Amp tinkerers and people who aren't afraid of 700 volts or so in here....

Moderators: Slowy, Capt. Black

User avatar
BY Cdog
#841467
It's time to cough up some coin for glass... any recommendations for getting the best out of the AB763? It's a Super reverb, so the complement will be 4x 12AX7, 2x 12AT7, 2x 6L6 and a GZ34 rectifier.

I put JJ's in my 18w (6V6) and am really happy with the sound, but that's Marshally not Fendery. Can't really afford to sniff corks here, but suggestions are welcome! :)

Need to order some this week so they land before the customs changes.
#841472
Cdog wrote:It's time to cough up some coin for glass... any recommendations for getting the best out of the AB763? It's a Super reverb, so the complement will be 4x 12AX7, 2x 12AT7, 2x 6L6 and a GZ34 rectifier.

I put JJ's in my 18w (6V6) and am really happy with the sound, but that's Marshally not Fendery. Can't really afford to sniff corks here, but suggestions are welcome! :)

Need to order some this week so they land before the customs changes.


What Customs changes?
User avatar
BY Cdog
#841474
Molly wrote:
Cdog wrote:It's time to cough up some coin for glass... any recommendations for getting the best out of the AB763? It's a Super reverb, so the complement will be 4x 12AX7, 2x 12AT7, 2x 6L6 and a GZ34 rectifier.

I put JJ's in my 18w (6V6) and am really happy with the sound, but that's Marshally not Fendery. Can't really afford to sniff corks here, but suggestions are welcome! :)

Need to order some this week so they land before the customs changes.


What Customs changes?



https://www.customs.govt.nz/about-us/news/important-notices/new-gst-rules-for-low-value-imported-goods/
#841475
Cdog wrote:
Molly wrote:
Cdog wrote:It's time to cough up some coin for glass... any recommendations for getting the best out of the AB763? It's a Super reverb, so the complement will be 4x 12AX7, 2x 12AT7, 2x 6L6 and a GZ34 rectifier.

I put JJ's in my 18w (6V6) and am really happy with the sound, but that's Marshally not Fendery. Can't really afford to sniff corks here, but suggestions are welcome! :)

Need to order some this week so they land before the customs changes.


What Customs changes?



https://www.customs.govt.nz/about-us/news/important-notices/new-gst-rules-for-low-value-imported-goods/


Ah...
User avatar
BY Slowy
#841491
If you ever try to buy one of Alexander Dumble's original amps, you'll have to concede he was doing something right.
He built all his amps around whatever the currently available modern valves were. He reasoned that they would need replacing and saw no reason to make things difficult for his customers.

I have/had original RCA Blackplate 6L6 and 6V6 and Mullards and Amperex of various types as well as others.

While I have preamp tube preferences, I suspect if you use a OD or distortion pedals, the output tube selection is less important. All the hype came from the valve's performance when the amp was dimed and the guitar plugged straight in. Very few of us play that way anymore. And yes Capt Black, I said very few. :lol:

I realise this a controversial comment and may well get me drummed out of our community.
User avatar
BY Cdog
#841494
Gah... It's a rabbit hole. Now I'm thinking of changing the rectifier to a 5U4GB... just read it drops ~50V compared to the GZ34... that would be useful, I really don't need the full 45W, and it will be fine with my PT. :thumbup:

Reading through some mods, I have some NOS ECC82s which might come in handy.
Tung Sols... Hmmmm
User avatar
BY Bg
#841505
Slowy wrote:If you ever try to buy one of Alexander Dumble's original amps, you'll have to concede he was doing something right.
He built all his amps around whatever the currently available modern valves were. He reasoned that they would need replacing and saw no reason to make things difficult for his customers.

I have/had original RCA Blackplate 6L6 and 6V6 and Mullards and Amperex of various types as well as others.

While I have preamp tube preferences, I suspect if you use a OD or distortion pedals, the output tube selection is less important. All the hype came from the valve's performance when the amp was dimed and the guitar plugged straight in. Very few of us play that way anymore. And yes Capt Black, I said very few. :lol:

I realise this a controversial comment and may well get me drummed out of our community.


Get out of our community, you didn't recommend digital!!

