 ma, just enough to keep them conducting through the tail of sustain.

revolver1
Senior Member
Posts: 392
Joined: Thu Jul 28, 2011 1:37 am
Just the numbers in order: 7

Re: The 6550 Experience

Post by revolver1 » Sat Oct 27, 2018 4:29 am

Thanks Dave, Today is the day then.

revolver1
Senior Member
Posts: 392
Joined: Thu Jul 28, 2011 1:37 am
Just the numbers in order: 7

Re: The 6550 Experience

Post by revolver1 » Sun Oct 28, 2018 4:08 am

Well that was a day filled with brown trouser moments :lol: but it's getting there, I could say it was quite sucsessfull.

I should probably try post a voltage chart but I'd need to get on the computer for that. Some voltages were higher and some lower, quite a variant but I'm not panicked.

So A.C. wall voltage was 233Vac there was a bit of fluctuation but that's just how the power is in London.

Heaters; (with all tubes in 2x JJ Gold pin 1x Millard Ecc81 2X New Sensor Tungsol 6550)
At V5 3.22Vac at V1 3.19Vac on each side. The extra resistors ive been waiting on turned up yesterday eavening so i will have a play around with it today and see if I can get it closer to 3.15Vac.

Plate Voltage 466Vdc. This has seriously shocked me since its 230vac on the 240v tap but hey I'm not complaining.

And with the 56k bias range resistor in place the lowest bias I could get to was 31.2mv and 32.2mv on the second 6550. Today I'm going to try an 82k in there and see if I can get down to 25ma.

On the plus side no red plating and nothing went bang :champ:

revolver1
Senior Member
Posts: 392
Joined: Thu Jul 28, 2011 1:37 am
Just the numbers in order: 7

Re: The 6550 Experience

Post by revolver1 » Mon Oct 29, 2018 5:13 am

It's getting there I think...... Definitely learning a lot here.

There was quite a bit of fluctuation in the wall voltage so I had to do a lot of observation.

For any one trying to reduce heater voltage (with limited experience like myself) I tried doing it without tubes installed thinking this was the best way to go about it. I don't know why but it made no difference until the tubes were installed. Go with 5watt minimum for the resistors. Draw should be about 3.5watts but they get really hot. Also if you can achieve the right resistance put the resistors in parallel for increased power handling but note resistors in parallel the overall resistance will be lowered but this can come in handy.

I went round the houses with the heater voltage thing but in the end It looks like I don't really need to lower the voltage at all so I just bridged out the terminals I took the heater wires to.

So with the wall voltage at 231vac I was seeing 3.16vac on either side of V5 and 6.35vac across V5. So it all seems about right.

The voltage was swinging about a bit but on the plates I was seeing between 460Vdc and 466vdc pin 3 of V4 and V5. This quite surprised me like I keep saying the PT is wired to the 240v tap running on 230v. Still it's giving me the higher plate voltage so no complaints.

With a plate voltage of 465Vdc on the plates at V5 I was seeing 464vdc on pin 6 and 457vdc on pin 4 on the other side of the 2k2 10watt resistor. The input to the screens seemed consistently 1vdc lower than the plates and 8vdc lower on pin 4. Does this sound right? This is the only bit that concerns me, unless I misunderstand I was expecting to see a bigger difference between plate and screen?

The kit voltage chart showers 5vdc difference between plate and screen and I'm only seeing 8vdc difference with the 2k2, is there not supposed to be a bigger safety margin?

I was seeing 1.5ma difference between the tubes, they were about .5ma closer when the bias was hotter.

I went with 150k bias input resistor and had to go to an 82k bias range resistor. The range starts at 31ma and gets to 25ma less than a quarter turn back. So I had it sitting about 25.5ma on V5 and 27.0ma on V4.

So it seems OK? High plate voltage, heaters are OK and 25ma bias. The only thing I'm not sure is OK are the plate and screen voltage? I'll post a pic later today. :thumbsup:

Post Reply