Dennis Had Inspire Amps

[BearCityUSA]

Originally Posted by Comzee

I have the IIPS and I've rolled many rectifiers (b4 and after upgrade). In either scenario I found rectifiers still give a massive difference in sound.

With that said, I wholeheartedly agree with gz34, it's the only rectifier I've tried with my kt150 that can somewhat flesh them out. Since the Fire-Bottle was never directly intended for KT150, I'm not sure even with gz34 it's really pushing them to full potential.

Anything other than gz34 really kills the kt150 (imo) (ymmv).

I do have a limited understanding of Electrical theory and design but it is my understanding that amps with the IIPS have diode rectification and as stated earlier the rectifier is acting as a feedback buffer of the "nasties" as Dennis calls them. I also understand the change from direct heated rectifiers to indirect heated rectifiers in the IIPS will change the "noise floor" but has no effect on the v-drop and rectification since that is done by Diode. With this said the GZ34 match with the KT150s in a IIPS optioned Fire Bottle/Hot Rod/KT amp is irrelevant except with regards to sound due to Noise Floor changes but not Power output. The Rectifier makes no difference to Power output. Of course none of this is relevant to the Inspire amps without the IIPS. For those the Rectifier tube is providing AC to DC rectification and is very relevant to Power, Sound, Etc.

BTW, a look at post #1 of this thread will show a KT150 Fire Bottle.

[pstrisik]

Originally Posted by BearCityUSA

<snip>

BTW, a look at post #1 of this thread will show a KT150 Fire Bottle.

Yes, mine is called a KT150. Dennis designed it with that tube in mind. I have since had the upgrade to IIPS.

I've never been able to warm up to the KT150 tubes though. They seem a bit sharp to me. I can't recall if I've tried them with the IIPS mod though, so probably worth another listen.

My list of things to try is still growing but our Alaska summer visitors are still coming and going!

[Wgarcia]

Since Had said it would work fine with 150s, and it's a December 1st, 2016 build date, I suppose I should assume it's a IIps, although I'm not certain what IIps means.

[pstrisik]

Originally Posted by Wgarcia

Since Had said it would work fine with 150s, and it's a December 1st, 2016 build date, I suppose I should assume it's a IIps, although I'm not certain what IIps means.

If you have a photo of the inside (bottom cover removed), there are a few here that could tell you. Dennis certainly could as well.

Here are Dennis' words:

"...a new circuit I have recently developed to prevent power supply distortions caused by the output tubes pushed into high and even higher non linear levels of output power. These distortions show up as a parasitic modulation products even on the smallest forms of the power supply. The actual sonic audible indications are sharp high frequency lisps on vocals and instruments becoming strident and for a better word ear piercing. I normally let me ear be the design chain but in this case I went to test equipment spectrum displays for analysis of the power supply wave form along with the output wave for and harmonic content. My goal was to limit odd order products in the output signal and in turn discover the source of many over load distortions. What I discovered was when an output device, in my case a vacuum tube, became non-linear and produced various spurious distortion products back fed to the power supply. In the case of a basic power supply suppling both the output devices along with the driving front gain sections I was able to detect these modulated parasitic products in the driver stage compounding the problem of output distortion of the final product.

I was surprised to find the nasties invading even the regulated power supply circuit I use for the input driver tube and output tube screen grids. My thought process, (dangerous!!!) took me to figure on a high impedance decoupling device of the power supply between the output and input devices with a shared power source. Well, since I gotta lotta time to think about circuits and not banks and employees … bingo … the light went off. How about the good ole two element vacuum rectifier vacuum tube. Yea, like and indirectly heated 5AR4, GZ34 and variants …. use the vacuum between the elements and see if the good ole rectifier tube could transfer the positive going DC voltage from the high B+ output tube potential to the lower (+250 VDC) regulated driver and screen grid supply. With some additional parts and old man soldering, it works and works well. I can now drive the you know what out of a single-ended amplifier and create a listenable signal even in complete over load with the 2nd order harmonic masking the third and fifth order nasties. How does it sound …. smooth, with honey flowing from the loudspeakers. "

[Rosco65]

With the IIPS, B+ is rectified by two solid state diodes before being passed through the Pi filter. The rectifier tube acts as a secondary diode pair for the regulated PS (150v, IIRC). This tube is followed by zener diode pair that regulates the voltage supplying the driver stage and the output tube grids. If - as Dennis strongly implies - the grid supply voltage is critical and sensitive, it may react differently to different rectifier tubes. No voltages in the amp should change (the B+ will remain as determined by the PS and current draw and the regulated supply should remain constant) but the recovery characteristics of each PS stage may vary. The B+ supply should recover almost instantaneously while the regulated supply may recover more slowly depending on current draw and the "speed" of the rectifier. Directly-heated, low-drop rectifiers "should" recover faster, if that is important. I'm not sure it is.

[Musica Amantem]

Originally Posted by Comzee

I have the IIPS and I've rolled many rectifiers (b4 and after upgrade). In either scenario I found rectifiers still give a massive difference in sound.

With that said, I wholeheartedly agree with gz34, it's the only rectifier I've tried with my kt150 that can somewhat flesh them out. Since the Fire-Bottle was never directly intended for KT150, I'm not sure even with gz34 it's really pushing them to full potential.

Anything other than gz34 really kills the kt150 (imo) (ymmv).

