Traynor Darkhorse 12au7 problem

[jdpas29]

Hello!  this board is nice and you guys seem very knowledgeable so i figured i would put this out there and see if anyone had any ideas.

i have a traynor darkhorse and the only real complaint i have with it is that the 12au7 channel has a fizzy, crappy sounding distortion.  it seems to be relative to how much drive is applied to it.  it only sounds good clean and at low volumes.

i was wondering if you guys could look at the schematic and tell me if it would be safe to attempt a tube swap to a 12bh7 as some have said it is a less fizzy sounding tube.  the only difference that seems to be a precaution is the heater current.  .3 for the 12au7 vs. .6 for the 12bh7.

thanks ahead for any advice...

[eleventeen]

I found no schematic in Doug's library...not knowing about the age of your amp, given that Traynors have much in common with Fenders, I would reco changing out the plate resistors before I changed tubes. I have been amazed at how much hiss and crappy noise you can get rid of just by changing these out. I had 3 old Fender amps---Princeton Rev, Deluxe Rev, and Pro Rev...all at least 30 years old, in the case of the Pro, 45 y/o, and simply changing out the (in the case of Fender, 100K) resistors worked a miracle in terms of getting rid of goofball noises and hiss.

[DummyLoad]

traynor darkhorse is fairly newer lineup. suggest trying NOS tubes. did it have the problem when you bought it? if it is a problem and it persists it's likely a bias issue that should be; a) left as-is, it's a design flaw, or b) circuit has a fault, in which case you should seek help of an experienced amp tech.

dark horse are built around a PCB and thy're not novice friendly to wrench on. can't find a schematic - just a bunch of gut shots.

--DL

[m3moser]

If you go to the Traynor website and look up the Darkhorse 15 then look at the service manual you will be rewarded with a full schematic of the amp.

[printer2]

You should have no problem running the 12bh7.

[smackoj]

is Traynor still the 'baby' of the guy named Traynor, or is it another corporate buyout arm of GE or Matel or Jim Beam?

just curious   

[frank57]

Here's the schematic and pcb layout .
Traynor amps tend to be well made.
I don't know about this head though.
I believe Long and Mcquade own them.

They're made in Canada not China.
Their new Ygl amps are quite interesting cathode biased amps with a lot of sustain.
http://traynoramps.com/guitar/ygl/product/ygl2/

In general people complain about the overdrive sound on the ycv 20 watt amp for example.
It's somewhat bass heavy.
But with some modification maybe that could be overcome?
But aside from that, they are dc powered and quiet with nice cleans.
I compared it side by side with  Jet city soldano 20 watt and those Jet city amps have the best overdrive by far in their price range.
Downside they are hissy when turned up ,no hum though.
Okay clean, what there is of it,but if you like a hint of distortion in the clean then there's more there.

[jdpas29]

i can't really read the schematic.  i do have access to it though.. i will post it later and let you guys take a look if you have time.  thanks for the replies...

and i have already tried several tubes in all positions for that channel including some nice NOS GE 12au7s.  some of them do appear to change the point at which the level of drive causes the distortion, but they all do it. 

[DummyLoad]

12AU7 channel is not really a channel - it's an output tube that kicks in when you flip the switch to triode mode. switching to triode mode also disconnects the 6V6 outputs. the LTPI may be smacking the 12AU7s too hard - back down on the gain - you need about 1/2 signal of what you'd use to make the 6V6 sound pleasant over-driven. what you're hearing reads like you're driving the 12AU7 into flowing grid current. 

IMO that's a crappy plan - i'd run it in 6V6 (pentode) mode and save the 12AU7 for something worthwhile. pre-amp looks like many others. tone stack switching is interesting. if yo want more pre-amp gain start with tone stack mods/bypass.

is Traynor still the 'baby' of the guy named Traynor

website claims that that they are still a privately held canadian company. traynor is owned by yorkville sound that was incorporated by two men named j. long & p. traynor

--DL

[Scsoul]

   I was wondering about the darkhourse my self somehow there going from 6v6 powertubes to a 12au7 powertube. how would the output transformer do this?  The one i played at the store sounded fine in both modes and using a 12au7 for one watt output seems like a good idea over powerscaling and vvr, i just dont understand how they use a OT for a pair of 6v6 and a 12au7          Scsoul

[DummyLoad]

how would the output transformer do this?

the same way it does for pentodes. nothing changes - the bias condition of the 12AU7 is set to match the OT Z rating. just like any other plan.  

--DL

[PRR]

> condition of the 12AU7 is set to match the OT Z rating

I figure the 12AU7 is biased for a 50K-100K load.

6V6es are biased for about 12K, 10K loading.

Suspect the actual load is 8K or 6K, popular g-amp values.

The 6V6 will take on a slight edge just before total overload, a common design practice.

The 12AU7 is seriously mis-loaded. Like a whaling ship with a bass-boat motor. What happens with mis-load? You don't get the full power possible. And do we really need Full Power? No, we already have the 6V6es onboard for that.

