Deric - Cool pics. ...er, where's the crossed wires? It looks like a TW amp, you know?
And my suggestion here was that it was not so much any consideration of using the 6-8 pin over the 1-3 pin by Soldano or KF, but instead just an economical use of the closest triod that made for a neat hookup with no crossed wires.
But were these pics meant to support that thought? If not, am I missing something?
Another express rewire
Moderators: pompeiisneaks, Colossal
Re: Another express rewire
Most people stall out when fixing a mistake that they've made. Why?
Re: Another express rewire
Rooster-
The builder could easily rotate the socket 180 degrees - and then cross wires - but that would be stupid, wouldn't it?
From what I can tell, it makes no real difference in the rest of the layout - noise wise or other - which way the socket is oriented. My "guess" is, the builder "chose" to orient the sockets in a fashion that makes the 2nd triode easily accessable - without crossing wires...
Is there any other reason to orient them this way? What am I missing?
I have done no testing. I am also a self proclaimed idiot.
I just don't see why it's so hard to believe the tube socket orientation was intentional...
FWIW, I have read several reports from people I trust (like Bob I's) that it does make a difference. I also "think" that the first time I heard of this was from a post in the Dumble forum. I "think" the info that started the discussion in that forum was quoted from a tube manual. I may be totally WRONG.
Unfortunately, the search function does not seem to be working for me right now.
The builder could easily rotate the socket 180 degrees - and then cross wires - but that would be stupid, wouldn't it?
From what I can tell, it makes no real difference in the rest of the layout - noise wise or other - which way the socket is oriented. My "guess" is, the builder "chose" to orient the sockets in a fashion that makes the 2nd triode easily accessable - without crossing wires...
Is there any other reason to orient them this way? What am I missing?
I have done no testing. I am also a self proclaimed idiot.
I just don't see why it's so hard to believe the tube socket orientation was intentional... FWIW, I have read several reports from people I trust (like Bob I's) that it does make a difference. I also "think" that the first time I heard of this was from a post in the Dumble forum. I "think" the info that started the discussion in that forum was quoted from a tube manual. I may be totally WRONG.
Unfortunately, the search function does not seem to be working for me right now.
Deric®
Re: Another express rewire
Deric - Cool. Honestly, the only reference to any tube positioning I have ever read comes from the former MO Valve Co., in regard to their power tubes, the KT88, KT77, KT66. What they suggested was to locate the keys 180 degrees to each other in any two tube configuration and space them 4" apart...... Man, did any guitar amp manufacturer take any notice of this info?
Anyway, if there was any logic to what pins to use it was/is surely all about the layout - and that is based on the circuit function and its need to avoid parasitic oscillations.
Really, when you think about the correct answer to this question - Is one triode of a 12AX7 designed to be quieter than the other? - it would have to come from the tube manufacturer. Has anybody seen any tube data from a tube manufacturer supporting this behavior? I have not. I have noticed that when only one side of a 12AX7 is used, the heaters to both triodes are typically connected. I am very sure this is because the filaments are wired in a humbucking manner, making for a quieter functioning tube. But whether the one triode is quieter when you short out the non-used triode or leave it unconnected I cannot offer any tube manufacturer's data to support either method over the other. If Kevin saw this in Hi-Fi applications maybe there is a reference from a tube manufacturer?
OK. my brain is toast here.........
Anyway, if there was any logic to what pins to use it was/is surely all about the layout - and that is based on the circuit function and its need to avoid parasitic oscillations.
Really, when you think about the correct answer to this question - Is one triode of a 12AX7 designed to be quieter than the other? - it would have to come from the tube manufacturer. Has anybody seen any tube data from a tube manufacturer supporting this behavior? I have not. I have noticed that when only one side of a 12AX7 is used, the heaters to both triodes are typically connected. I am very sure this is because the filaments are wired in a humbucking manner, making for a quieter functioning tube. But whether the one triode is quieter when you short out the non-used triode or leave it unconnected I cannot offer any tube manufacturer's data to support either method over the other. If Kevin saw this in Hi-Fi applications maybe there is a reference from a tube manufacturer?
OK. my brain is toast here.........
Most people stall out when fixing a mistake that they've made. Why?
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Fischerman
- Posts: 819
- Joined: Thu Dec 07, 2006 3:47 pm
- Location: Georgia
Re: Another express rewire
I've read that the second triode tends to be a hair more quiet but I have nothing to back it up. In the case of the SLO or TW, imo there's just not enough evidence to say...maybe they intentionally oriented the socket such that the second triode would be the input...or maybe they just oriented it the way they did and chose the closest triode. In the SLO, they certainly appear to have clocked it the way they did so that the heater wiring could be done that way (of course they could be clocked 180 degrees from the way they are and still achieve that).
As far as the reason why the second might be more quiet...IIRC it had something to do with the way we usually wire up the heaters for preamp tubes. These tubes are designed for 12.6v heater voltage but we use 6.3v and 'center-tap' it by tying pins 4 and 5 together. I think it was just the inner geometry of the tube or something.
FWIW, I just built a SLO clone. Regarding the SLO (which is a high-gain amp) and grounding...see all that preamp buss in the pics? The input jack and pot grounds all connect to it...then it connects to the preamp board ground (that green wire...the chassis is powder coated so the jacks do not make connection with the chassis)...then the preamp board ground connects to the power board ground...and the power board ground goes to the chassis ground bolt. One connection to chassis for the whole circuit...that's it. Well...the power tube grounds are a seperate buss with a wire to the bolt and the speaker jacks ground to that buss but other than that the circuit just has that one ground wire.
