TW Express clone with a Post PI Master Vol...

[dr.barlo]

Am itching for a EL34 Express real bad... Yet, it'd be loud, quite loud... So, the questions is: Should I go for a build with Post PI Master Volume... Of course, when set low, the breakup of the PI is gonna enter the equation and change things. Yet, when that MV is set quite high (full on), I am curious whether or not it'd effect the tone? I'd love to have one, if a post pi MV would not fiddle with the basic tone...

Thanks in advance...

BTW am thinking of Pacific OT and Heyboer PT? Winged C EL34s? Are Jupiter (tweed clones) caps really worth it? They are twice as expensive as Sozo's...

Best,

B

[billyz]

My experience with the Express is no master volume is going to sound good. I tried 6 different variations, both pre and post MV. None sounded very good to me. However the VVR does sound good.

The reason the Express does not respond well to MV's is because it is designed to overload the Power tubes first then the PI etc.

[martin manning]

billyz, did you mean to say the reason an Express doesn't respond well to MV...?

Was one of the six variations you tried the KF type-2 (aka LarMar)? If so this is the first time I've heard someone say they didn't like it. True it will reduce power tube clipping distortion, so if that's where the magic is...

[Colossal]

Are Jupiter (tweed clones) caps really worth it? They are twice as expensive as Sozo's...

The standard coupling/signal caps used in the Express were 600V Mallory PVC polyester film foil Orange Drops (PVC6122, PVC601, etc). They are no longer made. There are some to be had if you are a looking to make a spot-on clone or feel that you cannot do without for getting the Express equation perfect. A suitable substitute (and I believe Ken Fischer used them - TW historians please correct if I am wrong) are the Sprague (now SBE) 6PS series, also a polyester film foil OD cap.

Others here have used Sozos and Sprague/SBE 715P (polypropylene film foil) caps with success. The Jupiters you mention are clone caps of the old Astrons and were not used in Trainwreck amps (to my knowledge anyway).

Good luck with your build.

[billyz]

billyz, did you mean to say the reason an Express doesn't respond well to MV...?

Was one of the six variations you tried the KF type-2 (aka LarMar)? If so this is the first time I've heard someone say they didn't like it. True it will reduce power tube clipping distortion, so if that's where the magic is...

You are correct, my grammar checker has expired.
And Yes, the KF type 2 and a couple of his others . All you need to do is listen to before and after. The Marshall style MV's work fine for a JTM45 etc but they did sound too good on the Express I built.

[dr.barlo]

Are Jupiter (tweed clones) caps really worth it? They are twice as expensive as Sozo's...

The standard coupling/signal caps used in the Express were 600V Mallory PVC polyester film foil Orange Drops (PVC6122, PVC601, etc). They are no longer made. There are some to be had if you are a looking to make a spot-on clone or feel that you cannot do without for getting the Express equation perfect. A suitable substitute (and I believe Ken Fischer used them - TW historians please correct if I am wrong) are the Sprague (now SBE) 6PS series, also a polyester film foil OD cap.

Others here have used Sozos and Sprague/SBE 715P (polypropylene film foil) caps with success. The Jupiters you mention are clone caps of the old Astrons and were not used in Trainwreck amps (to my knowledge anyway).

Good luck with your build.

Thanks for the detailed info!

B

[dr.barlo]

billyz,

Do you think that (KF type 2) post pi mv changes the tone even if it were to be all the way up?

Am trying to understand.

Best,

B

[dr.barlo]

billyz, did you mean to say the reason an Express doesn't respond well to MV...?

Was one of the six variations you tried the KF type-2 (aka LarMar)? If so this is the first time I've heard someone say they didn't like it. True it will reduce power tube clipping distortion, so if that's where the magic is...

Could you guys post some pointers as to what this particular one is? I really would appreciate it.

Best,

B

[martin manning]

dr. b, see here: https://tubeamparchive.com/viewtopic.ph ... 827#174827

[dr.barlo]

dr. b, see here: https://tubeamparchive.com/viewtopic.ph ... 827#174827

Thanks!

B

[billyz]

billyz,

Do you think that (KF type 2) post pi mv changes the tone even if it were to be all the way up?

Am trying to understand.

Best,

B

The KF type 2 is pretty good wide open. There is some change but it is not objectionable. But what is the point, when you turn it down it gets pretty buzzy. Try it if you like it then good. I did not. The LarMar is variation on the KF2 MV.

[dr.barlo]

I was thinking of getting it done with a toggle switch, to be used to bypass the whole MV circuit at will...

The thing is, I don't wanna get it done with 6V6s. Would rather use EL34s. Yet, they are powerful. And often on stage and in gigs, the max I could go is like 18 - 22Ws. But maybe I should go for 6V6s... Am kinda confused right now.

The VVR changes the plate voltage no? So a question emerged in my mind. With Marshall Plexis (which I kinda know better) the plate voltage is sort of really important. And changes the character of the amp. I have a 1987 clone running at 400V, and it gives very fluid leads. Thus, wouldn't the tone of the TW Express change dramatically with a VVR? I mean when it is set to low values and all...

B

[martin manning]

There is really no need to bypass the Lar-Mar type PPIMV, as when it's full-on the circuit is identical to the non-MV circuit. The only reason I can think of that billyz heard some difference is due to the additional lead wire associated witht the MV circuit.

VVR will certainly change the tone as it is turned down because the load lines of all the affected tubes are shifting and traversing different portions of the plate curves. This is no different from your Marshall plate voltage experience.

[EL34junkie]

I cant hit you with a bunch of hi tech terms but I put a MV in the Express I just built for a guy and he loved it. He said it allowes him to do so much more with the amp. We had a couple of set backs but we got it where he wanted it and it sounds great. Now with that said......I dont have the ear for everything a amp can or will produce but he is a musican and so has his dad been for like 50 years. Pappa Bear has owned a music store for 32 years and assisted with advised and final tuning of the amp and he also said it turned out well on the tone side.

[dr.barlo]

Thanks guys. Hearing those is a relief!



B