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Cheap Forum Amp by Captainbeefheart


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[Moderator post: This is the post in the original thread abut a "Cheep Forum Amp." The threads have multiplied across a varaiety of subjects, on topic, off topic, and otherwise. I have consolidated them all here for eference and there area at least two forum members interested in the progress

 

From @captainbeefheart 

 

 

Since I have joined this great community I must say I am happy to have stumbled onto it. One thing that is trending is cheap tube amplifiers, well all tube amplifiers seem to be trending more and more but in general many just do not have the liquidity to just drop $2,000 on a new amplifier. What if we can have our cake and eat it too? What if we can knock that $2,000 price tag down to $200 for a true hifi tube amplifier?

 

Now my goal would be between 5 and 10 watts continuous output power 20-20kHz with no more than 1% THD at full output. But I am wondering if we should just up the game to 15 watts output but the price may jump up to $300-$350 area. What say you? Would people prefer the cheaper option with less power or spend a bit more and get the power output up to more reasonable levels. This is a Klipsch community and I know we do not need much power to get great sound, regardless spending $200 I think is easier to sell to the wife compared to $350, that's a car payment right there where $200 is a night out for two at a nice restaurant. 

 

Thoughts? Comments? Not worth it? Interesting?

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Are you thinking you would design and build something in the $200-350 price range for yourself, or do you want to do something you can make available to the community? DIY kit, or assembled?

 

As for myself, I would love to be able to get a decent little tube amp in that price range whether in kit form or assembled.

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16 hours ago, captainbeefheart said:

What if we can knock that $2,000 price tag down to $200 for a true hifi tube amplifier?

 

Now my goal would be between 5 and 10 watts continuous output power 20-20kHz with no more than 1% THD at full output. But I am wondering if we should just up the game to 15 watts output but the price may jump up to $300-$350 area. What say you? Would people prefer the cheaper option with less power or spend a bit more and get the power output up to more reasonable levels. This is a Klipsch community and I know we do not need much power to get great sound, regardless spending $200 I think is easier to sell to the wife compared to $350, that's a car payment right there where $200 is a night out for two at a nice restaurant. 

 

Thoughts? Comments? Not worth it? Interesting?

Can you give us a peep into what topology you have in mind? I'm dying...

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3 minutes ago, 001 said:

you can build a Crimson 275 for 1000$  --- -but you can build a way better Crimson 275 for 1500$  using great parts vs the cheaper parts they used---now that would be worth trying 

The 275 sounds fantastic as is I would be hesitant to change things (other than safety issues of course) in fear of screwing up the sound. If more power is required I'd look at something else personally.

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My 2c is to read what others have done for these on other boards.  These kinds of threads follow patterns and it'll save you time.  The "consensus"/choices differ everywhere so the amps do as well.  Just build what you want--in the end, that's what happens anyway and some will like it and some wont.  Money is always in the iron and those corners have already been cut in the other projects.  It's a bunch of work engineering for cheap :)  If you want it to be your own thinking and for the process, I 100% understand that, too.  Maybe just fix what you don't like in someone else's cheap-amp project if you want less work than ground-up/blank sheet design.  I can think of a couple/few that sound like your general intent if you strike-out.  Applaud the energy.

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20 hours ago, CWelsh said:

Are you thinking you would design and build something in the $200-350 price range for yourself, or do you want to do something you can make available to the community? DIY kit, or assembled?

 

This would be an assembled amp sold to only forum members. For the members that like to build there own I will provide whatever necessary information for them to make one on their own.

 

16 hours ago, tigerwoodKhorns said:

15 watts  and great sounding amp, based on some recent hoopla on the web, I am in if I am correctly guessing what might be being built.

 

If anything has been learned from the Crimson 275 drama is that a 15 watt amplifier can work for many forum members. The goal now is to put that in peoples hands for a very low price point.

 

16 hours ago, The Dude said:

Search this sub forum for the "little Darling", "little spud", as there are 2-3 SET and SEP monoblock designs that fit that budget, but only around 3 watts

 

I have made a few one 'tuber' or 'spud' amps before and 2-3 watts might be enough for some it's not enough for the majority. It is looking like we are aiming for 15 watts here.

 

5 hours ago, Curious_George said:

Can you give us a peep into what topology you have in mind? I'm dying...

