New to Tubes

[beaner]

Hello,

I'm new to the whole tube amp DIY. I've heard of them and sort of understand how they work. I"m now interested in building a nice amp for the bedroom. I'm thinking of something around 10-20watts that'll have a nice sound to it. I've enjoyed my home theatre system but there's something about the glow of a tube amp that I enjoy. Personally I've never heard a tube amp before but from what I understand they are very nice to listen to.

I've plugged around on the site for a while now, but am unsure of what designs are "good". Any information would be greatly appreciated.

Thanks

[TheGimp]

A lot will depend on what speakers you are using. The higher the efficiency, the smaller the amp can be and still have sufficient dynamic range.

If your speakers are 90db/W or better you can get by with something around 10W (unless you are into really loud music).

How proficient are you at soldering and construction techniques?

Read the stickeys on tube theory and safety before jumping in.

Are you interested in building a kit? Or building it from scratch?

The Baby Huey is reputed to be a pretty good design as is the Oddwatt.

I've got a design in progress in the Sven 6P1P PP amp that is similar to the Meng yue mini.

[Eli Duttman]

"The Gimp" made an important point regarding speaker sensitivity. Paul Joppa has given us a useful rule of thumb. Joppa's Rule states that in a "typical" listening space an amp/speaker combo should be capable of reaching 102 dB. SPL peaks at a 1 M. distance.

I will immodestly suggest "El Cheapo". With good O/P transformers and ultralinear (UL) mode O/P tubes, an honest 12 WPC is available. The schematic I've uploaded shows triode wired O/P tubes, but the change to UL is very easy to make. "El Cheapo" is an "integrated" amp and a separate preamp is not needed, when a CDP is the signal source. Building an "El Cheapo", as a 1st project, will test you, but it's definitely feasible. If interested, the LENGTHY saga of "El Cheapo" can be found here.

[beaner]

I'm fairly good with soldering, I'm a computer technologist and my father is an electrical guy, so I've been around eletronics in some form or another.

Most of my experience was in car audio, I've built a few competition systems, and am fully aware of the voltages induced by these. I've been zapped a few times by while troubleshooting some PA systems with my dad.

Personally I'd like to build one from scratch since there is a particular look that I like but I guess I could modify the case of a kit.

The speakers that I'm looking at pairing on this are probably going to be a DIY set of Tritrix or Triune's. The transmission line speakers are of interest to me and they seem to be getting some good review. I was thinking also of trying full range but am not familiar enough with them. To me having a dedicated mid/midbass and tweeter just seems to be able to create a broader range of sound. Correct me if I'm wrong I just don't know enough about full range.

[pjanda1]

I can vouch for the El Cheapo. If you are using lower efficiency speakers, you might consider building it with output transformers that have ultra-linear taps (like the Dynaco Z-565 clone), thus giving you the option for more power. I'm very happy running mine in triode, but I do have very efficient speakers. My guess is that the electrical construction of an EC wouldn't challenge you too greatly. Once of the biggest pains in building an amp, the creating the parts list and sourcing everything, is mostly taken care of with the EC. All-in-all, it'd be a great first project. Mine is the best amp I've heard in my system (so far), by a fairly wide margin.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

[Glowbug]

What kind of a budget are you thinking?

[thoriated]

The 'El Cheapo' sounds like a really good amp to get your feet wet in DIY with. Personally, I'd use straight metallized polypropylene capacitors instead of electrolytics for the final plate supply filter stages and to bypass the 6AQ5 cathodes Motor run capacitors look cool mounted on a chassis, IMO, and don't cost all that much if you buy them from a place like Newark.

[beaner]

I'm not sure on budget, since I have no idea what these will cost. I've seen everything from $100 up to well over $1000.

The hard part will be figuring out the diagrams. I may be a pia to a few of you.

