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Ampeg SVT Blueline Club, 68 to early 70's.

#161
Thank you for the tips, guys! Warm soapy water and a gentle touch for sure. It's most likely years of nicotine stains. At least it doesn't smell.

I was a bit surprised that it has a set of GE6550s in it. Of course there is no telling how much life they have in them. When the guy at the store had it apart he looked at the circuit and said that there weren't any funky or hack repairs. But for the life of me I can't figure out why somebody cut the two round holes in the back grill.

I'm a happy boy!;)
 
#163
Jerry J said:
Thank you for the tips, guys! Warm soapy water and a gentle touch for sure. It's most likely years of nicotine stains. At least it doesn't smell.

I was a bit surprised that it has a set of GE6550s in it. Of course there is no telling how much life they have in them. When the guy at the store had it apart he looked at the circuit and said that there weren't any funky or hack repairs. But for the life of me I can't figure out why somebody cut the two round holes in the back grill.
Click to expand...

IMO, they probably had two small fans in those holes in an attempt to make it run cooler, but i've found that when they're biased properly, it's unnecessary.
 
#166
GravyMan said:
Hi, Does anyone know if the 70' blueline polarity switches were originally black or were they chrome? And my amp has the 6146b tubes can I use 6146w's.Thanks
Click to expand...

I'm not completely sure it's original, but the polarity switch on mine is black. I'm running Phillips 6146W tubes in mine and it works great. I've heard it depends on the specific 6146W you use.
 
#167
I've seen some variation in the switch used in the earliest model, which is what you have if you are running 6146 power tubes. I've seen black flat actuators as well as black small bat types. I believe that the flat black was used originally, then they migrated to the small bat black actuator.

You can use the 6146W, which is a ruggedized military version in place of the 6146B. It is a good choice.


small black bat:
[Invalid or Expired Link Removed]

flat black:
[Invalid or Expired Link Removed]

​
 
#168
If I had to do it over again, I'd get 6146w's. My tube guy tried to talk me into them, but I had some silly romantic notion about restoring my Blue Line with only parts that would have been available in 69, and the 6146w's came out a short time later. Not that I'm complaining about my GE 6146b's because they work just fine, but the 6146w's were a couple bucks cheaper and military grade, and I've long since abandoned the idea of using only parts available in 69. Impractical and a bit dumb in retrospect ;)
 
#173
I wouldn't be surprised if the KT88s sound different. In addition to the inherent differences of the tubes themselves, you also increase the mismatch between the OT transformer primary impedance and the "ideal" value for the tube since the SVT tranny's impedance is already higher than what is spec'd for 6550s, and the KT88s like an even lower primary impedance. The mismatch isn't necessarily a bad thing (especially considering the high plate and screen voltages when running 6550s [not an issue with the KT88s]) unless you are into HiFi; it just affects bandwidth, power output, and THD in various ways.
 
#175
Sure, I think it's a viable alternative and folks seem to have positive experiences from a tonal perspective. I also like the fact that it gives you some more margin with screen and plate voltages.
 
#176
Since we are talking tubes....I've read some really good things about the SED Winged =c= 6550 tubes.

I've been thinking that since Uncle Sam is being good to me on the tax return, that I should pick up a set (septet) as a backup.
So not really looking for a debate on which tubes are good but more a question on "what's happened to the SED 6550 tubes? it seems as though they are pretty popular review-wise. But nobody seems to have them.
 
#178
JGR said:
I wouldn't be surprised if the KT88s sound different. In addition to the inherent differences of the tubes themselves, you also increase the mismatch between the OT transformer primary impedance and the "ideal" value for the tube since the SVT tranny's impedance is already higher than what is spec'd for 6550s, and the KT88s like an even lower primary impedance. The mismatch isn't necessarily a bad thing (especially considering the high plate and screen voltages when running 6550s [not an issue with the KT88s]) unless you are into HiFi; it just affects bandwidth, power output, and THD in various ways.
Click to expand...

Are you saying that if I switch to 6550s that I would be able to get more clean headroom? I'm not sure if I'm misinterpreting what you're saying, but I'm thinking that KT88s are dirtier. I don't have a problem with the KT88s, but it starts breaking up around half way on the volume on the first channel, and the second channel is basically always dirty at any volume.

Anyone please chime in with some info

Also, I'm going to have the amp serviced soon.. is there anything specific I should have checked?

So far on my list is this:
-Clean pots/switches
-Replace all preamp tubes
-Check power tubes/possibly switch to 6550s
-Check EXT SPEAKER jack

amp runs fine with one cab at 4 ohms, but doesn't sound right when you plug in a second cab for a 2 ohm load

output sounds weak at low volumes
 
#179
The first channel on your amp sounds about right in comparison with others as far as breakup. That'll vary with the output of your bass, but generally it starts in the 11:00-noon area. The second channel sounds ka-flooey, though. It's a bright channel and has a low end rolloff so it should break up even later than channel 1.
 
#180
JimmyM said:
The first channel on your amp sounds about right in comparison with others as far as breakup. That'll vary with the output of your bass, but generally it starts in the 11:00-noon area. The second channel sounds ka-flooey, though. It's a bright channel and has a low end rolloff so it should break up even later than channel 1.
Click to expand...

My bass has about average output... I have a 73-74 Grabber, with the pickup wired straight to the jack, no volume/tone. I know this is off topic, but taking the pots out of the path made the bass sound so much better. The right channel definitely sounds brighter than the left channel, but it's extremely dirty. I'll probably have that checked out too.
 

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