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-   -   Tube Pre-Amp < $200 (http://www.diyaudio.com/forums/tubes-valves/36533-tube-pre-amp-200-a.html)

gmilitano 22nd June 2004 10:46 PM

Tube Pre-Amp < $200
 
I am considering a budget pre-amp as a first tube project. I have initially selected the STA1 and the Foreplay pre-amps.

The STA1 pre-amp can be found at:

http://www.lh-electric.4t.com/sta1.html

While the Foreplay pre-amp can be found at:

http://www.bottlehead.com/et/adobesp..._stage_kit.htm

The STA1 costs about $139, but does not include an enclosure, RCA jacks or a selector switch. The Foreplay will be $179 as of July 3 but is a 100% complete kit.

While the Foreplay is complete, I do not like the tabletop enclosure, so the enclosure is of no value to me. The Foreplay also does not have bass or treble control which is something I would be looking for in a pre-amp. On the otherside, their website is excellent and there are several positive reviews of this pre-amp.

The STA1 uses three triode tubes (one more than the Foreplay) and comes complete with bass and treble controls. However, the website is not all that great and I have not seen any reviews of this product.

Now with that being said, could someone provide some comments about these pre-amps or any other budget pre-amp kits in the <$200 range (without enclosure). I realize that this is a low budget, but iit s in keeping with what I want to spend on a overall system which will still require a tube amp and a pair of mid to high efficiency speakers.

Cheers,
GM.

Sch3mat1c 22nd June 2004 11:05 PM

2 Attachment(s)
Skip a kit and build mine for $50. :D

Tim

arnoldc 22nd June 2004 11:19 PM

no experience here with STA1 pre, but have built a Foreplay. used to be you can buy the manual for $35, or so.

my foreplay used a different chassis and had the volume control and selector on front and the input and output jacks at the back.

it costs me 2,500 pesos (60 canadian) for everything, and was my first attempt in building a preamp. it sounds good and is a keeper in my system right now.

i'm not a fan of tone controls so the foreplay was ok (but DACT sound best in my system :D)

i think for $200 you have lots of options including tim's pre, fdegrove's pre, triode dick's 6072 pre, je labs 76 pre, etc. etc.

cheers!

http://wap.misnet.com.ph/arnoldc/foreplay.jpg

Eli Duttman 22nd June 2004 11:54 PM

GM,

What sort of source(s) are you using? In a digital only rig, the 2 V. O/P of a CDP will drive most amps into clipping. That means all that is needed is a buffered (cathode follower) level control.

Take a look down the page at the tubed tone control thread. The Baxandall circuits described, built around 4X 12AX7s, should yield the sound shaping ability you want.

A question for the "crew", could GM get away with using the active tone control circuitry at the preamp's I/P and follow it with a buffered level control? I ask as a 12AX7, even as a cathode follower, is not too good at driving a load.

desert rat 23rd June 2004 06:11 AM

Integrated Tube Amp
 
If you are only planning to run line sources through your system, you may want to conssider the K-12M Integrated Tube Amplifier Kit available from Arizona Hi-Fi (tubeaudio.com) or S-5 Electronics (www.s5electronics.com) for $139.00. This kit puts out 8 watts per channel into 8 ohms and has a volume control. It is very capable of driving medium sized fairly efficient speakers (e.g., B&W 500 Series) in medium sized listening rooms. The kit is pc board based and is easy to build in 2 to 4 hours. It has no cabinet but one is available for $95.00. A wood base is provided as a temporary support to mount the pc board and transformers. A photo and parts list is provided at the tubeaudio.com site.

It sounds great! It sounds better than my $1000.00 Musical Fidelity A3 Integrated Amplifier which surpasses most solid state integrated amps in its price range. It provides the depth, tonal accuracy and "in the room" sound quality typical of good tube electronics. The base response is also surprising for only 8 watts per channel.

If you want great sound on a really tight budget, this little integrated amp is highly recommended. The only drawback that I can see is that it has only one set of input connectors and, of course, no phono amp circuit.

gmilitano 23rd June 2004 02:37 PM

Quote:

Originally posted by Sch3mat1c
Skip a kit and build mine for $50. :D

Tim


Hi Tim,

I have a good understanding of electronics, but not tubes. I am looking for a kit that supplies all the parts I need to build.

Thanks,
GM.

gmilitano 23rd June 2004 02:41 PM

Quote:

Originally posted by Eli Duttman
GM,

What sort of source(s) are you using? In a digital only rig, the 2 V. O/P of a CDP will drive most amps into clipping. That means all that is needed is a buffered (cathode follower) level control.

