5F1 Tweed Champ Speaker & OT ?

[whodatpat]

I am contemplating an amp build. (I am still in the homework stages.) I am trying to stay as close to the original 5F1 design which calls for an;
Output Transformer that is 8 watts and 4 ohm
Power Tube is a single 6V6.
Speaker is an 8” 4 ohm

My question is about the speaker size and wattage. It looks like none of you ever leave the low watt 8” speaker in tact. Why? Is it a volume issue or a sound issue? I am not looking for volume out of a champ.
What is the “preferred” speaker upgrade? & Why?

When upgrading the speaker, I would expect the OT to need to be upgraded as well. However when I look at OT’s greater than the 8W, 4ohm, they list it as being for a two 6V6 amp. Would you have to add a 6V6 power tubes to go from 8W, 4ohm Hoffman #022921 to the 12W, 8ohm Hoffman #022905?


Also, I have a question about amp wattage VS speaker wattage. Isn’t it preferable to keep your speaker max wattage to the same ballpark as your Amp wattage? (ie. no 50 W speakers on an 8 W head.) Is there a table or a fast and tried rule?

Thank you for reading this far.

Patrick

[JohnnyCrash]

Originally Posted by whodatpat

My question is about the speaker size and wattage. It looks like none of you ever leave the low watt 8” speaker in tact. Why? Is it a volume issue or a sound issue? I am not looking for volume out of a champ.
What is the “preferred” speaker upgrade? & Why?

1. Sound.
2. Reliability.

The original speakers sounded terrible and they often blew (since most folks play the Champ dimed for overdrive).

In general, I prefer AlNiCo speakers in old school Fenders, BUT it Champs I prefer ceramic speakers.

AlNiCo's when pushed hard actually lose magnetic efficiency, which causes the high-end/treble to soften and the speaker compresses a bit. Mellow top and a tad of compression.

Ceramics do not do this. In Champ's I prefer this mainly for Tone (keeps bright and tight when driven by the loose Champ OD sound) and secondly for loudness.

Originally Posted by whodatpat

When upgrading the speaker, I would expect the OT to need to be upgraded as well. However when I look at OT’s greater than the 8W, 4ohm, they list it as being for a two 6V6 amp. Would you have to add a 6V6 power tubes to go from 8W, 4ohm Hoffman #022921 to the 12W, 8ohm Hoffman #022905?

Technically, an authentic replacement would be 6w, 3.2 ohms.

What you want to do is match up the 6V6's impedance with the OT's primary, then the OT will have. The wattage isn't as important, since it's sort of an indicator of power handling. You want at least 6 watts, but you can go higher (8 or 10 watts, etc).

The primary impedance (depends on the tube, in this case a 6V6) will determine the secondary impedance (4, 8, or 16 ohms most commonly).

Look for a Single Ended 5-10 watt OT that likes a primary around 7,000 ohms (6,500-10,000) and will give you secondaries you want according to load fed by the tube.

Try other sources, other than Hoffman if need be. I really dig Hoffman's products and services, but I often go elsewhere for my trannies. Try Hammond or Heyboer sellers, they seem to have more variety in trannies.

Originally Posted by whodatpat

Also, I have a question about amp wattage VS speaker wattage. Isn’t it preferable to keep your speaker max wattage to the same ballpark as your Amp wattage? (ie. no 50 W speakers on an 8 W head.) Is there a table or a fast and tried rule?

In the old school, the speaker is supposed to be rated similar to the amp for best efficiency/loudness. This isn't very ideal these days... a lot of folks crank low watt amps for overdrive. Power ratings were wattages before distortion/clipping. When an amp distorts it may be spiking past this range.

For this reason, if you're going to be cranking an amp, go with a speaker rated at least 1.5 times the amps output (a 9 or 10 watt speaker for a 6 watt Champ, a 75w speaker for a 50w amp, etc).

[whodatpat]

This one may do the trick.
Hammond 125DSE for $40.50 http://www.stf-electronics.com/Page0009.Html
•10 Watts audio
•70 Max. D.C. Bias
•Designed for general purpose or replacement use, in single ended, tube output circuits.
•Frequency response: 100 Hz. - 15 Khz (+/- 1db max. - ref. 1 Khz).
•Open style with minimum 12" long primary & secondary leads.
•All sizes use butt stacked cores (using 29M6 steel) with an air gap, to reduce D.C. core saturation.
•Primary impedance range from 2,500 to 10,000 Ohms.
•Secondary impedance range from 4 to 32 Ohms.

[JohnnyCrash]

I've used that one for a Champ build. I've since put in a 15w OT and made some changes to run other octal power tubes (6V6, 6L6, EL34).

[DrewB]

Another perspective...

