valve junior mod

[baddog]

I have a valve junior o bought recently and wah wandering if an output transformer swap would make a big change in the sound. I have some old transformers i have removed from tube & electric organs and was thinking about using one of them. How can i tell the diferance between an output transformer and a power transformer. I think i need an input of 5 to 7.7k for the input of the transformer and 4,8,16 ohm taps on the output side. And advice would be apreciated.

thanks

[stokes]

An OT should have a red CT and two other primary connections usually blue and brown.The secondary will have one black common or ground lead and depending on how many secondary taps will have a yellow and green,for the 4ohm and 8ohm taps.Those are the "standard" colors,some trannies dont follow that but most will.A PT will have more connections,depending on how many secondaries it has.The primary are usually 2 black,or maybe a black and a black with a stripe.The secondaries are usually 2 red and a red/yellow stripe CT for the high volts,2 yellow for a 5v rectifier heater and 2 green for the 6.3v heater.The 6.3v may or may not have a green/yellow stripe CT.Again these are the "standard" color codes and not all,but most do follow this.Be careful,there are a lot of volts in an amp,if you are not sure where the high volts are,I wouldnt recommend poking around in there,you could get hurt or dead.

[baddog]

valve junior mod

Is there a good websight that has info on transformers and sanders color codings?

thanks

[Alex R]

This might help you find out more about the transformers you have. For an AC source you can use a filament supply; keep the voltage you put on the secondary down this low or lower to avoid generating something really big 'n sparky in the primary as your voltage is likely to be multiplied by 25 or so.

http://www.radioremembered.org/outimp.htm

There are other sources on the web. Not sure there isn't something on Geofex.

The colours stokes gave you are widely seen.

[joey]

I have done extensive VJr modding and have done a scratch build using tag strips. The 'recommended' OTs for VJrs are Hammond 125DSE or 125ESE. I have the 125ESE and I can testify that the difference is night and day over the stock transformer.

However, it depends on which model of VJr you have. We are up to Version 3. Versions 1 and 2 had a badly matched OT (7.5K) but the new V3 has corrected the primary impedance to properly match the EL84s (5k). Although it is an improvement, it doesn't have the 'balls' of a 125ESE.

The differences to look for.

V1 had AC heaters that produced much hum. 7.5K primary OT.
V2 had DC heaters that improved hum but still 7.5K OT
V3 has a black PCB (instead of green) and a 5K primary OT.

So, you need an OT that will handle 7 Watts or more, 5K primary impedance and 16/8/4 on the secondary. The heavier, the better

[ess0506]

125DSE primaries?

Hi. I just registered for my first forum, just so I can ask this question. I have V2, my 125DSE just arrived, and I can't figure out what to do with the brown and blue wires (which I suspect are the "primaries").

On the stock OT, there is a wire that runs to T3 and another that runs to T4, but I don't know what that means, or what that can tell me about the brown and blue wires coming out of the 125DSE (if it matters, the blue one has text on it, the brown one is plain).

I think I can figure out the rest, as somewhere else it is posted that

green = 4 ohm
yellow = 8 ohm
white = 16 ohm
black = ground
orange = useless, just wrap it up

and so I feel comfortable just following those.

Incidentally, I had no idea this is what the 125DSE would look like - it's covered in tape (?). Thanks for any help.

[joey]

ess0506, you are correct. The brown and blue wires are the primaries and connect to the tags on the PCB where the old OT was connected. It doesn't matter which way round they go UNLESS you intend to do a negative feedback mod in which case, the phasing is important.

[Chuck_Farlee]

Just to add to what joey said:

Connect the brown primary wire to T3 (near the tube socket) and the blue wire to T4 (near the PS filter caps) to maintain proper phasing when using negative feedback.

chuck

[ess0506]

Thanks!

Thanks so much for your help, guys! I'm psyched to hear how the new OT improves the tone. I really appreciate your advice.

[ess0506]

update 125dse

Just an update that I installed the hammond OT yesterday and it works (I was worried I'd blow up the amp or something). I wish I'd recorded a before and after, to be able to really compare the difference it makes. I'm going to try it out at a band practice today to see if the increase in volume with headroom is enough to put it into usable territory. I'll just assume that the tone has improved as well. Thanks again for your advice.

[ess0506]

125DSE and now what? (need much more clean volume)?

Wow, forums are addictive. So I'm very happy with the improved tone due to changing out the OT, and while I suppose this shouldn't have been a surprise, the amp still is not loud enough to use with my band (the tone I go for is with the volume knob at about 11-12 o'clock, so much cleaner than most people, which doesn't allow for just cranking the valve junior to get the volume level I need). Now I find myself in something of a bind and am wondering if other people have tried getting the valve junior up to small club volume levels without having a crunchy/distorted tone.