 

As soon as I settle on one I don't mind letting you in on what it will be. I needed to get some design goals first which is why I asked about power needs first. I figured a 15 watt amp might be much more appealing to many. I agree that iron is the most expensive parts, I have some tricks that worked well for me in the past I need to revisit to get the what we need and still fit the budget and performance parameters.

 

2 hours ago, Racer X said:

A well designed 15 W tube amp for $350 would be the Holy Grail.

 

It's panning out a 15 watt tube amp is what we are going with.

 

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46 minutes ago, captainbeefheart said:

 

If anything has been learned from the Crimson 275 drama is that a 15 watt amplifier can work for many forum members. The goal now is to put that in peoples hands for a very low price point.

 

 

Someone out there is going to start a service upgrading the Crimson to its full potential.  I don't know how many units are out there, but I expect to see this when the builder refuses to do anything.

 

I am not familiar with the safety issue, which may be a deal breaker for liability reasons. 

 

 

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14 minutes ago, tigerwoodKhorns said:

 

Someone out there is going to start a service upgrading the Crimson to its full potential.  I don't know how many units are out there, but I expect to see this when the builder refuses to do anything.

 

I am not familiar with the safety issue, which may be a deal breaker for liability reasons. 

 

 

 

To do so one would need to increase the size of the fuses which will void any warranty in order to reach the rated continuous output power. The actual physical swapping of the output transformer isn't very difficult, but whoever decides to take on this venture I hope they remove the existing compensation networks and plot the phase shift between input and output. Then re-calculate the compensation networks for best stability with the new iron.

 

As for safety, after grounding the chassis and removing the resistor on the neutral noise would need to be checked and possible grounding changes may need to be done.

 

 

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There are quite a few established designs for tube amps, this is the one I almost pulled the trigger on:

 

http://tubelab.com/designs/tubelab-sse/

 

But, I will say the cost of parts is still up there and chassis/housings are surprisingly expensive.  Plus your time. I just finished an Aleph J build, and even reusing a Hafler 220 chassis I got for $20 it took quite a bit of fabrication. Not trying to be discouraging, but as someone that has been trying to find high-quality DIY designs and build them cheaply it always takes way more time and money than I expected. Still fun.

 

Another thought is the ACA, also a Nelson Pass solid state design. I know it's not tubes, but you do get 8 WPC class-a and the full kit is around $350.

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2 hours ago, captainbeefheart said:

 

This would be an assembled amp sold to only forum members. For the members that like to build there own I will provide whatever necessary information for them to make one on their own.

 

 

If anything has been learned from the Crimson 275 drama is that a 15 watt amplifier can work for many forum members. The goal now is to put that in peoples hands for a very low price point.

 

 

I have made a few one 'tuber' or 'spud' amps before and 2-3 watts might be enough for some it's not enough for the majority. It is looking like we are aiming for 15 watts here.

 

 

As soon as I settle on one I don't mind letting you in on what it will be. I needed to get some design goals first which is why I asked about power needs first. I figured a 15 watt amp might be much more appealing to many. I agree that iron is the most expensive parts, I have some tricks that worked well for me in the past I need to revisit to get the what we need and still fit the budget and performance parameters.

 

 

It's panning out a 15 watt tube amp is what we are going with.

 

With the goal of 15 watts I assume it is going to be a push pull design. I have one PP amplifier using the EL84 tubes. Sounds really good and will not break the bank building. 

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21 minutes ago, iaRIVR said:

There are quite a few established designs for tube amps, this is the one I almost pulled the trigger on:

 

http://tubelab.com/designs/tubelab-sse/

 

But, I will say the cost of parts is still up there and chassis/housings are surprisingly expensive.  Plus your time. I just finished an Aleph J build, and even reusing a Hafler 220 chassis I got for $20 it took quite a bit of fabrication. Not trying to be discouraging, but as someone that has been trying to find high-quality DIY designs and build them cheaply it always takes way more time and money than I expected. Still fun.

 

Another thought is the ACA, also a Nelson Pass solid state design. I know it's not tubes, but you do get 8 WPC class-a and the full kit is around $350.

And a newer version that is less cost available soon. Tube sound but SS. Excellent project for beginners who are afraid of the high voltages tube work at. That said tubes still rule when it comes to sound. 

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