My Second Express Build - Done (almost)

[Allynmey]

Omar, Steve at apex has Teflon solid in most colors now!

Allynmey

Also has 5KL 2W AB pots for $2.50

[Omar]

I bought the teflon wire that Angela sells. Kimber product I believe. The stuff ain't cheap at a buck a foot but works great and Steve had all the colors I needed. I know you are looking for the solid core stuff but the Kimber is 19AWG and it stays where you put it. Just a thought. The build looks really great!

Custom100 -
Thanks for the comment on the amp!

I won't do business with Angela. A couple years back I tried to buy some ceramic 9 pin socket for a custom build I was doing. Steve would not sell them to me because he said that although they would fit, they were not correct for a Fender chassis and would only sell me a Cinch socket. I explained to him that my build was a custom amp and not restoration and I preferred to use ceramics. He said that he refused to sell me the ceramics. I was stunned and said something to the affect of "so you don't want to sell me something that fits my chassis because you personally don't like a ceramic socket in a Fender chassis?" His response was that the Cinch are correct for the chassis and that's all he would sell me. I hung up in disbelief!

I know I'm not alone in issues with Steve.

Omar

[Allynmey]

Omar, Where did you buy the Power and standby switches? Also, the indicator lamp?

Allynmey

[Omar]

Omar, Where did you buy the Power and standby switches? Also, the indicator lamp?

Allynmey

Allen,
All were purchased from Metro Amp.

Omar

[Omar]

I got the play my Express this weekend extensively and make some tweaks. The first thing I did was change power tubes from some old Electro-Harmonix (I originally thought they were Sovtek's) EL-34's to the New Sensor Mullard EL-34 reissues. Huge difference! The tone was so much better. High's were not as cutting and the bass was not as flubby. The distortion tone also improved and was much more pleasing. One interesting thing I noted was how sensitive the amp was to the bias setting. The sweet spot was just under 40ma. At that setting the amp had a 'woody' characteristic. The 'woodiness' disappeared above and below that setting. I tried some 6L6's in the amp and kept going back to Mullard's.

The next change I made was to replace the 250pF in the 500pF in the tone section. I originally ordered the wrong part and replaced it with the correct value. That definitely lessened the amp's bite.

I fixed the bleed resistors off the filter caps from two 10k to one 220k that I had from my previous Express build. I'm not sure why but the amp sounded better. The low end seemed to be stronger. Doesn't make sense to me, can anyone explain this?

I re-wired the bright switch to be either no cap or 500pF. 500pF is too bright for me and I prefer to play with the no cap and dial in the high end with the Treble and Presence control.

I decided to forget about the post phase inverter master volume. The character of this amp really comes out when you are pushing the power tubes. I need to try the amp with my Dr. Z Airbrake.

The last thing I would like to do is replace the 12AX7's. I played around with a bunch I had and it was interesting how sensitive the amp is to different tubes. Tubes that tested fine in other amps were microphonic in my Express build. It's seems really sensitive. I was thinking about going NOS but the price is scaring me off. Any suggestions?

The amp is definitely interesting. I wouldn't say it's my number one amp since I'm more of a high gain guy. But it's fun getting the different tones out of the amp and I can't describe how different this amp is. The way the amp feeds back is just so cool! And the true tone of the guitar and pickup seem to come out. I'm really glad I built this amp!

Omar

[ampkits]

Hi Omar,

Having much fun I see..!

Nice amp you got there.

Just registered, not much to say yet. Will have a proto build for standard kit in a few days.

A bit different than the original, but minor. Cant justify prices of such things as 2W AB 100k resistor!

Thanks!

Nik

[UR12]

I fixed the bleed resistors off the filter caps from two 10k to one 220k that I had from my previous Express build. I'm not sure why but the amp sounded better. The low end seemed to be stronger. Doesn't make sense to me, can anyone explain this?
Omar

Omar

I will assume that you had about 400v on the cap connected to the 10k resistor. At 400v accross the 10k resistor , you were dumping about 40ma of current through the resistor. This 40ma was being lost. By changing to a 220k you reduced this to about 2ma so you freed up about 38ma for the rest of the amp to use. You now have a 20 - 25% increase in available power at your disposal to tighten up those bass notes since most of your power is consumed reproducing those bass notes.

[mac0611]

"I fixed the bleed resistors off the filter caps from two 10k to one 220k that I had from my previous Express build. I'm not sure why but the amp sounded better. The low end seemed to be stronger. Doesn't make sense to me, can anyone explain this?"

