[Zachh]

Hey fellow Canadians, this is my first post on an online forum.

I've been planning on building an amp with the eventual goal of building amps and selling them. My goal is to create an entry level tube amp (think blues Jr., but hopefully at an even lower price point) that a player looking for their first tube amp would consider.

While deciding between solid state and tube rectification, I noticed that solid state components (not just rectification, but amplifier boards as well) cost next to nothing.

What do you guys think of a full tube amp that has an equivalent solid state component for each tube? (A SS rectifier, small digital amp for preamp tube and larger amp for power tube)
In the event of a tube failing, a toggle switch could divert the signal flow to the SS board and get through the gig/practice session.

This feature would add <$15 in manufacturing cost, but I'm thinking the biggest issue will be keeping a steady enough base voltage so the tube bias doesnt jump way up when a tube is deactivated.

Thoughts? Does something similar exist?

 

[greco]

Welcome to the forum!

Your concept sounds very interesting.

I enjoy reading threads about electronics, so I hope this 'takes off'. I am just a neophyte electronics enthusiast.
However, we have many forum members that are amp techs and/or electronics gurus and they routinely start threads and/or comment.

I will be following this thread with interest.

Cheers

Dave

 

[cboutilier]

Paging @mhammer . He's actually a wizard by trade.

 

[Budda]

I would rather not have an extra part to replace or fix, instead a system like the ampeg SVT where if a tube fails, the pair gets taken out of the circuit.

Also, which consumers would require that level of failsafe in what you describe as an entry level amp? Simple, cost effective to the consumer and good (sometimes great) useable sounds out of the box are what entry level tube amps provide.

I think you are trying to solve a problem that doesnt exist.

 

[Zachh]

I'm very thankful for your feedback budda, I'm looking for what people think and you're right, extra parts is a considerable drawback.

I'm not so much solving a problem as adding a feature that some might want with little additional cost.

I'm aware of systems that deactivate dead tubes, H&K makes a big head I know that does that as well. My amp would be small, though, and will only have one preamp and one power.

When I got my first used tube amp, the tubes were getting a bit old and every time I turned it on I was nervous as to what odd noise might come out of it. Id use it at band practice, and if one day I powered it up and the preamp section was dead I would have loved to have gotten by with a SS board.

Being used to SS amps, I was pretty hard on my amps (like many young kids bringing them to school, band practice, gigs etc.) and I could benefit from fail-safes. The majority of higher end tube amps sold (boutiques, reissues,) I'm guessing sit in living rooms, while the hot rods and blues Jrs do the gigs.

 

[AlBDarned]

Sounds like a neat idea.

Welcome to the online forum world - where you can always count on spot-on helpful & polite interactions, every time.

 

[JBFairthorne]

I'm not sure that someone who's shopping for entry level products would have any clue about whether or not that's something they'd want/need in an amp. Add to that, most tube amp owners have spare tubes around...or spare amps. I just don't see the marketability of something like this.

 

[dtsaudio]

Since tubes and solid state operate completely different from each other, it isn't a simple matter of subbing in a transistor (or transistor circuit) to operate in place of a tube. You are talking about switching out a complete preamp or power section in the event of a failure. I fail to see how it would only add $15.00 to the cost. You might be able to find low cost modules, but after shipping and install time, let alone the parts cost themselves, you are going to well above $15.00. Also the complexity of the power supply to be able to supply low voltage to the SS part and HV to the tube part would make it far more expensive and possibly in the long run less reliable and safe.
Interesting notion, but I don't think it would be worth the effort.
My opinion might change if you could elaborate a bit more.

 

[Zachh]

Jbfairthorn, you're right, most players have extra amps or tubes, but not necessarily entry-level buyers. A set of tubes isnt expensive for a small amp, but being able to switch mid-song if a tube goes is a big step up. I'm mainly basing demand off the fact that I would have loved a "unkillable tube amp" when I was getting into the market, as it would also help me put off replacing tubes as long as possible (not what you're supposed to do, but a cash-strapped player will do it anyway).

Dtsaudio, you're right about it costing more than 15$ as when I wrote the initial post I hadn't done research on the power supply yet. The amp boards themselves can be had for cheap (usually with free shipping), but I'm not set on a power supply yet.

Most boards seem to run in the neighborhood of 5-24v, and ive noticed that tube transformers have an additional output for the tube filaments and pilot light, for example the fender champ transformer puts out 2.25 amps at 6.3 volts. I'm thinking that at least in the prototype stage i could tap the filament output for SS boards, adding a (very inexpensive) converter if the board is DC. If this idea ever went commercial I'm thinking the best would be to hire an electrical engineer to draw me a transformer with the appropriate outputs and have it made at ClassicTone or in China.

EDIT: shoot, the previous paragraph is wrong, the step down is done via a resistor since the filament and pilot light are a constant load, unlike an audio amp. The output is still 630v.

A solution I could see is to use components similar to a cell phone wall charger to tap the 120v main to 5-10v DC.

In terms of cost, most components I've considered so far can be had off eBay/Alibaba for cheap. The extra hour or half of assembly per amp would probably be the biggest cost.

Again, thanks everyone for the replies this is exactly what I was hoping for.

 

[tonewoody]

I think if you marketed an "unkillable amp" that lived up to it's name you might generate some interest.

I'm imagining a sales campaign where the amp is subjected to sensationalized abuse (tossed out of a plane, run over by a steamroller) and 'keeps on ticking'.
******
Entry level buyers probably don't gig so a tube failing isn't a big hardship.

If you enjoy electronics design and building prototypes for fun, give your idea a go. You might get some new ideas from the process. Is there a market for your idea as proposed? I don't think so.