5 watter

Karel-Mars · 2009-07-04T10:51:39+00:00

Hi Ampheads I have been wanting to build a 5 watter for a while, and when I found a seemingly appropriate power transformer, it was time to get the soldering iron out. I had a cabinet I made a while ago. I was curious how 8 inch MOD sounded like , so in it went! I had a chassis bent and planned a layout. Drilling was next. Drilling finished! Most hardware mounted. It is starting to look like an amp. The action now moves inside... The filament wires are in place, as well as the cathode resistor I decided to go with paper oil caps for a brown sound. Time to power up and hear the beast roar It sounds good... no hum and silent when cranked.

Karel-Mars

Tailon. wrote so how easily can the power , output transformers be found , and how easily can the choke be found ....... cos i want one .. ?

It is quite easy to find the transformers ? pm me for a quote

I making this available as a kit.

Karel-Mars

matta wrote Karel, did you try your design with an octal tube as well? What made you go with the EL84 over say a 6V6?

Good question ? the little power transformer delivered very low voltage. I measured about 108VAC without a load. I designed a voltage doubler power supply to give me about 250V DC. I know from experience that the EL84 still kicks ass at low voltage. Eventually, with the amp running I measured 220VDC. I find the EL84 very rewarding in "first amp" projects. (and I always have a EL84 lying around from a VOX retube :?)

I have built this amp with 6SL7, 6SJ7 and 6F5/6C5 pre-amp tubes with excellent results. The 6SL7 is an amazingly good sounding tube (get them from Mr Valve). On the output side I have used the octal 6V6/G/GT tube mostly.

Karel-Mars

aja wrote Interesting, like a stripped down version of this:

http://akavalve.blogspot.com/2008/12/fender-champ-comparing-5f1-and-5e1.html

Yes. Compare it to the GA5 from Gibson. No NFB and 220K anode/2K2 cathode resistors. The circuit is probably using the best elements of each.

Karel-Mars

JoeyBones wrote That looks way too simple. What's the catch ???

No catch. The greatest guitar amp in the world is also the simplest. It takes some people a lifetime to discover this :'(

TomCat

@ Karel

How easy is it to bump up the power to a 8 to 10 watter, for a little extra oomph...? (I presume a dual tube O/P stage would be required.....)

Also how readily available are tube rectifiers.....as opposed to SS....which are a dime a dozen........

[deleted]

Would you be able to give us sound samples of your amps? I know it can't do it justice really, but would be nice to hear your creations. . . I have looked at your site so often and wondered how the Mars Probe sounds like for eg...

If I could hear how good your amps are without having to drive all the way to the Cape.

AlanRatcliffe

Guys - if you want to make any requests of a commercial nature (price, etc.), please PM Karel directly.

matta

Karel Mars wroteYes. Compare it to the GA5 from Gibson. No NFB and 220K anode/2K2 cathode resistors. The circuit is probably using the best elements of each.

Thought it looked like a GA5 variant ?

Looking at I'd expect a nice crunch, bite, a bit more focused/smoother with the EL84, but little clean headroom? How responsive is the amp to touch sensitivity?

Did you A/B with and without the cathode bypass cap? Typically I've experienced that it NOT having one adds a bite more brightness/bite?

Interestingly you have put the VOLUME pot after the the pre-amp ahead of the output stage, the GA5 has it between the each half of the 12AX7? Essentialy yours is a 'Master Volume'. Sonically did you notice a marked difference?

Those are also pretty massive filter caps, considering the GA5 were 10uF each, your first 2 are 220uF, are you finding this reduces your hum alot (lower ripple)? I doubt you would get away with similar valves HAD you gone with a valve rec, which bring me to the next point...

Why SS rectification? It is cheaper,but misses a bit of the SAG one has come to expect from valve recs esp. the smaller 5W's like Tweed Champ 5F1 for eg. It of course lowers costs, making it it a more affordable build, but interested to know if you A/B'd it against a valve rec and noted any differences and which/why you preferred one over the other?

Also how readily available are tube rectifiers.....as opposed to SS....which are a dime a dozen........

Tomcat, they are just as easily available as any of the other valves, but costs play a factor most of the time, as mentioned above.

No catch. The greatest guitar amp in the world is also the simplest. It takes some people a lifetime to discover this

Less it more in more ways than one!!! And I'm in complete agreement ?

Matt

Karel-Mars

Brentcgp wrote Would you be able to give us sound samples of your amps? I know it can't do it justice really, but would be nice to hear your creations. . . I have looked at your site so often and wondered how the Mars Probe sounds like for eg...