I figure 0.25 Watts in 12AU7 mode. (Natch 10W-15W in 6V6 mode). 15dB difference in power. 5:1 difference in sound pressure (roughly "volume"). A good difference.

I'm not sure if the 12AU7 mode will sound good or bad. I suspect it sounded good in the prototype. You say it was good in the store (the unit _you_ got or a demo?). If it does not sound good now, I'd check those voltages, see if something is sick.

Next to the two 5W resistors is R38, 1K8 2w. One end is zero. What is the other end in triode mode?

[DummyLoad]

What is the other end in triode mode?

isn't it the cathode bias R for output 12AU7?

18.7V/1800R is ~10mA for both tubes. wouldn't optimum load be ~25K a-a?

[PRR]

I was asking jdpas29 to measure that point and see if it agrees with the docs.

Yeah, it should be 18-some volts, but IS it?? (on his unit) Cheap or solder-joint resistor could go bad, etc etc etc.

10mA at 300V is 30K equivalent load on power supply. The CT load should be twice this.

Fer example: Two 6V6 at data-sheet conditions (something like 300V 75mA IIRC) is 4K to power supply, something like 8KCT optimum load, as datasheet shows.

[DummyLoad]

10mA at 300V is 30K equivalent load on power supply. The CT load should be twice this.

yeah sorry, brain fart - i based my calcs on pk. current - 10mA*sqRT2 - or (377V/14mA)

--DL

[jdpas29]

i can't read schematics.  i was just posing the question to see if you guys could decipher the problem for me. 

i doubt there is anything wrong with the amp as far as damage, but i suspect the design is flawed.  what someone said earlier about input making a big difference makes the most sense because the only way the 12au7 part of the amp sounds good is clean and at low power from the preamp gain.  any heat on the preamp tubes makes the 12au7 go into a crappy, fizzy distortion.

would this be a fixable thing for a tech to do or does it make much sense to even fool with it?

i have a baby now and my wife gets pissed about the volume regularly so i would like to have this channel available for use.  it wouldn't bother me if it actually had less power than it does so if it was a matter of a resistor or small part being changed out around the 12au7 on the board, i would be willing to do that.

thanks for all your insight.  you guys are super helpful and on the ball. 

[jdpas29]

knowing what you guys know about this circuit, is there any possibility that switching to a 12bh7 would help?

it's not an expensive tube (though i am likely to buy NOS RCA for this application), so i wouldn't mind just getting one and trying it out... my only concern is damaging the amp due to the heater voltage difference or some other deal that i don't know about.   

[HotBluePlates]

knowing what you guys know about this circuit, is there any possibility that switching to a 12bh7 would help?

Probably not.

You could try it if you already have one, or have something else that uses a 12BH7. But that tube is basically a 12AU7 with a higher-dissipation plate.

I think it's a design problem. -18v is very close to the 12AU7's -24v cutoff voltage. It's supposed to distort, but you may not like the way it does it with this particular transformer load. And it doesn't make financial sense to add a 2nd OT just for the 12AU7 in a production amp.

I'd like to hear this amp to see what the distortion sounds like that you're not liking. Traynor has sound clips, but doesn't say what power setting they were using.

[DummyLoad]

jump to 2:00 for 12AU7 demo.

https://www.youtube.com/watch?v=7rlKHeJNs90

--DL

[HotBluePlates]

Well, the 12AU7 sounded nice while she was playing it.

So is there a problem with the amp? Maybe. I can't help but wonder about:

"... the 12au7 channel has a fizzy, crappy sounding distortion.  it seems to be relative to how much drive is applied to it.  it only sounds good clean and at low volumes."

It should sound good with some distortion, as the video proves.

If not a problem with the amp, the statement makes me fear a case like a friend of mine who always set the master of his JCM800 low and dimed the preamp gain. For what he was playing, I talked him into trying diming the master, and just turning up the preamp volume til he got the distortion (now output tube instead of preamp tube distortion). He liked the sound a lot better, then proceeded to set the amp excatly like he had it before... 

So if it isn't an exaggeration about only sounding good "clean" (our definitons of that may differ), then try a new 12AU7 or get the amp checked out. But I don't see anything in the cirucit that would make a 12BH7 work where a 12AU7 doesn't.

Plus, that's saves 12BH7's for guys like me who have equipment that must use those and not a 12AU7.

[DummyLoad]

actually not a bad sounding amp for the $$. unique. i take back what i said about that being a crappy plan. if your amp doesn't sound similar to that video demo i posted, PRR may be on the mark regarding a circuit problem. as you can see in the video, she went full up volume and while on 12AU7 output stage and that sounded decent enough.

--DL

[Willabe]

If not a problem with the amp, the statement makes me fear a case like a friend of mine who always set the master of his JCM800 low and dimed the preamp gain. For what he was playing, I talked him into trying diming the master, and just turning up the preamp volume til he got the distortion (now output tube instead of preamp tube distortion). He liked the sound a lot better, then proceeded to set the amp excatly like he had it before...  

Yeah well, you can lead a horse to water but you can't make him have good tone.   


                  Brad