As I see it, my options are thus: (1) just be happy with a great sounding amp that I can only use at home without a drummer. If this is the case, I do have another very old tube amp (Sears Silvertone) that is adequate for my volume needs. I just really like the tone of the valve junior now that I've done some mods and prefer that sound. It also has a lot less hum than the old one, and the old one still needs to be cranked a bit past what I like to get the volume I need. HOWEVER, what about option (2), which would be to somehow re-amp the valve junior? Ideally this would be done on the cheap, and with minimal active electronics (I prefer passive to active systems). I also have a crate powerblock, which is plenty loud but sounds terrible on its own, although I think the power amp section itself is supposed to be quite transparent. So my idea would be to get some kind of thing to take the valve junior signal post poweramp (behringer and others make passive boxes that supposedly accept speaker-level signals and let you route a line-out from it as well as let the signal continue to the speaker cabinet. I could take that line out into the crate poweramp section, and use that to get the volume I need (bringing another speaker cabinet, which I have). Of course, now I've doubled the amps and cabs that I'd have to bring to a gig (many of the places I'd be wouldn't have a house system to use), and that's one more amp to plug in and hope the wiring will support. Alternately, I could mic the evj and use a PA that I have and just hope I don't get feedback and can set the levels for a decent mix. Alternately, I could get something like the Weber MicroMass attenuator to get a line-level into something else, and that's passive and I could just bring the one cabinet, but I suspect I might be disappointed with the sound that attenuation brings, having read reviews. I do not own or want to buy a stack (the cabinet I currently use with the valve junior is ebay brand 1x12 but sounds good with a very efficient Eminence Texas Heat speaker).

So I guess my big question is, am I simply barking up the wrong tree? Should I just be happy with having a quiet amp that sounds great in my house, and either be happy enough with a different one that's loud enough at practices and gigs but doesn't sound great, or consider buying a new tube amp some day that suits those needs? I've also considered other ways to get a tube-amp sound into the crate, like getting a cheap preamp like the ART Tube MP Studio Mic Preamp or the expensive Weber Mass Pedal or something else. Then I think I'm barking up the wrong tree again and that there’s a reason why people have higher watt tube amps for gigs and that I’m just trying to turn an apple into an orange using pieced together equipment and spending about as much as a new tube amp anyway. Another option would be some sort of tube amp emulator, but the tone I look for is much cleaner than those seem to go for, and now that I’ve tasted evj bliss, I might not be happy with an emulator. If anyone has any insights into getting the valve junior to small club levels (with a band) or otherwise, I'd be grateful.

Thanks,
Eben

[Chuck_Farlee]

Eben,

Last weekend I was experimenting with recording my Valve Junior using a Behringer GI100 4X12" cab emulator. This is an active DI box that goes between the output of the amp and the speaker. You have to have a speaker load connected or you will burn out your output transformer. I built a small eyelet board with four 33 ohm, 5W resistors in parallel to use as a dummy load instead of the speaker.

Hughes and Kettner makes a higher quality, better built version called the Red Box. From the schematics I've seen, some versions are active, some are passive.

The Behringer has a line out via an XLR connector (as does the Red Box.) Conceivably you could connect this line out to your Crate Power Block amp's line in and use the output section to drive a speaker cabinet.

If you have a PA, you can hook up the cabinet emulator's line out for volume and use the amp's speaker for monitoring.

You can get similar results using the line out from the Weber attenuators, which are passive devices.

If you are DIY minded, you can also add a post OT line out to your amp. Google Herzog and Firezog. I've also used the line out circuit from the Yamaha T-100/T-50. These do not have any frequency compensation circuits, so they may or may not sound good to you.

The downside is that you have to bring more gear with you to play. With one loud amp, all you have to is set up and play. Using a Valve Junior with a some kind of line out adds to the complexity.

You also may or may not like the tone. I got mixed results when recording. The clean sounds were OK, but the distortion sounds I got had a nasty, fake quality I just couldn't put my finger on. YMMV.

There is also miking the Valve Junior's cabinet, which has its own set of advantages/disadvantes.

HTH,

chuck

[ess0506]

Chuck,

Thanks for your thoughtful and informative reply. I was thinking about that Behringer DI since people seem to love it, I'm just wary of both Behringer and anything with a plug (when I can avoid it). I'm not DIY enough with electronics to do anything without idiot-proof directions, and even then it's a risk. I'm going to look over your ideas some more. At this point, a passive dummy load with a line out (like the Weber Micro Mass) looks the most attractive to me, putting that into the crate, and hoping that I don't mind the sound of attenuation as much as like not having to carry more than one speaker cab (also, I like the idea of the load design that Weber uses, although I'm really just going by their marketing). I'm still going to look over those other options you mentioned, though.

Eben

[Regis]

It sounds like you like the VJ, cool. Thing you discovered is that getting a good clean tone at gig volume levels is not really possible with a 5 watt amp.

If you don't mind my saying so, all that stuff about dummy loads and direct boxes and cab simulators sounds like a government solution.

In other words, a lot of complexity with minimal results.

If it were me, I would run the amp through a very efficient speaker cab. The louder and more efficient the speaker you use the less you will have to drive the amp. That, and put a mike on it for gigs.

[Chuck_Farlee]

I was experimenting with the Valve Junior/Behringer GI100/dummy load plugged into a tubed power amp just the other day.

I have to agree with Regis, it is a gov't solution; complex but doesn't really sound that good. I tried it mainly because I wanted to see if it worked, and I already had all the equipment on hand. I wouldn't recommend buying all the gear to try it out.

An interesting experiment (to me at least) but ultimately dissapointing.

chuck