UL12 gives a great explanation.

I thought the 470K 3 watt resistor in the schematic is supposed to be the bleeder resistor. This where I'm not following. Are these 2 220K resistors based on the francesca pictures?

[UR12]

"
I thought the 470K 3 watt resistor in the schematic is supposed to be the bleeder resistor. This where I'm not following. Are these 2 220K resistors based on the francesca pictures?

The 470 on the schematic is wrong compared to the original Franchesca pics. The Franchesca used 2 100k 3w resistors in series for a total of 200k. Omar just substituted 1 220k resistor instead of the 2 100ks. Actually, since the resistors are only used as a bleeder resistor, the 470k would probably work fine. It would just take longer to discharge the cap.

There is one other mistake on the Kelly 90 schematic. It shows a 500pf and a 10pf on the bright switch. It should be a 500pf and a 100pf according to all of the previous schematics I've seen. Although I built my first wreck with the 10pf and it sounds just fine. One thing that I found that was cool was that you can move the switch to the 500pf for a Strat and the 10pf for a LP. Maybe we should re-label the switch Strat / LP

[mac0611]

Thanks for the clarification, UL12. I was hoping that was the answer that would be provided. This seems to be a key area in which the distortion characteristics of the amp will be affected.

[UR12]

The amp is definitely interesting. I wouldn't say it's my number one amp since I'm more of a high gain guy.
Omar

Omar

Now ya got me interested.......what's your #1 amp??

This seems to be a key area in which the distortion characteristics of the amp will be affected.

Not sure what you mean by that can you clarify? Are you talking about the bleeder resistor?

[Omar]

Hi Omar,

Having much fun I see..!

Nice amp you got there.

Just registered, not much to say yet. Will have a proto build for standard kit in a few days.

A bit different than the original, but minor. Cant justify prices of such things as 2W AB 100k resistor!

Thanks!

Nik

Nik,
Welcome to the group. Thanks for your work on the chassis. As you can see it turned out nice! I'll be contacting you soon for my next project.

As I mentioned in an another post, I have mixed feelings about Trainwreck kits being offered. I don't want to see Ken work being profited from without his blessing. But from the difficulty it took me to scour the internet for all the parts I needed, I can understand the convenience factor. Hope you don't take it the wrong way Nik!

One thing I will say is that it doesn't seem to be just the parts that are important with this amp. The actual layout seems to be a big factor. I cannot verify this 100% but can speculate based on the difference in sound between my builds.

Omar

[Omar]

I fixed the bleed resistors off the filter caps from two 10k to one 220k that I had from my previous Express build. I'm not sure why but the amp sounded better. The low end seemed to be stronger. Doesn't make sense to me, can anyone explain this?
Omar

Omar

I will assume that you had about 400v on the cap connected to the 10k resistor. At 400v across the 10k resistor , you were dumping about 40ma of current through the resistor. This 40ma was being lost. By changing to a 220k you reduced this to about 2ma so you freed up about 38ma for the rest of the amp to use. You now have a 20 - 25% increase in available power at your disposal to tighten up those bass notes since most of your power is consumed reproducing those bass notes.

UR12
Thanks for the explanation but wouldn't 40ma imply that all the current is getting dumped across the 220k resistor? I would think that current is flowing to the rest of the B+ circuit. I guess the best thing would have been to measure the voltage drop between the two 10k before I removed them to calculate how much current does flow.

Omar

[Omar]

The amp is definitely interesting. I wouldn't say it's my number one amp since I'm more of a high gain guy.
Omar

Omar

Now ya got me interested.......what's your #1 amp??

My number one amp would be my Fatman amp. It's a single channel high gain amp based on the Soldano SLO/Bogner Ecstasy topology (4+1).





Omar

[Mark]

Dear Omar

I don't think Nik making kits is a big deal as people who have to have a Trainwreck will hunt down the real deal and pay the big bucks. For these people the fact that Ken Fischer hasn't touched the amp means to them in no way is it a Trainwreck in any shape or form, which is an opinion they are entitled to.

I think Nik is operating in the low end of the market that Ken Fischer wouldn't be comfortable in. I think it has been pointed out previously that Ken Fischer isn't paying royalities to Vox for lifing the AC-30 design for his Rocket amps.

Nik does good work, I have bought an 18 watt chassis from Nik and I'm completely happy with his service. I'd buy another chassis or Trainwreck chassis from him.

Definitely not trying to flame anyone, just my point of view.

P.S. Nik I would like to hear more about your chassis/products related to this type of amp, please send me an email.