Preamp Tubes? - Who, What, When, Where, Why, and How?

[guitarmartin416]

OK, so I tried the amp at rehersal....
Desperately need power tubes (volumes lacks as amp warms up, and gettin strange harmonics too) Marty you said my amp design is basically the same as a 1987 correct? I have removed the tremelo wire from the PCB but that had no effect on the normal channel ( was suppose to ) I think I'm gonna go with el34's instead of the crap 5881's in it. I believe I only need to swap the screen resistors from 470 5w to 1k 5w (correct me if I'm wrong)
So I really cant tell if my pre amp tubes sound good or not. They sound WAY better than they did, but in a band mix it sounded stail. No smooth drive like I was goin for, and I've heard tale that I should swap the Filter caps from 50x50uf to 32x32uf and the other to 16x16uf ( how does this effect tone?)
Other than that, now you have explained the gain stage line up on my amp, what is a good order to start my pre tubes? I'm not real straight on the mixed gain stage thing, you're saying V1 V2 and V3 are all integrated gain stage?
I only ran a balanced tube in the PI cause sombody told me I should....what is the difference?

....... sorry for bein a pain in the a@#!!!!

 

[guitarmartin416]

Where's my guru's today????

 

[core]

6100LM Update

Hi guys, just wanted to give an update on the 6100LM. Got it back from the shop and it seems to be in great working order and sounds great.

He rebiased it and I can now see the orange glow a lot better with a ting of blue. He didn't have to change the power tubes as the bias was all it needed. He changed a couple preamp tubes and that was all for that. He resoldered a few connections and especially around a certain chip that this amp has. What it does I forget, I think it has to do with the XLR out which now is nearly silent through my recording gear. Before it was very loud and obnoxious.

The only problem it still has is a crackle here and there which I can live with except when recording with a mic I would need to eliminate that. But maybe it will add to it lol!

Now that I know what the amp is about and has been checked out I may start to delve into older preamp tube brands as you guys are doing. Starting with Marty's suggestions for putting a 7025 in V1 and going from there.

I have a question and maybe someone can help. When going from the XLR into the recording interface, power amp muted on this amp is this cutting out any additional gain stages or circuitry that adds to the gain? What I hear in the monitors is a very low gain tone quite unlike what comes through the cab. Is this normal or should I be hearing the whole tone as I would through a cab?

The only reason is I do late night recordings when my wife is asleep and I want a similar tone. If not I can always add some tone in cubase. It's not bad actually.

 

[MartyStrat54]

OK, so I tried the amp at rehersal....
Desperately need power tubes (volumes lacks as amp warms up, and gettin strange harmonics too) Marty you said my amp design is basically the same as a 1987 correct? I have removed the tremelo wire from the PCB but that had no effect on the normal channel ( was suppose to ) I think I'm gonna go with el34's instead of the crap 5881's in it. I believe I only need to swap the screen resistors from 470 5w to 1k 5w (correct me if I'm wrong)
So I really cant tell if my pre amp tubes sound good or not. They sound WAY better than they did, but in a band mix it sounded stail. No smooth drive like I was goin for, and I've heard tale that I should swap the Filter caps from 50x50uf to 32x32uf and the other to 16x16uf ( how does this effect tone?)
Other than that, now you have explained the gain stage line up on my amp, what is a good order to start my pre tubes? I'm not real straight on the mixed gain stage thing, you're saying V1 V2 and V3 are all integrated gain stage?
I only ran a balanced tube in the PI cause sombody told me I should....what is the difference?

....... sorry for bein a pain in the a@#!!!!

Have you thought about replacing the tubes with KT66's? That's what the original's ran. I've been dying to try those. I finally bought and amp that will run those and I think I will get a pair of Gold Lions to try in it. It would take a little bit of modding to get the amp to run EL34's. Swapping the screen resistors is one thing, but you have to alter the bias circuit to allow the adjusting of the 34's. Also, 6L6's use 900mA per tube for the heater and 34's use 1500mA per tube. You have to consider whether the power tranny is stout enough to supply the 6.3V to the preamp and power tubes.

As I said, you have a lot of tubes, but you do not know what you have. It's a crap shoot and all you can do is try some and hope you are happy with the combination. I would put your best tube in V1 and then the best RCA Black Plate in V2. The PI (V3) does not have to be balanced. The amps circuits are not balanced, therefore you do not need a balanced tube. Some guys like a highly lopsided PI tube as it generates a complex harmonic content. Something like a 12DW7 is popular with harmonica players. It is a 12AX7 on one triode (100 gain factor) and a 12AU7 on the other triode (17 gain factor). Now that's lopsided.

