Ampeg Rocket

[michael peck]

tubes are 6sL7 6sL7 6v6 6v6 5y3. volume pot# 1376218 and ba811-1532, tone pot 1376241 and ba811-2308, have to borrow a digital camera to get ya pic but input jacks are angled and say guitar / accordian/ mic, also has tremelo pots , speed and intensity. amp is very loud, and has beautiful sound, better than my fender 60 watt tube, this amp im using exclusively on our next cd for guitar, but i plug my mandolin in direct to mixer

[guitician]

I have an Ampeg M-12 that was all original when I got it. It never had any "drive" to the circuit so I checked all the signal paths and found that the input jacks were mis-wired from the factory. I wired them per the schematic on the back panel and now it ROCKS. It's a dual channel version of yours with a third 6SL7. I also wired a 3 conductor power cord and replaced a couple of the "frako" bypass caps that failed.

[Prairie Dawg]

i found serial# its 212150, i dont think its a 50 watt, too light only wieghs 25lbs, but has fat chunky sound at low volumes even, do you know age from this or wattage?

Look at the speaker-indicates it is a 1957 vintage speaker. The amp's around the same vintage if it is an original speaker. Check some EIA codes on the iron, that should tell the tale.

XXX first three numbers are the manufacturer
X last digit of year
xx week of the year.

[olddawg]

i found serial# its 212150, i dont think its a 50 watt, too light only wieghs 25lbs, but has fat chunky sound at low volumes even, do you know age from this or wattage?

It's around 17 watts RMS.

[loosecounty]

I have been up to my eyeballs in one of these Ampeg Rockets for months. My rocket is a 59' ,and is ( I believe ) identicle. When I got the amp it had a "ratty" distortion. I replaced everything one might replace but it still sounded ratty. I believe part of the problem might be the floating paraphase type PI, Which might be tricky to balance. Who knows. Anyway , afriend suggested that I try a conjunctive filter, which I did and........WOW!! That was the silver bullet in this amps case. Totaly killed that ratty distortion, tightend up the bottom, and just made it thump. Not much headroom, but much better. I have thought about rewiring it to a cathodyne PI, and putting in the paul C mod because right now its a real rock n' roll monster but doesnt do anything else very well. .........And there is a lot of stuff in that PI set-up. Truthfuly I think its has the most "parts" of any phase inverter I have seen.

[olddawg]

I have been up to my eyeballs in one of these Ampeg Rockets for months. My rocket is a 59' ,and is ( I believe ) identicle. When I got the amp it had a "ratty" distortion. I replaced everything one might replace but it still sounded ratty. I believe part of the problem might be the floating paraphase type PI, Which might be tricky to balance. Who knows. Anyway , afriend suggested that I try a conjunctive filter, which I did and........WOW!! That was the silver bullet in this amps case. Totaly killed that ratty distortion, tightend up the bottom, and just made it thump. Not much headroom, but much better. I have thought about rewiring it to a cathodyne PI, and putting in the paul C mod because right now its a real rock n' roll monster but doesnt do anything else very well. .........And there is a lot of stuff in that PI set-up. Truthfuly I think its has the most "parts" of any phase inverter I have seen.

I have a 1960 Ampeg Rocket. Made in New Jersy. I have never been satisfied with the "ratty" distortion that it has when cranked. Could you discribe this "conjuctive filter" modification. I would like to try it on mine.

[loosecounty]

I would be happy to. The conjunctive filter is a resistor/and a capacitor in series across the OT primary (or power tube plates) . I used a 10K 10 watt resistor and a .002 ceramic disk cap.
Each output tube has a pin on the tube socket that goes to the plate. This filter goes from one output tubes "plate pin" over to the next output tubes "plate pin". Solder one resistor lead to one plate ,then solder one cap lead to the other plate. Now you solder the other resistor lead and the other cap lead together. Basicly you build a little bridge over the two output tube sockets, that looks like this
plate#1....to......resistor...to...capacitor...to...plat e#2
Its that simple. One more thing, the cap I used was a 2000 volt '2kv' cap
I dont think this matters but thought I would mention it. I started with a .047 wich was too bassy. The smaller the cap the more trebble. you know.

[Bruce / Mission Amps]

One more thing, the cap I used was a 2000 volt '2kv' cap
I dont think this matters but thought I would mention it. I started with a .047 wich was too bassy. The smaller the cap the more trebble. you know.

Ya know what? ... I think it matters a lot!!
In an old mid 60's EL34 VOX amp of mine, I actually blew up one of two 630v poly caps (wired in series to get 1260v of protection).
Plate voltage was about 485vdc and it still did something one day to blow one of the caps wide open.
Why? I don't know because the knee Fs of that filter has to be very high indeed.
So was the amp oscillating at that moment in high power ultrasonics when it blew the cap? I guess so.
I've seen this in old Orange amps too and it was a "must use" in their 200 watt PA amp!! I think they had 2Kv caps at .0047uF.
So, even though your amp has lower B+ voltages, if you can, I'd suggest at least two .0047uF@630v caps in series with the 10K@10 watter.

