I didn't really want to buy a tube amp, as I've seen what it can do to a man. Also I'm very happy for now with my Lone Wolf Harp Break. While I was looking for a larger solid state amp to play it through I came across this one, it was only 59 GBP including delivery. At that price I thought it was worth a go. I know it's a Joyo, but then my son has one of their pedals and it's great for guitar.
It's new but an older model than the current one JTA-05 on their website and has these things... - A solid wood cabinet, only the back covers are particle-board. - Upgraded by the importer with a Jensen C8R speaker - Tag-board circuit - A Ruby 12AX7 preamp tube - 6Z4 rectifier - 6P6P output tube
It does actually work, and does indeed do the tube amp thing. With my playing/mic, breakup starts at around 3 on the dial but is quite controllable.
What does the team think? Is it worth using, or as the basis for something to modify one day?
It's far too loud for routine home practice, I'm wondering about adding a simple attenuator. Any advice would be helpful. Would an L-Pad circuit be the thing to do? I understand the theory, but have no practical experience. For instance, how careful do you have to be around the switching to ensure there is never an open circuit?
Last Edited by MindTheGap on Dec 15, 2013 4:41 AM
£59!!!! Damn that's absolutely dirt cheap. It looks to be basically a 5F2A style circuit. Which is great circuit for harp. It has a Jensen speaker too which are good speakers. Have you upgraded the speaker or is that the default speaker? Mark Burness (5F6H) would be best able to advise you on an attenuator. Do you you have any audio clips of the amp being used for harp. It would be interesting to hear it in action.
Kingley - Thanks for the info about the circuit, I'll look it up.
The guy who imported it swapped the speaker, he said that it made a big improvement to the sound.
Cheap, yes indeed. Enough to make it worth a bet. I can't imagine it's as good as a 'name' amp. But I went into a shop selling vintage amps in Oxford and they had a Fender Champ (don't know the year) for 850GBP. Hmmm. Too rich for my blood.
OK, I'm not tooled up to do vids, but I might manage a sound clip.
Rogonzab - just to mention again it's the older model. The current one listed on the website, JTA-05, has two inputs and no tone control and different tubes.
Here is a sound clip. I recorded in a shed onto a tablet pc, and had to put cushions around the amp to get the level down and keep from deafening myself. So it's not the most faithful recording lol.
The recording sounds quite trebly, and it is, but in real life the bass notes are strong compared to a guitar practice amp of a similar size.
Last Edited by MindTheGap on Dec 15, 2013 10:20 AM
Sounds pretty good to me. You got yourself a great deal with that amp. It's definitely a keeper. If you send Mark Burness an email I'm sure he'd be able to advise you on attenuators.
Kingley - Mark kindly sent me plenty of info on how to add an attenuator, and not wreck the thing in the process.
Right now, I will use it with the Harp Break pedal, which was the original idea, which means I can keep the volume down and still get a broken-up sound.
We learners are always being told that it's acoustic tone that matters, not the amp, right? :-)
Last Edited by MindTheGap on Dec 16, 2013 10:06 AM
rogonzab - Well, it's not a complete lemon it seems, which it could have been. Good enough anyway for me to learn on for now. Here is a clip with Lone Wolf Harp Break. For which the windows of the shed remain intact.
But of course, the Harp Break is from the USA too, but then there is a distributor in the UK. Not in Chile?
Last Edited by MindTheGap on Dec 16, 2013 10:36 AM
rogonzab - thank you I will :-) It's aesthetically pleasing, seeing the gentle glow of the valves, reminds me of my very early childhood when some old radios still had them.
Anyone - I don't want to get into customising amps (famous last words) but when the time comes to replace the 6P6P valve, can I used a 6V6GT as a direct replacement? I've read that they are equivalent, and I'm not sure I can buy a 6P6P anywhere.
Last Edited by MindTheGap on Dec 16, 2013 11:21 AM
Yes, a 6V6GT would be a correct replacement. 6P6P is a Soviet designation for the 6V6. The 6Z4 might be a bit harder to acquire. I believe they're similar to a 6X5. ----------
Yes, but the 6X5 is an octal tube. And from the picture above, the only octal tube in the amp is the 6V6 equivalent. One looks like an AX7, and the last looks similar to a 6X4. So I'm guessing the 6Z4 is alike a 6X5 in a 6X4 glass tube. Gap, is this the case? ----------
I did some googling, and it seems there is no direct replacement for the Chinese 6Z4. The 6X4 is the same electrically but has a different pinout. And there is some confusion with the American 6Z4/84, which is altogether different.
I can't immediately find a UK source for these - ebay has some from Taiwan 10USD for two. That doesn't seem likely to succeed though.