If I could hear how good your amps are without having to drive all the way to the Cape.

I am working on getting some samples together. I'll post it a.s.a.p.

Karel-Mars

TomCat wrote @ Karel

How easy is it to bump up the power to a 8 to 10 watter, for a little extra oomph...? (I presume a dual tube O/P stage would be required.....)

It is easy to bump up the power. An EL34 would give between 8 and 10 watt in a similar amp. This shifts the amp design to a new category. Power consumption doubles and the output transformer impedance is different. I would put this package (8watt combo) into a bigger housing. This bumps up the cost of the amp.

Karel-Mars

matta wrote
Karel Mars wroteYes. Compare it to the GA5 from Gibson. No NFB and 220K anode/2K2 cathode resistors. The circuit is probably using the best elements of each.
Thought it looked like a GA5 variant ?

Looking at I'd expect a nice crunch, bite, a bit more focused/smoother with the EL84, but little clean headroom? How responsive is the amp to touch sensitivity?

I always go back to Gibson design if I can. Chokes in the power supply and no NFB.

Yes, there is little clean headroom. The way to play clean, is to crank the amp and roll down the guitar volume control. This way you can get a tube compressed clean tube tone that sounds groovy (what ever that means 8))

If I want to do blues, I turn down the amp volume to 4 and turn up the guitar.

For me touch sensitivity is a function of the high frequency responsiveness of the amp. Good high frequency response - good sensitivity. There is no negative feedback loop, which always improves touch sensitivity. The paper oil caps gives a nice woody/paper/warm sound, but does compromise the touch sensitivity. But this is the point: for a recording amp you want roll off on the top. I was expecting the MOD 8inch to be a tad bright.

To compensate for the paper/oil caps I went with metal film resistors. They generate less hiss/white noise on a high gain amp; and this a pretty high gain amp.

I want to compare the touch sensitivity of paper oil with orange drops and silver/mica NOS. I'll see if I can record some samples of the different caps.

AlanRatcliffe

TomCat wrote How easy is it to bump up the power to a 8 to 10 watter, for a little extra oomph...? (I presume a dual tube O/P stage would be required.....)

Easier to build it in a larger cab with a larger, more efficient speaker like a Celestion Blue, which has a 100dB sensitivity as compared to the 93dB of the MOD 8".

TomCat

@ Alan, Karel and Matt

Thanks for the info.

I'm seriously looking at an amp build.

I like the idea of an 8W Class-A with the Celestion blue. Maybe have it as a two channel (Clean low gain and distortion high gain, foot switchable)

@ Karel/Matt.....If I put a design schematic together, would you guys be willing to have a look at it for me.

I have two HiFi tube amps at home that are not working at the moment, along with a tube preamp that I could use for parts, valves etc.
I have at this stage no clue what the tube compliments are. I will have a look at these over the weekend.

Karel-Mars

Show us your design ?

matta

TomCat wrote@ Karel/Matt.....If I put a design schematic together, would you guys be willing to have a look at it for me.

Sure thing! Just post it and I'm sure we will both do what we can to help out! Karel is MUCH better at Valve stuff than I, I'm more in transistor land, but have a decent grounding in valveville as well and learning more where I can.

Matt

TomCat

@ Karel and Matta

Thanks guys....give me some time to condense the vaporware between my ears into something that makes sense...... ??? ???

I'll PM you both when I have the design down as some sort of schematic.

TomCat

Ok...Started to do some research.

My starting point was the Fender Princeton 5E2 which uses a 6V6GT output tube. Looks like power to be about 5 watts.
THD is about 12%

First question......Is there a higher power replacement to the 6V6GT

I have also looked at the EL34, which is a pentode as opposed to the tetrode of the 6V6. I see the THD of the EL34 to be about 10% at 8 Watts...slightly better than that of the 6V6.

Would the EL34 could work in the same princeton CCT without the suppressor grid.....or will I need to use a higher powered tetrode....as in question above.

Would I also be correct in assuming that pentodes generally are better as OP tubes?

Thanks

Ray

Karel, I dropped you PM.

Karel-Mars

Hey All

I have made some clips of the amp. I used a small electret computer mic and recorded it in Audacity on my Thinkpad. Ibanez SG copy with Dimarzio pups.

[url=http://download_page.php?id=143242]download_page.php?id=143242[/url]

[url=http://download_page.php?id=143251]download_page.php?id=143251[/url]

[url=http://download_page.php?id=143252]download_page.php?id=143252[/url]

AlanRatcliffe

The links are incomplete Karel...

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