Vibrolux Reissue Problem

[Greg_L]

I'm curious about the kit. I saw the photos of the parts supplied on the Fromel site but there is not much detail provided. Were there parts value changes or just parts that were said to be better? Also, were there any circuit wiring (or cuts & jumper) changes or just one-for-one parts changes? I'm not asking to disclose the exact details of the kit. Just the general approach.
Thanks,
Tom

My friend has the "Custom Vibrolux Reverb Cream Knob".
https://fromelelectronics.com/collec...ucts/vblx-mods

Most of the parts were just a swap. We didn't cut any traces or anything. Some of the parts were a different value though if I remember correctly. I believe the biggest changes were probably just bright cap and tone stack values but I truly don't remember specifics. I just know the amp definitely changed for the better. We recorded A/B sound clips and the improvement was significant.

[The Dude]

I have nothing against the Frommel kit conceptually, but I do think it's overpriced. You can buy the parts yourself and do the mods for a much lower price. I must clarify, though- this is not a dig on Frommel mods. I understand that they have to make some money for the effort, marketing, etc. And, for a novice without much technical knowledge, a kit is probably a good way to go.

[SoulFetish]

One of the things that always bothers me about any kit-mod you can buy, is that it seems NONE of them just come with a friggin schematic. Often, customers will have us (techs) install these kinds of mods, and it is such a huge time waster to deal with a pictorial and written instructions.

[Tom Phillips]

I think that the Fromel kit price is fair considering the effort to put it together, document it and market it. However, I am not a supporter of such shotgun parts replacements in general. I think that one or two of the parts changes and the global negative feedback circuit change (which has been mentioned in this thread but which I have not yet deciphered from the kit instructions) will make most of the difference in the amp performance. Other parts changes, I believe as a procedure, should be based on test and replace as necessary decisions. The rub of this is that the evaluation time may be excessive for some owners or self proclaimed amp techs. As long as the amp owner is satisfied with the results, I suppose all is good. There is always the possibility that the amp owner will feel that "I paid $$$, therefor the result is an improvement." That could be the same thing that happens with audiophiles who claim great improvement for the multi hundred dollar patch cables or speaker cables they purchased. And that's what I have to say about that!

[Greg_L]

I didn't even know these Fromel kits existed until I had one in my hand. My buddy found it on his own and brought it to me. It was all pretty easy and we did it over some tacos and beers. No big deal.

I could have "blackfaced" his amp on my own but truthfully I was more than happy to just swap out the parts willy nilly and just do what the kit said to do. It worked out very well. No problem. I'm not gonna be puritanical about it. The amp is pretty damn nice now and that is the goal, isn't it?

[Chuck H]

The amp is pretty damn nice now and that is the goal, isn't it?

Yep But...

If it smoothed out the taper on the volume controls then it also lowered the gain of the amplifier. Taken at face value that means the mod is only useful for players that don't use the extra gain these amps were designed for. That's not a problem except that it's not indicated in print by Fromel so that players can make an informed choice.

[Greg_L]

Yep But...

If it smoothed out the taper on the volume controls then it also lowered the gain of the amplifier. Taken at face value that means the mod is only useful for players that don't use the extra gain these amps were designed for. That's not a problem except that it's not indicated in print by Fromel so that players can make an informed choice.

Maybe but the "extra gain" in the amp sounded pretty crappy so whether they need it or not they'd probably be better off with it tamed down a bit. I know everyone's tastes are different but I'd find it very hard to believe that anyone would prefer that amp's sound before the Fromel kit. You don't buy a Vibrolux Reverb for high gain.

[g1]

I think that the Fromel kit price is fair considering the effort to put it together, document it and market it. However, I am not a supporter of such shotgun parts replacements in general. I think that one o the global negative feedback circuit change (which has been mentions but which I have not yet deciphered from the kit instructions)

Step 7 in the kit.
Here's the funny part. The 'Custom Vibrolux' cream knob amp is a Zinky tweaked version of the '63 Vibroverb re-issue (see attached). The fromel kit basically removes the zinky mods and turns it back into the '63 re-ish. The cap changes are all same value, just 'upgrades'.
The only change that remains different from the '63 will be the reverb drive 12AT cathode resistor becomes 1K (from 2K2) and the cap feeding the reverb pot becomes .0022 (from .0033).

That's not a problem except that it's not indicated in print by Fromel so that players can make an informed choice.

How about Step 8, removing the OT protection diodes and calling it 'noise reduction'. Or removing the reverb from the normal channel.