Ready to go SMPS for 15W tube amps!

[Cliff Schecht]

My dad just sent me this:
http://www.siliconray.com/rtp-15-switch ... ifier.html

$65

Here were my initial thoughts:

I suspect the guitar guys will have mixed feelings about these while the hifi guys will love them. As you know part of the appeal of tube guitar amps is the dynamic sag that occurs in the power supply (really only in push pull amps) and it seems like every time someone tries to improve the formula, people don't really like it. For example the lower ESR film caps that came out to replace electrolytics in tube amps aren't very popular with guitar guys, the caps are too "fast" and you get a much quicker transient response. I suspect a better power supply with lower output impedance will have the same effect, it'll be too quick to respond and will change the feel of the amp. Whether people like that or not I guess is yet to be determined.

[diagrammatiks]

It's nice.

It shouldn't significantly change the feel if you use other methods of snubbing the hash noise and build some sag into the resistor string.

[jelle]

2xel84 pp..... I wonder if this power supply would survive an 18w Liverpool.... Would be cool if it worked.

[Alexo]

Claims to be 300 ma on the HV, more than enough for a quad (or sextet!) of 6V6's or EL84's... although the listing suggests 6V6 SE (?)

[Teleguy61]

Any guinea pigs out there?
Love to see someone try it and report.

[Structo]

They don't really say how clean the output voltage is or even if it is DC.

But I assume it is DC.

I thought I read before that switching power supplies tended to be pretty noisy in audio circuits?

On the 18 watt and small PP amp circuit schematics I have they look for 325-380v on the plates.

Do you have to do some magic with this to get there?

[M Fowler]

RTP-15 is designed for integrated amplifiers has output power of 15Wx2 (PP) or 8Wx2(SE).
- Input voltage: 100V-240V
- Output HV: 280V 300mA
- Output LV: 6.3V*1A, 6.3V*2A, 6.3V*2A, regulated seperately

I'm pretty sure that is 280vac

[markr14850]

I'm pretty sure that is 280vac

If it's AC, it's at >80 kHz

[VacuumVoodoo]

It's DC. It's a SMPS AC/DC supply not an AC/AC inverter or DC/AC converter.

[sparrott]

Well I took a leap and ordered one to try out, if anything it would make a decent bench supply for prototyping preamps. It says the switching frequency is above 80Khz so it should have minimal effect on the noise level. I had used switching supply before for the filaments and the one thing I ran into is the filaments are a very large current draw when the tube is cold, this causes some problems with the soft start circuitry. The supply may pulse a few times before fully starting, so a load isolation relay may be in order.

[bal704]

Interesting. What are the L,N and E terminals? I assume those are for the AC in? Also, it has one 280V output. If that's your B+, does that voltage get used for B+1 and B+2 etc as well?

Sorry if those are stupid questions, but I've never seen one of these before.

[sparrott]

Interesting. What are the L,N and E terminals? I assume those are for the AC in? Also, it has one 280V output. If that's your B+, does that voltage get used for B+1 and B+2 etc as well?

Sorry if those are stupid questions, but I've never seen one of these before.

Should be Line, Neutral, and Earth. Switching supply often do two conversions, rectified line voltage -> 300 to 400v for power factor correction and then 300V to 400v -> 12v, 5V or whatever. My guess is that they are regulating/isolating the power factored corrected voltage for the B+ out. So the power limitation stems not from the 280V 300ma but from a standpoint of if the other voltages are a max capacity, the 280v out will run out of power.

[collinsamps]

Am I that only one that thinks replacing one high quality component that will generally outlast the amp itself with a few hundred other components of questionable durability is a bad idea?

[VacuumVoodoo]

With all the new legislation re power factor correction, zero stand by power etc linear power supplies may soon be a thing of the past. I think we should at least investigate SMPS and perhaps look at novel ways of using them in guitar amps.

[M Fowler]

Never mind I decided I wouldn't waste my time on this device.