Last Edited by MindTheGap on Dec 17, 2013 12:18 AM
You could rewire the rectifier socket to take a 6X4 : To convert: Move connection from pin 7 to pin 6 and then take lead off pin 5 and connect to pin 7.
but...you may never need to replace the rectifier. and when i needed to replace a 6X4 i found them rather pricey actually. best deal i could get was from the UK but over $30 AUD per tube. Personally i'd not be too worried about buying 6Z4 from Taiwan. i rather wish i'd been awake to the possibility of using a 6Z4...especially given the reason i needed to replace my 6X4...um...wiring issue :0\ looks like a pretty cool cheapie you have there, 'gap :0)
SuperBee - thanks for the info. Given what you say, I will first try the ones from Taiwan. Two for 6.32GBP include shipping - how can this be? What a world we live in eh? If that works then hopefully that's a my lifetime's supply of rectifier tubes. If it doesn't work I can look at rewiring.
Do different tubes types tend to fail sooner, e.g. power tubes tend to go first etc.?
I knew it would go like this...
Last Edited by MindTheGap on Dec 17, 2013 6:00 AM
"Do different tubes types tend to fail sooner, e.g. power tubes tend to go first etc.?"
Tubes usually only go bad if some other component directly connected to a tube goes bad or some other electrical connection shorts out. IME, power tubes are at highest risk to go bad, rectifier tubes next, phase inverter tubes next, and then preamp tubes. But as long as tubes are well looked after and they're connecting components remain intact, tubes can last a LONG time. If you have a local tech with a tube tester, I highly advise taking your tubes in and getting them checked. It's good peace of mind. The 6Z4 might be a little tricky to test, but as long as you have the tube diagram for it, the tech should be able to recalibrate the test settings from the 6X4 to accommodate the 6Z4.
----------
Hawkeye Kane
Last Edited by HawkeyeKane on Dec 17, 2013 8:54 AM
For completeness here are photos of the variable attenuator I added to the amp. The pot knob sits flush with the back of the cabinet. I used spade connectors so that if it doesn't work out I can remove it easily.
BTW the spare 6Z4 rectifiers arrived in fine shape.
Does Joyo sell their amps in the USA ? Ive checked on line and havent found a dealer. They also make a 12 W 1x12 and a 40 W 2x 12 class A point to point hand wired. Make me very curious. If made in USA they would cost a fortune.
Slimharp - I don't live in the USA so can't say I'm afraid. Out of interest I have found someone in the UK selling the new JTA-05, but it's £200. Just personally if I were in the US then I would be going for that Memphis Mini for my needs - something set up properly for harmonica, and someone to contact if there are problems. If this one goes south, aside from replacing the tubes, then I'm unlikely to get it repaired. I know a man, but time is expensive.
Last Edited by MindTheGap on Feb 09, 2014 5:38 AM
Thanks MindtheGap. I thinks Ricks amp is awesome. I was thinking along the lines of a bit more powerful amp like the Joyo 12 -12 or 40. I see they are not inexpensive. I would never buy one unless I could hear it or play through one. I think the beauty of them is the Class A wired Point to Point circuitry. I would imagine they could be tweaked a bit for harp. The Memphis Mini is very nice, I just dont like relying on a P.A. as you never know what set up the house or band will have. Now if there were a Memphis Mini 20w that would be a different story - Rick !
Last Edited by Slimharp on Feb 09, 2014 6:40 AM
Slim, I have no plans to offer a 20-watt amp. No way I want to compete with Bruce Collins. If you are interested in a great harp amp with about 20 watts I strongly recommend the Mission Delta Sonic amp.
The Memphis Mini amp is not a Joyo. It originates in the same factory in Hong Kong that makes amps for several brands. It is built to our spec and completed here in America with tubes, speaker, tone circuit, and line out. We check every solder and test every amp. I personally play every amp before it ships.
Slimharp, Technically the Joyo is not point to point. I read an interesting article that I will partially share with you, along with the link.
"There are five basic types of guitar amp wiring in my mind, and often two or more kinds are combined in a single unit (I'm ignoring solid- state amps, as they exclusively use the Total PCB method listed below).
Point-to-point - Each component is connected to a tube pin or solder lug or jack. There are no "boards" whatsoever. Examples of this style of construction include most old tube hi-fi equipment, 70-era Sunns, and more recently BadCats. Tag Board - the classic Fender and "plexi" construction methods. Most components are soldered to a long board with eyelets. These are in turn connected by wire to the tubes, transformers, pots, etc. Turret Board - The classic Hiwatt/Harry Joyce style, this is similar to tag board construction, but uses metal turrets which extend out from the board, which most of the components are connected to. Partial PCB - Used by most modern large manufacturers starting in the late 70s/early 80s. Most components are soldered to a Printed Circuit Board, which has copper lines or traces on the underside of the board surface that the components are soldered to, and which also make circuit connections. Example of this style of construction include the early (vertical input) JCM800s, Biacrown-era Hiwatts, and Soldano SLOs. This method basically used the PCB as an advanced tag board, and many wires are still needed to connect the tubes, etc. Total PCB - Used by most modern large manufacturers starting in the mid-80s to the present day. Everything is soldered to a PCB, including pots and tube sockets. This makes it easier and cheaper to manufacture, but harder to service and modify, and there is some question about the reliability of the PCBs holding the sockets of the extremely hot power tubes." http://mhuss.com/AmpInfo/
Last Edited by MJ on Feb 09, 2014 8:46 AM
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