Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: JunkDr on July 26, 2016, 09:49:35 pm
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Hello All,
I am building an 5E3 clone and am looking for some clarification / recommendation regarding capacitors. First off, it is not a Hoffman kit (sorry) I bought it off eBay from a local guy here in Ontario CA about 5 years ago and it has been on the shelf up until last winter when I thought I should get at it. This "kit" turned out to be based on someones college electronics project and is based on an original Tweed Deluxe owned by their professor. I did not check everything out when I received it and once I started working on it I found quite a few things wrong with the parts supplied. For example, there were four resistor values that were wrong by a factor of 1000's of ohms - I had to order the proper values. The filter caps are MEIC brand and I am not happy with that so I ordered F&T's. They supplied a 12AY7 and I acquired a 12AU7. My question is in relation to the tone caps - they actually provide a choice in the "kit", ETR MET's and Orange Drops both of the same stock value. I have searched a bit and there seems to be a natural bias towards Orange Drops and I am wondering if the hype around those justifies using them? As this site seems to have a vast, experienced knowledge base I am wondering what some of you think I should use?
On another note, this kit has an upgraded PT which has a band of copper sheet around the laminations for noise suppression. I am not sure how to ground that band and don't want to make the grounding mistakes that are so common. Any suggestions?
Thanks for any input, Jeff in Belleville ON CA.
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> resistor values that were wrong by a factor of 1000's of ohms
Do you mean 680 Ohms was 2,680 Ohms?
Or 220K was 222K?
Tubes are not real fussy. Generally 20% variations hardly matter.
> based on an original Tweed Deluxe
And old amp parts drift. Sometimes for the worse; sometimes an old amp sounds "really good" and someone thinks duplicating the as-found values will re-create That Sound.
> supplied a 12AY7 and I acquired a 12AU7
12AY7 is original-correct. 12AX7 is the usual replacement for somewhat higher gain. 12AU7 would only be used to majorly cut the gain for HIGH output sources (harmonica mikes).
> ETR MET's and Orange Drops
MET: www.etr.com.tw/eng/dc_use_film_capacitors/m_polyester/dc01_07.htm (http://www.etr.com.tw/eng/dc_use_film_capacitors/m_polyester/dc01_07.htm)
Both caps are "better" than Leo was buying in 5E3 days. ODs were the reference upgrade cap for many decades. ODs actually come in several film types. Golden-ears hear differences. I don't, certainly not after the second beer or first power chord. If there is a difference, which is better may be different for different players, speakers, genres, or picking styles. So "experienced knowledge" may not help YOU. Certainly you'll never get thrown out of the band for using the wrong-color caps, as long as they carry signal.
Anyway, if this is Turret Board, you can replace the caps in 15 minutes, try both ways. (Eyelet would be authentic, and tuffer to swap-out.)
And tube-amps are not like a concrete foundation, where if you screw-up you have to live with it. They can always be fixed.
Get organized, comfortable workspace, and just do it.
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Thanks PRR,
I should have waited to post this morning, I'm sharper then! I reversed the tube thing - I got a 12AU7 and I bought a 12AY7, the correct original tube spec.
When I said 1000's of ohms this is what I meant - required a 5600, they supplied a 5.6 (not a 5.6 K, the band colors tell the tale), not close enough I'm sure.
It is an eyelet board and that part is mostly built but is not in the chassis yet, I was just wondering about the caps before I go much further (I opted for the MET caps when I put it together in the early spring). I have been more focused on getting the cabinet built while there is nice weather to work outside. Tweed cloth covering next - that will be taxing I'm sure!
Thanks, Jeff
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(not a 5.6 K, the band colors tell the tale)
Just to be sure, measure that with your DMM. I usually measure mine anyway because I can't remember the color codes. Well, except for red-red-red and red-red-yellow.
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I did that too as sometimes I don't trust my vision on these but these were blatant, gross errors. Anyway, I appreciate the remarks about the caps - especially the fact that we can get a much better, cheaper, smaller cap then Leo could get at a reasonable price in his time. ETR MET it will be. I really hope to have this live before winter, too busy.