Take a look down the page at the tubed tone control thread. The Baxandall circuits described, built around 4X 12AX7s, should yield the sound shaping ability you want.

A question for the "crew", could GM get away with using the active tone control circuitry at the preamp's I/P and follow it with a buffered level control? I ask as a 12AX7, even as a cathode follower, is not too good at driving a load.

Hi Eli,

My main source will be digital (CD Player), however, I do have a small vinyl collection which is why I am interested in a pre-amp.

I'm sorry, but I was unable to follow you on the clipping bit? Are you saying that a CD source should not go through Pre-Amp?

Cheers,
GM.

gmilitano 23rd June 2004 02:45 PM

Re: Integrated Tube Amp
 
Quote:

Originally posted by desert rat
If you are only planning to run line sources through your system, you may want to conssider the K-12M Integrated Tube Amplifier Kit available from Arizona Hi-Fi (tubeaudio.com) or S-5 Electronics (www.s5electronics.com) for $139.00. This kit puts out 8 watts per channel into 8 ohms and has a volume control. It is very capable of driving medium sized fairly efficient speakers (e.g., B&W 500 Series) in medium sized listening rooms. The kit is pc board based and is easy to build in 2 to 4 hours. It has no cabinet but one is available for $95.00. A wood base is provided as a temporary support to mount the pc board and transformers. A photo and parts list is provided at the tubeaudio.com site.

It sounds great! It sounds better than my $1000.00 Musical Fidelity A3 Integrated Amplifier which surpasses most solid state integrated amps in its price range. It provides the depth, tonal accuracy and "in the room" sound quality typical of good tube electronics. The base response is also surprising for only 8 watts per channel.

If you want great sound on a really tight budget, this little integrated amp is highly recommended. The only drawback that I can see is that it has only one set of input connectors and, of course, no phono amp circuit.


I am aware of the S5 amp and it is likley the Amp I will go with. I have read several good things about that amp. The reason I am interested in a pre-amp is I will need a phono pre-amp and I am I would like a tone control as the speakers I would be hooking up to (till I build new ones) are a little harsh.

Thanks for your input,
GM.

Eli Duttman 23rd June 2004 04:28 PM

Quote:

I'm sorry, but I was unable to follow you on the clipping bit? Are you saying that a CD source should not go through Pre-Amp?
GM,

IMO, a CD source should go through a tubed line stage. However, that line stage should have approx. unity gain with the level control fully advanced. A cathode follower fills the requirement. To use such a line stage in a system with a turntable requires that the phono stage be high gain. 50-55 dB. of net gain will raise the O/P of a "typical" MM cartridge to approx. the same level as that produced by a CDP.

IMO, your tone control requirement forces you to scratch build, as such circuits are NOT popular in high end tubed preamps, either commercial or DIY.

Put your general knowledge of electronics to use. FET circuitry can go a good way towards teaching you about tubes, as both FETs and tubes are high impedance voltage controlled devices. The characteristic curves of FETs and pentode tubes are quite similar in appearance. You must show RESPECT for the high voltages tubed circuitry operates at. 1 hand in a pocket or behind your back is MANDATORY when tinkering. Lack of respect can cause your death.

gmilitano 24th June 2004 06:32 PM

Quote:

Originally posted by Eli Duttman


IMO, a CD source should go through a tubed line stage. However, that line stage should have approx. unity gain with the level control fully advanced. A cathode follower fills the requirement. To use such a line stage in a system with a turntable requires that the phono stage be high gain. 50-55 dB. of net gain will raise the O/P of a "typical" MM cartridge to approx. the same level as that produced by a CDP.

IMO, your tone control requirement forces you to scratch build, as such circuits are NOT popular in high end tubed preamps, either commercial or DIY.

Put your general knowledge of electronics to use. FET circuitry can go a good way towards teaching you about tubes, as both FETs and tubes are high impedance voltage controlled devices. The characteristic curves of FETs and pentode tubes are quite similar in appearance. You must show RESPECT for the high voltages tubed circuitry operates at. 1 hand in a pocket or behind your back is MANDATORY when tinkering. Lack of respect can cause your death.

While I have read a little bit about a tubed line stage and cathode followers, I will have to do some checking up to fully understand your comments.

But in general, I think you are saying that the STA1 kit (http://www.lh-electric.4t.com/sta1.html) would be appropriate for use as only a phono pre-amp but not for a digital source.

For a digital source, going directly into an integrated amp such as the S5 kit (http://www.s5electronics.com) would be appropriate.

If I wanted to have tone control over the digital source, I would likely have to build something from scratch.

Sorry for being so repetative, but I wanted to make sure I understand.

Cheers,
GM.


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