Quote from: bluesky6 on May 20, 2014, 10:07:16 AM

Quote from: Roly on May 20, 2014, 05:51:57 AM
Aside from agreeing with Enzo's precision lawnmower, the Frontman is the last circuit I would suggest as a first build project. 

^^^ agree x10000

The Fender SS pre-amp circuits are really VERY complex compared to some others that I've seen.

I would humbly suggest the Vox Pathfinder 10 circuit as a good starting point for a DIY build. It has a very simple PRE->GAIN->TONE approach with just 3 op-amps. The same design approach (including clipping diodes) are used in the Pathfinder 15R, SS Cambridge Reverb, AC15VR (with transistors) etc.

I had a Vox pathfinder 15R. It was a good amp that also offers a lot for the money, but the tone of it compared to the Frontman was a bit too nasal and boxy for my taste. This is where the Frontman works for me. It's not nasal, boxy or midrangey like many other amps I compared it with. The voice is super clear or maybe somewhat scooped, which is where my preference is.

Quote from: Roly on May 20, 2014, 02:11:41 PM

I hope you are rich, or ready for disappointment.  I wouldn't even bother giving you a quote because I know what I'm doing and my time alone would dominate the cost; corollary, any quote that is "reasonable" and not several times the price of a new Frontman could only come from somebody who doesn't really know what they are doing and you are going to get burned when they discover they are out of their depth - seen it before.

And if you are going to have an amp built by somebody who doesn't know what they are doing - you may as well cut out the middle-man and build it yourself, right?     The main reason I built all my own gear was because I couldn't afford commercial gear, and it became a habit.

Mass production reduces the individual price of an amplifier very considerably, but a hand-built one-off, even a direct clone, becomes a lot more expensive when you factor in the cost of a skilled tech to build it.

Commissioning a build also bypasses several of the advantages of actually doing it yourself, learning, being empowered over your gear rather than a victim of it, or hostage to a builder who may lose interest, service techs who have to deal with a unique beast (which no tech particularly likes because the assurance of a factory build is off the table).

bluesky has some more good suggestions for first builds.

Yes of course DIY would be the better way to go, but the learning curve would be too steep for me to tackle at this time. Probably best to stick with common sense and forget about this little amp as a long term investment. In any case whoever designed the circuit achieved a seriously good result IMO. The low end that comes out of this thing is especially good.

Quote from: J M Fahey on May 20, 2014, 09:15:50 AM
Not exactly.
They gave you a couple options, you pick which one applies .
1) What he (and Enzo) said that if you don´t hear any noise (or it´s inaudible when actually playing, not at 3 AM in a silent bedroom) it´s not worth replacing it with an "exotic" .
2) And if you have "unbearable"  noise, then maybe you have a bad Op Amp, in which case replace with *same type* (you are not improving but repairing).
3) and if you hear some background hiss, it might be useful to use, say, a $3 low noise Op Amp instead of the original (excellent, by the way) $0.50 one.
Although don´t be surprised to find little improvement.

But beyond that, don´t waste money.

The only big improvement in beginner type amps comes from fitting a much better speaker.

Which won´t improve noise by the way, but audible power, punch, body, clarity.

EDIT: in case you wonder, the Op Amp which *might*  improve noise floor is U1 TL072 type (a 50 cents part) , which I guess they are suggesting replace by LM833 (a, say, U$3 part).
No need to buy the one Nasa uses to listen to signals from Saturn (not kidding) which has half the noise of the LM833 for, say, 500U$.

NOTE: we are all guessing you are referring to a subtle "hisssssss"  you hear in the background **with guitar volume ant tone controls on 0**
Any other noise (buzzing, hum, etc.) which you can hear while playing usually comes through the guitar pickup picking ambient noise and interference, a different problem unrelated to Op Amp changes.

Thanks. Yes the noise I'm referring to is amp background hiss, present when no guitar is plugged in.

Thanks very much Roly for the thorough rundown. Quite informative.

What got my attention with this amp is that compared to many other amps (mostly all tube) I put next to it, this little guy gives me the best clean tone. Boggles the mind how the cheapest amp sounds best (to me anyway)!...

I can see now that the design of this circuit is what makes it a disposable amp. Quite unfortunate.

So I gather that this passage below from your earlier post would not apply to the Frontman, and there is no op amp in it that can be upgraded to lower it's noise floor?

Quote from: Roly on February 09, 2014, 03:25:34 AM
Originally the preamp gain came from "low noise" BC109C's, but still had quite a significant and audible noise floor.

The pre I built to replace it was nominally the same except it used LM833's (at a buck-and-a-half a pair) for the gain.

The second shock is that it is now so quiet you can't tell if it's turned on without looking at the pilot light.  {It can be a little unnerving on stage actually because now there is no audible clue that you have left the gain really cranked and are just about to give everyone an unintended blow-wave.}

Quote from: Enzo on May 19, 2014, 09:45:52 PM
It would be arduous for an inexperienced person.  An experienced tech wouldn;t do it, really.   I don't mean this unkindly, but it strikes me as like taking your lawn mower apart and having all the parts precision machined to NASA tolerances.


What is cheap about the amp is the labor to make it.  The controls on the panel are cheap, sure, but even "good" ones don;t cost much.  The speaker is super cheap.  But equating the cost of parts with durability is not fair, I think.  The transformer may be marginal, but unless you abuse it, it ought to go forever.  Same with the cheap speaker.

I buy "good" resistors for my shop, and they cost a penny.   Fender pays a lot less even than that for a resistor, but resistors don;t burn out on their own, they burn when transistors elsewhere fail.


If it is noisy, then one of your op amps is noisy, I'll bet my lunch money.  A new one of the same type will probably cure it.  or you could buy some "low noise" op amps for a few cents more.   Hifi guys like to find esoteric Burr Brown op amps for their stereos, but I think that is a waste of money and effort.

I think a point to point version of this would be a pain in the butt to make, How will you be mounting and wiring those ICs?   You can buy nice fancy $5-10 controls, and what you will have is controls on the panel with a more industrial "feel" to them when you turn them.  Electronically they will be the same.


And after all that, any amp sounds like the sum total of all its parts.   You build an all new one, and a new one made of different parts, there is a good likelihood it will not sound the same as the original.


It would be a good project to learn about amp construction though.

Thanks for your reply.

I realize this idea defies common sense and conventional wisdom to a certain extend.

If the existing circuit is not inherently doomed to early failure then I would be happy to only upgrade any components that would help reduce the noise level. As you say and also was mentioned on an earlier post, I believe there is an op amp that can be upgraded to improve the noise spec (?) I should look into that.

Quote from: joecool85 on May 19, 2014, 08:24:28 PM
It could be done, but would be a long arduous process. I say go for it, it'd be a great learning process.

Thanks for your reply. Would you say it would be an arduous process for an experienced tech, or only for a inexperienced beginner like myself?

Greetings all, first post here. Glad I found this thread. I'm officially a fan of the Frontman 25R. The clean tone that comes out of this thing is pretty amazing. Best clean tone I've come across. Now the weak point of this amp is the noise floor, which is higher than I would like, and also that this thing is built presumably using the cheapest components available, which implies that durability will not be something to count on.

So I've been pondering the idea of having a point to point version made of this amp using all top shelf components (clean circuit only, no hi gain section, aux in or headphones out). I would then put this circuit in a new chassis and cab.

Anyone care to comment on how crazy this idea might be?

I'm not a tech BTW, so I don't know all the details involved in amp circuit design.

Thanks for any input!