Edcor OPT's w/ SimpleSE

[awhite1159]

Starting new thread for my SimpleSE build since I am not a Newbie anymore. I am in the process of building so I am a Doobie. But of course still being a beginner, I have another question.

As luck would have it, I somehow or another upgraded every part in the amp except for the OPT's and as I understand it, this is one of the components that has the greatest impact on sound quality. I currently have the Edcor OPT's but I am seriously considering getting the Hammond's that George mentions when suggesting the Edcor's as a cheaper alternative. I heard that the Edcor's are 'bass-lite' and this concerns me. Should I be concerned? Also, I have the JJ EL34's and Gold Lion KT88's. Which of these would give better sound quality?

Thanks to everyone so for all the help thus far.

Andy

[tubelab.com]

The big Hammond OPT's are far from bass lite. The 1628SEA's have the best bass of any SE OPT that I have ever tested. When connected to my 15 inch OB speakers the walls move and the bass can be heard inside the house across the street (SimpleSE amp). These transformers are large (11 pounds) and are somewhat lacking in response above 15KHz. They are also over $100 each.

The small Hammond 125CSE's are very similar to the small Edcor transformers in performance, but cost $10 more. I have not tested the larger 125 series Hammonds.

An SE OPT is a compromise in performance. The large ones make great bass, but are more inefficient, and may lack good high frequency response. The smaller ones have great HF response, but tend to saturate on heavy bass.

There is a middle ground (around 5 to 7 pounds each) that seems to give the best sound without giving up too much bass. The best performance / cost ratio comes from the Transcendar OPT's found on Ebay. I liked them so much that I bought 10 pairs. That particular transformer is no longer available, but he still has SE OPT's available. I have not tried their "budget" OPT's yet though. Other transformers in this range are the One Electron UBT series, and the Electra Prints. The Electra Prints are considered one of the best. I have a set in my TubelabSE and they do sound great.

[awhite1159]

Sorry George, you must have posting while I was editing my post. I meant 'Edcor' not Hammond. Consider it done. I ordered the monster Hammonds.

Here is a pic of it so far. I have to wait for the Hammond OPT's but will probably start wiring it up. (Stuck tubes in tosee what it wouldlook like. I mounted the big CAP underneath. Replacing ugly choke too.

[tubelab.com]

I am afraid that those big Hammonds won't fit the chassis that you show. They are large. I remember that the dimensions given on Hammonds web site for some of these transformers are WRONG! Don't drill any holes until you have them in your hands. I learned this the hard way.

As far as output tubes are concerned, the EL34 has greater detail, but the KT88 has more bass. Quality is in the ear of the beholder, try them both. I am using Electro Harmonix KT88's in my SimpleSE when I use my big speakers. When I use the small speakers, I use EL34's. I have since built a 3rd SimpleSE that uses 6V6's. It only makes about 2 watts but sounds sweet. I have been playing that one a lot lately.

[awhite1159]

The area where the Edcors are sitting is 5" x 8.25". Gee that would suck. Well, if I have to I will build another cabinet. I got plenty of wood left over from my horn builds.

[tubelab.com]

I measured the overall size of the 1628SEA's in my amp. They are just under 5 inches deep (end bell to end bell), 3 3/4 inches wide (at the center of the core) and 4 1/2 inches tall.

I checked these measurements against the dimensions published by Hammond :

http://www.hammondmfg.com/1627.htm

I found that my transformers DO NOT MATCH their specs. The 1628SEA's that I have match the dimensions shown for a 1630SEA. Did Hammond screw up and send me the wrong transformers? They have 1628SEA labels on them, but I have not tested them to see if they are really 5K ohm transformers. I would be interested to hear what size yours are when you get them.

I received an email several months ago claiming that Hammond had screwed up the wiring on a batch of these transformers. The writer forwarded an email from a "Hammond Engineer" stating that the red and blue wires were swapped. This would affect the ratio of the UL tap. My transformers are connected the way that Hammond shows on the same page and they seem to work well. I have not yet tried swapping the wires to see what happens.

[awhite1159]

Sounds like I might have got lucky with the space I have free for them. Thanks for the info. When I get them next week I'll let you know what size they are.

[awhite1159]

I'm trying to get as much of the wiring completed as I can while waiting for the OPT's. The AC receptacle appears to need correct wiring since I notice one is marked neutral. Does it matter where the neutral and hot go into the circuit? I know this is a stupid question since it is AC but I seem to remember (But I may be wrong) this needs to be correct for safety reasons.

[tubelab.com]

Common wisdom says put the fuse and the switch in the HOT lead. This is what I do. Some receptacles have the fuse inside them. It is usually in the HOT terminal. This is what I use, and I connect the switch to the fused terminal.

I have seen arguments for doing it other ways, but the only one that I buy is using a double pole switch and switching both HOT and NEUTRAL.

[awhite1159]

Thanks George. Thats exactly what I did since I figured it was safest to completely remove any voltage from the pwr trans primary when off. I can't wait to get this powered up. Based on the the fact that I upgraded all the components and the fact I built this, I think this will replace my main system. I bought a Chinese made amp about a month ago (Fountek Altitude 3500) out of curiousity and I suspect this may sound better. Less wattage but I found I only need 2 or 3 watts to get loud with my horns.