[loosecounty]

Thanks Bruce. The conjunctive filter was a bit "outside the box" for me and I dont know the math behind it. Not only that but there isnt really much info on the net about it. If you look in the RCA book explains how to spec the uf value of the cap but not the voltage rating. Its good to hear your take on it. Even though we have never spoken before I am familiar with some of your products. A friend of mine bought one of you 5e3 kits a while back and it really was top notch. Especialy the chassis. Its as good as it gets , period.
While on the subject ,I have been shopping around for a few custom trannies for some build ideas, (I wont mention any names) but I think the company I have been talking with is the same company you use.( same type lettering on endbells). Mark is the guy I have talked with and he seems very helpful. What has been your overall experiance working with those guys?
By the way, if you ever make it up my way ( Alaska) , drop me a line and I will take you out fishing.
Thanks for the input on the conjunctive filter.

[Bruce / Mission Amps]

Thanks Bruce. The conjunctive filter was a bit "outside the box" for me and I dont know the math behind it. Not only that but there isnt really much info on the net about it. If you look in the RCA book explains how to spec the uf value of the cap but not the voltage rating. Its good to hear your take on it. Even though we have never spoken before I am familiar with some of your products. A friend of mine bought one of you 5e3 kits a while back and it really was top notch. Especialy the chassis. Its as good as it gets , period.
While on the subject ,I have been shopping around for a few custom trannies for some build ideas, (I wont mention any names) but I think the company I have been talking with is the same company you use.( same type lettering on endbells). Mark is the guy I have talked with and he seems very helpful. What has been your overall experiance working with those guys?
By the way, if you ever make it up my way ( Alaska) , drop me a line and I will take you out fishing.
Thanks for the input on the conjunctive filter.

Well there could be more then one Mark at a few of the higher end tranny winders! ha ha... unless it is Mark Sacketti who really seems to know what he's doing and helped me with some of mine.

[loosecounty]

Very interesting, wink, wink.
I could just order some (off the shelf trannies) ,but nobody seems to have exactly what I want. Thats why I was considering a small "custom spec" order from (you know who), and was interested in what you thought about dealing with them. There are no 5e3 type builds on my horizon right now but if there were I would definitley buy one of your 5e3 trannies. You have your voltages correct IMO. It seems like most 5e3 trannies are speced so there voltage would be almost too high with a 5y3, but what if I prefer a 5v4 (which I do) then your B+ is way too high and the whole thing starts to sound bad.
Its funny that you should reply to my (conjunctive filter) post , because I have thought about calling you before and running a couple things by you. Seeing the way you speced the 5e3 tranny I believe we are on the same page regarding voltage levels, which seems to be the exception not the norm. I just finished drawing a schematic from a 1940's sherwood master tweed amp that you might appreciate. This perticular amp was totaly rewired a LONG time ago and is the best sounding 6v6 amp I have ever heard. and the simplest. I bring this up because it had 313 volts on the plates. let me know if your interested and I will fax you the schematic.

[loosecounty]

Very interesting, wink, wink.
I could just order some (off the shelf trannies) ,but nobody seems to have exactly what I want. Thats why I was considering a small "custom spec" order from (you know who), and was interested in what you thought about dealing with them. There are no 5e3 type builds on my horizon right now but if there were I would definitley buy one of your 5e3 trannies. You have your voltages correct IMO. It seems like most 5e3 trannies are speced so there voltage would be almost too high with a 5y3, but what if I prefer a 5v4 (which I do) then your B+ is way too high and the whole thing starts to sound bad.
Its funny that you should reply to my (conjunctive filter) post , because I have thought about calling you before and running a couple things by you. Seeing the way you speced the 5e3 tranny I believe we are on the same page regarding voltage levels, which seems to be the exception not the norm. I just finished drawing a schematic from a 1940's sherwood master tweed amp that you might appreciate. This perticular amp was totaly rewired a LONG time ago and is the best sounding 6v6 amp I have ever heard. and the simplest. I bring this up because it had 313 volts on the plates. let me know if your interested and I will fax you the schematic.

[remolino82]

Very interesting, wink, wink.
I could just order some (off the shelf trannies) ,but nobody seems to have exactly what I want. Thats why I was considering a small "custom spec" order from (you know who), and was interested in what you thought about dealing with them. There are no 5e3 type builds on my horizon right now but if there were I would definitley buy one of your 5e3 trannies. You have your voltages correct IMO. It seems like most 5e3 trannies are speced so there voltage would be almost too high with a 5y3, but what if I prefer a 5v4 (which I do) then your B+ is way too high and the whole thing starts to sound bad.
Its funny that you should reply to my (conjunctive filter) post , because I have thought about calling you before and running a couple things by you. Seeing the way you speced the 5e3 tranny I believe we are on the same page regarding voltage levels, which seems to be the exception not the norm. I just finished drawing a schematic from a 1940's sherwood master tweed amp that you might appreciate. This perticular amp was totaly rewired a LONG time ago and is the best sounding 6v6 amp I have ever heard. and the simplest. I bring this up because it had 313 volts on the plates. let me know if your interested and I will fax you the schematic.

my friend
a have a sherwood master 8422 and i saw in the forum that you have DONE A a schematic from a 1940's sherwood master tweed amp.
do you would send it me to my email?
i will apreciate if you help me
i am from south america , chile

my email is
R@MOLINA.IN

[moonbird]

Could I get a copy of your schematic???

I just finished drawing a schematic from a 1940's sherwood master tweed amp that you might appreciate. This perticular amp was totaly rewired a LONG time ago and is the best sounding 6v6 amp I have ever heard. and the simplest. I bring this up because it had 313 volts on the plates. let me know if your interested and I will fax you the schematic.

I have one of these -- but have not broken down to trace it. Could you please send a copy of the schematic you made to moonbirdmusic [at] yahoo <dat> com. If a fax is easier -- I can give you that too. Thanks very much.