Changing your power filters will alter the sound in what is best described as tightness and looseness. Going from 50's to 32's will induce a little more ripple in the power supply and give the amp a looser sound.

I would get rid of the 5881's as you don't know how old they are and they could be causing 70 per cent of your crappy sound. I would suggest the KT66's. If you can't spring for the Gold Lions, there are two other companies that make them. Also, the bias setting is really important on this amp. You don't want to run this amp cold or it will sound like shit.

Post up what you plan to do.

 

[guitarmartin416]

I'm thinkin I may try the KT66 just for the simplicity of it, do I need to change the resistors or anything or are they direct replacement? I'm goin for that bigger smooth drive and clean (you think those will do that?), I don't want to use any pedals if I dont have to.

By the way, I read the post on Wilder's BB Blackface mod...... that was some sick shit!!!!!! If only I had the money! P2P is the way I would rather go, thats what all my Fenders are. I get more nervous as I read about the OT on these amps too.
I'm gonna test all my pre tubes, if you know anybody lookin for some, let me know. I could use the cash or I'm always down to barter for other stuff.

 

[guitarmartin416]

Re: 6100LM Update

Hi guys, just wanted to give an update on the 6100LM. Got it back from the shop and it seems to be in great working order and sounds great.

He rebiased it and I can now see the orange glow a lot better with a ting of blue. He didn't have to change the power tubes as the bias was all it needed. He changed a couple preamp tubes and that was all for that. He resoldered a few connections and especially around a certain chip that this amp has. What it does I forget, I think it has to do with the XLR out which now is nearly silent through my recording gear. Before it was very loud and obnoxious.

The only problem it still has is a crackle here and there which I can live with except when recording with a mic I would need to eliminate that. But maybe it will add to it lol!


Now that I know what the amp is about and has been checked out I may start to delve into older preamp tube brands as you guys are doing. Starting with Marty's suggestions for putting a 7025 in V1 and going from there.

I have a question and maybe someone can help. When going from the XLR into the recording interface, power amp muted on this amp is this cutting out any additional gain stages or circuitry that adds to the gain? What I hear in the monitors is a very low gain tone quite unlike what comes through the cab. Is this normal or should I be hearing the whole tone as I would through a cab?

The only reason is I do late night recordings when my wife is asleep and I want a similar tone. If not I can always add some tone in cubase. It's not bad actually.

when running a tube amp in particular, you have 3 main factors in your gain....
Power Tubes
Pre amp Tubes
Speakers
......all have a huge impact on your tone, muting your amp takes things out of the "tone equation" speaker break up is huge!to really get a good sounding gain, I'm afraid you will have to wait till decent hours of the day....or piss off the neighbors!!!!

hope that helps a bit.

 

[RiverRatt]

You have any Brimars for sale/trade? I'd like to try one.

 

[MartyStrat54]

Yeah Jon went with the Gold Lion KT66's and he said they smoked in that amp. They are a direct drop in, because that's what should have been in the amp instead of the 5881. Someone changed them out to the 5881's.

Just like a 6CA7 is the American version of an EL34, a KT66 is the British version of a 6L6. Although these tubes have the same electronic specifications, they all sound different. A KT66 to me is a superior 6L6 with it's own tonal characteristics. I think you will like the way they sound.

 

[guitarmartin416]

Yeah Jon went with the Gold Lion KT66's and he said they smoked in that amp. They are a direct drop in, because that's what should have been in the amp instead of the 5881. Someone changed them out to the 5881's.

Just like a 6CA7 is the American version of an EL34, a KT66 is the British version of a 6L6. Although these tubes have the same electronic specifications, they all sound different. A KT66 to me is a superior 6L6 with it's own tonal characteristics. I think you will like the way they sound.

Thats what I hear.... thanks for the reassurance! too bad I live so far, I'd love to do some comparison things with you...I'm still in the learning stage! lol

 

[MartyStrat54]

Brought this over to have another look at it.

 

[guitarmartin416]

You have any Brimars for sale/trade? I'd like to try one.

so far, I have a shitload of '58 RCA blackplates, some '64 Telefunkin, and haven't checked the codes on the miscellaneous tubes yet....all from vintage organs and stuff. I'm sure nothing after '67 I'll let you know.