When I built my 5F1, I knew and 8" speaker wasn't going to give me what I wanted. I also knew that I didn't want to be limited in speaker selection when tinkeritis set in, as it invariably does. For those reasons, I decided on an 8-ohm output transformer and a 12" speaker in a 5E3-sized cabinet. I haven't regretted making those decisions.

I'm not saying this is the way to go, but consider your options and what you ultimately want the amp to sound like, based on what you already know you like. That's the great thing about building your own amps. You have the ability to mix and match the "pieces" to what works well for you.

[JohnnyCrash]

Originally Posted by DrewB

Another perspective...

When I built my 5F1, I knew and 8" speaker wasn't going to give me what I wanted. I also knew that I didn't want to be limited in speaker selection when tinkeritis set in, as it invariably does. For those reasons, I decided on an 8-ohm output transformer and a 12" speaker in a 5E3-sized cabinet. I haven't regretted making those decisions.

I'm not saying this is the way to go, but consider your options and what you ultimately want the amp to sound like, based on what you already know you like. That's the great thing about building your own amps. You have the ability to mix and match the "pieces" to what works well for you.

+1

Nearly all of my amp builds are heads... I use multi-tapped OTs so I can swap the heads with any 4, 8, or 16 ohm cabs/speakers I want. You can install a second output jack as well as a impedance switch on a combo too.

Installing an impedance switch isn't too bad at all :)

[JamonHamon]

Originally Posted by DrewB

Another perspective...

When I built my 5F1, I knew and 8" speaker wasn't going to give me what I wanted. I also knew that I didn't want to be limited in speaker selection when tinkeritis set in, as it invariably does. For those reasons, I decided on an 8-ohm output transformer and a 12" speaker in a 5E3-sized cabinet. I haven't regretted making those decisions.

I'm not saying this is the way to go, but consider your options and what you ultimately want the amp to sound like, based on what you already know you like. That's the great thing about building your own amps. You have the ability to mix and match the "pieces" to what works well for you.

+1
Victoria uses a Jensen Alnico P12q in there 12" Champ Clone and its the best

[Dacious]

Single-ended output transformers need an airgap, so they are inherently different to a push-pull output tranny which along with the centretap does not. Hammond makes the 125SE output tranny in a variety of sizes, all within $5-10 of each other. It can be wired for multiple primary and secondary impedance and most people report good results.

Early makers used small iron and as few windings as possible in their O/Ts for the sake of economy, the reason for the 3.2 ohm outputs on some amps - less windings on the primary. You have the opportunity to use more windings and bigger iron, but going overboard is pointless - and may even be detrimental. A 10 watt-rated O/T will be more than enough to provide solid response across a wide spectrum, given the power generated by that amp.

Similarly with speakers, connecting 20 or 30 watters in a 5w amp will tend to trade efficiency for life, and you can still kill a 100 watt speaker (not to mention the output section) with a square sine wave (over)driven out of a 5 watt amp. Small amps don't produce lots of power, so they really need a tight voicecoil gap and efficient speaker. With a speaker rated 3,4,5 times the power you will lose some response due to the looser airgap, stiffer cone, surround and spider. You'll then buzz the rest of the amp harder trying to drive it.

Better to marginally oversize as JC suggested, if you are going to do lots of Angus impersonations, IMO. For me, a Weber signature speaker would probably provide all the 'fi' whether hi or lo, you are going to need. Part of the charm of Champs and similar is the sheer 'garage-ness'. Get too fancy and it just becomes a sonically-compromised expensive small amp.

[Brick]

For me, I stuck with an 8" speaker. That is the true champ sound. Weather you like it or not is subjective. I have a 15" 4 ohm cab I can use if I want. Put a mic on an 8" speaker and a champ becomes a recording monster.

[JohnnyCrash]

Originally Posted by JamonHamon

+1
Victoria uses a Jensen Alnico P12q in there 12" Champ Clone and its the best

I generally dislike Jensen R series (25 watt) alltogether and prefer the N (50 watt) over the Q series (35 watt), in general. In something as small as a Champ, the R or even Q will be a good choice and the N will not be necessary at all... I'd say go with a Jensen P12Q... or even a 10" speaker, the P10Q.

Confused yet? HAHA

In a Champ, a Jensen P12R may be cool, but in other higher powered amps, they suck. A Jensen P12Q may be the ticket as well and a P12N will be overkill as Dacious mentioned.

Originally Posted by Brick

For me, I stuck with an 8" speaker. That is the true champ sound. Weather you like it or not is subjective. I have a 15" 4 ohm cab I can use if I want. Put a mic on an 8" speaker and a champ becomes a recording monster.

I can't stand 8" speakers in general, but have heard a few "better" ones. I usually run my tweed Champ head build through a Jensen AlNiCo P15N cab and it sounds incredible.