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elgee 14th October 2011 06:43 PM

Building a tube integrated amp
 
Hello there. I've had problems with my Marantz PM 6010 OSE amplifier and am looking to upgrade it. I've read quite a lot about the advantages of tube over solid state and would like to try a tube amp out.

I don't have a fantastic amount of money (maybe 300ish) and was wondering whether a kit would be feasible? Or, whether I would be better off looking either second-hand or cheapish imports (Chinese I guess but I'm a bit wary of being stung for import duties etc.) and maybe upgrading parts as and when I can afford them.

I would welcome any advice you could give me.

I'm an almost complete novice when it comes to electrical circuitry, with limited soldering skills. I think I'm quite a practical person and can usually pick things up reasonably quickly so I think I could take on a challenge like this and enjoy it.

Thanks,

Les

boywonder 14th October 2011 07:00 PM

How sensitive are your speakers? What are your listening habits? (acoustic guitar, heavy metal, etc)...size of your listening room?

What are your sources? CD player, Ipod, etc.....

You can certainly build an amp within your budget; the speaker sensitivity and listening habits/room size will help determine how much power you need. If you need lots of watts due to low sensitivity speakers, that costs $$.

Since you are interested in an integrated amp, that assumes that you don't have a preamp, correct? Do you just need a volume control or do you need the ability to switch between inputs?

Do you have a multimeter (or two)?

One more thing, if you are more interested in enjoying music rather than learning about tubes and building amps, a nice second hand tube amp is probably the way to go, as building one usually won't save you money (unless you've got a good iron/chassis donor to start with)

DF96 14th October 2011 07:07 PM

Learn to solder well on a cheap kit, maybe some ancilliary box rather than a full amp. Take things one step at a time.

chrisb 14th October 2011 07:08 PM

Quote:

Originally Posted by elgee (Post 2745863)
Hello there. I've had problems with my Marantz PM 6010 OSE amplifier and am looking to upgrade it. I've read quite a lot about the advantages of tube over solid state and would like to try a tube amp out.

I don't have a fantastic amount of money (maybe 300ish) and was wondering whether a kit would be feasible? Or, whether I would be better off looking either second-hand or cheapish imports (Chinese I guess but I'm a bit wary of being stung for import duties etc.) and maybe upgrading parts as and when I can afford them.

I would welcome any advice you could give me.

I'm an almost complete novice when it comes to electrical circuitry, with limited soldering skills. I think I'm quite a practical person and can usually pick things up reasonably quickly so I think I could take on a challenge like this and enjoy it.

Thanks,

Les


Kinda depends on what you mean by "integrated" amp - in the old days that could mean lots of inputs, RIAA (and more) EQ, tone controls, speaker switching, tape dubbing, yada, yada

In today's world, a power amp with sensitivity of less than 3 volts, and a volume control, even absent switching for any number of inputs greater than one is often described as an integrated

That said, yes, there are lots of options for a DIY or fully parted kit tube-amp - so logically the next question is what speakers will you be using them with /how much power do you (think you'll) need? Keep in mind that many of the very good sounding inexpensive tube amps are of the SE variety - speaker sensitivity aside, not all of these are comfortably matched with the more complex crossover networks often found in multi-way loudspeaker systems . Some elaborate XOs for 3 & 4 ways can have more circuit components than a small SE amp.

elgee 14th October 2011 07:45 PM

Sorry for the delay - I posted a quick reply but nothing happened and I ended up being logged out.

The speakers are Kef Q80's with sensitivity of 89/90dB. The room is 25 x 10 feet with an additional 10feet inthe middle making a T shape. I listen to mainly classical but also anything from Queen to Elton John to Coldplay etc.

I use a cd at present but an extra output might be useful for the future. I suppose I mean an amp that will play my music in 1 box when I say 'integrated' - I' suffering from lack of knowledge of terminology I'm afraid.

I do have a multimeter.

I think I would really enjoy the challenge of building one, but, I can see that buying good used and possibly making improvements would alsomake sense - provided I could find such an amp of course - not sure where to look?

Thanks for the quick responses.

elgee 14th October 2011 08:19 PM

Mulling over yourm advice several questions spring to mind:

If I go for a build project what sort of quality am I likely to get compared to my Marantz PM6010? Where would you recommend I go to get a good kit from for around 250-300?

If I buy used, where is the best place to look for good quality at a reasonable price?

Are there any particular makes/brands that I should look out for or that you would recommend?

Eli Duttman 15th October 2011 01:07 AM

Before you part with any "coin of the realm", tell us more about your KEF speakers. What is their nominal impedance? How is the 89 dB claimed? What is the impedance minimum? Those answers will tell us if the claimed 89 dB. sensitivity needs derating and if the speakers are usable with tubed power amplification to begin with.

Speaker makers make lawful claims that don't pass careful technical srutiny. A sensitivity rating of 89 dB. with 2.83 V. of drive into 4 Ω is, in fact, 86 dB., as 2.83 V. into 4 Ω is (sic) 2 W. A nominally 8 Ω speaker with 1 or more dips in its impedance curve down to 4 Ω has to be regarded as a 4 Ω unit, when combined with tubed power amplification. Tubed power amps don't have the gargantuan damping factors associated with SS power amps.

elgee 15th October 2011 01:03 PM

I looked up the Q80 spec on the Kef website:

Specification: Q80
System type: Two-way, floor standing
Enclosure type: Passive radiator
Dimensions (H x W x D): 855 x 246 x 274mm (33.6 x 9.72 x 10.8 inches)
Weight: 14.5kg (32 lbs)
Nominal impedance: 8 ohms
Amplifier requirements: 10-120W (into 8 ohms)
Frequency response: 57Hz to 20kHz +/-3.0dB (-6dB at 40Hz)
Sensitivity: 89dB at 1m for 2.83V (corrected for wall mounting)
Maximum output: 110dB
System: SP3137
Drive units: B200 bass/midrange unit (SP1280), BD200 passive radiator (SP1288), NT25 tweeter (SP1353)
Crossover network: SP2189

Hope this is useful.

I have also run these wired in series with a pair of Modaunt Short MS25Ti bookshelf speakers which seems to give a 'fuller' sound (not sure how this would be described in hi fi terms?). The Marantz semmed to handle this without too much effort. I couldn't find any info on these speakers though.

Les

boywonder 15th October 2011 02:37 PM

elgee: Eli is asking for an impedance plot; impedance vs freq.......may be worth a quick web search but we're not holding our breath that you'll find one.

If you have a function generator, amp and a multimeter, it's a fairly simple exercise to create one. If you don't have access to a function gen, you can download free software to run on a PC to generate sine waves.

Could be an interesting first project to get your feet wet.....

elgee 15th October 2011 07:21 PM

Ah. No luck so far. Information on the older Kef's is very sparse.

I'll try again and let you know if I have any luck.

Les


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