.....now if I can find some decent KT66's

 

[guitarmartin416]

P.S. I love this forum.....why did I wait so long?

 

[MartyStrat54]

Okay. After looking at this I will say a 7025 will give you the best Clean channel and it is independent of any other preamp tubes. If you can't find a good NOS RCA 7025, then I will say try a TAD7025. V2B and V6A and B are your Crunch channel. This is the primary gain tube for both the Crunch and the Lead channels. This is a very important tube. I would strongly recommend an NOS tub in this slot. If not, then a Tung-Sol. V3, V4, V5 and V6 can be either Tung-Sol's or Mullard RI's.

Personally, if it were mine. I'd run an RCA 7025 in V1 and then a Telefunken in V2 (as this is the flavor tube for both the Crunch and Lead channels). V3 and V6 would be Raytheon Black Plates and V4 and V5 would be either Raytheon Gray Plates, Matsushita Slant Getters or GE Short Black Plates.

 

[guitarmartin416]

Yeah Jon went with the Gold Lion KT66's and he said they smoked in that amp. They are a direct drop in, because that's what should have been in the amp instead of the 5881. Someone changed them out to the 5881's.

Just like a 6CA7 is the American version of an EL34, a KT66 is the British version of a 6L6. Although these tubes have the same electronic specifications, they all sound different. A KT66 to me is a superior 6L6 with it's own tonal characteristics. I think you will like the way they sound.

will the KT66's fit? I have the thinner cab on my BB

 

[MartyStrat54]

Well it's the tube that came stock in it. Give the Tube Depot or Tube Store a buzz and ask them. I'm just saying that the Bluesbreaker sound was the KT66's.

 

[guitarmartin416]

Well it's the tube that came stock in it. Give the Tube Depot or Tube Store a buzz and ask them. I'm just saying that the Bluesbreaker sound was the KT66's.

The original BB had a cab of 10.5", mine is only 9 or so. hope thats enough

 

[core]

Re: 6100LM Update

when running a tube amp in particular, you have 3 main factors in your gain....
Power Tubes
Pre amp Tubes
Speakers
......all have a huge impact on your tone, muting your amp takes things out of the "tone equation" speaker break up is huge!to really get a good sounding gain, I'm afraid you will have to wait till decent hours of the day....or piss off the neighbors!!!!

hope that helps a bit.

Thanks, yeah I kinda figured that. It'll do for scratch tracks and when I'm ready to go for it I'll record the good stuff mic'd up.

 

[core]

Okay. After looking at this I will say a 7025 will give you the best Clean channel and it is independent of any other preamp tubes. If you can't find a good NOS RCA 7025, then I will say try a TAD7025. V2B and V6A and B are your Crunch channel. This is the primary gain tube for both the Crunch and the Lead channels. This is a very important tube. I would strongly recommend an NOS tub in this slot. If not, then a Tung-Sol. V3, V4, V5 and V6 can be either Tung-Sol's or Mullard RI's.

Personally, if it were mine. I'd run an RCA 7025 in V1 and then a Telefunken in V2 (as this is the flavor tube for both the Crunch and Lead channels). V3 and V6 would be Raytheon Black Plates and V4 and V5 would be either Raytheon Gray Plates, Matsushita Slant Getters or GE Short Black Plates.

Ok great, I will take those into consideration although I'm not quite understanding the V6A and B. This is one tube correct? And I'm assuming V2 is split into two for CH2 and CH3?

Luckily they are not in immediate need anywhere so I can spend some time to hunt down some NOS ones without dropping a lot of cash all at once. This gives me a lot to go on. Thanks again!

 

[RiverRatt]

Personally, if it were mine. I'd run an RCA 7025 in V1 and then a Telefunken in V2 (as this is the flavor tube for both the Crunch and Lead channels). V3 and V6 would be Raytheon Black Plates and V4 and V5 would be either Raytheon Gray Plates, Matsushita Slant Getters or GE Short Black Plates.

You must be liking those Matsushitas! Having any luck finding them? I've gotten two really good deals on them. Under $50 for five tubes, shipping and all. They are an incredible value right now (although there is one dude asking $115 for a pair). There's a guy on ebay who has 10 MIJ Raytheons in one lot, but I don't think they are Matsushita.

 

[LuredMaul]

I joined this forum based on reading this thread.
On that note Thanks to all who recommended the Tunsol-Re-issue and Mullard 12ax7's in V1 & V2 of myy TSL100.
I now have almost a 3D effect in the mids rather than overly compressed JJ soup.