I was also looking at a few that had some VU meters on them some using the E80 which looked interesting. The analog VU meters reminded me of my dad's old home system back in the 80's

[rmyauck]

Beaner,

I bought Pete Millet's Red board for that kind of power, and am trying to decide on good output transformers as they say that is one thing that makes a tube amp. My budget has been allocated on another project too, so it is on hold. The only thing with this board is that the tubes are no longer in production, other wise supposed to sound great. It uses before not wanted NOS (New Old Stock) TV tubes for the output tubes to give 18W/CH PP (Push Pull with 4 Output tubes) It can be souped up for considerably more power as George from Tubelab.com can attest with bigger Output tubes. He actually has a board just out called the Simple PP with 18W/CH with production tubes. I just read he should have the pats list and instuctions out in 2-3 weeks. These are some of the the pretty affordable and easiest to build in the close to 20W range. You will also discover the SE or single ended amps with 2 output tubes, the affordable ones being just under 10W/CH and not using DHT (directly heated tubes) tubes. There are also the Dynaco ST-70 boards that give 10-20W/ Ch in Triode mode. Best to get new improved circuit boards from various vendors. Geek on this form has new boards out for that too. Just google the name I mentioned for info. I mentioned boards as they are easier for a beginner and you get consistent results, but maybe you prefer P2P (point to point) wiring like you see on old equipment. Can be easier to modify etc. You can also take a schematic for a board and make your own P2P amp. Harder to get right. ( Hum & ground issues) For a low cost great sounding P2P Checkout El Cheapo Amp by Googling name. It's on Audiophiletalk.com You can buy a kit of parts from Jim McShane(except iron) You could use new production type tubes in it such as 6V6GT and the Triode Electronics Output transformers for 6-12W/CH depending if run in Triode or UL Ultralinear Mode. Triode supposed to sound better but lower power is produced. Some prefer sound of 6V6GT over EL84 tubes. 6AQ5 is supposed to be a miniature 6V6GT, but is no longer in production. I think 6V6GT is toughest as used in quitar amps. Of new production Tung Sols might be pretty dam good, from what I read. I have an old RCA 1949 8R71 AM/FM radio with SE type amp (single 6V6GT output tube) and with a CD player plugged into it's RCA jack it sounds sweet. Some say EL84 sound the best and you gain power too.
If you spend many hours on this diyaudio siteyou can pick up a lot of info and other links. So much to learn! You can then decide SE or PP circuit boards or p2p etc. You may not want any SS in amp part. I think most against SS will accept Diodes though. I have seen lots of great help available if you have questions.

I bought an old Harmon Kardon Citation II amp to rebuild and am awaiting parts from Jim McShane. Google Jim McShane Tubes for more info. Supposed to sound fantastic W/ 35W/CH in Triode and 65W in UL mode. Expensive project though! I have old inefficent speakers that need lots of power! Actually how much power needed of course depends on speakers. You might have seen that that field can get very expensive for huge high efficiency speakers.

I took quite some time to write and I see I've repeated a lot, and I see you don't want boards, but may help others!

Cheers

Randy

[Jim McShane]

Originally Posted by thoriated

The 'El Cheapo' sounds like a really good amp to get your feet wet in DIY with. Personally, I'd use straight metallized polypropylene capacitors instead of electrolytics for the final plate supply filter stages and to bypass the 6AQ5 cathodes Motor run capacitors look cool mounted on a chassis, IMO, and don't cost all that much if you buy them from a place like Newark.

If I might toss my $0.02 worth in - any spare money should go into the iron. The PS is VERY good as it stands. The #1 factor limiting El-Cheapo performance is the iron.

Get the best OPTs you can afford (within reason) - we've found the circuit is good enough to justify the investment. And for power iron keep in mid that about 200-210 volts on the 12AT7 plates and you're in the "sweet spot". B+ of about 350 or so is needed. If you're worried about the 'AQ5 screens then use 6V6GTs instead. No changes are needed to run 6V6s in El-Cheapo.

If you wanted to replace the 4.7 uf Solens with some nice motor runs that would be excellent - especially in the B2+ supplies for each channel where a couple big uf oilers would be nice indeed in parallel with the F&T. But focus on the iron first.