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Old 3rd June 2009, 07:44 PM   #1
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Default Oh my where to begin!? PTP related question.

Well this is sort of an introduction thread and a question in one. I'm new to these (DIY) parts of the audio world. I've been a headphone fanatic for a few years now, owning a slew of headphone and headphone amps. Well I want to get together my first truly nice speaker setup and I want to DIY the whole thing end to end. So I've been reading the last few days trying to wrap my head around so much information about tubes. I've read the stickies and done some searching. I found a ton of useful information but I'm still confused at some things which is to be expected. Well enough rambling...

I'm thinking that my first amp build is going to be a TubeLab SE amp but I have the desire to do this in a PTP fashion and not on a PCB. Has anyone done a TubeLab PTP build? From looking at pics of the PCB assembly process I don't think this would be overly difficult but having never build an amp I could be terribly underestimating. Oh and I do have some previous electronics experience, I can read schematics and also solder. I've just never dealt with tubes or transformers.

-Jim
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Old 3rd June 2009, 09:24 PM   #2
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First I would recomend deciding what speakers you are going to use. DIY or something you purchased, doesn't matter. You need to know how efficient the speaker are so you can build the proper amplifier. If you end up with speakers that are the normal 88-90 db efficiency then you will need at least 20 to 25 watts of power taking most things into consideration. If you have a large room and or listen to dynamic music loudly you will need even more power, 50 to 60 watts.
If you build or purchase something much more efficent in the 95 to 100 db range then you can get away with less power in the 10 to 15 watt range.
Single ended amps, like Tubelab's very nice efforts, need to understood to be able to get the best sound out of them. Unlike push pull amps you can not run single ended amps to their power limits because of the high distortion at power levels close to the limit. As a rule of thumb you can only count on about half of the output as usable in a single ended amp. So if you have a single ended amp that puts out say 10 watts, you can only count on 5 watts before the distortion gets to point where it gets overwhelming.
Before starting to build anything pick up Morgan Jones' excellent third edition. This will give you a good reference book to start. For first project I would start with a Dynaco ST 70 and modify it to get some experiance and then do a TubeLab project.
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Old 4th June 2009, 04:32 AM   #3
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Assuming that SE power is sufficient (as discussed above), you can certainly P2P wire a simple SE but for $35+shipping the PCB is very convenient. Even with P2P wiring, you will most likely wire a proto board (or two) with a handful of components for the CCS, etc.

If you would like to build monoblocks, then P2P wiring the SSE makes more sense, IMO since the SSE PCB is a stereo layout.
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Old 4th June 2009, 07:05 PM   #4
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From what I've been reading I've been leaning towards building some BLH type enclosures similar to the 208Esigma enclosure. I'm primarily looking at the FE206/7E drivers but I'm also interested in how the Sonido SFR-200 would perform in the 208Ez enclosure. From the data I found both of their efficiencies are 95db.

I will look into that Dynaco thanks! Do you think a SE will drive either of my above selections alright? I don't have a very large room, 16'10"x11'. I don't listen to music at really high volumes. Most things I listen to are Classical, Jazz, Folk, acoustic type stuff.
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Old 4th June 2009, 08:26 PM   #5
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Since your room is not large and the speakers you are discussing are relatively efficient and you don't do head banger listening levels you should be able to use a single ended amp.
The TubeLab board would be a great choice. Do not sweat the point to point wiring. TubeLab boards are very well made. Lots of help available from folks on the forum who have already built amps and George at TubeLab is very helpful with builders problems. Plus his board makes chassis building relatively simple.
For output tube I would recommend going with the KT 88 to get something close to 10w out will give you some head room which is needed. You do not want some flea spec power, 1-3w. You will have very little head room and when you turn up the sound the amp will quickly be running into clipping at peaks and running into the distortion limit. For a 95 db speaker 10w will give you very nice service.
You need to choose as good as a output transforme as you can afford and you will get excellent sound. Do not cheap out on the output transformer. It is the most important component in the amp and will be the determining factor for the sound of the amp.
I have been running Lowther PM2As in rear loaded horn cabinets for over a decade, very similar to the speakers you are thinking about. I have run many types of amps both solid state and tube and found that flea spec power can sound nice but has very little control of the bass and tends to clip. Almost all the solid state amps had great bass but sound a bit sterile compared to the tube amps. At the moment I am running a Audio Matiere Majuscule tube integrated. The sound is just amazing.
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Old 4th June 2009, 08:46 PM   #6
newtube is offline newtube  United Kingdom
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Hi fella. . .

I had previously had a yamaha AX596 amp, a 100w per channel monster before my first tube amp (a s5 electronics kit) push pull 8w and i was genuinly surprised at the output and quality of the sound. . . i thought it would sound weak but it was quite good for a cheap kit, but then. . .

I bought george's simple se board and collected the parts to build it, all i can say is that if you have some fairly efficient speakers then you will be amazed at how full and substantial the sound is, mine are 90.5db and play in a 14ft square room and its a very good sounding amp indeed.

Get some good iron and quality parts and your onto a winner.
Cheers and have fun mate.
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Old 4th June 2009, 09:44 PM   #7
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You can build a Simple SE in PTP fashion. There have been a few users that have done exactly that. Most were succesful, but one builder had an amp that hummed, and I (or anyone else on this forum) can't easilly troubleshoot something that we have never seen.

There is also a very similar design that was popular on this forum a while back. Search for "mikael kt88" and look at the construction techniques used.

Keep in mind that one of the big issues in building your own PTP amp is the layout and grounding of the circuitry. If this isn't right you could have hum and possible oscillation. The Simple SE PC board was designed to solve these issues making the possibility of "first time success" very high.

If you are determined to use PTP construction, I would suggest reading Morgan Jones books on tube amp construction, and read some forum posts on grounding, and hum. Understand the concepts before spending a lot of time and money. Many feel (based on old information) that PC boards destroy the sound, and that PTP will result in a better amp. I am not going to get in the middle of that debate, but I can say that PTP construction requires a bit more care and knowledge unless you are copying a known good design.
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