My ears arent up to discerning valve makes, however I know some valves sound better in an amp. And its all down to swapping them around. I've had fantastic jj's and I've had less than good jj's. Primarily it depends on the amp I believe.

A valve that sounds awesome in one amp can sound shit in another.
My tin ears explanation.
#841542
Just my 2c but I think reliability/lifespan is the only objective selling point of valves/tubes. The rest is up to your taste. I think JJs are good, reliable bang-for-buck tubes but I do like TungSols as an 'upgrade' in vintagey amps. TungSols make great 12AX7s, EL84s, 6L6GCs, KT66s and EL34s - not sure about the rest. Svetlana makes great EL34s and KT-series, Sovteks are bog-standard solid tubes that seem to be loved by 5150 and JCM900 owners, etc, etc. They all have their good points. On the other hand, I don't like EH, Ruby and Shuguang tubes - they often seem to be the failed preamp tubes I find myself replacing and I think Ruby makes a particularly weak EL84. Of course, YMMV.

As for rectifiers, the NOS stuff is great because they're still reasonably priced and they're built rugged but new production rectifier tubes aren't something to be avoided either. Generally, when they fail it's because of something else (shorted power tube or a stressful filtering design), so it's hard to assess & compare brand reliability here.
User avatar
BY Cdog
#841560
RectifiedAmps wrote:Just my 2c but I think reliability/lifespan is the only objective selling point of valves/tubes. The rest is up to your taste. I think JJs are good, reliable bang-for-buck tubes but I do like TungSols as an 'upgrade' in vintagey amps. TungSols make great 12AX7s, EL84s, 6L6GCs, KT66s and EL34s - not sure about the rest. Svetlana makes great EL34s and KT-series, Sovteks are bog-standard solid tubes that seem to be loved by 5150 and JCM900 owners, etc, etc. They all have their good points. On the other hand, I don't like EH, Ruby and Shuguang tubes - they often seem to be the failed preamp tubes I find myself replacing and I think Ruby makes a particularly weak EL84. Of course, YMMV.

As for rectifiers, the NOS stuff is great because they're still reasonably priced and they're built rugged but new production rectifier tubes aren't something to be avoided either. Generally, when they fail it's because of something else (shorted power tube or a stressful filtering design), so it's hard to assess & compare brand reliability here.


Thanks for the reply.

I'm thinking of running 5881s in the amp to quieten it down and get a bit more compression. (90% of it's use will be at home) Comparing some 5881s from different brands, JJ and Tung Sol... The JJ 5881 state a max Anode potential of 500V, compared with the Tung Sol 5881 at 400V. The SR circuit is designed for 6L6GCs, running at 460-470V to the Anodes. Using a different rectifier 5U4GB, I'm expecting to get around 420-430VDC to the Anodes, but this is still over the Tung Sol's max. Question... how conservative is that Tung Sol max rating, do you think? Is it worth the extra few bucks for the Tung Sol, or play it safe and go JJ?
#841565
Cdog wrote:I'm thinking of running 5881s in the amp to quieten it down and get a bit more compression. (90% of it's use will be at home) Comparing some 5881s from different brands, JJ and Tung Sol... The JJ 5881 state a max Anode potential of 500V, compared with the Tung Sol 5881 at 400V. The SR circuit is designed for 6L6GCs, running at 460-470V to the Anodes. Using a different rectifier 5U4GB, I'm expecting to get around 420-430VDC to the Anodes, but this is still over the Tung Sol's max. Question... how conservative is that Tung Sol max rating, do you think? Is it worth the extra few bucks for the Tung Sol, or play it safe and go JJ?


Yeah, the JJ 5881 seems to be a bit closer to a 6L6GC than the TungSol version. I doubt 30VDC or so over the maximum will matter much, and the TungSol datasheet shows traces as high as 600V, too. Maybe just give extra respect to the other parameters a bit more and don't flog them - ie. don't bias them unusually hot or run flat-out into an attenuator. The idle voltage should also drop a fair amount when you drive a signal and increase current draw, especially if you're using a saggy rectifier source. Also, if you're building it from scratch I'd suggest omitting the standby switch since they only cause more problems than they solve - if it's a pre-drilled kit chassis, you could use the hole for a panel-mount B+ fuse instead.