Finished Trainwreck.. a few issues..Help Needed.

[higain99]

Hi Everyone,

Just finished my trainwreck express build and I followed the testing power up procedures and all the electrical values looked good. I do have a few questions though.

1) I was testing my amp with a guitar and speaker and a current bulb limiter (150w bulb). When i crank up the amp the light begins to glow stronger, turn it down light goes off. I presume it is fine but just wanted to be sure i don't blow any transformers up etc.


2)When i turn it on it is really buzzy and raspy and kind of flabby distorted sounding. I am using PEC pots so i made my own grounding buss so i am presuming this is potential area of that problem..? is theresome easy techniques of determining this.

Any help would be appreciated..

Thanks!!

[Littlewyan]

1) If you're cranking the amp and playing through it then yeah thats normal. If you crank the amp without a guitar plugged in and it glows brighter then that may not be good. That would indicate oscillation.

2) Do you mean the tone is raspy and flabby sounding or do you mean there is a raspy sound when you're not playing?

[higain99]

Thanks for info and reply littlewyan --> greatly appreciated!


Update: So electrically everything was working fine but it was raspy and buzzing and everything. It turned out to be a bad input jack. Was fooling around with the amp input and decide to route some pedals into it and all of a sudden it came to life... WOW! This thing is loud.

Is this thing always loud? The volume doesn't seem to have any taper t it. Is this just the circuit design?

Again Thanks for the reply and help.

[Littlewyan]

Yes its always loud. The volume is really just a gain control. The amp uses power amp distortion and to get power amp distortion you first need to push the power amp to it's full rated 35W Clean output before you get the distortion. This amp starts distorting with the volume on 1 so at 1 on the volume you're already at 35W! Then as you increase the volume the power amp distortion increases. Hopefully that made sense, if you want to know more I can go into more detail.

Have you got an attenuator? Cos if you don't you'll make your ears bleed unless you have ear defenders lol

[higain99]

haha yeah my ears are still ringing from last night. I thought i was deaf before, now i can hear again!! haha That is a very unique design to just run it full blast. The tone is amazing on it, a little to bright for my taste but that can be tweaked. You can tell its a very sensitive circuit, almost on the verge of oscillation. How do you run yours?

[Littlewyan]

All controls at 5 with the bright switch on the 500pf setting. Sometimes I turn the volume up to 7 to reduce the effect of the bright cap and give me bit more distortion. I always use an attenuator, only once in my mate's barn I tried it without the attenuator for like a minute before I was told to turn it down. I could be heard from their house!

Speakers and guitars greatly influence the tone of these amps. What are you using?

[higain99]

I am using an refurbished randall non slant cab with some brand new warehouse 2-et65's and 2-invador 50s. also have a 5150 cab with a 74 marshall super lead and a carvin legacy vl100 head. I thought the marshall was an ice pick in the mid /treb department. The Express makes that sound like a bass amp. no attenuator yet (but looks like that is a prequisite for this thing)> Did you make your attenuator?

[Littlewyan]

I use a 2x12 with Eminence GB12 Speakers.

No I got mine built for me for £100 I think it was. Its different to a normal attenuator though. You have two input sockets for the amp, one brings it down to quarter power and the other half power. You then use a Rheostat to attenuate the signal even more.

[geetarpicker]

You might try a few different volume pots if it comes on too quickly. Try to find a log or analog taper pot with no more than a 10% taper. What I mean by 10% is a 1 Meg volume pot that only reads about 100k or even less on 1/2 volume. On my '85 Express the amp is still clean up to almost 1/3, by 1/2 it is getting somewhat crunchy, however the taper is such that there is still a noticeable difference between 3/4 and full up. My volume pot on this amp actually reads about 1.3meg overall but only 80k On 1/2, point is it comes on quite gradually! Ken knew how to find Pots that really worked well with his circuit, but sadly many modern pots in clones act more like light switches.

[higain99]

Thanks GP. I will try some different pot options for the volume. Appreciate the advice.

[RJ Guitars]

... WOW! This thing is loud.... Is this thing always loud?

I assume this is an Express build? They tend to be pretty loud for sure. Did you have any luck running pedals through it? The Express doesn't take pedals especially well but maybe you found something that works for you?

I'd be curios to take a look at it if you have any photos.

thanks!

rj

[higain99]

Hi RJ,

I have only tried a modded Boss Sd-1 on it, wasn't the most pleasant sounding. I am running a Line6 DL4 delay unit in front and it sounds pretty good just that this thing is causing me hearing damage. SO LOUD!! I posted some pic's for you guys and appreciate all of your guys input to this forum.

Any recommendations on some tubes?

[RJ Guitars]

Yeah, these will really make some noise. There are many ways to quiet it down... Some guys like the master volume and others like the power scaling but I prefer an attenuator. In all cases I've found that the amp starts to loose much of it's character when you really knock the sound down a bunch. This seems to be the real struggle with the Express...

I've got a few different Express builds that I put together and the old European EL34's are generally the best sounding in any of them. You can use modern production tubes to test out and break in the amp but somewhere down the line you'll probably want to find some old Siemens or other high $$ tubes. I have one decent set of not so old Svetlana EL34's that also sound pretty good. Preamp tubes seem to be be hit and miss, but it helps to have a stash to just roll in and out of the stages until you get the best you can get.

[Littlewyan]

I've got a great sound out of my Express using modern valves. I actually prefer the modern pre amp valves to all of the NOS valves I've tried and I've tried Mullard, Sylvania and Amperex Bugle Boys.

V1: EH 12AX7
V2: JJ 12AX7
V3: EH 12AX7
V4: TAD EL34-STR
V5: TAD EL34-STR

[jazzbass]

You might try a few different volume pots if it comes on too quickly. Try to find a log or analog taper pot with no more than a 10% taper. What I mean by 10% is a 1 Meg volume pot that only reads about 100k or even less on 1/2 volume. On my '85 Express the amp is still clean up to almost 1/3, by 1/2 it is getting somewhat crunchy, however the taper is such that there is still a noticeable difference between 3/4 and full up. My volume pot on this amp actually reads about 1.3meg overall but only 80k On 1/2, point is it comes on quite gradually! Ken knew how to find Pots that really worked well with his circuit, but sadly many modern pots in clones act more like light switches.

Please Geetarpicker can you please tell me the brand and the type of Log or analog taper pot with no more than 10% taper
Thank you