As far as the reason why the second might be more quiet...IIRC it had something to do with the way we usually wire up the heaters for preamp tubes. These tubes are designed for 12.6v heater voltage but we use 6.3v and 'center-tap' it by tying pins 4 and 5 together. I think it was just the inner geometry of the tube or something.
FWIW, I just built a SLO clone. Regarding the SLO (which is a high-gain amp) and grounding...see all that preamp buss in the pics? The input jack and pot grounds all connect to it...then it connects to the preamp board ground (that green wire...the chassis is powder coated so the jacks do not make connection with the chassis)...then the preamp board ground connects to the power board ground...and the power board ground goes to the chassis ground bolt. One connection to chassis for the whole circuit...that's it. Well...the power tube grounds are a seperate buss with a wire to the bolt and the speaker jacks ground to that buss but other than that the circuit just has that one ground wire.
Re: Another express rewire
OK, back to my amp....
I played it for a while last night with my strat. I really didn't like it - especially bad on chords. Lead tones were better, but I still have the "phase distortion sound" that I mentioned earlier on sustained notes. I tried my Marshall "clone" for comparison - much better clarity/tone and NO hum even with the volumes all the way up.
My previous wiring in the express had better tone but more hum. I'm going to get some different tube sockets and try that.
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As for the second triode being more quiet than the first, IMHO, it depends on the tube. If you're that concerned, I would think that you would have to try a few tubes to find the best one for the half of the triode you need. In general (especially in new production) tubes are not too consistent.
I played it for a while last night with my strat. I really didn't like it - especially bad on chords. Lead tones were better, but I still have the "phase distortion sound" that I mentioned earlier on sustained notes. I tried my Marshall "clone" for comparison - much better clarity/tone and NO hum even with the volumes all the way up.
My previous wiring in the express had better tone but more hum. I'm going to get some different tube sockets and try that.
---
As for the second triode being more quiet than the first, IMHO, it depends on the tube. If you're that concerned, I would think that you would have to try a few tubes to find the best one for the half of the triode you need. In general (especially in new production) tubes are not too consistent.
Re: Another express rewire
Kevin - Yeah, I know it seems like a bother, but you will thank yourself for making the swap. Just remember that the amp is so simple in its signal path that everything will make a difference.
Good effort, BTW. Most folks would have said WTF and been done with it. It will make a difference, you'll hear it. Too, when you wire it up, now when you look at the pics the hookup wiring will all fall into place. Like eating good cake.
Good effort, BTW. Most folks would have said WTF and been done with it. It will make a difference, you'll hear it. Too, when you wire it up, now when you look at the pics the hookup wiring will all fall into place. Like eating good cake.
Most people stall out when fixing a mistake that they've made. Why?
Re: Another express rewire
I bought a pair of shoes from a drug dealer the other day. I dunno what he laced them with but I’ve been tripping all day,
Re: Another express rewire
Well, that was what I needed to see. I hate to ask it but can it be assumed that all 12AX7s behave the same way? Well, no matter really. Now I can think that KF probably based his V2 hookup based on documented tube data, and not some random decision. Good to know.
Thank you for the data digging LeeMo, you have enlightened me.
Thank you for the data digging LeeMo, you have enlightened me.
Most people stall out when fixing a mistake that they've made. Why?
Re: Another express rewire
That is interesting.
This is in reference to a "cascade" amplifier (which is different that V2 in an Express). One could imply that since using the pins 6,7,8 triode as the first stage in a cascade configuration gives better performance, that the pins 6,7,8 triode is better than the pins 1,2,3 triode. However, it doesn't exactly say that.
I'm going to have to dig out my Radiotron handbook and see if it mentions anything.
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Fischerman
- Posts: 819
- Joined: Thu Dec 07, 2006 3:47 pm
- Location: Georgia
Re: Another express rewire
It just says 'best hum performance'. Cascading the two sides just means that the first triode's hum gets amplified by the second triode...so choosing the more quiet triode for the first one reduces hum.
As far as KF doing it for that reason...I have no idea...I'm not convinced of it yet though. Aside from this 'best hum performance' issue, it's kind of a 50/50 shot either way as to which triode is used first. I'm certainly not prepared to say that everyone who used the 'B' triode first did it for this reason and those that didn't do it were 'inexperienced' and made a mistake. Hell, I'm inexperienced and I've been doing it that way for years but only because I had heard that it was potentially a tiny, tiny bit less noise but it just as easily could have been a 'mistake' on my part. I even 'reverse' V2 in Marshalls (or any GS/CF pair) because of it but not because I've ever heard a difference...more of a Pascal's Wager kind of thing.
As far as KF doing it for that reason...I have no idea...I'm not convinced of it yet though. Aside from this 'best hum performance' issue, it's kind of a 50/50 shot either way as to which triode is used first. I'm certainly not prepared to say that everyone who used the 'B' triode first did it for this reason and those that didn't do it were 'inexperienced' and made a mistake. Hell, I'm inexperienced and I've been doing it that way for years but only because I had heard that it was potentially a tiny, tiny bit less noise but it just as easily could have been a 'mistake' on my part. I even 'reverse' V2 in Marshalls (or any GS/CF pair) because of it but not because I've ever heard a difference...more of a Pascal's Wager kind of thing.
Re: Another express rewire
Mojotone site is down - was going to order some new sockets 