In my system the Low Vdrops work great (-17 to -20). I'm currently very fond of the 5Z4 (Brimar), which I find as good or even better than the Westinghouse-labelled Amperex Holland 5AR4 (GZ34), for most applications, especially with 6550 and KT-88. I assume this is also a good alternative for larger tubes

[Comzee]

Originally Posted by Musica Amantem

I'm currently very fond of the 5Z4 (Brimar),

Have not tried that one yet, here's a few I have tried:
JJ GZ34 || JJ 5U4G || nos RCA 5v4g || JAN-Sylvania 5Y3WGTA || Mullard f31 fat base gz34 || Preferred Series 274b || Bendix 6106 (5Y3 Variant) || Sophia Electric 274b mesh || Psvane 274b treasure mkii || Sylvania 5931 (5U4WG sub) || GE NOS 5R4GYA || Philco Sylvania 5U4G Hanging Filament || RCA 5R4GY hanging filaments single bottom getter || PHILIPS 5R4GYS (made in holland) || NOS 596 (sub for 274A 5U4G 5R4)
1940s RCA Jan Crc 5R4GY hanging filaments double bottom getter

A few others I can't remember.

For anything but the kt150, I prefer by a wide margin the 596 rectifier

As far as iips, not sure what it is if power output is always the same.
I can say when I use anything but gz34 with my kt150 it kills the bass, recesses the mids.

[Wgarcia]

I happen to have some 150s left over from a previous amp (they seem to sound fine in the Fire Bottle), and I suppose I'll have to take a pic to post here as Dennis is incommunicado…no problemo.

[Musica Amantem]

Originally Posted by Comzee

Have not tried that one yet, here's a few I have tried:
JJ GZ34 || JJ 5U4G || nos RCA 5v4g || JAN-Sylvania 5Y3WGTA || Mullard f31 fat base gz34 || Preferred Series 274b || Bendix 6106 (5Y3 Variant) || Sophia Electric 274b mesh || Psvane 274b treasure mkii || Sylvania 5931 (5U4WG sub) || GE NOS 5R4GYA || Philco Sylvania 5U4G Hanging Filament || RCA 5R4GY hanging filaments single bottom getter || PHILIPS 5R4GYS (made in holland) || NOS 596 (sub for 274A 5U4G 5R4)
1940s RCA Jan Crc 5R4GY hanging filaments double bottom getter

A few others I can't remember.

For anything but the kt150, I prefer by a wide margin the 596 rectifier

As far as iips, not sure what it is if power output is always the same.
I can say when I use anything but gz34 with my kt150 it kills the bass, recesses the mids.

Impressive list! The IIPS works if you are typically borderline clipping. If you have enough headroom reserve, then it should not make a difference.

If you really want dynamic bass, use a filter to unload the lowest 100 Hz frequencies from the Amp and channel those to a SUB ... The effect is really great, at least in my rig. Also, KT-150 would probably be better off without a PRE, assuming the sensitivity of the speakers is high enough for these low-power amps. As good as the PRE is in small or medium-sized tubes, it imparts too bold a boost for larger tubes, and the effect is a muddied sound where there is less definition across frequencies. This is just my opinion, mind you, but consider it as a possibility of your unsatisfactory results with all those rectifiers.

I would argue that a powerful rectifier coped with powerful tubes may be too much of a good thing, but you already tried all kinds of rectifier specs with those KT-150, so I will take your word for your conclusion. IME, low V-drops work great with larger tubes because these prevent typical sag from the tubes' response. I agree the KT-150 would benefit from low V-drops like the one you prefer and the suggested 5Z4.

[x3workshop]

Originally Posted by Musica Amantem

Someone in this forum suggested to use a simple plug-and-play, inexpensive filtering gadget to improve the Amp's performance and allow better bass (please identify yourself, so we can give you credit) ... Well, I tried this gadget today and I'm so impressed I will never go back to the original setup.

With the RED MOD High-Pass filters at 100 Hz (the gadget), the Amp works without the overload of those difficult first 100 Hz frequencies. Passing those exclusively to the SUB (set with a line cross-over at 100Hz), bass lines are seamlessly connected between under and over 100 Hz (there is a tangible difference between reinforcing the bass and complementing it), and the Amp's performance has improved noticiably.

I have so far only tried this with PRE and AMP running GL KT-77's, which used to be somewhat bass-limited in my rig. Not anymore! This setup has been my favorite for a while, and now it is gorgeous! I cannot imagine what this will do with tubes specified at lower max plate current in Triode at 250 V, i.e., EL-34, 6P3S-E (6L6), 350B and 6V6's.

The cited smaller tubes (except the EL34, which I have never tried) struggle with body of sound in my system, essentially due to their limited electrical capacity, while having to deal with the highly demanding low frequencies ... Although I have yet to confirm this with smaller tubes, I bet now I'll be able to enjoy them much more.

Anyone in possession of one or more SUB's must give these a try, they really work.

MA,

That was me that suggested the F Mods.

Been away from the forum for a bit. I've actually been caught up with listening to a Citation II that I recently rebuilt along with a pair of my rebuilt Acrosound UL II's. NOT SET! They're glorious amps though!

The F Mods solved the nagging problem of the Inspire losing steam when I was pushing it hard. Once I sent <100hz to a sub and lightened the load on the Inspire it came alive for me. I won't go back.

Now if you really want to see what else you can gain, try subbing a 6BL7 into your LP-27a.